Question:
Since I know some of of a Bass Fishing Tips you do engage in amp customization, I thought I’d pass on to you some of the things I have learned about lead dress in an amplifier, which is probably one of the hardest things to do correctly. Although most typically a problem when high-gain stages are present, even Fender had its share of of a Bass Fishing Tips trouble with lead dress starting with the second generation Silverface amps, and these amps can be hardly considered high gain. Most Fender fans will say that Fenders were always less prone to oscillations that Marhalls, making it sound as if there is something superior about the design. While it’s true that Marshalls almost always behaved worse, it warrants pointing out that Marshalls typically run at higher levels of gain,of a Bass Fishing Tips so it’s the old apples and oranges stuff. Most people read about this subject, and know a few things, such that grid leads “should be” short, etc. But, the shortest path between two given points is not necessarily the best for tone’s sake. In the specific case of Fender amps, there is a grid lead that goes from the rightmost volume control to the 2nd stage of the “vibrato” input. This is the single longest lead in the hole amp, and the one that can give you a tremendous headache if you’re building additional gain stages within the amp. No pain, no “gain” though (yes, pun intended). [Also, even if you're not considering customizing any amp, you can always improve the stability of your later Silverface amp by tweaking the lead dress and getting read of the tone-eating caps at the power tubes] I found that moving that wire around could do one of three things: give a good sound, make the amp break into oscillation (whether you can HEAR the oscillation or just “feel” it -of a Bass Fishing Tips- the old parasitic type), or result in a very nasal sound. You can do the lead dress by trial and error, and maybe you’ll get there, but there is a way a found to be more effective and it does work indeed. Use a long wire, temporarily of course, to make the connection whose lead dress you want to optimize. If you pull that wire away from the rest of the circuit, you will hear the tone is unfettered, even across all frequencies and without any unwanted side effects — well, you will most likely find this anyway.of a Bass Fishing Tips Get a cable with alligator clips on both ends; wrap a portion of that wire around the grid lead. Leave one end of the alligator wire not touching anything (you can clip it to the insulation of the cable so that is doesn’t move around), and with the other end, start probing the entire circuitry. When touching plate connections, remember you’re dealing with 200+ volts, so… be cautious. What’s going on here is that now you’re capacitance coupling your grid lead wire to all other points of the circuit via that alligator clip patch wire, which is similar to what would happen if you lay your wired back into the circuit. As expected, plate leads from stages which are in phase with the grid wire in question will make your amp squeal like a pig when you touch them with the alligator clip, so you’ll want to stay far from those wires. Conversly, plate leads out of phase with the grid lead will KILL TONE big time, again keep your distance. In some extreme cases, you may lose almost all your ouput, but even if that doesn’t happen,of a Bass Fishing Tips you will think there is a wah-wah stuck on the bass side of the throw because of the degenerative feedback that’s taking place. Additionally, there are several points within the circuit that will also affect the sound, although maybe not as severely. Also, bear in mind there is some stuff going on underneath the chassis as well, so if you’re probing around open areas of the chassis and find that, although it should “all be ground,” there is a still change in tone, well.of a Bass Fishing Tips.. it could be your reverb transformer, the filter capacitor can, etc. What to do? Map out the areas of the circuit where it is “safe” to run your lead dress, based upon your experimentation as described above, and you will end up with an optimum path for the grid wire. In most cases, this will not be a straight line — which is obviously the shortest distance, belying the rule suggesting to use the shortest possible lead for grid connections. If you HAVE to go across another wire which you’ve determined to be an offender with the probing excercise, cross it perpendicularly; this will minimize capacitance coupling and the tone will be most likely preserved. What about using shielded cable? Yes, absolutely, that will help provided you be sure to ground one end of the shield;of a Bass Fishing Tips other people recommend you not ground either end and, and instead connect one end of the shield to the corresponsing stage’s plate; I have found this to be another tone killer, and there is the potential hazzard of having a hot shield. It’s been my experience that shielded wire is not bullet proof and might be subject to the same effects I mentioned earlier, although to a lesser extend if you do things correctly. Using generic microphone cable is bad, probably even worse than using no shileding at all if you have cheap wire. It doesn’t provide good protection against cross talk and the copper mesh will be an antenna atracting all kinds of stray signals to your lead wire. Even if you ground the shield, you’ll be stuck with a signal riding on top of your grid wire, and there will be some interaction and or modulation. Foil type shielded cable, although much more expensive, is the only way to go.of a Bass Fishing Tips If you’ve seen MESA/Boogie schematics, you will notice that some models (the Marks II and above, for instance), have all kinds of capacitors in their overdrive sections that either shunt to ground or bypass the plate load resistors. Some writers have said that it helps control an otherwise extremely buzzy sound, and that it helps to stabilize the design. Yes, it stabilizes the gain stages, but the midrange heavy tone which results may not be what you’re shooting for.of a Bass Fishing Tips Regarding the buzzy sound, if you can allow your highs to go through all the stages unaltered, they will not sound so buzzy anymore: the will be sweet because they break up easily and give lots of harmonics, resulting in your amp being extremely touch sensitive — one of the keys to the sound of Dumble amplifiers, for example. If you think you can “control” the treble response thoughout the preamp overdrive stages, a la MESA/Boogie, and then use a presence control to bring the amp back to life, it won’t work even close. The presence control will sound stiff and flat because the treble it will let through doesn’t have as much harmonic richness since the highs were stopped at the overdrive stages. I do not like the presence control on the Mark II and IIIs for this very reason; implement the same feedback network on a more harmonically rich amp and the difference is striking. [Since I have had a chance to see the guts of some very old Boogies, it seems to be that the Boogie midrange heavy tone may have evolved out of necessity, because the chassis were very crowded and the amps would have been unstable without dumping a lot oh highs to ground. However, there is no denying that Boogie came up with a legendary sound, a great sound in many people's opinion.] Hope this helps some people out there to save some of the time I had to spend lead dressing my amp. Some books address various anti-microphonic techniques (long plate connections, short grid connections, shielding, etc.), but that alone will sometimes not be enough. I encourage everyone form staying away from using small capacitors to get rid of oscillations if you can..of a Bass Fishing Tips. yes, that method does work — and so does turning off your amp, for that matter — but it simply nukes tone. Common tech tips, such as wrapping a loop of cable around a lead wire and connecting one end of the loop to whatever quiets down the amp are the same as using capacitors to combat oscillations, so use the as your last resort if you have to. ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan, Los Angeles, CA /_/ /_/ /_/ /_/ /_/ /_/__/ http://home.earthlink.net/~ayan
Response:
Thanks Gil for a genuinely useful post.
