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The ultimate DIY? A Stax SRM-T2!


spritzer

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On my right channel issue, I've noticed that the right set of EL34's had a bit of 'ringing' noise to them. So I measured the offset which was about -67V (with no headphones plugged in) vs about +2V offset on the left. It wasn't fully warmed up when I measured this though. Balance was close to perfect (0.1V) if that says anything. I tried swapping left & right sets of EL34s, and using 6DJ8s instead of JoaMats solid state input. No change though. Could the sand responsible for handling the offset just be bad? Or something else?

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I've replaced the J79 closest to the front panel now. Seems to have done the trick, offset is now normal on the right channel. No extra noise so far either.

Thanks for the help Craig & JoaMat. :)

Edited by s_r
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The batteries measured fine last I checked, the K216s beside the J79s all measure similarly to each other. Replace the LF353 maybe? No change after swapping out the LF353 either.

Edited by s_r
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Haven't checked that yet. Where's the best place to measure that? Could try the +200V output of the battery, or the final output, like the measurements I did some months back.

Edited by s_r
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So after setting up my scope to see if there was any oscillation, the distortion and high offset disappeared. Afterwards the distortion would show up after a few hours of it being on, and it's sometimes cured by just unplugging/replugging the headphones. Feels like I'm chasing after Schrodinger's distortion :ph34r:

Whatever the case, I've put heatsinks on both the 3840s and LSK389s now.

WBrcoS2.jpg

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Those look real. That said, I am aware of fake 2sk389, but then they used relabelled 2sc3381, so pretty doubtful they would fake a 2sc3381 when they would more likely label them as 2sk389... I did see some questionable 2sc3381 with flat legs, but the ones pictured are squared, which matches the spec sheet.

 

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