Sibilance produced from HH Scott LK 72 Amp

[MadcapLaughs]

hello,

Wondering if anyone had any ideas about why my Scott lk 72 integrated amp might be generating sibilance on all my LPs? I am sure that my turntable had been correctly set up as it does not produce ANY sibilance when plugged in to my Sansui receiver and Yamaha integrated amp phono stages. I have tested to see if tube socket connections are solid. I should mention that the amp has been completely recapped (orange caps in the phono stage and all over). Power tubes biased, overhauled completely. I have NOS telefunken long plate 12ax7 in the preamp, I have swapped in RCAs with same results. Am I out of luck here, do I need to just move on to an outboard phono pre? It is such a nice preamp except the sibilance butchers any enjoyable lp with vocals.

 

[captouch]

Sounds like something is wrong with your LK72 phono stage. By using the same TT with multiple other receivers, with no sibilence heard, that should eliminate the TT being the culprit. Is there equal sibilence in both channels?

I assume the AUX and other inputs of the LK72 don't result in sibilence at all?

The LK72 was a kit, so it's possible that the builder has a misplaced component somewhere in the phono stage. I had a Fisher KX-100, a kit version of their X101B, and it gave me funny waveforms even after it was completely overhauled. It turned out two caps were swapped in one of the channels and swapping them back to their proper locations fixed it.

Also, you have 2 12AX7's for the preamp stage and two different ones that are only used in the phono stage IIRC. You tried replacing the phono stage ones, correct?