Response:
<SNIP I found that moving that wire around could do one of three things: give a good sound, make the amp break into oscillation (whether you can HEAR the oscillation or just “feel” it — the old parasitic type), or result in a very nasal sound. You can do the lead dress by trial and error, and maybe you’ll get there, but there is a way a found to be more effective and it does work indeed.
With out the use of a scope for, the detection of the OSC *above human hearing*, the comparison of phase relationships, modulated carrier existence, High Freq Blooming or spiking on signal peaks, etc,…. Without the right test equipment, this is could be like going on a search for the Hope Diamond in the Carlsbad Caverns with nothing more than a candle to see your way. Use a long wire, temporarily of course, to make the connection whose lead dress you want to optimize. If you pull that wire away from the rest of the circuit, you will hear the tone is unfettered, even across all frequencies and without any unwanted side effects — well, you will most likely find this anyway. Get a cable with alligator clips on both ends; wrap a portion of that wire around the grid lead. Leave one end of the alligator wire not touching anything (you can clip it to the insulation of the cable so that is doesn’t move around), and with the other end, start probing the entire circuitry. When touching plate connections, remember you’re dealing with 200+ volts, so… be cautious.
Years ago we called this sort of thing, using a sniffer wire for sniffing around circuit layouts. Even used air coils or caps on a clip lead depending what you happen to be sniffing for. Scope probes are the best sniffer wires there are. What’s going on here is that now you’re capacitance coupling your grid lead wire to all other points of the circuit via that alligator clip patch wire, which is similar to what would happen if you lay your wired back into the circuit. As expected, plate leads from stages which are in phase with the grid wire in question will make your amp squeal like a pig when you touch them with the alligator clip, so you’ll want to stay far from those wires. Conversly, plate leads out of phase with the grid lead will KILL TONE big time, again keep your distance. In some extreme cases, you may lose almost all your ouput, but even if that doesn’t happen, you will think there is a wah-wah stuck on the bass side of the throw because of the degenerative feedback that’s taking place.
I have never incountered this extreme case in my years at the bench. Theory would allow it to happen, though in the proper design practices for audio I had learned in school, never. Additionally, there are several points within the circuit that will also affect the sound, although maybe not as severely. Also, bear in mind there is some stuff going on underneath the chassis as well,
You LOST me here. Is Underneath the same side as the control grid wire and ckt components? Or are you refering to the other side of the chassis. In which case, this makes no sense to me at all. so if you’re probing around open areas of the chassis and find that, although it should “all be ground,” there is a still change in tone, well… it could be your reverb transformer, the filter capacitor can, etc.
This wire is acting like an aerial for anything that wants to ride in on it. Like fishing, you could catch the good, the bad, or the ugly. Even a close by radio station too. WNJR and I are old friends. <SNIP If you’ve seen MESA/Boogie schematics, you will notice that some models (the Marks II and above, for instance), have all kinds of capacitors in their overdrive sections that either shunt to ground or bypass the plate load resistors. Some writers have said that it helps control an otherwise extremely buzzy sound, and that it helps to stabilize the design. Yes, it stabilizes the gain stages, but the midrange heavy tone which results may not be what you’re shooting for. Regarding the buzzy sound, if you can allow your highs to go through all the stages unaltered, they will not sound so buzzy anymore: the will be sweet because they break up easily and give lots of harmonics, resulting in your amp being extremely touch sensitive
Then, if we remove these shunt and plate load bypass capacitors, in the Meas Boogie, this we will get the results in your last sentence. Hope this helps some people out there to save some of the time I had to spend lead dressing my amp. Some books address various anti-microphonic techniques (long plate connections, short grid connections, shielding, etc.), but that alone will sometimes not be enough. I encourage everyone form staying away from using small capacitors to get rid of oscillations if you can… yes, that method does work — and so does turning off your amp, for that matter — but it simply nukes tone. Common tech tips, such as wrapping a loop of cable around a lead wire and connecting one end of the loop to whatever quiets down the amp are the same as using capacitors to combat oscillations, so use the as your last resort if you have to.
If you Don’t recommend using a wire loop, Shunt Cap, and the use of shielded wire adds capacitance when grounded just like a shunt cap…. What is your recommended cure for this without nuking tone? Just looking to learn something new. Regards, Rich Koerner, Time Electronics. http://www.timeelect.com
Response:
Posts like that are making good to this NG ! Thanks , Gil Jukka — Remove “no_spam” to send a reply
Response:
With out the use of a scope for, the detection of the OSC *above human hearing*,
Very true, I use a scope too. Regarding the parasitics, you can’t hear the high frequency oscillations but you will most likely feel them becasue they will swamp your amp down and will modulate your guitar signal. Even if it’s an oscillation you can hear, the scope will give additional information, like telling you how far back, menaing how many stages back, the oscialltion can be found, thus giving you an idea of the where the “problem area” that started it all is. [Note: if you think you can afford a scope, check out electronic swap meets; you can find old Heathkits -- which will work just dandy for guitar stuff -- for $10-30] However, a scope will only allow you to see regenerative feedback. If you have denegerative feedback you’re SOL unless you are *listening* — or unless you have a sweep generator and monitor all the frequencies at once, hmmm you may need a spcetrum analyzer rather. While the scope may indicate your, say 1.2 KHz, test signal is unaffected by moving the wires around, a 4 KHz signal could be meeting a different fate. In the end, the amp has to sound good… so the scope can help, but the ears are the boss in my book. Years ago we called this sort of thing, using a sniffer wire for sniffing around circuit layouts. Even used air coils or caps on a clip lead depending what you happen to be sniffing for. Scope probes are the best sniffer wires there are.
Shoot Rich, you — or Webber or O’Connor — should have written about it so that I would have had some guidance myself. 
That is the very reason I posted this here, hoping to help others; I don’t claim to be the first one to have used this type of method, but I have already applied for a patent on it and if you keep saying you knew it before me I am going to have my lawyer contact you! :/ BTW, I prefer to call it lead dress optimization, rather than “sniffing,” although that’s just a matter of personal preference… or maybe even whatver types of words are more fresh in one’s memory. :) keep your distance. In some extreme cases, you may lose almost all your ouput, but even if that doesn’t happen, you will think there is a wah-wah stuck on the bass side of the throw because of the degenerative feedback that’s taking place. I have never incountered this extreme case in my years at the bench. Theory would allow it to happen, though in the proper design practices for audio I had learned in school, never.
