Vox AC30/ 6 (TBX). Add an MV ?

[Chuck H]

That's exactly what a MV is supposed to do: Varying loudness without changing the tone.
Don't expect a MV to add distortion.

Right! This^^^^^^^^^^^^^^^^^^^^^^^^^^^

This is "gain structure". If the amp you have gets much of it's distorted tone from clipping the power tubes, and the master volume is before the power tubes the power tubes will not be distorted when drive to them has been reduced (simple). That said, preamps can generate distortions of their own. Though typicially at higher drive levels than where the power tubes do (NOTE: Otherwise it would be impossible to get a full volume clean tone from the amp!). So when a master volume is included you should actually expect LESS distortion than what you get with no master volume, but playing at higher volume with the power tubes driven into distortion.

There is one exception... Modern high gain amps are typically designed to get distortion from the preamp and then the power amp is (by design) limited to amplifying ONLY what the preamp is doing in it's distortion generating. This is a good case for why such amps are often channel switching. Because it takes a different preamp topology to achieve max clean tone than it does to achieve max "preamp distortion" tone. So different "channels" are needed for intuitive performance.

I don't fault any guitar player, and that includes you SeaChief, for seeing the state of modern amps and distortions hard to grasp. This divide in understanding has been the bane of designers since square wave clipped signals became popular in the 60's!!! So no one is accusing anyone of "failing" to understand the circumstances. Learning gain structures as they apply to guitar amps can be hard for the lay players. I only ever pointed it out here because it would benefit you a lot on the path you're taking. Especially considering that you know tone and own a Twin Reverb and an AC30 for your own reasons. You know what these amps sound like. So how to make them sound like that without skinning the neighbors? I like attenuators because I feel these tones are best represented when the amps are at least humping the way they did on the recordings, right.?. But the simpler "master volume" solution is SOOOO attractive and circuits abound from people that claim to have managed what it will take to "unlock your amps tone" BULLSHIT. (<period) Master volumes suck the life out of vintage design amps like the TR and AC30. But that isn't to say that they don't have merit BECAUSE...

Players who understand the gain process through an amplifier can make concessions or corrections for what's NOT happening and find themselves on the happy side of what they get for a tone. These players are in the minority. Much to the shagrin of designers. That said...

A guy who has a GREAT understanding of gain structure without being an official electronics nerd would be Pete Thorn. His *outube videos are a great source for players to glean some understanding of what gear implementation and manner of use mean to "tone".

Not sure if this helps. I'm trying a different idea.

[Helmholtz]

So I was instead then having the Vol set to 10, & gradually brought up the MV (I can't recall) which meant the same ammount of distortion was heard.. just at various volume levels

That's exactly what a MV is supposed to do: Varying loudness without changing the tone.
Don't expect a MV to add distortion.

[Sea Chief]

Your initial experience with the Music Man was incorrect. It was either broken or badly set up.
If you use this experience as a basis for understanding the MV concept you will never get it,.
When the master was set full and you slowly brought up the channel volume, it should have been clean and stayed clean until you hit the full power output of the amplifier.
A master set full up should give you the same response as not having a master at all. If you played around with the Crate amp you mentioned, that's how it would function (see post #36).

This is all I can do here. Good luck.

So I was instead then having the Vol set to 10, & gradually brought up the MV (I can't recall) which meant the same ammount of distortion was heard.. just at various volume levels (but no doubt you'll cast doubt on this too).

You assume my amp was broken, but it was perfectly fine/ never put a foot wrong, same when bought as it was when I sold it on. And exactly the same as a 2-10 I played in a shop I mentioned, which wouldn't have been FS, if it was faulty.

This doesn't mean I understand MV any more though, just by switching these two knobs' settings around. Not one iota.

Capt

[g1]

Your initial experience with the Music Man was incorrect. It was either broken or badly set up.
If you use this experience as a basis for understanding the MV concept you will never get it,.
When the master was set full and you slowly brought up the channel volume, it should have been clean and stayed clean until you hit the full power output of the amplifier.
A master set full up should give you the same response as not having a master at all. If you played around with the Crate amp you mentioned, that's how it would function (see post #36).

