buzzing sound

[Thomas72]

Hi Everyone,
I just finished building my SEX kit and all measurements checked out good. However, I noticed a constant (not changing with volume) buzz on the left channel with the right channel being dead silent (besides the music, which sounds fantastic!). The first thing I tried was to switch the tubes and now the buzz is on the right channel, which leads me to believe that the tube has an issue.

Any ideas what else, besides the tube, could be wrong?

Thanks,
Thomas

 

[fullheadofnothing]

If it moves with the tube, you have found the problem. Most 6DN7s will have sat unused for decades by the time a S.E.X. builder plugs one in. Let the tube cook for at least 50 hours and the hum will probably subside.

 

[Thomas72]

Thanks Joshua. I had the amp on for the last few days but the hum did not go away.
Today I got a shipment of 6DN7 tubes and replaced the one in question and the hum is gone!

Without the hum it's just fantastic - so enjoyable! The S.E.X is such a nice kit - building it was fun but now enjoying the music is just great!

Thanks,
Thomas

 

[mcandmar]

There is a simple mod you can try with two 100ohm resistors that would probably cure the hum problem with those tubes.

See the bottom of this post if you are interested in giving it a try, http://bottlehead.com/smf/index.php?topic=5316.msg51191#msg51191

 

[Doc B]

If the left channel was quiet the power supply filtration is sufficient for his application. That mod won't fix the problem of a single tube with heater-cathode leakage. If it didn't improve with some cook time, replacement is the proper solution.