Well, you can to check it out by coupling your last high gain stage output with an amp’s first or second stage, whichever is out of phase, and see what you get. If you get no side effects, it means you mave have not had much high end frequency content to begin with. Regarding *PROPER DESIGN PRACTICES FOR AUDIO*, I am truly dissappointed in that comment given the nature of this forum! Do you by that mean not running 12AX7s beyond their voltage headroom, or not saturating the power tubes so that there is no DC on the output trasnformer? How about the 470 vdc on the Fender reverb drive plates? :) You see my point, a guitar tube amp is hardly an example of proper audio design, thank God. Additionally, there are several points within the circuit that will also affect the sound, although maybe not as severely. Also, bear in mind there is some stuff going on underneath the chassis as well, You LOST me here. Is Underneath the same side as the control grid wire and ckt components? Or are you refering to the other side of the chassis. In which case, this makes no sense to me at all.
Underneath meaning on the underside of the chassis chassis. The choke, reverb transformer and output transformer all radiate, and there are wires carrying DC and pulsating DC (B+) coming from the capacitor can. All of those places have their own peculiarities and there are holes in the chassis to allow wired to go from one side to the other. I found differences, but maybe my ears (and scope) are too sensitive… I am just reporting findings. Whether things make sense or not is beyond the scope of my original article. Bottom line is, the chassis is ideally all at the same potential, but parts of it will be more suceptible to stray signals than others. Then, if we remove these shunt and plate load bypass capacitors, in the Meas Boogie, this we will get the results in your last sentence.
Your observation could be either sarcastic or naive, now be honest Rich, which one is it? I can guarantee you that if you remove all of the badwidth limiting caps in a Mark IIC+ or III, you won’t be able to turn the gain up without all kinds of oscillations — and no, I’m not willing to put any moeny on that, but looking at old Boogie layouts, I am sure. Will you “get there,” tonewise, if you pluck the caps out? If that’s all there was to voicing an amp… besides, “getting there” probably doesn’t mean the same thing to all people. What I will say, and it’s easy to confirm, is that it is very different to restrict bandwidth and overdrive that is it to overdrive and restrict bandwidth. Boogie tends to do both, I have found it more preferable to overdrive and then restrict bandwidth if need be. The difference is, in the case of Boogies, the sound will be pretty even throughout the guitar’s range, and hence the (in)famous Boogie midrange. But if you’ll notice on a Boogie, playing higher up the neck will make the sound smaller and smaller (say at the 22nd fret on the high E string), or, if you turn the presence up, the signal will not get smaller but it will get harsh. This is not a bad thing, it just is the way it is. Now, play a Dumble, and the higher you go up the neck, the bigger the notes get. It is a double edge sword though, because the Dumble can get out of control and start feeding back more that you’d like it to, but, when you manage to be in control of the amp, which requires an accurate touch, the responsiveness it has is simpy not matched by any other amp I have ever played through, and there have been quite a few. By the way, I don’t mean to pick on MESA/Boogie. They are good amps and since they’re very popular, people probably can relate to what I’m writing if I cite well-known examples. If you Don’t recommend using a wire loop, Shunt Cap and the use of shielded wire adds capacitance when grounded just like a shunt cap….
Let me try to explain what I tried to convey before. I have found it to work best for me to try to get the lead dress right without any crutches if I can help it; this has been the best solution in my case, but whatever tonal goals I had in mind may differ from yours, although I believe that good lead dress will always be the best possible scenario. Using shunt caps are tone shaping tools is fine, after all the whole guitar amp is a bunch of shunting caps in disguise. However, using shunt caps as means to kill oscillations will compromise tone, unless you just happen to LIKE the tone that results better, and that is a very personal call. It’s funny though, because after writing the initial article, I got a few emails from people saying that they had always “lived” with the shunt caps but realized the sound was a little more on the dead side. Regarding shielded cables, the primary reason for using them is to not allow hum to get into the early stages of ampification. As you’d have it, I do use foil-shielded wire from the input of my amp to the first control grid. The farther down the signal path you travel, the less of a need there is to shield grid wires because there is less gain ahead. Any wire, shielded or not, residing inside of a steel chassis will be a capacitor shunt. Some shielded cables will have lower capacitances than others (and of course the longer the wire, the greater the capacitance and subsequent loss of highs); I suggested experimenting with diiferent types/brands — using high quality stuff — or, if you can get away with it, no shielding at all on the 2nd and 3rd stages. Much has been written about guitar cords and how some sound very trebly, etc. Now, if the type of cable can make a big difference working with the small signal, and *around* 10K impedance, from a guitar, you realize the effect it will have on much larger signals, with very large impedances, such as those found at the plates of preamp tubes… What is your recommended cure for this without nuking tone? Just looking to learn something new.
I wrote a whole thing on it… When I started rebuilding my amp, a few months ago, I got tips from lots of people, among them my Boogie-loving buddy, Tremolux. He told me that suppressor caps killed tone, and I happen to concur with Tremo, 100%, although he’s really a vintage amp guy and I’m not. So, I recommend to try the lead dress optimization method that you, Rich, knew for so long but never told me about! ) Gil — ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan, Los Angeles, CA /_/ /_/ /_/ /_/ /_/ /_/__/ http://home.earthlink.net/~ayan
Response:
Since I know some of you do engage in amp customization, (snip)..
