Help with tube amp/capacitor discharging noise?

[justin_tx_16]

Hey guys.

Several years ago (2002) I bought a Sonic Adventure Reality+ headphone tube amp. I posted about it here on the bulletin boards way back when. I just love it. It is more or less a clone of the Stello HP100 Preamplifier/Headphone Amplifier.

This amp is paired with a HeadRoom Total BitHead DAC through my iMac and outputs to my Sennheiser HD600 headphones with upgraded cables.

Yes, I know, speaker forum for headphones but trust this is relevant to you guys

I noticed several weeks ago that my amp started hissing at me. I opened it up, looked for anything obvious, didn't find anything, closed her up and tried again. Hiss. Then, as all cavemen would do, I (lightly) rapped the top of the amp with my hand (ouch) and boom, hiss gone, beautiful music back.

All has been well, until today. The left channel is doing this weird thing where a hiss starts to build up, gets loud and louder over a few seconds and then pops. The volume of the music isn't affected and once it pops the hiss is gone for a while. Then it comes back.

Meanwhile, I noticed on some tracks that the right channel can get crackly but this is only with certain songs so perhaps that is an issue with the compression of the AAC files from iTunes (256kbps).

Could it be that one of the tubs is just loose (hence the jostling fixed it) or does it sound more like a capacitor going bad since it is now a rising hiss followed by a pop? I'd hate to blow out my HD600s so I've turned off my amp for now until I get some advice from you guys.

Thanks so much for your help. I can open her back up and shoot photos of the inside. At one point I posted 300dpi scans of the circuit board and a friendly Klipsch member sent me some tubes to try out. I still have them in their boxes and can give them a try.

Thanks so much for your thoughts.

[Marvel]

Nice to hear from you , Justin. Hope all else is going well with you.

How many hours do you have on that thing? You could try pulling the tubes and cleaning the pins. If you have a spare tube/s, you could also try changing them out. What tubes does this use?

Bruce

[justin_tx_16]

Nice to hear from you , Justin. Hope all else is going well with you.

How many hours do you have on that thing? You could try pulling the tubes and cleaning the pins. If you have a spare tube/s, you could also try changing them out. What tubes does this use?

Bruce

Thanks for the quick reply. Yes things are going great for me these days. Very happy working my own marketing business from home here in San Francisco. I've come a long way since I started here a freshman in high school!

Took your advice, opened it up, removed the tubes, used a microfiber cloth to rub down the connections and reseated them.

Plugged it back in and it seems to be doing just fine. Haven't had the discharging and hiss, so far.

Here is a scan of the inside

It came with two sets of DuMont 6922 E88CC tubes (which are what I am using right now) and one set of GH23n-EB 3707 tubes.

I have been digging around trying to find the other tubes I have but apparently I've misplaced them since the move to San Francisco last Christmas. I'll keep searching them out.

The sound after the reseating seems dramatically different than before. I'd hate to think it's just in my head (haha) but the right channel crackle I mentioned on particular songs is gone and the low-end is deeper/richer/cleaner. Can cleaning and reseating tubes really make this much of a difference?

Thanks again for your helpful suggestion, seems to have solved it. The discharging sound made me worried it was a capacitor on the way out. On your question on how many hours on this thing, a few hundred I'd wager. It sat unused for the majority of three years but is now used daily as I work from home these days.

If you or anyone else has a suggestion on a set of tubes I should try in place of the DuMont 6922s I'd love to give it a go.

Cheers!