This is all I can do here. Good luck.

[Sea Chief]

Did you read the description?
If you did, you would see that vol1 is equivalent of gain, and vol2 is equivalent of master. As I also mentioned, you are getting hung up on the names and blocking yourself from understanding the concepts.

Hi g1, of course yes I did, until my head hurt. About 6 times.

I was immediately flummoxed because I had thought the MV was Vol1. Because I assumed adding this MV knob, was something to do with overdriving the preamp. I asked if this MV was something to do with the preamp section (but no reply). So logic dictated that it could only be so.

But here, your now suggesting it's Vol2. Not Vol1. Vol2 in your diagram... is relevant to the POWER amp section.

So I am even MORE lost after reading your post here, than I was beforehand. I'm getting more & more lost. I thought I had the basis of understanding, that being you introduce an MV at the preamp area. Because ther's already a flaming great big VOLUME knob on the amp, which can only be changing the level of the whole bloomin thing, meaning it has to be changing the level of the POWER amp section.

If I add another Volume knob, & the general idea as I thought it was, is to introduce this at the preamp (somewhere: after tube 1,2,or 3? I asked this but no reply) area let's say... then in your diagram Vol1 should be MV. And Vol2 should be Vol. But you say it's the opposite. So I've never in my life been so bewildered, & tbh I just can't cope anymore trying to understand it. I don't think I'll be able to now, so much my head aches with this, & I just get more & more confused.

All I can do is ask how to affect the changes. I'll try the link C1 again, but if I turn either knob to 10, & the sound reduces to zero.. I have to conclude it is NOT working. For whatever reason. I cannot cope with someone saying that is to be expected. That is not logical.

What I can do, is affect the change someone else did -with the very amp I have- (not a similar one from 1970), as Pedro's is. I just need to ask him whether the addition he did, the mod he added, was effective. Properly decent. If it's only "hmm.. it was okay but a bit 'meh' " then I have to skip this 2nd idea, & consider a VVR. My lovely amp Pro even said he'd make me one to put in. But I do need to consider whether I have to have reasonable Volume to make it effective (rather like an attenuator does), because if so.. then it might be a pointless exercise. But if it can be reversed without bodging a hole in the amp or anything then nevertheless probably worthwhile for a last-last-gasp try.

Thanks, SC

[Sea Chief]

I think I'm going to have to start afresh. I'll ask on another website, & try a completely different way of asking what A MV is.

I've obviously worded my questions totally wrongly, to get in such a muddle. I must reconsider how to ask this question.

--

On a different tangent though: I remember going in a shop, & playing a Music Man 2-10. It had a Volume & a Master Volume (as my 4-10 did). I was 18 years old. I didn't know what the difference was between these two knobs, but after a while of trying them interacting with each other, I found that turning one to 0 and the other to 10.. produced no audible noise. When I then increaced the 0 knob UP.. I got noise, & it was distorted. Turning it up further increaced the volume, but not the ammount of distortion. So at this point I could eatablish that the knob that was set to 10... was the one providing the distortion.

I switched this exact 'experiment' round, so the other knob was on 10, & the first one was on 0. I got the same results: firstly no noise, then by increacing the first knob up from 0, a distorted noise increacing in volume ( but not level of distortion).

The only discernable difference between these two identical 'experiments'.. was one produced a better quality of tone, than the other. Regardless of whether it was the one with more distortion.

So here, I was able to use a Volume knob AND a Master Volume knob, perfectly able................... even though................ I had absolutely no clue as to why I got the results I did. I just got them. I played the guitar. I didn't need to know the physics of why the first way the two knobs were set, seemed definitely better than the reversed way round, of the second way the two knobs were set.

What I'm trying to do, is add this second knob. What I realise is, that with all the will in the world to try & explain the physics of these two knobs interactions to me, I may not get there. BUT that doesn't mean I am prevented from adding it, if it's proven that I can solder something in perfectly well.

