Master volume + Resonance control on single, dual gang pot?

GlideOn

Member
Got hooked on RobRobinette's site lately as the guides basically share a lot of info with my Traynor YBA-1 amp.

Having some success following guide and modifying my 68' Traynor YBA-1 lately. Voiced a lead channel, tweaked the voicing a bit and it sounds so much better suited for guitar now.

But I have been mulling as to what to do for arguably the most important/useful mod so far - the master volume.

Right now I just have a 250k leftover Stratocaster pot hooked up with some alligator leads to the Phase Invertor coupling caps and it works...better than expected! I can definitely get bedroom level overdrive sounds and doesn't rob any discernable juicy, clear, sustaining tone to my ears.

But the problem isn't the master volume - it's the new lead channel 0.68/2.7k voicing which dump a lot of bass at cleaner volumes for the sake of that glorious distortion at higher volume settings.

As I understand it, a resonance control interacts late in the chain connected to the NFB to subtract or introduce bass.

My thought is this (excuse me if I'm not the first), but - what if we were to use the Trainwreck 3 type volume which is a VERY simple 1meg pot with middle and end ligs hooked up.

But what if we were to use a dual gang pot and on the rear of pot have a resonance control...wired backwards?

That way when the Master volume and overall decibels go up, the bass goes out...

...And when volume go down - bass goes in?


Would this work?
 
Not sure what the problem is that your trying to solve. You’re removing the versatility for the benefit of not adjusting 2 knobs. I’m a big fan of keeping the signal chains apart from each other.
 
scottosan":3qg8s0vv said:
Not sure what the problem is that your trying to solve. You’re removing the versatility for the benefit of not adjusting 2 knobs. I’m a big fan of keeping the signal chains apart from each other.

*you're* :D



The age old problem with Marshall voicings - not enough bass for cleans. I would in theory like to add bass for cleans but gradually remove them as I turn up the volume.

A resonance control though is very late in the circuit, not really related to the master volume at all. Not really an issue when you use shielded wiring and the Traynor is a very quiet amp to boot.

Due to a lack of open slots on a basic YBA1 type amp, I think I think it would be clever to hide some controls in the form of either push/pull pots or dual gang pots. For the YBA-1 there's an extra hole rear of the amp where the ground switch used to be. I have a modern 3-prong plug so no need for that anymore and it freed up a hole. Not looking to drilling new holes into the faceplate or chassis if possible.



It's purely by coincidence that a certain Master Volume and Resonance Control both call for a 1meg log/audio pot. In theory, reversing the right and left lugs for the resonance control will do opposite of adding bass as you turn up the master volume - it will cut - which is a desirable attribute to have, right?
 
GlideOn":19ibvhzr said:
scottosan":19ibvhzr said:
Not sure what the problem is that your trying to solve. You’re removing the versatility for the benefit of not adjusting 2 knobs. I’m a big fan of keeping the signal chains apart from each other.

*you're* :D



The age old problem with Marshall voicings - not enough bass for cleans. I would in theory like to add bass for cleans but gradually remove them as I turn up the volume.

A resonance control though is very late in the circuit, not really related to the master volume at all. Not really an issue when you use shielded wiring and the Traynor is a very quiet amp to boot.

Due to a lack of open slots on a basic YBA1 type amp, I think I think it would be clever to hide some controls in the form of either push/pull pots or dual gang pots. For the YBA-1 there's an extra hole rear of the amp where the ground switch used to be. I have a modern 3-prong plug so no need for that anymore and it freed up a hole. Not looking to drilling new holes into the faceplate or chassis if possible.



It's purely by coincidence that a certain Master Volume and Resonance Control both call for a 1meg log/audio pot. In theory, reversing the right and left lugs for the resonance control will do opposite of adding bass as you turn up the master volume - it will cut - which is a desirable attribute to have, right?
the problem is the the tonal effect of the resistance in each part of the circuit isn’t going to be linear with the other. Most people like more resonance at lower volumes. It does take much volume before the resonance is no longer necessary.
 
GlideOn":1u21hh26 said:
The age old problem with Marshall voicings - not enough bass for cleans. I would in theory like to add bass for cleans but gradually remove them as I turn up the volume.

You could use a dual gang pot.

One is the volume, the other is a variable "FAT" control. the FAT control has say a .022uf on one outer lug, and .0022uf on the other outer lug, the wiper connects to the volume pot input lug, the signal connects to both of the other leads of the two caps.

So basically as you turn the volume up the the FAT control wiper moves closer to the .0022uf cap attenuating lower frequency.

I can draw you a diagram if need be.
 
GlideOn":519e3wyb said:
It's purely by coincidence that a certain Master Volume and Resonance Control both call for a 1meg log/audio pot. In theory, reversing the right and left lugs for the resonance control will do opposite of adding bass as you turn up the master volume - it will cut - which is a desirable attribute to have, right?
Your idea of adding more resonance as you turn the master down with a dual gang pot and wiring the resonance pot backwards certainly has merit, and is worth experimenting with.
I'm assuming that the single pot master vol in your first post is a simple Vox-style cross-line master. If so, then 250k is the correct value for that style master vol.
1 meg is a good pot value for resonance.
It just so happens that Fender uses a 250k / 1Meg pot for their TBX tone control.
example here, but there are other sources and brands. Note that this particular pot has a center detent. Hopefully not a deal breaker for you.
https://www.mojotone.com/guitar-parts/P ... ne-Control
Not sure what the tapers are, but worth a shot. It's a cheap experiment.
 
