[Smugsie]

I tried searching the forums, but to no avail I couldn't get the answer I wanted. Mostly because I don't know how to word this specifically.

However in 30 minute to hour increments, I get these intermittent buzzing noises that sound like "buzzbuzzbuzz...buzzbuzzbuzz...".
This issue usually occurs with really old active speakers, and I'm getting a vibe it's coming from my DAC. My source is a Dared Mp5 and it's really old, bought from someone else on this forum.

So I'm wondering where the source of this problem comes from? I'm thinking I could just buy the part (I.E. an OPAMP or something) and repair it myself, I really like this DAC/AMP and it's way too expensive/vintage for me to replace. 

 

[PleasantSounds]

Most likely it's one of the tubes. If both channels are affected then I'd try replacing the rectifier.

 

[Smugsie]

  Most likely it's one of the tubes. If both channels are affected then I'd try replacing the rectifier.

It's just one channel.
Oh thank goodness, an excuse to buy tubes! I was going to roll new ones anyway.
I'll let you know if it works!

 

[Smugsie]

Welp.. after I re-inserted my tube I didn't get anymore stuttering... but now the problem is... I mixed my tubes and I can't tell which one is new!

They're all 6N1P-EB's and I can't tell the condition of them...

 

[PleasantSounds]

If you can't identify the tubes by their physical appearance (i.e. wear marks, serial numbers) then it's going to be quite hard to do that without proper equipment. At least I have no ideas how one could do that in home conditions.
 
You could try listening tests - check for differences in volume level: chances are they won't be identical between the sets.
 
And look at the bright side: at least the "buzzbuzzbuzz...buzzbuzzbuzz..." is gone