So all I can do, is ask how something is soldered in. Where to put X. Once this is done, & the second knob is added & functions... I'm effectively back as my 18 yr old self was, playing my guitar. With these two knobs interacting together. Without knowing why they are doing so, or needing to know.

Thanks, SC

[g1]

I just don't understand why, if I'm desperately trying to understand what Master Volume is, a diagram is provided.. without the inclusion of the term Master Volume. As much as it's kind of you to try & help, I find this omission fundamentally unfathomable, & quite bizarre.

Did you read the description?
If you did, you would see that vol1 is equivalent of gain, and vol2 is equivalent of master. As I also mentioned, you are getting hung up on the names and blocking yourself from understanding the concepts.

[Sea Chief]

But in this diagram, Master Volume... isn't even there. So I can't make head nor tail of it even if it seems simple in principle (that means me looking at it, & there being few components within it to consider).

I just don't understand why, if I'm desperately trying to understand what Master Volume is, a diagram is provided.. without the inclusion of the term Master Volume. As much as it's kind of you to try & help, I find this omission fundamentally unfathomable, & quite bizarre.

If someone could just answer my question I highlighted in bold, I might be able to start somewhere.

I can't possibly consider Gain yet: the statement that it is either Volume or Master Volume is again, utterly confounding to me. I have a Gain knob. When I turn it, alot of distortion happens. This is nothing whatsoever comparable in any way shape or form to any Volume knobI've ever encountered on either of my BIG (non master vol amps), or on the Master Volume knob on my Music Man 4-10. Totally different. It therefore can't possibly be 'just a Volume knob'. Sorry, but with the amp I have with this Gain knob phenomenon (Randall RD5), this is impossible.

The Gain knob sounds like a distortion pedal. An effect. In fact when you turn it, the -volume- barely even changes!! (just more distortion happens).

Anyway. If anyone can answer the highlighted question, appreciated. Capt

[g1]

I'll try to keep it real simple with a rudimentary block diagram. It's not a perfect description, but should help with the general concepts.
You are getting stuck on terminology like 'master' and 'gain' when in simplest terms, they are just volume controls at different points in the circuit. When I said to consider a non-master amp as the same as a master-volume type amp with the MV stuck on 10, I hope you keep that in mind.
With the master stuck on 10, the gain (or preamp volume) will just control the loudness of the amp, you won't be able to get any dirty tone until it's way too loud.
For an example, say 1Volt signal at power amp input gives full volume output.
Now, if I can drop the level after the preamp (using vol2 aka MV), I can increase the signal level through the preamp and get some clipping or distortion before that 1volt of signal gets through to the power amp. So I drop the MV down to a low setting and crank the preamp vol (vol1 aka gain) and get some preamp distortion because I am over-driving the preamp.

[Sea Chief]

Fwiw NO ONE has demonstrated a lack of confidence in you or berated you. I did point out that you don't have a firm grasp on gain structures. Which you aptly demonstrate in the following posts. And as to who was right or wrong regarding nebulous problems and their ultimate solutions, the key adjective here is nebulous. Sometimes you have to throw things at the wall until something sticks. Not at all sure why you would choose to take offense and instigate conflict when no such insults were intended. Only the truth of the matter. You don't understand gain structures and that is part of why you have trouble getting the tones you want from the gear you have. This is just a fact. One everyone on this thread has to deal with to reach any sort of solution. What I said was intended to help.

Ok taken on board. But effectively what I'm asking is the difference between 'gain structures' (your wording, not mine as I don't know precisely what this term means).. & then in reply, I'm twice now effectively replied with * 'you just don't understand gain structures' implying how can anyone possibly help, if I don't understand gain structures.

It is incredibly frustrating Chuck. It's like groundhog day, going round chasing my tail, back to square 1 & getting nowhere.

I've asked a good few times, what is the difference between Volume, Master Volume, and Gain. But get your stock* answer. And of course others follow your lead, which means after 3 pages I've got nowhere.

