Lets discuss amp tone and how it changes w/volume and why

[Chuck H]

I agree with you. I was just pointing out that there is a thread to answer to. Daz will get through the first many years like we all did. With some incorrect assumptions and no clear understanding of what's actually going on (some of us still do that). But there's still a real issue to solve for and I think the people here were very graceful with me some nineteen years ago. I try to do that.

And, incidentally, I do know there is an impedance issue WRT the MV at different settings and the TS. I "believe" this is what's causing the perceived phenomenon. I may have worded that poorly.

Peace.

[Chuck H]

Yup. You could solve part of the problem with a fixed divider and a tube recovery stage (and incidentally add an effects loop at the same time!). You could also do it with a SS recovery stage

[soundguruman]

"it's more educational to plug the amplifier into an oscilloscope and examine what really happens in it instead of trying to guess what happens based on what you hear."

See, that's where you miss the point. You're not a musician, or maybe you're a beginner musician....
You don't understand what a musician requires; or is needing.
Listening to it is a big part of making it a success, instead of just making it "work."

Further there are many malfunctions, which can only be identified by playing (a guitar) through the amp...
and very difficult or impossible to capture on an O scope.
This is where a lot of techs don't detect what a musician is hearing.However to the musician, it's the most important thing.

[teemuk]

That's like the lamest excuse ever to not do something which could prove extremely educational.

See, I can spend an hour listening an amp introducing a certain effect but unless I exactly know what that effect is forehand I will never learn anything about the things I hear.

And I do want to know what exactly I'm hearing. This way I can figure out how to adjust that effect. Without that ability you might as well be deaf because you never have any chances in turning what you hear into direction you prefer. Except by a lucky chance of course. Only thing you can do is listen. While others become trendsetters and leading innovators. In my opinion, making things "work" is as much a key to success as being able to listen.

It's like learning to play guitar. You can listen to the instrument as long as you want but without understanding how the instrument works and interacts with musical theory you will never be able to create anything worthwhile with it. If you just want to listen then perhaps you should reconsider changing your profession from a musician to shrink.

So, Mr. Daz here has a problem where his amp's tone changes unpleasantly after certain settings. The way I see it, he can guess what causes this effect, or he can take a more professional route: plug the amp to oscilloscope or perhaps a spectrum analyzer, replicate the incident and find what the effect he is hearing actually even is. After we have pinpointed something concrete we can start figuring out what causes that effect. We can figure it out because electronics have certain laws that they follow.

Perhaps we already know what that effect is. Daz has given us clues, albeit at the moment they are quite vague and could in practice mean just about anything. At this point we just don't have enough data for anything concrete.

I'm not saying that instrumentation gear always works in solving problems. But it's at least a damn good start.

This is an interesting and educational topic. I'd hate to see it degenerate into empty talk with no real information or educational value at all.

Probably Daz agrees with me on this as well. After all, he is trying to figure out WHY his amp's tone changes with volume. He probably wants to do something for that issue do, "make it work" so to speak. Unless we know the answer forehand to what it is that Daz is hearing then in answering to "why" we must resort into using instrumentation gear to measure the amplifier in order to find out what electrical effect Daz ultimately hears as this unpleasant change in tone. It could be an acoustic issue as well. So? Then we just need different kind of test equipment. But ultimately without the measurements that give us that solid data we are just flying blind.

Further there are many malfunctions, which can only be identified by playing (a guitar) through the amp...

Bullshit! It's all about setting test conditions and measurement gear right. For example, whether to test with continuous signals or with pulse responses. What kinds of signals to use and what kind of test equipment to use. If the first test setup doesn't reveal anything it doesn't mean something can't be tested. It just means that someone didn't know how to perform the test.

[soundguruman]

"That's like the lamest excuse ever to not do something which could prove extremely educational."

You really do miss the point, completely.
It's music electronics. Half of what's there, you are not even paying attention to.

[eschertron]

Let me jump onto this dogpile and assert that instrumentation without a hypothesis is not science. It may be 'educational' but that's not the same thing. What I read into Daz's post is a request for discussion and the creation of hypotheses that might explain the auditory effects. Some ideas have already been suggested that can be turned into a testable hypothesis. That's an important step in the process for any kind of real investigation. I'd like to see this thread continue without sidetracking into the "corksniffer vs technician" debate.

