Amp/Preamp Asylum

Posted by casouza (A) on June 09, 2012 at 13:46:34

In Reply to: RE: ARC SP10 linestage mods posted by Frank Waller on June 08, 2012 at 11:54:46

Frank, I do not own and SP-10 however I have heard it hundreds of times at a friend's home.
I have a couple of suggestions:
-the simplest mute circuit is the one that does the least harm to sound quality: use the ARC mute switch to short the output to ground (no photo-transistors, use a pice of wire and the switch contacts), all connected after the output coupling cap. Operate it manually and wait 3 minutes after power on to un-mute. Always mute when switching inputs, cables or turning off the preamp.
-Instead of spending your money on three brands of so-so 6922s, spring for a full set of Amperex 7308 tubes. These are are extremely quiet, balanced triode tubes designed to. military specifications, e.g. they stand a much higher plate voltage than 6922 and are specified to last 10,000 hours, about four times as much as regular 6922s on an SP-10. To boot, Amperex have the best bass quality / punch in the 6922 / 7308 tube family.
Good luck
C.