Thanks for taking the time to share this info you gathered, no doubt, through great trial, error, and personal time expended. It’s obvious that you care about the quality of your work…
Response:
Shoot Rich, you — or Webber or O’Connor — should have written about it so that I would have had some guidance myself. That is the very reason I posted this here, hoping to help others; I don’t claim to be the first one to have used this type of method, but I have already applied for a patent on it and if you keep saying you knew it before me I am going to have my lawyer contact you! :/
<Smile There are many things others have done before the both of us have. They just never cared to own it in the form of a patent. There is one out there that was a mod of mine back in 1970. The lawyer said it wasn’t worth it as I could not get it but take from the owner and place it back in the public domain. Well, it ain’t making them a fortune, and I’d rather keep my money. Through the years I have been asked to write on the subjects in my field. I guess being a writer is not what I do best. Though technical writing was part of my studies in school. I had managed a good mark there. So, I guess I could do it if I had the time. Maybe when retirement hits, computers take dictation, and then edits the text for the publisher automatically could make it happen. After I had gotten out of my electronics schooling I worked for a short while repairing vacuum tube HiFi and Communications gear. I had learned the art of sniffing from the older experienced techs there. Later I had worked for Magnus Organ designing there testing fixtures for their PC boards. This was the bottle neck in their production line. Interfacing the test gear to different parts of the ckts to not only test, but reveal where the problems where that needed correction. Here, again I learned a lot from those I had worked with of the old time tested methods for the creation of improvements. Well, you can to check it out by coupling your last high gain stage output with an amp’s first or second stage, whichever is out of phase, and see what you get. If you get no side effects, it means you mave have not had much high end frequency content to begin with. Regarding *PROPER DESIGN PRACTICES FOR AUDIO*, I am truly dissappointed in that comment given the nature of this forum! Do you by that mean not running 12AX7s beyond their voltage headroom, or not saturating the power tubes so that there is no DC on the output trasnformer? How about the 470 vdc on the Fender reverb drive plates? :) You see my point, a guitar tube amp is hardly an example of proper audio design, thank God.
In theory class we had to design ckts that met givin parameters givin by the instructor. This was sometimes in the form of a quiz or exam. Then in lab class, we had to build them in many different forms. For example, one in Point-To-Point wiring in a metal chassis, one on a perf/breadboard with wires all over the thing, or lead tied forming pathes on a PCB style arrangement. Here we learned about the problems in layout and lead dress in the many types of ckts we had to build in the various methods. This had become a design consideration to be kept in mind during the inital design process. Very important in RF ckt design. I had learned a lot from my teachers the tricks in dealing with these problems. Underneath meaning on the underside of the chassis chassis. The choke, reverb transformer and output transformer all radiate, and there are wires carrying DC and pulsating DC (B+) coming from the capacitor can. All of those places have their own peculiarities and there are holes in the chassis to allow wired to go from one side to the other. I found differences, but maybe my ears (and scope) are too sensitive…
Oh!!! OK!!! <Dawn Breaks I need more sleep!! A vacation would be better. I am just reporting findings. Whether things make sense or not is beyond the scope of my original article. Bottom line is, the chassis is ideally all at the same potential, but parts of it will be more suceptible to stray signals than others.
Yes, the fields from the iron, not to mention the Eddy Currents in the metal chassis itself are there too. That is something that is most often not considered in most designs. Had found one years ago as the cause of nasty hum in a Kustom 200 once. Just had to sniff the eddy current in the metal to find a new place for a ground. Drilled a new hole, and bolted down a ground lug. Bang, no hum. Used a SEARS CRAFTSMAN Heavy Duty screw driver as a probe for that one. I called them and they changed the location after that. Your observation could be either sarcastic or naive, now be honest Rich, which one is it? I can guarantee you that if you remove all of the badwidth limiting caps in a Mark IIC+ or III, you won’t be able to turn the gain up without all kinds of oscillations — and no, I’m not willing to put any moeny on that, but looking at old Boogie layouts, I am sure.
Neither. It just depends on which cap, and control settings, if the cap/caps can be removed without consequence. I know what you are driving at. However, you make it too absolute. This may not be the case in every Mesa amplifier, Fender, marshall, etc,… What I will say, and it’s easy to confirm, is that it is very different to restrict bandwidth and overdrive that is it to overdrive and restrict bandwidth. Boogie tends to do both, I have found it more preferable to overdrive and then restrict bandwidth if need be. The difference is, in the case of Boogies, the sound will be pretty even throughout the guitar’s range, and hence the (in)famous Boogie midrange. But if you’ll notice on a Boogie, playing higher up the neck will make the sound smaller and smaller (say at the 22nd fret on the high E string), or, if you turn the presence up, the signal will not get smaller but it will get harsh. This is not a bad thing, it just is the way it is. Now, play a Dumble, and the higher you go up the neck, the bigger the notes get. It is a double edge sword though, because the Dumble can get out of control and start feeding back more that you’d like it to, but, when you manage to be in control of the amp, which requires an accurate touch, the responsiveness it has is simpy not matched by any other amp I have ever played through, and there have been quite a few.
Never had the Dumble to play around with. I’ll just take your word for it till the opportunity presents itself. However, I’ve modified amps to do this. Some are not easy, or cheap to do this to. Let me try to explain what I tried to convey before. I have found it to work best for me to try to get the lead dress right without any crutches if I can help it; this has been the best solution in my case, but whatever tonal goals I had in mind may differ from yours, although I believe that good lead dress will always be the best possible scenario.
I do agree with you here. This would just be a school lab layout class problem. We would have to solve the problem of lead dress, and still have the meet the instructors specs for the “A”. this is something not considered by today’s designers, so shunt caps will appear. Today’s ckts could grow up a little. But so would the price of the amp. Profit is still the bottom line, not a well engineered guitar amp. Using shunt caps are tone shaping tools is fine, after all the whole guitar amp is a bunch of shunting caps in disguise. However, using shunt caps as means to kill oscillations will compromise tone, unless you just happen to LIKE the tone that results better, and that is a very personal call.
Now we enter that area of personal taste. Followed by opinion after opinion. For who’s taste do I design for here? What musician trend do I lean it toward? I’ll stop myself now before I drive myself crazy. I hate it when this happens. I wrote a whole thing on it… When I started rebuilding my amp, a few months ago, I got tips from lots of people, among them my Boogie-loving buddy, Tremolux. He told me that suppressor caps killed tone, and I happen to concur with Tremo, 100%, although he’s really a vintage amp guy and I’m not. So, I recommend to try the lead dress optimization method that you, Rich, knew for so long but never told me about! )
I’m sure in time others will say the same of you too. Stay with it, your doing fine. You have more of a handle on it then most. Keep learning from others, then pass it on. <something I’m passing on from long age that hangs as a sign on my wall There are in Fact two Things, Science and Opinion; the Former Begets KNOWLEDGE, the Latter IGNORANCE! – Hippocrates Learn to Separate the two. It is a lot easier to design a killer all tube stereo system because the standards act as guide lines. In the guitar amplifier game, things are so subjective that to come up with A-One-Design-Fits-All, is a quest for the pill that turns water into gas for the car. I don’t see it happening. That’s why I work one on one, and either rebuild/mod an existing amp, or build a one of a kind custom for that one individual only. By doing this I know I will have a satisfied customer, like the tailor/seamstress of long ago made for their customers that were only for them and on one else. <A parting after thought The “Voicing” of a guitar/bass amp is only one part in Voicing the total system!!! Consider, from the Touch of the String, to the Listeners Ears, from the Stage, from the Radio, the TV, Your CD! That’s the Big Picture I See. Can You See What’s Involved? That “Voice” Must Translate Well that Whole Distance. For real Understanding, Learn well this road, this Voice must take. You will discover how un-important … read more »
Response:
[snip] Years ago we called this sort of thing, using a sniffer wire for sniffing around circuit layouts. Even used air coils or caps on a clip lead depending what you happen to be sniffing for. Scope probes are the best sniffer wires there are.
