Tone control for GGG Red Llama

[poppyman]

Hello,
I've built a few GGG red llamas and I wanted to mod one of them.

So I built the BMP tone control as shown on the beavisaudio website and added it between the PCB (C6) and the volume pot (R7).

Unfortunately I thought the tone range was pretty short to my taste.

I wanted to try the SWTC option but my very low electronic skills didn't help find the proper values for the components of the tone stack (even with the tone stack calculator: I have it but I don't understand how to use it properly  :/ )

I kinda understood it was linked to the value of the volume pot but not much more...Did anyone did that before?

Is there recommended values for the tone pot and the other components (whether it's the BMP stack or the SWTC stack) for better results?

Did I wire the BMP tonestack in the wrong place?

Thank in advance.

Notes: output cap (C6) = 10uF, volume pot (R7)= 10k log,beavisaudio  BMP tonestack pot I used = 100k lin.

[Mark Hammer]

The action of the SWTC IS effective, but it doesn't produce as robust or obvious a result for 40-60 degrees of rotation as a BMP-type control does.

Here is a suggested set of values to use.  Have the 1uf output cap feed a 470R fixed resistor.  Run that resistor to one outside lug of a 5k pot.  Run the other outside lug to the stock 10k volume pot.  Run a .047uf cap from the tone pot wiper to ground.

This will provide an approximate 1/3 drop in maximum output level (still acceptable given how hot the normal output is), and a 6db/oct rolloff with a treble-cut corner frequency ranging from an estimated 620hz up to 7.2khz.  There will still be some audible treble even at maximum cut, but it will sound much "rounder"

Alternatively, since this may not provide an obvious enough change for some, consider a fixed 2-pole filter with 3 different settings.  So, the same 1uf output cap goes to a pair of 2k2 fixed resistors in series, and then to the same 10k output pot.  That will also produce a 30% drop in maximum output level.  Get yourself a 3-position DPDT toggle switch (on-off-on).  Run a wire from the junction of the two 2k2 resistors to one of the switch commons, and another wire from the 2k2/10kpot junction to the other switch common.  Now solder a .047uf cap to each outside lug on one side of the toggle.  Solder a .022uf cap to each of the outside lugs on the other side of the toggle and connected their free ends to the free ends of the .047uf caps on the other side.  Connect those 4 free ends to ground.

The result will produce a 12db/oct rolloff at 3.3khz, at 1.5khz, or no rolloff.  With a one-pole filter, the difference between 1.5khz and 3.3khz would not normally be very noticeable, but with a 2-pole filter it generally is.  Whether those three settings give you what you want is a whole other matter, but it is easy enough to recalculate and select other cap values.

With C = .01uf, f = 7.2khz
With C = .015uf, f = 4.8khz
With C = .027uf, f = 2.7khz
With C = .039uf, f = 1.9khz
With C = .068uf, f = 1.1khz
With C = .1uf, f = 720hz

Note that there likely will be some audible popping when using the switch to engage either of the filter settings, so try not to do it with the amp at 11.  

[poppyman]

Mark!

Thank you so much for the quick  and very detailed and clear answer!

Both solutions sound easy-ish for my skills. I really like the Red Llama circuit , so I might just end up try both solutions on different units.

thanks again. 

[familyortiz]

Here's a gallery link to a simple R/C low pass filter that I put on my Red Llama. The values are perfect for my taste... goes from the stock harsh square wave ice pick to getting more low tones out of it. IMO, a tone control is a must for the Red Llama.

http://www.aronnelson.com/gallery/main.php/v/familyortiz/TONE+CONTROL.jpg.html

[moosapotamus]

I always thought it would be cool to use the 4 unused sections of the 4049 to add the runoffgroove Mr.EQ to a Red Llama.

~ Charlie

[jrod]

I always thought it would be cool to use the 4 unused sections of the 4049 to add the runoffgroove Mr.EQ to a Red Llama.

~ Charlie

Oh hell yeah! That's a great idea!

[familyortiz]

I always thought it would be cool to use the 4 unused sections of the 4049 to add the runoffgroove Mr.EQ to a Red Llama.

~ Charlie

+1 on hell yeah, that's a great idea!

[Mark Hammer]

One of the perks of that is that the builder won't end up posting questions aboutwhat to do with the unused sections and "why is my RL so noisy?". 

[Electron Tornado]

Might be interesting to take the 1M resistors to ground and replace them and their bypass switches with 1M pots. On the mid control, use a 1M pot, connecting each end lug to one of the 2n2 caps and the center lug to ground.

[jrod]

Sorry to hijack your thread poppyman!

Would this work for adding the Mr. EQ?


By fuzztx at 2012-02-17

Basically I just added the tone control to the end of the Red Llama but moved some connections around. I also moved the volume control to the end of Mr. EQ. Not sure if the "Level" control still needs to exist on the Mr. EQ. I also removed the input cap and resistor from the Mr. EQ only because I didn't they needed to be there after the RL output cap.

[moosapotamus]

That would probably work. One thing that catches my eye is that the second stage of the WHRL and the first stage of the MrEQ might be somewhat redundant - they are both gain stages. I wonder if you really need both of them? I think the output of the WHRL might be pretty hot without the volume control, and I'm not sure what that will do to the MrEQ - more overdrive, maybe prevent it from cleaning up? I don't know for sure, but maybe someone else would have a better idea if any of that is worth being concerned about.

~ Charlie

[jrod]

I see what you are saying, Charlie. I agree that the first stage of the Mr. EQ should probably be removed so that only the tone portion remains.

I figured the volume control would work better at the end of the combined circuits, but I wonder if it would work better between the two.  

Thanks for your input, Charlie!

EDIT: I updated the schematic with the first stage removed. I am not sure it the 560K - 100p in series should also be removed.

[moosapotamus]

If I were you, I'd probably breadboard this to hear what's what.

RE: The 560K/100p and the 470K/2n2...

Preceding each peak stage is a parallel resistor and capacitor network. This forms a high-pass filter that preserves the treble content through the bridged-T notch filter.

Again, if you breadboard it, you could see if you like it or not, or even try different values.

~ Charlie

[OiMcCoy]

I know I am late to the party, but has any one tried this to confirm it works yet?

[mth5044]

It will work - it's putting two circuits in series. Whether it sounds good or not is another question!