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s_r

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Everything posted by s_r

  1. s_r
    Alright, I went ahead and did that. The current usage for each channel was close to identical, at about 47mA. I also plugged in some headphones and each channel exhibits some weird behavior. Left only results in no audible noise, but the channel itself is much quieter. So maybe the noise is still there, just quieter since the whole channel is? Right only still gives the same noise, and the channel is about the right volume. I'm starting to think this is where the black magic is required.
  2. s_r
    I measured R33 at about 93mA. What would be the best way to measure each channels current usage? Connect one channel at a time and measure R33 for each?
  3. s_r
    Years ago pedefede mentioned that replacing the 10k trimmers with some vishay PTF56 resistors (since they're 5ppm) did the trick. If it isn't the input tubes that's the next thing I'll try. Anyone happen to have 9kOhm PTF56's lying around?
  4. s_r
    The trimmers are the regular bourns ones. I remember lower ppm trimmers being mentioned in this thread a while back, but that they were much more expensive.
  5. s_r
    Well I've swapped out the takmans in the battery for xicons, but the noise is still present. George suggested that it might be the input tubes which are noisy. Aside from that I'm not sure where to look.
  6. s_r
    Yea, that noise is similar. But it's less crackly/more like white noise on mine. Guess the next step is to try swapping the takmans for xicons. For what it's worth, even despite the noise I can tell this amp will be something truly special.
  7. s_r
    The 390k/820k resistors are takman metal films (REYs). Would be slightly annoying if they turned out to be the culprit, given their price. Anyway here's a pic showing their height off the board. I get continuity between the ground screw of the amp and the backplate screws of the PSU. Not between the two sets of backplate screws though. The noise didn't seem to change at all when adjusting the trimpots. It's also close to identical on both channels, but not quite. If it helps the input tubes are JAN Philips 'low noise' 6922s.
  8. s_r
    Well I've managed to solve the hum at least (noise still remains). There's continuity between the two chassis, between pin K & IEC ground, and between circuit ground & IEC ground. Essentially I've done the grounding the same way you have. The resistors are all lifted off the board by a few mm. I'll take a picture later that shows that height.
  9. s_r
    Nope, not while the batteries are within proper range. Gonna try cleaning the pins of the input 6922s in case that cures it. If it doesn't I'll probably look at the grounding in the PSU, since I do hear a faint hum (which I think might be 60Hz) among the noise.
  10. s_r
    Well after fiddling with the trimpots for a while the noise doesn't want to disappear. I'd run out of adjustment range (as in the LEDs would turn off) in either direction before any change in the noise happened. Any ideas?
  11. s_r
    Yep, the boards are the later version. The noise is also not a solid tone but a wider (white?) noise. Will try adjusting the pots in a bit.
  12. s_r
    Good news: George's suggestion worked. Things just sort of fell into place once the 22k resistor was adjusted to ~6.55V. Then all the batteries could adjust to +200/-541V. Offset and balance are also nice and low. Unfortunately now that I've actually plugged in a pair of headphones, I'm hearing a constant noise. Doesn't change at any position of the volume pot either.
  13. s_r
    So I've gotten to the point in my build where I can fire up the amp itself. Unfortunately some LEDs are unlit and the batteries don't want to change their voltage (+250V/-559V) with the trimpots. Specifically D1, D6/D7, D10/D11 and D24 are unlit. Aside from those the LEDs outside of the batteries are dim. The PSU voltages measure dead on. Any obvious culprits I should check?
  14. s_r
    Just to add, the HV900 boards should be the single type. So it'd be 4 HV900 boards per amp that way. Also, could you offer the 450V fat/split PSU boards as well?
  15. s_r
    Won't it need the output boards, driver boards, and the HV900 boards? The driver board is different from the regular carbon amp board last I checked. It might make more sense to offer the boards as a full set, but either way I'm interested.
  16. s_r
    For the new fat/split carbon PSUs, what wattage should the two 249kOhm resistors be? Would 1/2W suffice?
  17. s_r
    That was fast. Looks good Kerry.
  18. s_r
    Paid. Thanks for running this.
  19. s_r
    I'll switch to the FT caps as well then. From 20x mundorf caps to 50x of the FT ones.
  20. s_r
    Paid. Thanks again for running this.
  21. s_r
    I'm interested, depending on how much a matched quad totals in the end.
  22. s_r
    Correct me if I'm wrong, but aren't the v2 attenuators capable of balanced stereo on one board? Also just to check, all that's required to use this is the attentuator(s), an uno, a separate +5V supply, and either a pot or rotary encoder?
  23. s_r
    Correct quantities for me as well. Gift payment is fine. Thanks for organizing this
  24. s_r
    I'm assuming only one value will be ordered then? Either way I'm in for at least 20.
  25. s_r
    Is that for 680uF or 470uF?
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