[snip] As a young punk tech I was shocked (NPI) when one of the old hands took the ground wire of a scope probe, connected it to the tip and started waving it around a circuit board. I thought ground was ground and you couldn’t possibly see a signal come through. Well, of course, he puts the “sniffer” over near the microprocessor (1MHz 6809) and lo and behold there’s ugly looking signal floating through the air and into the probe/antenna. A lesson I’ll never forget. – Punkerdubh
Response:
tip on a lead dress…..hmmmmm…..well it would come in handy for a woman if she was exposed to nuclear fallout……. IceHouse Sorry, I couldn’t pass this one up.
Response:
Posts like that are making good to this NG ! Thanks , Gil Jukka — Remove “no_spam” to send a reply
Hear, Hear! Really great stuff. Thanks guys and don’t stop! — Best, Tom For great Rock’n'Roll, Vintage Racing, ’50’s Autoracing photos and more please drop by: http://www.webcom.com/tomkat
Response:
Hey Gil Ayan: For those of us who have a scope (don’t forget the picture of my scope is on Dave Stork’s web page)….Could you describe what the high frequency signal might look like with a 1 kHz input signal… Cordials Dr. Stereo – Hide quoted text — Show quoted text -Gil Ayan wrote Very true, I use a scope too. Regarding the parasitics, you can’t hear the high frequency oscillations but you will most likely feel them becasue they will swamp your amp down and will modulate your guitar signal. Even if it’s an oscillation you can hear, the scope will give additional information, like telling you how far back, menaing how many stages back, the oscialltion can be found, thus giving you an idea of the where the “problem area” that started it all is.
Response:
A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own… — To reply remove NOSPAM from address. – Hide quoted text — Show quoted text – Hey Gil Ayan: For those of us who have a scope (don’t forget the picture of my scope is on Dave Stork’s web page)….Could you describe what the high frequency signal might look like with a 1 kHz input signal… Cordials Dr. Stereo Gil Ayan wrote Very true, I use a scope too. Regarding the parasitics, you can’t hear the high frequency oscillations but you will most likely feel them becasue they will swamp your amp down and will modulate your guitar signal. Even if it’s an oscillation you can hear, the scope will give additional information, like telling you how far back, menaing how many stages back, the oscialltion can be found, thus giving you an idea of the where the “problem area” that started it all is.
Response:
Hey yes, another Tom: Is your name really Gil Ayan? Can you read? Are you trying to be funny? Three strikes.. Cordials Dr. Stereo – Hide quoted text — Show quoted text – A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own…
Response:
Gil is the one you DIDN’T call with half a million stupid questions. — To reply remove NOSPAM from address. – Hide quoted text — Show quoted text – Hey yes, another Tom: Is your name really Gil Ayan? Can you read? Are you trying to be funny? Three strikes.. Cordials Dr. Stereo A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own…
Response:
Hey yes, another Tom: Is your name really Gil Ayan?
No, his name is Tom, and he is my pal. Course, is your name Stereo, and are you a doctor? 
BTW, my name is Gil Ayan. 
) Can you read?
He can, I assume, as he gave a good response to your question… Are you trying to be funny?
Tom is a great source of knowledge, even if his jokes were bad, I could live with that. Having gotten the administrative items out of the way, your question was about seing oscillations on a scope? I dont know whether youre serious, but let me just write for the sake of those who may not be too familiar with a scope, ok? Adjusting the vertical gain of the scope, you can amplify your noise floor as much as possible; rather than a flat line, thermal noise alone, when magnified, will look fuzzy and sloppy, but ressemble a flat line in some way. When you hit the oscillation, be it by increasing the amps gain or moving wires around, you will see a sine wave appear on the screen, like Tom described. Of course, there could be (more likely scenario) more than one frequency present, in which case the waves modulate each other and things could look messier still. However, you can tell that the amplitude level of these things is WAY above the old noise floor. Furthermore, if you get your amp oscillating pretty bad, measure the AC voltage at some of the tube grids (rather, measure the voltage just before the grid stopper, otherwise your voltmeter will load down the grid and you wont be able to read much at all). I have found that a little squeal may be actually developing a 100 VAC signal in there! Of course, impedances are huge so there is virtually no current present, and sticking your finger at the grids will not make you twitch, but voltages are very large sometimes. Now, if you decide to touch the grids, remember their next door neighbours, the plates, are at about 200 VDC and they will make you twitch and perhaps even temporarily lose control of your sphincters; they probably wont do you any harm though. Three strikes..
Hmmmm… whose three strikes are you talking about? SOme have a hell of a lot more than that and obviouslu keep posting. A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own…
I still fail to see whats wrong with Toms answer. He is right, a picture says 1000 words… Gil — ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan /_/ /_/ /_/ /_/ /_/ /_/_ http://home.earthlink.net/~ayan
Response:
Hi Gil Ayan: Hey yes, another Tom: Is your name really Gil Ayan? No, his name is Tom, and he is my pal. Course, is your name Stereo, and are you a doctor? BTW, my name is Gil Ayan. )
DS: You may be new to this ng…..My full name is Gary Coplin,,,,I work at Rockin Robin guitar in Hou. TX…. If Tom is your friend, what is his full name and where does he work? Lately we have been asking for full disclousure around here…. Can you read? He can, I assume, as he gave a good response to your question…
DS: No responce was required from him. My question was directed at you, Gil. Are you trying to be funny? Tom is a great source of knowledge, even if his jokes were bad, I could live with that.
