SOT: When electronics look good.

[brett]

Hi
this had aesthetic appeal for me when I plotted it.
(Or maybe I'm simulating too much?)

It's the simulated output of a fuzz I'm working on. (And I do I hear you all scream "too many fuzzes already!")
cheers

[Cliff Schecht]

I'm seeing some high-pass filtering on that wave (albeit slight). Is this intentional, or are you setting your interstage coupling capacitors too small?

[Quackzed]

  I'd like to see that 0mv line, kind of like the starting line...

[brett]

Hi

I'm seeing some high-pass filtering on that wave (albeit slight). Is this intentional, or are you setting your interstage coupling capacitors too small?

Wow.     I was wondering about that, too.  That happens in the last stage, which is just a BJT booster. I *think* the input impedance of that stage is about 60k (100k and 470k bias resistors (parallel = about 80k), 1k emitter resistor and BJT with hFE of 200 (about 200k).  80k parallel with 200k = 60k).  Together with a coupling cap of 0.1uF the rolloff freq for a sine wave should be 30 Hz.  But I get a little high-pass filtering at 1kHz.  What's going on?  Is it the square-ness that requires a larger cap?  Any advice would be much appreciated.

I'd like to see that 0mv line, kind of like the starting line...

The lines are all for 0.5 mV p-p input.  The lines are for different settings of the gain control.  I'm quite happy with the versatility and tone of it.   

PS my working name is my stupid sense of humour.  The Ferret has the teeth at one end and a long tail at the other.   

[Cliff Schecht]

Yes, you need a larger cap. You're still getting attenuation at 1 kHz because the attenuation (and associated phasing) is still enough to attenuate and shift your fundamental frequency (1 kHz). You could try going a whole size larger (1uF+) until the high-pass effect goes away completely.

[brett]

thanks Cliff.  You are a champion.
this has surprised and educated me.
I went big and changed it to 22uF.  Even at 2.2uF there was still a small phase shift and "wedging" of the wave.

[George Giblet]

The tilt from high-pass filtering isn't  good indication of what you will hear. 

If you take a 100Hz squarewave and high pass filter it with a 10Hz HPF, ie. quiet a low cut-off compared to the fundamental, so the filter is doing very little, you will still see significant waveform tilt.

For an untilted view use look at the DC coupled outputs.