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Reply with quote  #1 
Guys - after 2 weeks of audio bliss, I briefly had my masterpiece up very loud, then my digital source went to full volume (2V output from Schiit Multibit DAC).

The sound was loud and distorted, and as I went to turn it down, it then went far softer and horribly distorted. Masterpiece appears fine, still driving headphones.

I have opened and discharged the SOB and everything looks okay - nothing is visibly failed.

What should I be looking for? I presume I have blown the 12AT7 Tubes (distortion is both channels). I do not have a tube tester.

I am sad and I feel like such a dick!

David Loader
Reply with quote  #2 
Hmm - presume you've checked the fuses and bias?
David Loader
Reply with quote  #3 
I don't think you'll have blown the input tubes - at worst they will just have clipped.  SOB needs 2.4V before it reaches its full rated output.

Sounds to me as though maybe one or more of the output stage fuses opened up because of the sustained current.
Reply with quote  #4 
Yes looks like you are right. 1 fuse on each side is OC - visually looked ok but tested open.

I will replace and check bias and hopefully okay from there. Hopefully a cheap lesson for me to learn.
Reply with quote  #5 
and we are all good. thank god 😉
David Loader
Reply with quote  #6 
Good news.  I've had fuses let go a few times in my own SOB over the years although it's mainly been faulty tubes that have blown them.  The result is low volume and a highly distorted sound, as you described.
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