Add tone stack to a Buss Fuzz

[rockaffe]

In the last few days I've started trying some modifications on simple circuits (bass fuzz in this case), and after some fun with diodes and resistors I've entered the wonderful world of the tone stack.
Following the guide in the DIY Faq of this forum I added the circuit parts just after the decoupling capacitor just before the output, and everything went as expected.
So I tried to implement also the circuits on this page:

http://www.muzique.com/lab/swtc3.htm

but the result was absolute silence.
As with previous tone stacks, I made the additions right after the capacitor just before the output.
Where am I doing wrong?

[antonis]

1. What's the value of Collector resistor..??
2. Does Tonestack comes after any hard clipping configuration..??

[rockaffe]

Collector resistor is 10k (transistor is mpsa13), there's no hard clipping.
Here is the schematic I'm working on

[antonis]

So, are we talking about something like this..??



P.S.
The capacitor between BJT Collector and Volume pot is a (AC) "coupling" or "DC blocking" capacitor..
Coupling caps are the ones in series with signal path - decoupling ones are those shunting the signal (usually to GND)

[rockaffe]

So, are we talking about something like this..??

Yes, exactly. The cap value is 0.047u

[antonis]

Although 47nF there couldn't make the circuit absolute silent, I'd try to make it 470nF - 1μF to see if something gets audible..

P.S.
I presume you've already verified circuit continuity..

[rockaffe]

Continuity is ok, but no sound no matter the cap size

[antonis]

It's time for audio probe then..

edit: Before audio probing, I'd check for shorted tonestack caps..
(especially for 47nF one..)

[Dormammu]

Continuity is ok, but no sound no matter the cap size

Does the circuit itself work ?

[rockaffe]

Continuity is ok, but no sound no matter the cap size

Does the circuit itself work ?

Yes

[Dormammu]

Does the circuit itself work ?

Yes

In this case, if serviceable parts are used and the installation in the "tonestack" is not screwed up — complete silence is impossible.

[ElectricDruid]

A short across the 47n tone cap would kill the output. How is this circuit put together? Veroboard? Breadboard?

[rockaffe]

A short across the 47n tone cap would kill the output. How is this circuit put together? Veroboard? Breadboard?

It's on breadboard.

[antonis]

Have you an audio probe..??

If not, just put DMM's probes across 47nF cap legs (the one going to GND and the other connected to 4k7 resistor and Tone pot CW lug) and set DMM on "resistance" mode..

You should get a soaring measurement up to 100k and 110k (dependent on Tone pot setting..)
(circuit powered OFF, of course)

In case you get a low resistance measurement (e.g. 47 Ohms attenuates Collector signal by 1/1000), you've nailed the problem..

[GibsonGM]

Pull the 47n out of circuit and see if you get sound at the time you measure its resistance     Same for 100n if still no sound...

[antonis]

Pull the 47n out of circuit and see if you get sound at the time you measure its resistance     Same for 100n if still no sound...

Not so scientifically artistic approach, Sir..!!

[GibsonGM]

   Of course not!  We ARE musicians here (most of us...)   

[duck_arse]

  Of course not!  We ARE musicians here (most of us...)   

I'm not.

can we have a photo of the thing on the breadboard, and where are the diodes --- how many diodes, are there switches on the diodes --- on the circuit diagram?

[rockaffe]

  Of course not!  We ARE musicians here (most of us...)   

I'm not.

can we have a photo of the thing on the breadboard, and where are the diodes --- how many diodes, are there switches on the diodes --- on the circuit diagram?

Thank you all for the replies. Today I've breadboard it again and it works, so as always it was a careless mistake 

[antonis]

Not located mistakes remain lying in wait ambush..!!