Noisy Right Channel

So I had my stereo playing while I was getting ready for work today, and when I changed the disc, I noticed some noise coming from the right speaker, when there should have been, you know… silence. Noooooooo!

I wouldn’t describe it as a hiss, hum or static. More like an irregular crackle, similar to a radio that is between stations.

The sound didn’t increase or decrease with adjustments to the volume control. It was present regardless of whether my dac’s inputs were set to coaxial (cd transport) or usb (streamer). Was present with my dac powered off. Was present with preamplifier switched to other (unused) inputs.

My interconnects are all shielded, and, along with my speaker cables, are not routed in close proximity with my power cables.

turning off my preamp (whilst leaving amp on) did cause the sound to cease.

Is it possible that this is a symptom of a (6h30) tube approaching the end of its service life?

Any suggestions for troubleshooting?



Switch your tubes channel to channel and see if the noise switches channels. If it does get new tube(s). Perhaps just reseating your tubes will solve your problem.

Yes just happen to me last week. Newbee offers good troubleshooting advice. I switched out my preamp PAIR of tubes since I had some NOS matched Sylvania(s) to replace the GE that went bad. Good Luck.

Also consider using some contact cleaner on the tube pins and sockets. Think about it, on a tube amp with four output tubes two drivers, depending on the tube types, that is somewhere around 40 or more mechanical connections that need to be made. Corrosion or a bad connection on just one pin can create the noise you describe.

Sometimes switching tubes from left-to-right fixes the problem because the act of removing and reinserting tubes knocks off enough corrosion to address the issue.

Of course, tubes do age and/or go bad, so that could still be the issue. But the experiment above doesn't take much time and is completely free so is always worth a try.

Thanks guys… I popped the case open and swapped the left channel tube with the right channel tube, and the noise I was hearing followed the tube and is now coming through my left channel. Cool.
Should I be concerned about continuing to use my preamp while I wait for a new pair of tubes?

Any recommendations for where to order a matched pair of Sovtek 6h30’s?

looks like has them listed at $89.00/pair and has them listed at $127.78. doesn’t seem to have them listed for sale in matched pairs, but has them at $53.95ea. In any event, I’m unfamiliar with all three of these companies so some guidance would be much appreciated.



curious about your suggestion to unplug everything for 24hrs…

Better wait for new ones. To be on the safe side.

There is a chance that this tube will do more things other than be only noisy.


FWIW I don't feel that usually having 'matched' pairs is all that additive. At least I never used them in my ARC pre. Unless your pre-amp has provision for biasing small tubes I'd just cheap out and buy the Sovteks from the Tube store. If they are not perfect performers just use them until you can get better ones, i,e, a matched pair of them, a pair of matched EH's or some NOS (and very expensive ones) and keep them for spares and use them in an emergency like now.  

I had the same problem after I modified a Marantz Model 7 preamp (following personal guidance from Saul Marantz himself!) and had soft hiss and crackling in the right channel. Turned out I installed a defective coupling Mylar capacitor (Mylar because it was 1976), or else I applied to much heat on the capacitor leads while soldering in place. Problem went away after replacing the capacitor.

Could be a bad capacitor, as well as a failing tube.

Matched pairs is more of a power output tube issue than a preamp concern, though I certainly acknowledge that some are paranoid about this issue at every level. 

I’ve bought tubes from Viva, they may not be the cheapest but they usually have what I need and ship the same day.

Here’s a link to Upscale’s tube FAQs.