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For quite some time now, I get this very infrequent pop in the left channel only of the phono stage of my preamp - a Beard CA-35. I retubed about a year or so ago, the original tubes were ECC82: I replaced 2 with Sovtek 12ax7 and 1 with (NOS) Philips ECG JAN 5814A.The pop is very high energy and goes very low in frequency (DC?)as my left woofer makes a full excursion. However, it is so transient I cannot diagnose it's source myself. Immediately after the pop, the music continues to play as per normal. Also, it happens only once per 20 minutes of play or less so it's hard to track down.
I've tried to ignore it up til now, or assumed I had bad connections elsewhere in the system (there are many) that might have caused it. But now I think it's a tube. And it's now especially important to me as I am getting a new Ortofon Kontrapunkt cartridge and expect my vinyl listening time to go up dramatically.
Help if you can.
Thanks,
Derrick
Follow Ups:
Have you cleaned and lubed switches and any other similar contact points?
Are you sure it's not linked IN ANY WAY to the signal source (particular LPs, particular pickup placing, time of day (I know when TV broadcasts commercials without ever turning it on: AC hash becomes worse as neigbors flip channels or go out to make some tea).Otherwise, it's all said before - check every solder joint, every socket. A simple tube change can be misleading: you'll shake it up changing tubes, the trouble will disappear for a while just to show up some day.
Hi, a couple of things, were your old tubes ECC83 or ECC82 as you have written. I believe that the 12AX7 is an ECC83 and the ECC82 is a 12AU7.
The 5814 is a 12AU7, according to a tube dealers chart.
I'm not familiar with your preamp, so maybe they are interchangable.
Have you tried switching the two Sovteks, if the noise changes from the left channel to the right, then you most likely have a bad tube. It was also suggested that you put the original tubes back in and see if the noise goes away. Another thing to consider, would be to order some new/nos tubes, whether you need them or not, it's good to have a spare set and it would give you a chance try a different brand. Just be sure to verify what number tubes your preamp actually uses.
Good luck,
Jeff
It turned out to be a faulty solder in my tube preamp. One of the resistors was shorting to the circuit board. The preamp was an Audio Research LS-7. The problem was a little tricky to diagnose but easy to fix.
If you kept your old tubes try swapping the old ones back in and see if the problem goes away. If it doesn't go away it could be a capacitor breaking down (like a coupling cap). A bad solder joint could also cause a random noise like that.
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