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

[g1]

I don't understand you see, how a crappy 5w Randall RD5 (2 tubes) has a knob called 'Gain', which you just turn.. & disortion happens. It's not called an MV. So wtf is it exactly? And does it bear any similarities to an MV?

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.

[Chuck H]

g1, Sea Chief has never come to terms with the nebulous descriptions of gain and volume by manufacturers because he doesn't trouble to understand gain structures. I know that 90% of the population figures these things out intuitively on spot while using products but there's the other 10% that think "gain" and "volume" should be defined in concrete. And I can't argue. Having to define these things on the fly for every circumstance is a real pain in the ass. And it would be nice if the moniker attached to a knob was a known effect. But even now, today in this long lived world of this genre terms like gain, distortion and even "master volume" continue to have variable meaning dependent on manufacturer or design. This said...

You and I can simply look at a schematic and understand what these things mean. Sea Chief's trouble is the inability to do that. Any argument that there is not enough definition in the allocation of function is valid. But there is no chance of it being reconciled unless one has the skills to define a circuit by looking at the schematic. So for the lay player any knob marked "volume", "gain" or even "master" has to be evaluated in use and not always consistent with what it means on their other amps. AND...

Asking any lay player to come on board with what "we" understand about the circuits is seldom gratified. Sea Chief may never understand the intricacies of gain structure. Even though it would help him there's nothing more we can do than we have to help him understand it.

[g1]

Asking any lay player to come on board with what "we" understand about the circuits is seldom gratified. Sea Chief may never understand the intricacies of gain structure. Even though it would help him there's nothing more we can do than we have to help him understand it.

Well, at least he has the Crate there as an example. If he sets the 'volume' up full, it will act like a non-master amp with the 'gain' control now the only volume control.

[Sea Chief]

Pedro Vecino Hi thanks for adding the two schematic diagrams. And your reply there gave me confidence to maybe try the C1 link mod again.

Can you put up the whole schematic though? I still need to establish if the one I put up in #3.. is correct. There are usual members who have such low confidence in me (even though I can rebuild a Twin Reverb bettering the original, & my hunch that a fault plaguing it for 2 years -wasn't- a conductive board, but a bad component [one loose heater wire is akin to a bad component in my book]) that anything I put up is immediately acredited as being wrong.

I did ask what a master volume was too, but instead of answers I'm just castigated for not knowing what a master volume is (&/ or for not knowing the difference between vol gain etc but at the same time saying it IS confusing that different Co's use different terms, for these very same things!!).

I might not ever know the answers to the mystery of what MV/ vol/ gain is, but that doesn't mean I can't add a link, try your double-pot addition, or even solder in a much more complicated VVR circuit. If my Twin Reverb sounds great (finally) this at least proves that my solder joints ARE up to par.

Thanks, SC

[Sea Chief]

Well, at least he has the Crate there as an example. If he sets the 'volume' up full, it will act like a non-master amp with the 'gain' control now the only volume control.

Hi g1.

Sorry I don't understand this post. It's too confusing for me, so I'm left equally as confused as when I asked what this (Randall) amp's gain knob actually was.

Thanks for trying to help though, instead of berating me.

SC

[g1]

Sorry I don't understand this post. It's too confusing for me, so I'm left equally as confused as when I asked what this (Randall) amp's gain knob actually was.

Turn the Crate vol. control up full and leave it there. Now you have the equivalent of a non-master amp and the gain pot acts like the volume pot on something like a non-master Twin.
You won't get any dirt by turning up the gain, it will just get loud. Try it.

[Sea Chief]

Turn the Crate vol. control up full and leave it there. Now you have the equivalent of a non-master amp and the gain pot acts like the volume pot on something like a non-master Twin.
You won't get any dirt by turning up the gain, it will just get loud. Try it.

Ok I can visualise doing this (the Randall.. not Crate: annoyingly it isn't working!! Haha, something simple I know that much, but I do have todo another QUICK thread, as there's no way I can sort it as it is). So let's say I do both knobs as you suggest in this post.

I can't understand what I am supposed to ascertain, by hearing the clean tone, from doing this. I can't understand the point of why your suggesting turning these two knobs, in this fashion, if the end result, is no distortion, if the whole point of the thread, is to achieve distortion. I can't see any logic in doing it.

I am consistently flummoxed by every facet of this business. Even simple suggestions like your post here, is unfathomable to me (in fact it seems actually counterintuitive).

Thanks again though, 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

[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

[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]

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

[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]

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

[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]

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