buschfsu

one knob squeezer and the sym pot
« on: May 04, 2006, 09:59:58 AM »
http://www.thatcorp.com/datashts/dn125.pdf

the one knob squeezer schematic is at the bottom of the page...

Anyone know what the SYM pot (R10) is or how its adjusted.  Im guessing its similar to a tube bias thats adjusted via a trim pot and forgotten about but i don't know how to evaluate it other than by ear.

anybody???
PRR said...
OHM'S LAW. Not as an abstract thing: you should be able to glance at a small circuit and "instantly" know I and V, the way a soccer player glances at the ball and knows the angle and kick


pmroz

one knob squeezer and the sym pot
« Reply #1 on: May 04, 2006, 11:02:15 AM »
.
No need to guess. There's an explanation for SYM on the That 4301 datasheet. Check Fig.2 (R5 is SYM) and text for adjustment procedure.

Many 'design notes' assume you've already digested the datasheet. The note you linked also includes a (more technical) explanation for SYM, but the 4301 datasheet was, at least in my case, easier to understand here.
Paul

buschfsu

one knob squeezer and the sym pot
« Reply #2 on: May 04, 2006, 11:42:26 AM »
got it, looks like its to reduce THD due to gain cell mismatch.  im guessing a scope is the only way to measure THD?
PRR said...
OHM'S LAW. Not as an abstract thing: you should be able to glance at a small circuit and "instantly" know I and V, the way a soccer player glances at the ball and knows the angle and kick

Michael Krusch

one knob squeezer and the sym pot
« Reply #3 on: May 04, 2006, 12:00:15 PM »
The distortion of an unsymmetrical 4301 is not as high to see it in the scope. You can use a software like Audiotester http://www.audiotester.de/ to adjust the distortion.
Or you can use your ears. Feed the chip wish a sinus and adjust for dullest sound (if you hear any difference).

buschfsu

one knob squeezer and the sym pot
« Reply #4 on: May 04, 2006, 12:30:41 PM »
thanks!!
PRR said...
OHM'S LAW. Not as an abstract thing: you should be able to glance at a small circuit and "instantly" know I and V, the way a soccer player glances at the ball and knows the angle and kick


 

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