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Can someone explain hiwatt and SC presence circuits?

3/28/2006 10:46 AM
SatamaxCan someone explain hiwatt and SC presence circuits?
Hi everybody!  
 
Well, i've been struggling for a while trying to understand thoses hiwatt and sound city presence circuits. Well, i guess, 1n and 100K pots to ground drain the trebles to the ground, but why is the other side connected to the NFB, tail resistors and grid circuit of the PI in the case of the hiwatt? http://mhuss.com/Hiwatt/Schematics/DR_4InputPre_v2.gif  
 
And it seems to make even less sense on the SC  
http://www.luthierguitares.com/sound%20city%20120.jpg  
the 22N connected to the presence pot, and to the cathode resistors of the gain stage! Why? Signal can't go through the pot from plate to cathode, so can't cancel itself partly bleeding some frequencies to ground. Then is the 2K2 and 4.7K making a voltage divider sending part of the cathode signal to the 22n cap and 100k pot, bleeding some frequencies to ground, but why would they do that? Kind of variable bypass cap? Can anyone coment? Explain? Thanks guys.  
 
Best regards.  
 
Max.

 
Replies:
Rick Erickson [QUOTE]Kind of variable bypass cap?... -- 3/28/2006 12:39 PM