Does adding a master volume control hinder tone?

[Falloffthebonetone]

Say you have a non-master volume amp, and you're thinking about installing one.

I hear this has a detrimental effect on the tone, but I have no idea how or why.

Can anyone help me with this? I assumed it would just mean another controllable variable. Like wouldn't having the master volume all the way up and using the other volume as just regular volume produce the same effect as having no master volume?

 

[devastone]

Re: Does adding a master volume control hinder tone?

Theoretically, close, but it is still a path to ground, the higher the resistance of the pot you use for the MV, the less effect it will have.

If you are thinking of adding a MV to a non-master amp I would definitely put in a PPIMV (post phase inverter master volume), it puts the master volume just before the power tubes instead on in the preamp like most stock master volumes.

 

[Little Pigbacon]

Re: Does adding a master volume control hinder tone?

Would the PPIMV have to be dual-gang (stereo) for the two phases of the signal after the PI?

 

[crusty philtrum]

Re: Does adding a master volume control hinder tone?

Would the PPIMV have to be dual-gang (stereo) for the two phases of the signal after the PI?

Nope. But either way, there will be an effect on the sound of the amp due to the loading of either a mono or stereo pot. UNLESS one creates a 'no load' MV pot that disconnects itself entirely from the circuit when set to one end of it's rotation. (of course a push-pull pot or a separate switch could also be used to switch the MV completely out of the circuit).

The problem has become that people want to own a big, (usually dirty) amp to cover everything from large gigs to appartment playing, and recent-ish technologies have been creating things to address that ... M/V, power soaks, power scaling, etc.). But all of those things compromise an amp's core tone. The reality is that a player needs more than one amplifier to cover all the likely bases if they want uncompromised sound in all their playing situations.

 

[Little Pigbacon]

Re: Does adding a master volume control hinder tone?

That's probably true. I always thought my TSL100 sounded better at bedroom volume than it did cranked.

 

[Darg1911]

Re: Does adding a master volume control hinder tone?

Depends on the type of master volume. LarMar PPIMV is common in Marshall builds for example. Requires a dual gang pot and moves the bias resistors off the board and locating them at the pot (change value of resistors due to parallel resistance with pot). There is less negative feedback as the pot is rolled down and less response from presence and tone controls. Below about 50%, presence and tone controls don't have much effect. Wide open, I think for all intents and purposes, it's audibly out of circuit. I cant hear the difference anyway but it's not like I've installed a switch to A/B it.

 

[Falloffthebonetone]

Re: Does adding a master volume control hinder tone?

Nope. But either way, there will be an effect on the sound of the amp due to the loading of either a mono or stereo pot. UNLESS one creates a 'no load' MV pot that disconnects itself entirely from the circuit when set to one end of it's rotation. (of course a push-pull pot or a separate switch could also be used to switch the MV completely out of the circuit).

So essentially the same as a guitar volume/tone pot. Cool. Thank you.

 

[devastone]

Re: Does adding a master volume control hinder tone?

All of the PPIMV circtuits I've seen/used are dual pots for the 2 sides of the PI.

 

[zzmoore]

Re: Does adding a master volume control hinder tone?

All of the PPIMV circtuits I've seen/used are dual pots for the 2 sides of the PI.

Yeah, i do not understand, in a P-P amp, how you can run two out of phase signals into One Pot, and then run that One Pot into two power tubes that are amplifying two out of phase signals.?

 

[Myaccount876]

Re: Does adding a master volume control hinder tone?

Depends on the amp - some are more affected than others.

A simple in-line master volume right in front of the phase inverter, which is what most old Fenders and Marshalls had in addition to some type of treble bleed, will most definitely keep the phase inverter from being driven opposed to how it would be without a master volume.

Post phase inverter master volumes combine the out of phase signals after the phase inverter, and blend them to cancel out the signal to varying degrees. Now you can drive your phase inverter with the full preamp, but now you've affected the way the power valves are driven - even with the volume all the way up.