So. If I can try once again with the following (I just can't word it any differently): can someone please tell me if this is correct, as a basic starting point:

Am I correct in thinking that Master Volume has some correlation/ relationship with overdriving preamp something (one tube? 2? All of them? The whole preamp circuit?) and nothing to do with the power amp/ tube section?

I think this may be a starting point to understanding these 3 entities, the difference, if there is any difference. But I don't know. I'm just blindly asking trying to find a starting point, with no rule book as to specifically what to ask.

Thanks SC

[Chuck H]

[USER="534"] There are usual members who have such low confidence in me

Fwiw NO ONE has demonstrated a lack of confidence in you or berated you. I did point out that you don't have a firm grasp on gain structures. Which you aptly demonstrate in the following posts. And as to who was right or wrong regarding nebulous problems and their ultimate solutions, the key adjective here is nebulous. Sometimes you have to throw things at the wall until something sticks. Not at all sure why you would choose to take offense and instigate conflict when no such insults were intended. Only the truth of the matter. You don't understand gain structures and that is part of why you have trouble getting the tones you want from the gear you have. This is just a fact. One everyone on this thread has to deal with to reach any sort of solution. What I said was intended to help.

[Sea Chief]

There is only one schematic. The one #3 that you posted is the same one I included. There is no possibility of error.

Hi Pedro- great thank you for confirming this.

I'm now inclined to perhaps try your addition- can you just tell me: how effective is it? I mean I don't want, or expect alot of distortion, but just want -some- in a typical OD sort of way, with the knob max rotation. Is the sound quality achieved good?

I think I read (which is why I'm considering the MV in this AC30, not my Twin Reverb) that due to the considerable number of preamp tubes in a TB ac30, that this should facilitate the possibility of achieving -decent quality- preamp overdrive. Which I -think- is the basis of what MV is all about.

Thanks, SC

[Pedro Vecino]

Would anyone who knows this amp, know if the schematic I added in #3 is correct for this amp??

There is only one schematic. The one #3 that you posted is the same one I included. There is no possibility of error.

[Sea Chief]

The RD5 has a 'gain' AND a 'volume'. The volume control is what is acting like a MV. You can only crank up the gain if the volume is set low. If volume was set full and you tried to crank the gain, you would be fleeing for the river.

Sorry I missed this post g1. I do know right here is the nub of what I'm trying to understand. But it only accounts for 2/3rds.

There is Volume, Gain, & Master Volume to consider. So here, we're only considering two of the three facets/ things/ whatever on earth they are (if they are similar then we can call them something, I guess).

I'm confused here because, I thought this Gain phenomena in this Randall, being seemingly nothing but an 'distortion effect' in terms of what it sounds to me like it is (it sounds nothing other than a built-in distortion pedal: & so I had thought it can only possibly be therefore, an added circuit with transistors/ resistors/ caps, simply shoved into the amp. At some preamp point. Presumably perhaps the middle somewhere.

But to pull the rug from under me, in this post, the first to answer in any way my question as to what on earth it actually is, you say.. that it's effectively an MV.

Eh?? I'm now even more bamboozled than ever. I've never heard any MV sounding like a fuzzy distortion pedal. I've only eve4 heard one sounding like a mild OD sort of distortion. Not like a built in Boss Turbo Overdrive, like this Gain knob sounds like. I've played two MV amps, both adding a fairly average (if not 'a bit crappy') quality of mild distortion, by way of turning them full. A UL135w Twin Reverb (not my current one, which has done away with it entirely) & my Music Man 4-10: a similar 'meh' sounding distortion using the MV.

So something is massively different with this Randall RD5's Gain knob, to my MM 4-10's Master Volume knob. Chalk & cheese tbh.

Thanks, SC

[Sea Chief]

Once I can establish if my schematic is definitely correct, I can maybe progress.

Would anyone who knows this amp, know if the schematic I added in #3 is correct for this amp??

(I've tried asking Pedro Vecino twice, but alas no response).

Thanks, SC