i had a spitty sound in my system which i narrowed down to a failing 6SN7. once i replaced the 6SN7, the spit went away. i'd check your input tubes before you replace your output tubes.
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Cheers for ideas to my sonic maladies,
The amps were bought as demos. I have no idea as to the hours on any of the tubes. As long as the circuit is good as I tend to believe, I have no problem with valve refurbishment even in light of my dodgy employment situation,
I will look at all valves as suspect.
As I listen to it now all is good, till the next sonic hiccup.
Again after listening for an album/CD right amp will fill with the finger on the stylus sonics, albeit very briefly. ( scratch, scatch, silence) argh!
The left amp has stopped the low level humming for now.
I now fear as to the recent performance, that there may be a thermal element, gee I hope not. As to complicate my diagnosis.
Thanks for the response.I am going to get 4 new 6SH7 tubes to start.
The other amp has started doing the ground hum thing again.
The fix still is light pressure on the tube cage. Will I be best off removing the cage?
This hum is intermittent, but shows up more often after the amp has played through a couple of CD's.
I am aware that there may be difficult to diagnose .Help?
The hum may (though I don't know and am not personally experienced with that amp) be caused by the power transformer inducing a resonance in the tube cage after the temperature has risen in both. Yes, the simplest fix in that case would probably be to just remove the cage. Tube cages always add resonance to the amp chassis to some degree anyway, just from airborne vibration (similar to a turntable cover in that respect), so sound can sometimes be improved a bit by their removal, and they can also make it harder to notice early visual evidence when something may go wrong with a power tube during play.
Thanks to all for offering advice to my sonic woes.
I am waiting for a special screwdriver from IAG in England to remove the tube cage. I hope this will stop the annoying hum in the one amp. I still plan to retube these from top to bottom. That way I will know the ages of the valves and such.
I appreciate all tips.