I'm an advocate for the "quit being a teacup and let the amp be loud". The whole idea of an amplifier is to amplify (i.e. make louder) the signal. Why would you want to make "louder" quieter? Just get the right amp and run it wide open, whether its a low wattage amp or a high wattage amp. If you turn up the channel volume as loud as is appropriate for the situation and there's still not enough overdrive for your liking, just roll with it. You may surprise yourself with what playing with less gain can do for you.

 

[Falloffthebonetone]

Re: Does adding a master volume control hinder tone?

Depends on the amp - some are more affected than others.

A simple in-line master volume right in front of the phase inverter, which is what most old Fenders and Marshalls had in addition to some type of treble bleed, will most definitely keep the phase inverter from being driven opposed to how it would be without a master volume.

Post phase inverter master volumes combine the out of phase signals after the phase inverter, and blend them to cancel out the signal to varying degrees. Now you can drive your phase inverter with the full preamp, but now you've affected the way the power valves are driven - even with the volume all the way up.

I'm an advocate for the "quit being a teacup and let the amp be loud". The whole idea of an amplifier is to amplify (i.e. make louder) the signal. Why would you want to make "louder" quieter? Just get the right amp and run it wide open, whether its a low wattage amp or a high wattage amp. If you turn up the channel volume as loud as is appropriate for the situation and there's still not enough overdrive for your liking, just roll with it. You may surprise yourself with what playing with less gain can do for you.

I'm looking at some used amps and I found an ampeg v4 that had one installed. Wondered if it was a detriment or a plus.

 

[zzmoore]

Re: Does adding a master volume control hinder tone?

Depends on the amp - some are more affected than others.

Post phase inverter master volumes combine the out of phase signals after the phase inverter, and blend them to cancel out the signal to varying degrees. Now you can drive your phase inverter with the full preamp, but now you've affected the way the power valves are driven - even with the volume all the way up.

Can you explain this.?
You are taking a P-P amp, with a PI that is necessary for the P-P to function, because you need two "equal" and out of phase signals, and then you..... "blend them to cancel out the signal to varying degrees".
Now that you have done that.....how are you going to send the two out of phase signals, that the P-P amp needs, to the power section.?

 

[zzmoore]

Re: Does adding a master volume control hinder tone?

Nope. But either way, there will be an effect on the sound of the amp due to the loading of either a mono or stereo pot. UNLESS one creates a 'no load' MV pot that disconnects itself entirely from the circuit when set to one end of it's rotation. (of course a push-pull pot or a separate switch could also be used to switch the MV completely out of the circuit).

The problem has become that people want to own a big, (usually dirty) amp to cover everything from large gigs to appartment playing, and recent-ish technologies have been creating things to address that ... M/V, power soaks, power scaling, etc.). But all of those things compromise an amp's core tone. The reality is that a player needs more than one amplifier to cover all the likely bases if they want uncompromised sound in all their playing situations.

Can you post a schem that uses a single PPIMV Pot.?
Thank You

 

[Darg1911]

Re: Does adding a master volume control hinder tone?

Can you post a schem that uses a single PPIMV Pot.?
Thank You

There is one. Crossline MV. But it's called by other names. I'll see if I can find a diagram or schematic on the web. Worst case, I can upload a diagram from my machine to photobucket. I think I have it saved in one of my folder.

Edit ... found the link. About 1/2 way down the page. Referred to as Type 3 (Ken Fisher). https://robrobinette.com/The_Trainwreck_Pages.htm

 

[Little Pigbacon]

Re: Does adding a master volume control hinder tone?

I figured it was some high-falootin' balanced thing.

 

[zzmoore]

Re: Does adding a master volume control hinder tone?

Oh Yeah.....i forgot about the cross-line. The guys at Matchless used that a bit, as well as other people. And it does just that. I never thought it was near as good as The Lar-Mar, but that is JMO..... it certainly is a solid example of a single pot PPIMV.
Well Done

 

[Boogie Bill]

Re: Does adding a master volume control hinder tone?

