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PV12A "ringing" ??

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P51guy
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PV12A "ringing" ??

Post by P51guy » Sat May 13, 2017 4:04 pm

I'm getting an inconsistent ringing sound from the PV12A. It doesn't change amplitude and is not source related. It may be the balance control, as when I was rotating all controls the sound did get louder when I rotated the balance control. All tubes were replaced less than six months ago.

Any thoughts?

P51guy
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Re: PV12A "ringing" ??

Post by P51guy » Sat May 13, 2017 7:14 pm

I've isolated the ringing to the right channel. Tapping on the chassis of the PV12A produces a louder ring, so might be a bad tube. I had an inexpensive DAC lose much of the right channel and quite possibly sent an unwanted signal to the preamp. I've ordered 3 new tubes and have one question: Is V1 & V5 left or right channel?

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Re: PV12A "ringing" ??

Post by admin » Sun May 14, 2017 7:11 pm

I seem to remember V5 being used for both channels. Not sure about V1. We do have the schematics for the PV12 in our database so I would have a look at that.
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Current Conrad Johnson Equipment in System: Evolution 2000, PV-12L, and D/A-2b.

billyz
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Re: PV12A "ringing" ??

Post by billyz » Tue Nov 14, 2017 2:11 pm

Most likely the 12au7 line stage /cathode follower.
In the pv12 these are very prone to microphonics.
I am currently some 6189's Jan tubes and they sound great and very low noise/microphonics.
The rca cleartops are usually very low in microphonics but much leaner sounding.

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