DS: Yes I agree….It’s just some times hard to tell when folks think they are being funny or when they are just being a condesending AH…. Having gotten the administrative items out of the way, your question was about seing oscillations on a scope? I dont know whether youre serious,
(DS: I am very serious about this due to some posts during Jan 98 about “frequency bubbles” for lack of a better term ) but let me just write for the sake of those who may not be too familiar with a scope, ok? Adjusting the vertical gain of the scope, you can amplify your noise floor as much as possible; rather than a flat line, thermal noise alone, when magnified, will look fuzzy and sloppy, but ressemble a flat line in some way. When you hit the oscillation, be it by increasing the amps gain or moving wires around, you will see a sine wave appear on the screen, like Tom described. Of course, there could be (more likely scenario) more than one frequency present, in which case the waves modulate each other and things could look messier still.
DS: It will look like a unmodulated if carrier? A fat line accross the tube….. – Hide quoted text — Show quoted text -However, you can tell that the amplitude level of these things is WAY above the old noise floor. Furthermore, if you get your amp oscillating pretty bad, measure the AC voltage at some of the tube grids (rather, measure the voltage just before the grid stopper, otherwise your voltmeter will load down the grid and you wont be able to read much at all). I have found that a little squeal may be actually developing a 100 VAC signal in there! Of course, impedances are huge so there is virtually no current present, and sticking your finger at the grids will not make you twitch, but voltages are very large sometimes. Now, if you decide to touch the grids, remember their next door neighbours, the plates, are at about 200 VDC and they will make you twitch and perhaps even temporarily lose control of your sphincters; they probably wont do you any harm though. Three strikes..
DS: Like you said….Just a try at humor but to let Tom know that he wasn’t helpful here. Hmmmm… whose three strikes are you talking about? SOme have a hell of a lot more than that and obviouslu keep posting. A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own… I still fail to see whats wrong with Toms answer. He is right, a picture says 1000 words…
DS: I guess no one enjoys being talked down too…..Do you? Thanks for a very, very good and courteous answer that should be helpful to all… Gil — ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan /_/ /_/ /_/ /_/ /_/ /_/_ http://home.earthlink.net/~ayan
Cordials Dr. Stereo
Response:
I’ve posted my name on this NG at least 100 times you frequency-bubbled amp-killin’ boob. — To reply remove NOSPAM from address. – Hide quoted text — Show quoted text – Hi Gil Ayan: Hey yes, another Tom: Is your name really Gil Ayan? No, his name is Tom, and he is my pal. Course, is your name Stereo, and are you a doctor? BTW, my name is Gil Ayan. ) DS: You may be new to this ng…..My full name is Gary Coplin,,,,I work at Rockin Robin guitar in Hou. TX…. If Tom is your friend, what is his full name and where does he work? Lately we have been asking for full disclousure around here…. Can you read? He can, I assume, as he gave a good response to your question… DS: No responce was required from him. My question was directed at you, Gil. Are you trying to be funny? Tom is a great source of knowledge, even if his jokes were bad, I could live with that. DS: Yes I agree….It’s just some times hard to tell when folks think they are being funny or when they are just being a condesending AH…. Having gotten the administrative items out of the way, your question was about seing oscillations on a scope? I dont know whether youre serious, (DS: I am very serious about this due to some posts during Jan 98 about “frequency bubbles” for lack of a better term ) but let me just write for the sake of those who may not be too familiar with a scope, ok? Adjusting the vertical gain of the scope, you can amplify your noise floor as much as possible; rather than a flat line, thermal noise alone, when magnified, will look fuzzy and sloppy, but ressemble a flat line in some way. When you hit the oscillation, be it by increasing the amps gain or moving wires around, you will see a sine wave appear on the screen, like Tom described. Of course, there could be (more likely scenario) more than one frequency present, in which case the waves modulate each other and things could look messier still. DS: It will look like a unmodulated if carrier? A fat line accross the tube….. However, you can tell that the amplitude level of these things is WAY above the old noise floor. Furthermore, if you get your amp oscillating pretty bad, measure the AC voltage at some of the tube grids (rather, measure the voltage just before the grid stopper, otherwise your voltmeter will load down the grid and you wont be able to read much at all). I have found that a little squeal may be actually developing a 100 VAC signal in there! Of course, impedances are huge so there is virtually no current present, and sticking your finger at the grids will not make you twitch, but voltages are very large sometimes. Now, if you decide to touch the grids, remember their next door neighbours, the plates, are at about 200 VDC and they will make you twitch and perhaps even temporarily lose control of your sphincters; they probably wont do you any harm though. Three strikes.. DS: Like you said….Just a try at humor but to let Tom know that he wasn’t helpful here. Hmmmm… whose three strikes are you talking about? SOme have a hell of a lot more than that and obviouslu keep posting.