[Chuck H]

SGM, I think the teemuk's point is a very good one. The premise you're coming from is extremely valid and is, in fact, the acid test for any amp. Teemuk isn't saying that everything can be quantified on paper better than it can with the ears (or even the whim). What he's saying is that to know what it is you're fixing, changing, adjusting, etc. gives one a fighting chance at processing and replicating a desirable or reparative outcome. No, a spectrum analyzer can't tell me that where a 250pf cap sounds "weak" and a 100pf cap sounds "weaker" that a 680pf cap will be the right change to suit my desired outcome. But it CAN tell me exactly what happened and an oscilloscope can tell me what happened to the waveform. Now suppose you're working on a different amp but you want a similar outcome? Circuit impedances are different, gain structures are different, bias points are different, etc. With concrete info like spectrum analyzer results and Oscope results you can poke around and likely find a good place to start and what to change. And once you find that you can likely do some math and figure out exactly how much to change it! Of course you'll listen to the changes and use your ears to decide, but you can make tremendous headway in much less time. This, to me is creative freedom. It beats the hell out of blindly "trying stuff till something works". I did a lot of that when I started and IMHE knowing IS better than guessing. That isn't to say that knowing is better than hearing what you like. Knowing is a means to hearing what you like. Teemuk also never said that making something "work" was the end game. Reading his post I get the impression that he's saying getting a result is the end game. Big difference. It's not uncommon for a guitar amp circuit to be doing something a little unusual. In this event, especially in this event, it's better to know what slightly weird thing is happening if you want to have creative control over it.

[daz]

The problem is he's looking at it from his perspective, not mine. I do things my way, and while he may find my way wrong or stupid or whatever, I'm not him. It's obvious at this point that others and myself are happy to discuss it without trying to force me to do it thier way, not to mention others have acknowledged they too have run into this issue and know exactly what I'm talking about. I didn't post here for a lecture. I posted here to listen to guys like chuck discuss it and possibly cause a light bulb to go off. Mr muk is insistant i do it his way, but the fact is i'm not going to to, not to mention with no scope i can't anyways. And by the way, there are legions of guitar players that are amazing without learning theory at all.

[teemuk]

not to mention others have acknowledged they too have run into this issue and know exactly what I'm talking about.

Do they?

Yes, they might be familiar with audible effects you are referring to but do they know what causes them?

I don't see any way how things like this could be figured out and solved solely by talking and by making hypothesis. Ultimately, someone needs to step up and verify those hypothesis.

All I'm saying is that you make things much easier on yourself by addressing this issue by testing your amplifier and finding out the root causes for effects you are hearing. If you want to do things your way and not do that then I guess it's your problem. Good luck!

[daz]

If you want to do things your way and not do that then I guess it's your problem. Good luck!

Yes, I DO want to do it my way. If you want to call it my problem thats fine. I didn't come here to debate how i should live my life in any context.

[Jazz P Bass]

Have you considered a 'resonance control'?
aka: Peavey.
Here is a nice site on the subject: Redplate City: Peavey Ultra Plus Resonance circuit

[daz]

Have you considered a 'resonance control'?
aka: Peavey.
Here is a nice site on the subject: Redplate City: Peavey Ultra Plus Resonance circuit

I've tried those before but never liked the effect too much. And it doesn't work when i have the NFB pot past a certain point. There has to be more NFB than i want for it to have an effect. Presence on the other hand still has quite an effect even when i have the 250k NFB pot (in series with a 33k resistor) at full resistance. I don't think it would do what i want in this case tho even if i use enough NFB, but i may give it a go and see. Nothing to lose and 1 minute to implement.

[cooldude666]

Seems like we could have avoided a bunch of arguing with just a quick audio recording. Throw a mic in front of your amp and actually capture the effect.

[Chuck H]

Teemuk should start a movement. Anyone who tinkers with their amp without a full complement of bench test gear should expressly NOT be allowed to join the forum! Guitar players that "tinker" with cap values and clone builders that assemble kits simply waste our time when they sign on here whining about problems that have no solution without test figures. In fact, those types that are already here should be kicked off! No wait... Killed! Actually killed... And eaten. We should kill and eat them. That way their miserable lowly existence will have amounted to something. They will be honored to know they have nourished the owners of bench test gear! With this grace in their favor perhaps they can enter into the kingdom instead of languishing in the lake of fire.

[daz]

LOL!!! Eaten ! Trust me, you don't wanna eat me. Us old guys would be tough and stringy. Well...maybe if u used a crock pot.