Volume loss after adding BMP tone stack to Fuzz Circuit

[BennyBoy]

Hi everyone,

First time poster here!

I am working on modifying a very simple silicon fuzz circuit right now, and ended up adding a BMP tone stack with my own unique values for EQ, and it sounds really great! However, because of the nature of the tone stack, I end up at unity output gain with the volume pot maxed out. How can I solve this problem?

I tried adding a gain stage after the tone stack that is identical to the first gain stage of the fuzz, however this just ended up adding more distortion than any noticeable volume increase.

Thanks!

[antonis]

Hi and Welcome..

Try to add a recovery stage, copied from Big Muff..

[antonis]

a BMP tone stack with my own unique values for EQ,

Could you plz elaborate those values..??
(mainly for resistors..)

Or better, a complete schematic of your build..??

[BennyBoy]

Thanks for the suggestion! Just take the output stage right from a Muff? Will this work with the transistors I am using with my project (MPSA18)?

[BennyBoy]

a BMP tone stack with my own unique values for EQ,

Could you plz elaborate those values..??
(mainly for resistors..)

Sure! The resistors I am using are unchanged, I just changed the cap values. The high-pass is 22k and the low-pass resistor is 39k.

[antonis]

Just take the output stage right from a Muff? Will this work with the transistors I am using with my project (MPSA18)?

Definatelly, yes..!!
(I'd suggest the version of 390k 470k/100k for voltage divider bias configuration and 10k/2k2 for Collector / Emitter resistors respectively..)

P.S.
What's the value of Tone pot..??

[BennyBoy]

a BMP tone stack with my own unique values for EQ,

Could you plz elaborate those values..??
(mainly for resistors..)

Or better, a complete schematic of your build..??

Here's a schematic of my build, sorry it's not very clean, did it in a hurry.

[antonis]

Do you use MPSA13 or MPSA18..??
(there is a major difference in Base-Emitter voltage drop, hence in bias configuration resistor values..)

P.S.
Are you sure about T3 good working condition..??

[BennyBoy]

Do you use MPSA13 or MPSA18..??
(there is a major difference in Base-Emitter voltage drop, hence in bias configuration resistor values..)

Sorry, that was unclear! I've tried both, but think I'll be sticking with the MPSA18s now. Are the suggested bias resistor values you shared for the MPSA18?

Thanks for all of the help!

[antonis]

Yes.. Use 470k/100k and 10k/2k2..

With a cap in between Tone pot wiper and bias configuration of course..

[BennyBoy]

Yes.. Use 470k/100k and 10k/2k2..

With a cap in between Tone pot wiper and bias configuration of course..

Thanks so much! Any suggestion on the value of that cap? Is 100n okay, as that is what is used throughout the rest of my circuit?

[antonis]

Any suggestion on the value of that cap? Is 100n okay, as that is what is used throughout the rest of my circuit?

It should be more than OK..

T1 and T2 input impedances are much lower than recovery stage mentioned above (about 80k), hence C1 and C3 respective HPFs corner frequencies already overlie 100n/80k one..
(47nF should also be fine..)

[BennyBoy]

Any suggestion on the value of that cap? Is 100n okay, as that is what is used throughout the rest of my circuit?

It should be more than OK..

T1 and T2 input impedances are much lower than recovery stage mentioned above (about 80k), hence C1 and C3 respective HPFs corner frequencies already overlie 100n/80k one..
(47nF should also be fine..)

Thanks for all of oyur help antonis! How does this look?

[antonis]

Excluding C2 and T3, it looks fine to me..

[BennyBoy]

Excluding C2 and T3

Sorry, what do you mean about them?

[Dormammu]

Sorry, what do you mean about them?

C2 eats too much signal.
Perhaps there is an error in the circuit and it should be 100-1000 pF
T3 does nothing useful.

[BennyBoy]

Excluding C2 and T3, it looks fine to me..

Did I do something wrong in laying out the schematic?

[BennyBoy]

Sorry, what do you mean about them?

C2 eats too much signal.
Perhaps there is an error in the circuit and it should be 100-1000 pF
T3 does nothing useful.

C2 was in the original fuzz that I based this of off, but that fuzz had no tone control. When I built this without the tone control (or the 3rd gain stage) that capacitor kept the tone much more low end oriented, but perhaps I don't need this with the BMP tone stack.

What do you mean about T3? That was also in the original fuzz circuit that I based this off of.

[Dormammu]

I would also suggest such values for the BMP:
R7=22K, C5=22nf, P2=15-30K

[Dormammu]

C2 was in the original fuzz that I based this of off, but that fuzz had no tone control. When I built this without the tone control (or the 3rd gain stage) that capacitor kept the tone much more low end oriented, but perhaps I don't need this with the BMP tone stack.

What do you mean about T3? That was also in the original fuzz circuit that I based this off of.

In this application, T3 cuts off one halfwave of the signal, like a diode.