- Hide quoted text — Show quoted text -A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own… I still fail to see whats wrong with Toms answer. He is right, a picture says 1000 words… DS: I guess no one enjoys being talked down too…..Do you? Thanks for a very, very good and courteous answer that should be helpful to all… Gil — ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan /_/ /_/ /_/ /_/ /_/ /_/_ http://home.earthlink.net/~ayan Cordials Dr. Stereo
Response:
<great post and classy participation snipped Gil – you’ve given me a good subject to think about. Every time I open up my homebrew it sounds different – sometimes it’s whatever mod I just made, sometimes I suspect it is due to the lead dress factors you have been kind enough to discuss in detail. With your suggestions and my o’scope, I may have some new weapons to fight the deadly flab-tone! Nice job, thanks. -j
Response:
God!…don’t you have a spellchecker in your newsreader?…if you do, please use it and try to learn something in the process. A.T. – Hide quoted text — Show quoted text – Hi Gil Ayan: Hey yes, another Tom: Is your name really Gil Ayan? No, his name is Tom, and he is my pal. Course, is your name Stereo, and are you a doctor? BTW, my name is Gil Ayan. ) DS: You may be new to this ng…..My full name is Gary Coplin,,,,I work at Rockin Robin guitar in Hou. TX…. If Tom is your friend, what is his full name and where does he work? Lately we have been asking for full disclousure around here…. Can you read? He can, I assume, as he gave a good response to your question… DS: No responce was required from him. My question was directed at you, Gil. Are you trying to be funny? Tom is a great source of knowledge, even if his jokes were bad, I could live with that. DS: Yes I agree….It’s just some times hard to tell when folks think they are being funny or when they are just being a condesending AH…. Having gotten the administrative items out of the way, your question was about seing oscillations on a scope? I dont know whether youre serious, (DS: I am very serious about this due to some posts during Jan 98 about “frequency bubbles” for lack of a better term ) but let me just write for the sake of those who may not be too familiar with a scope, ok? Adjusting the vertical gain of the scope, you can amplify your noise floor as much as possible; rather than a flat line, thermal noise alone, when magnified, will look fuzzy and sloppy, but ressemble a flat line in some way. When you hit the oscillation, be it by increasing the amps gain or moving wires around, you will see a sine wave appear on the screen, like Tom described. Of course, there could be (more likely scenario) more than one frequency present, in which case the waves modulate each other and things could look messier still. DS: It will look like a unmodulated if carrier? A fat line accross the tube….. However, you can tell that the amplitude level of these things is WAY above the old noise floor. Furthermore, if you get your amp oscillating pretty bad, measure the AC voltage at some of the tube grids (rather, measure the voltage just before the grid stopper, otherwise your voltmeter will load down the grid and you wont be able to read much at all). I have found that a little squeal may be actually developing a 100 VAC signal in there! Of course, impedances are huge so there is virtually no current present, and sticking your finger at the grids will not make you twitch, but voltages are very large sometimes. Now, if you decide to touch the grids, remember their next door neighbours, the plates, are at about 200 VDC and they will make you twitch and perhaps even temporarily lose control of your sphincters; they probably wont do you any harm though. Three strikes.. DS: Like you said….Just a try at humor but to let Tom know that he wasn’t helpful here. Hmmmm… whose three strikes are you talking about? SOme have a hell of a lot more than that and obviouslu keep posting. A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own… I still fail to see whats wrong with Toms answer. He is right, a picture says 1000 words… DS: I guess no one enjoys being talked down too…..Do you? Thanks for a very, very good and courteous answer that should be helpful to all… Gil — ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan /_/ /_/ /_/ /_/ /_/ /_/_ http://home.earthlink.net/~ayan Cordials Dr. Stereo
Response:
So posting your name and phone number one more time won’t hurt you will it? Cordials Dr. Stereo – Hide quoted text — Show quoted text – I’ve posted my name on this NG at least 100 times you frequency-bubbled amp-killin’ boob.
Response:
Hey Alan Thompson: I use outlook express and I will try to check my spelling more closely…Is there a browser available with a better checker? Cordials Dr. Stereo – Hide quoted text — Show quoted text – God!…don’t you have a spellchecker in your newsreader?…if you do, please use it and try to learn something in the process. A.T. Hi Gil Ayan: Hey yes, another Tom: Is your name really Gil Ayan? No, his name is Tom, and he is my pal. Course, is your name Stereo, and are you a doctor? BTW, my name is Gil Ayan. ) DS: You may be new to this ng…..My full name is Gary Coplin,,,,I work at Rockin Robin guitar in Hou. TX…. If Tom is your friend, what is his full name and where does he work? Lately we have been asking for full disclousure around here…. Can you read? He can, I assume, as he gave a good response to your question… DS: No responce was required from him. My question was directed at you, Gil. Are you trying to be funny? Tom is a great source of knowledge, even if his jokes were bad, I could live with that. DS: Yes I agree….It’s just some times hard to tell when folks think they are being funny or when they are just being a condesending AH…. Having gotten the administrative items out of the way, your question was about seing oscillations on a scope? I dont know whether youre serious, (DS: I am very serious about this due to some posts during Jan 98 about “frequency bubbles” for lack of a better term ) but let me just write for the sake of those who may not be too familiar with a scope, ok? Adjusting the vertical gain of the scope, you can amplify your noise floor as much as possible; rather than a flat line, thermal noise alone, when magnified, will look fuzzy and sloppy, but ressemble a flat line in some way. When you hit the oscillation, be it by increasing the amps gain or moving wires around, you will see a sine wave appear on the screen, like Tom described. Of course, there could be (more likely scenario) more than one frequency present, in which case the waves modulate each other and things could look messier still. DS: It will look like a unmodulated if carrier? A fat line accross the tube….. However, you can tell that the amplitude level of these things is WAY above the old noise floor. Furthermore, if you get your amp oscillating pretty bad, measure the AC voltage at some of the tube grids (rather, measure the voltage just before the grid stopper, otherwise your voltmeter will load down the grid and you wont be able to read much at all). I have found that a little squeal may be actually developing a 100 VAC signal in there! Of course, impedances are huge so there is virtually no current present, and sticking your finger at the grids will not make you twitch, but voltages are very large sometimes. Now, if you decide to touch the grids, remember their next door neighbours, the plates, are at about 200 VDC and they will make you twitch and perhaps even temporarily lose control of your sphincters; they probably wont do you any harm though. Three strikes.. DS: Like you said….Just a try at humor but to let Tom know that he wasn’t helpful here. Hmmmm… whose three strikes are you talking about? SOme have a hell of a lot more than that and obviouslu keep posting.
