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In Reply to: RE: Its not the input tube... posted by Nickel Core on November 11, 2014 at 07:58:50
Can you swap the chokes, then the caps left to right? If it is a bad part, it would be nice to track it down.
dave
Follow Ups:
HI,
I changed the coupling caps, put the old grid chokes back, swapped (almost) everything, but I still have the same 'issue' with the the speaker cone on my right channel 'oscillating'.
However, I might actually not be oscillation. I never saw the effects of 'rumble' on any system. What i suspect is that by lowering the coupling cap value from .47uF to .33uF my system has become more sensitive to rumble.
When I play the system from another source, the 'oscillation' is gone. The cone only moves excessively when I use the turntable (which I do all the time). The 'other source' is a computer which then plays via an inverse RIAA, soo that all components are in place.
Why the 'rumble' is only present on one channel beats me however. The coupling caps are matched.
Thanks for you help. I wanted to discuss more about the theoretical benefits of grid chokes, but I think Tre summed it up already, and there is not much more to discuss. You might be right for about 5 years already about this subject.
Maybe the low resistance DC path is not the cause of the perceived benefits of grid chokes, and its just the high reactance. Grid current as a whole might be much less of a problem in practice then in theory. Maybe thats why the 'ringing' is also not so much of a problem.
NC
I changed caps, but sill oscillation when music plays :( :(
When the amp is on for a longer time, the oscillation seems to reduce.
I'm starting suspect one of the caps in the PSU may have problems...
What a hobby...
NC
if the amp uses a PCB, might also check for cracked solder joints between the pcb trace and tube socket. especially if the effect changes as the amp warms up.
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