Just FYI, and a IMHO....

I would not make an "irreversible" mod to a vintage amp, like a BF Fender or NMV Marshall. There are just so many good amps on the market with a MV, it's not really necessary to start drilling holes in these classic amps. Almost everyone I know who has done this was less than satisfied with the result, and regretted doing the mod.

Bill

 

[devastone]

Re: Does adding a master volume control hinder tone?

The crossline MV is interesting, first single pot PPIMV I've seen. Although the page you linked to says that the type-2 (dual ganged 100K pot) is the most transparent.

 

[Myaccount876]

Re: Does adding a master volume control hinder tone?

Can you explain this.?
You are taking a P-P amp, with a PI that is necessary for the P-P to function, because you need two "equal" and out of phase signals, and then you..... "blend them to cancel out the signal to varying degrees".
Now that you have done that.....how are you going to send the two out of phase signals, that the P-P amp needs, to the power section.?

It's a simple blend circuit. Whenever you blend the positive signal with the negative signal coming out of the phase inverter, there will be some cancellation. The more of one signal you blend with the other. When they're fully blended - nothing is being sent to the power section. Whatever signal you don't introduce for cancellation (via variable resistance) just goes to its respective valve(s). Your volume is at "0" when the signals are fully combined, and at "10" (I prefer "11") when the signals have maximum resistance between them to prevent them from being blended/cancelled. IIRC, this can be done with a single potentiometer.

At least, that's one way of doing it. Another master volume circuit that I forgot to mention is just a standard volume pot wiring (input, output wiper, & ground)for both the positive and negative ends, and the two pots are combined in a dual gang pot. Both types of PPIMV circuits still affect how the output stage is driven. Even with 1M resistance between ground or 1M resistance between the signals from being blended - there is still some signal shunted to ground or some signal cancellation. The only way to avoid that is infinite resistance (meaning no master volume circuit).

And yep, single ended amps would be affected by a master volume too - arguably more so as you don't get an extra gain stage (unless it's an unbuffered cathodyne circuit - those are at unity) from the phase inverter (as there is no phase inverter in single ended amps) to make up for the signal loss by having a channel volume. If I had a single ended amp, I'd probably add a switch to completely take out the preamp volume control (and the master volume if it's there) all together so I could really run the amp fully open. There's also a couple oddball amps out there that use a transformer instead of a phase inverter tube. The only amps that come to mind that use a transformer there are late '60s Gibson amps like the GA35RVT. These work as phase inverters by the input being on the primary winding, and a center-tapped secondary. Picturing the schematic drawing for a center tapped secondary, the signal between the upper winding and the center tap is positively phased, while the signal between the lower winding and the center tap is negatively phased. Also worth noting - transformers work only with AC (hence why you need a rectifier on a power transformer's secondary), but the input and outputs of a phase inverter are supposed to be AC - so it's kind of a neat idea of phase inversion. However, this circuit yields no additional gain, so there's that disadvantage. Also, the two signals being output from a phase inverter don't necessarily have to be equal - its ideal that they are, but push pull circuits will still work (while sounding different) if one side is amplified more than the other because of something like unbalanced triodes (won't happen on a cathodyne - so there's an advantage of that circuit).

 

[Myaccount876]

Re: Does adding a master volume control hinder tone?

I'm looking at some used amps and I found an ampeg v4 that had one installed. Wondered if it was a detriment or a plus.

If it was installed by someone else, then there's no way of knowing what was done without taking a look inside. I'd just try it out if possible and if the amps sounds good - go with it. A master volume shouldn't make a great amp sound bad/removing a master volume shouldn't make a bad amp sound great. A great amp is still a great amp no matter what. I'd argue that anything that prevents an amp from being fully driven, which is just about every type of master volume circuit, is a drag, but you could always make it switchable. Just remember to turn the channel volume down before switching it out.