- Hide quoted text — Show quoted text – A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own… I still fail to see whats wrong with Toms answer. He is right, a picture says 1000 words… DS: I guess no one enjoys being talked down too…..Do you? Thanks for a very, very good and courteous answer that should be helpful to all… Gil — ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan /_/ /_/ /_/ /_/ /_/ /_/_ http://home.earthlink.net/~ayan Cordials Dr. Stereo
Response:
Outlook Express has a perfectly adequate spell checker, you just have to turn it on! DB) Using OE . . . – Hide quoted text — Show quoted text – Hey Alan Thompson: I use outlook express and I will try to check my spelling more closely…Is there a browser available with a better checker? Cordials Dr. Stereo God!…don’t you have a spellchecker in your newsreader?…if you do, please use it and try to learn something in the process. A.T. Hi Gil Ayan: Hey yes, another Tom: Is your name really Gil Ayan? No, his name is Tom, and he is my pal. Course, is your name Stereo, and are you a doctor? BTW, my name is Gil Ayan. ) DS: You may be new to this ng…..My full name is Gary Coplin,,,,I work at Rockin Robin guitar in Hou. TX…. If Tom is your friend, what is his full name and where does he work? Lately we have been asking for full disclousure around here…. Can you read? He can, I assume, as he gave a good response to your question… DS: No responce was required from him. My question was directed at you, Gil. Are you trying to be funny? Tom is a great source of knowledge, even if his jokes were bad, I could live with that. DS: Yes I agree….It’s just some times hard to tell when folks think they are being funny or when they are just being a condesending AH…. Having gotten the administrative items out of the way, your question was about seing oscillations on a scope? I dont know whether youre serious, (DS: I am very serious about this due to some posts during Jan 98 about “frequency bubbles” for lack of a better term ) but let me just write for the sake of those who may not be too familiar with a scope, ok? Adjusting the vertical gain of the scope, you can amplify your noise floor as much as possible; rather than a flat line, thermal noise alone, when magnified, will look fuzzy and sloppy, but ressemble a flat line in some way. When you hit the oscillation, be it by increasing the amps gain or moving wires around, you will see a sine wave appear on the screen, like Tom described. Of course, there could be (more likely scenario) more than one frequency present, in which case the waves modulate each other and things could look messier still. DS: It will look like a unmodulated if carrier? A fat line accross the tube….. However, you can tell that the amplitude level of these things is WAY above the old noise floor. Furthermore, if you get your amp oscillating pretty bad, measure the AC voltage at some of the tube grids (rather, measure the voltage just before the grid stopper, otherwise your voltmeter will load down the grid and you wont be able to read much at all). I have found that a little squeal may be actually developing a 100 VAC signal in there! Of course, impedances are huge so there is virtually no current present, and sticking your finger at the grids will not make you twitch, but voltages are very large sometimes. Now, if you decide to touch the grids, remember their next door neighbours, the plates, are at about 200 VDC and they will make you twitch and perhaps even temporarily lose control of your sphincters; they probably wont do you any harm though. Three strikes.. DS: Like you said….Just a try at humor but to let Tom know that he wasn’t helpful here. Hmmmm… whose three strikes are you talking about? SOme have a hell of a lot more than that and obviouslu keep posting. A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own… I still fail to see whats wrong with Toms answer. He is right, a picture says 1000 words… DS: I guess no one enjoys being talked down too…..Do you? Thanks for a very, very good and courteous answer that should be helpful to all… Gil — ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan /_/ /_/ /_/ /_/ /_/ /_/_ http://home.earthlink.net/~ayan Cordials Dr. Stereo
Response:
Do your own work. — To reply remove NOSPAM from address. – Hide quoted text — Show quoted text – So posting your name and phone number one more time won’t hurt you will it? Cordials Dr. Stereo I’ve posted my name on this NG at least 100 times you frequency-bubbled amp-killin’ boob.
Response:
Hey Gil Ayan: For those of us who have a scope (don’t forget the picture of my scope is on Dave Stork’s web page)….Could you describe what the high frequency signal might look like with a 1 kHz input signal… Cordials Dr. Stereo
What this person is referring to is the fact that a graphic on my web page happens to resemble his Hameg oscilloscope. I’m removing that graphic from my page tonight. — Dave Stork Stork Audio New York http://members.aol.com/StorkAudio For email replies, remove “nospam” from address
Response:
Doc,I(blushingly admitted)use spellcheck in Outlook as well.The trick is that when the checker doesn’t know the word,you look it up and put it in the checkers’ list.after a while you don’t have to do that very often. – Hide quoted text — Show quoted text – Hey Alan Thompson: I use outlook express and I will try to check my spelling more closely…Is there a browser available with a better checker? Cordials Dr. Stereo God!…don’t you have a spellchecker in your newsreader?…if you do, please use it and try to learn something in the process. A.T. Hi Gil Ayan: Hey yes, another Tom: Is your name really Gil Ayan? No, his name is Tom, and he is my pal. Course, is your name Stereo, and are you a doctor? BTW, my name is Gil Ayan. ) DS: You may be new to this ng…..My full name is Gary Coplin,,,,I work at Rockin Robin guitar in Hou. TX…. If Tom is your friend, what is his full name and where does he work? Lately we have been asking for full disclousure around here…. Can you read? He can, I assume, as he gave a good response to your question… DS: No responce was required from him. My question was directed at you, Gil. Are you trying to be funny? Tom is a great source of knowledge, even if his jokes were bad, I could live with that. DS: Yes I agree….It’s just some times hard to tell when folks think they are being funny or when they are just being a condesending AH…. Having gotten the administrative items out of the way, your question was about seing oscillations on a scope? I dont know whether youre serious, (DS: I am very serious about this due to some posts during Jan 98 about “frequency bubbles” for lack of a better term ) but let me just write for the sake of those who may not be too familiar with a scope, ok? Adjusting the vertical gain of the scope, you can amplify your noise floor as much as possible; rather than a flat line, thermal noise alone, when magnified, will look fuzzy and sloppy, but ressemble a flat line in some way. When you hit the oscillation, be it by increasing the amps gain or moving wires around, you will see a sine wave appear on the screen, like Tom described. Of course, there could be (more likely scenario) more than one frequency present, in which case the waves modulate each other and things could look messier still. DS: It will look like a unmodulated if carrier? A fat line accross the tube….. However, you can tell that the amplitude level of these things is WAY above the old noise floor. Furthermore, if you get your amp oscillating pretty bad, measure the AC voltage at some of the tube grids (rather, measure the voltage just before the grid stopper, otherwise your voltmeter will load down the grid and you wont be able to read much at all). I have found that a little squeal may be actually developing a 100 VAC signal in there! Of course, impedances are huge so there is virtually no current present, and sticking your finger at the grids will not make you twitch, but voltages are very large sometimes. Now, if you decide to touch the grids, remember their next door neighbours, the plates, are at about 200 VDC and they will make you twitch and perhaps even temporarily lose control of your sphincters; they probably wont do you any harm though. Three strikes.. DS: Like you said….Just a try at humor but to let Tom know that he wasn’t helpful here. Hmmmm… whose three strikes are you talking about? SOme have a hell of a lot more than that and obviouslu keep posting. A book like ” a child’s introduction to using the oscilloscope in troubleshooting” might have what you are looking for and usually can be found at any used bookstore. But you would rather ask someone else than learn on your own… I still fail to see whats wrong with Toms answer. He is right, a picture says 1000 words… DS: I guess no one enjoys being talked down too…..Do you? Thanks for a very, very good and courteous answer that should be helpful to all… Gil — ______ __ __ ______ __ __ / __ / / /_/ / / __ / / / / Gil Ayan /_/ /_/ /_/ /_/ /_/ /_/_ http://home.earthlink.net/~ayan Cordials Dr. Stereo
Response:
Categories: Bass Fishing Tips | 
No Comments »
) Jim