Adjusting bass early (like the cathode combo you mentioned) will sound different than adjusting it late (like a resonance). Still worth experimenting with but thought I'd mention it.

The Marshall 6100LM had a cool feature that completely changed the NFB circuit when you switched from dirty to clean. I'm surprised more amps don't do that.
 
I was just looking through the Trainwreck pages, and I see that a 1 meg pot is recommended for the Type 3 master vol.
I know vox uses 250k in their HW amps, but I guess you could use any value really. A dual 1 meg pot would probably be easier to source than the one I linked to above, so maybe just start there.

Also, amps using a cross-line master don't typically have negative feedback, as far as I know.
I'm not sure how well a resonance control would work in an amp with a cross-line master vol, but if you have the 250k pot installed in your amp and the presence control functions correctly, then the resonance control should function about as effectively as the presence control does at the various master volume settings.
The issues with most amps using a Type 1 or Type 2 post phase inverter master is that the post PI master is in the negative feedback path, and as the master is turned down, the presence and depth become less and less effective because the amount of NFB is also reduced.
I have no idea what happens with a Type 3 master and presence and depth controls, but I'm actually curious to find out how well it works out.
You are just going to have to try it and let us know how it goes. :thumbsup:
 
You're going to find the effective resonance will be 90% most sensitive the last few Kohms and not much change relative to master volume level over the majority of the sweep. To see the change you're wanting to see, you're going to have to reduce the gain with a lot more negative feedback than previous.

This is just what I believe will occur. There's not much you can do other than try it and use it as a learning experience. No harm no foul.
 
So I performed the mod...had to chain it to the presence and then to the NFB to work, but...it worked!

But...not as well as I hoped.


The problem is taper. While I'm sure 1meg is technically the right value, it just doesn't work as desired slaved to a volume control.

I wish I was savvy enough to calculate a better taper with a series of resistors or caps, but truth told it was also noisy in my amp, even with shielded wiring.

I find it more useful to use a 1meg pot on its own and setting as desired.



I DID however, use a separate dual ganged pot and combined Channels 1 and 2 on a single control and am very happy with the results!

I always found I was adjusting them identically and thought it would save space to just combine the two.


Before you say that I did it "ass backwards," I actually split the cathode bias and coupling cap values too (.0047 and .022)

So I have two different gain tones, cold .68/2.7k and hot 25uf/1.5k bias' singing in harmony. Very cool and useful mod!


fusedbrain":h0ndrcrg said:
GlideOn":h0ndrcrg said:
It's purely by coincidence that a certain Master Volume and Resonance Control both call for a 1meg log/audio pot. In theory, reversing the right and left lugs for the resonance control will do opposite of adding bass as you turn up the master volume - it will cut - which is a desirable attribute to have, right?
Your idea of adding more resonance as you turn the master down with a dual gang pot and wiring the resonance pot backwards certainly has merit, and is worth experimenting with.
I'm assuming that the single pot master vol in your first post is a simple Vox-style cross-line master. If so, then 250k is the correct value for that style master vol.
1 meg is a good pot value for resonance.
It just so happens that Fender uses a 250k / 1Meg pot for their TBX tone control.
example here, but there are other sources and brands. Note that this particular pot has a center detent. Hopefully not a deal breaker for you.
https://www.mojotone.com/guitar-parts/P ... ne-Control
Not sure what the tapers are, but worth a shot. It's a cheap experiment.


Yes, I've heard of the TBX tone control and have it on a buddy's Wide Range Telecaster. It's actually very useful with the 220k taper mod. Don't know of any application for amps yet.

However after being unsatisfied with the 1meg taper of the resonance control, I think you may be onto something by suggesting a 250k/1meg dual gang TBX for resonance instead...


CNutz":h0ndrcrg said:
GlideOn":h0ndrcrg said:
The age old problem with Marshall voicings - not enough bass for cleans. I would in theory like to add bass for cleans but gradually remove them as I turn up the volume.

You could use a dual gang pot.

One is the volume, the other is a variable "FAT" control. the FAT control has say a .022uf on one outer lug, and .0022uf on the other outer lug, the wiper connects to the volume pot input lug, the signal connects to both of the other leads of the two caps.

So basically as you turn the volume up the the FAT control wiper moves closer to the .0022uf cap attenuating lower frequency.

I can draw you a diagram if need be.


Yes!!!

I think after trying the "reverse resonance" mod, I find it more useful to have it independent of the volume control. Unless the taper could be better adjusted to have a later drop in bass, its' not as useful as I'd hoped.

Scottosan was right.


But a variable "fat" boost could be what I was actually going for. I don't need an absolute bass resonance boost, but fattening the cleans is probably more appropriate.


Not sure I follow where you'd connect it to - am I understanding the they go right off the coupling caps for channels 1 and 2?
 
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