rascalseven
Well-known member
Just finished my LA-2A clone, and have a problem I can't seem to find discussion on. I am experiencing significant DC offset (or rather extreme 2nd order distortion?). Here's what my humming looks like:
As the signal gets louder it seems to cross a rather dramatic threshold into obvious clipping -- very easy to see that threshold in the picture.
I've been over the build several times now, (used Kent's layout, but with values of original drawings instead of his Jensen-type I/O mods.... used original UTC iron in my build, so stuck with the values on the original drawing). Everything seems to check out. I've swapped tubes with entirely different set, but still have same result.
Oh, and the result is the same with the T4B opto removed from the unit or with it in the unit, but the 'reduction' knob full CCW (no limiting). When it's compressing this distortion is quite reduced, and with lots of reduction can be made to not cross into the ugly clipping at all, though it still sounds a bit odd... I think half the waveform is still a bit trippy.
Any ideas what might be causing this? I'd be tremendously grateful for help. It's unusable, and I'm currently at a loss. Will hit the sack, and perhaps a fresh brain might make sense of it tomorrow....
Thanks so much!!!
As the signal gets louder it seems to cross a rather dramatic threshold into obvious clipping -- very easy to see that threshold in the picture.
I've been over the build several times now, (used Kent's layout, but with values of original drawings instead of his Jensen-type I/O mods.... used original UTC iron in my build, so stuck with the values on the original drawing). Everything seems to check out. I've swapped tubes with entirely different set, but still have same result.
Oh, and the result is the same with the T4B opto removed from the unit or with it in the unit, but the 'reduction' knob full CCW (no limiting). When it's compressing this distortion is quite reduced, and with lots of reduction can be made to not cross into the ugly clipping at all, though it still sounds a bit odd... I think half the waveform is still a bit trippy.
Any ideas what might be causing this? I'd be tremendously grateful for help. It's unusable, and I'm currently at a loss. Will hit the sack, and perhaps a fresh brain might make sense of it tomorrow....
Thanks so much!!!