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Re: Crybaby GCB-95 buffer ?

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8/11/1999 4:41 PM

Re: Crybaby GCB-95 buffer ?

Thank you for your help

I'll unsolder this 22pf capacitor when I'll have a soldering iron... (that's the good name in english?). My electronic retailer is closed (because of holidays) and will reopen 8/24/99. I only have an enormous 40W soldering iron and I don't want to kill my pedal with this.

The treble loss in my pedal is not so important. Seems like playing with very old strings (and I tell you once again: ALL the stock Crybaby bypasses sound this way. I really think this darlington buffer is bad in its concept). I also use a Sovtek Big Muff so when I plug both, I really think I'm owning a 62' Strat with the original strings !!! I'll put your (incredible) Millenium bypass into my Big Muff later.

By the way, this Millenium bypass is really elegant (diode leakage current,really true-bypass). What a great improvement of the Rat bypass. Congratulations !!!

I'll post other questions about the Colorsound Tonebender clipping section and the EH Small Stone "strange-feedback-loop-in-the-phase-stage" soon. Hope eveybody will like them!

One last thing: I don't have an oscilloscope and a function generator. Think it would be interesting to measure the REAL input impedance of the darlington buffer at high frequency (about 10kHz). If anyone has the time to do this...

8/11/1999 5:05 PM

quote:
"I'll post other questions about the Colorsound Tonebender clipping section and the EH Small Stone strange-feedback-loop-in-the-phase-stage" soon"

One of those is pretty easy. Check the "Technology of Phasers and Flangers" at GEO" target="_blank">http://www.geofex.com">GEO for a description of how that works. It's not really a feedback loop, but rather a fixed-C, variable R network like other phasers, just *very* weirdly executed. The OTA is the variable R, the capacitive current and the variable-R current add at the current-source output of the OTA.

What's your question on the CS TB clipping stage?

8/11/1999 5:44 PM

Wait a minute, I roll up my sleeves !

1) About the Small Stone.

I have ever understood the basic phase stage(with a phase spliter). I have also understood the MXR trick with the JFET drain-source resistance controlled by the gate-source voltage. Thanks to your article, I have finally understood the Small Stone concept (my sleep has been disturbed for a long time...) with this "negative resistor" simulation. I haven't think a very long time since I read your article but I would have simply showed a part of the input voltage to the negative input OTA. It seems that both input voltage and OUTPUT voltage are equally showed to the negative pin. Would it work without the resistor between the output and the negative input ?

2) About the TB

First, I must tell you I protoed it with AC 128's.

My problem is that I admit the base-emitter diode with the 1N270 looks like a classical clipping section. But the transistor is not biased. Its base receive more or less current(controlled by the 'Fuzz' variable resistor) of the input signal. So when the input voltage is positive, the current goes in the 1N270 (so nothing on the collector) and when it's negative, it goes in the transistor base (so a current appears in the collector). THIS IS NO CLIPPING AT ALL. IT'S JUST A TERRIBLE MESS. In fact, I'm sure my explaination is totally wrong. Help me. I also measured -35mV at the Q3 base. WHY ??? The transistor is not biased at all!!!

One last question (I started a collection): I found a bunch of Ge diodes in my father's components box. They are labelled with colors like resistors (just like the AA119 I've purchased). Does anyone know this diode code?

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