Amp/Preamp Asylum

Posted by 3+4=5 (A) on September 25, 2017 at 10:55:34

In Reply to: RE: Audio research SP 11 mk 2 weird issue. posted by SchoolOfRock on September 24, 2017 at 12:39:21

I own a ARC Sp-15 which is also a two box ARC of similar type.
The AC SP-10, SP-11 and SP-15)
Anyway, SO I have the same separate front panel phono impedance switch.

That switch is in the phono low level circuit. Before any amplification.

I would think it is a Damaged SWITCH. or less likely blown/damaged 47k resistor.

Switching tubes around changing the sound is just normal tube oddness.
The failure is in the switch itself. Most likely some sort of fault to ground at the 47K position.
Replace the switch and I bet all will be well.

ADDED: even cleaning the switch may clear up the issue. IMO. Try a contact cleaner sprayed into the switch.. moving the knob around back and forth. (with the pre turned off of course)

Edits: 09/25/17