4 knob tone stack

[tubenit]

On the D-inspired amps I've done, the "mids" are critically important in the tone and definitely influence the overdrive tone in the amps.

I've been wondering how to shape the mids more and came up with this idea.  IF you look at the Duncan Tone Stack Calculator and use the "Vox" program to approximate the values closer to this tone stack,  you will see that a .01 mid cap greatly increases the low mids and the .05 (or .047) cap has less low mids.   

http://www.duncanamps.com/tsc/

The idea is to use the mid shape pot to dial in the type of mid tones that you want.  I realize there are other ways to approach this also.

I am thinking this could be very useful on some builds where the mids are so critical in the OD tone.

Thoughts?    And does anyone have a 4 knob tone stack schematic that is used with a tube (not solid state) amp ?

I just thought of this idea this morning so I have not tried it yet.

With respect, Tubenit

[kagliostro]

Ciao Jeff

This Tone Control (from Weber AB200 Kit) didn't has 4 pot but has 4 knobs and the rotary switch seems there with the purpose to tailor the mids



Here (Ampmaker Kit) the approach is different, the knobs are only 3 but one is devoted to control the mids in a different gain stage



Franco

[SILVERGUN]

This is what I did on a friend's harp/guitar amp...
I wanted to give him the ability to tailor mids between a more standard scooped out stack for playing guitar, or a mid heavy tone for playing harp through the same amp.
Not 4 pots, just 3 pots and a rotary switch.
I "borrowed" the approach for the schematic from Sluckey's AC15
 
EDIT:
Looking back over this I now see that you appear to have been looking for different input...I took it as a chance to throw out ideas, when it looks like I missed the intent of your post.
YOUR idea does look like a smart way to have somewhat of a sweepable mid shape control!

[mwelch55]

What about the Engl 530 Tonestack?

Mike

[tubeswell]

Hi Jeff


Make the 100k slope resistor variable.

[kagliostro]

There is also the Merlin's version of the James with the shift control option, but it is a 3 knob Tone Control





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With 4 knobs (one is a double pot) there is also the Blackstar (they call it ISF)



Patent and explanations (with graphics)
https://docs.google.com/file/d/0BwMWxzd7lEJ4WWZselRsb3R5Q0U/edit?pli=1
Demo
https://youtu.be/C7Xig5d3Mao

but I don't know if this can be of your interest also because it is in a SS circuit and to use it in a tube amp requires some experiment

suggested values to be tried for tube amps are:

C1 = 470nF, C2 = 220nF, C3 = 220nF and C4 = 4.7nF, R4 = 1k -- pot near for sure is a dual 10k linear pot

Franco

[SILVERGUN]

Based on your idea, I adapted my drawing to reflect a possible application for the standard TMB stack.
I will be trying this in the near future and report back with findings. Not too tough to hook up.
 

[kagliostro]

Ciao SILVERGUN

a possible alternative ?





Franco

[SILVERGUN]

Thanks Franco,
Yes, I can try it that way as well.
I imagine pot values will be critical to getting the blend correct.

[kagliostro]

For "my" version try 1M

I borrowed it

the pot connected that way is a way to avoid the use of a rotary switch with capacitors when you have it following a pentode preamp stage

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This is what propose Tubeswell



Franco

[Ed_Chambley]

Hi Jeff


Make the 100k slope resistor variable.

I have used this idea a lot, but I cannot come up with a name for it.  I did label it as a mid shift on one amp, but not exactly the same.  I also make the Bass cap switchable between Stock Fender and Marshall.  Clean to mean, but I will say I have never tried it with an overdrive.

[tubeswell]

This is what propose Tubeswell



Franco

Yeah, that's what I'm talking about

[kagliostro]

I've find also this schematic (of a modded Alembic F2B)

it is one other option to have a 4 knob TS with two knobs devoted to the mids





Franco