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mike stehr

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Everything posted by mike stehr

  1. 12AX7 in a SRPP configuration. I can't even recall what SRPP means...series resistance push-pull? Series reactance push-pull? Totem pole... I ginned up a 6SL7 in SRPP to drive a 71A. It sounded nice. I would think it would drive a 45/2A3 as well.
  2. I have a 331A, which I think is the same unit but without the mode switch or high pass filter. It is in good working order as it was acquired from a retired audio engineer. I have a HP 654A test oscillator as well. While it does have an issue, (dodgy range switch?) if you let the unit sit powered up for a few hours it will work fine and puts out some beautiful sine waves. I'm currently trying to revive a HP model 205AG audio signal generator, which is an older Navy unit. Like you mention, the older HP distortion analyzers are good for use with tube amplifiers.
  3. "Pure hand-made, the whole machine is welded with scaffolding." Must be a tall amplifier...
  4. McIntosh MC275 MK VI Clone | Audiokarma Home Audio Stereo Discussion Forums
  5. Didn't the Chorus II use a non-polar electrolytic for the 6uF capacitor in the midrange section of the network?
  6. The evaluation board for TI 3255 has a reset toggle switch if I recall...
  7. I used a stepped bit. I have a smaller one, and a larger one that maxes out at 1-3/8". How often will one need a 1-3/8" chassis punch/die? They can leave a nasty burr on the bottom of the piece being drilled. But if one can flip the piece over and get at the burred side, one can use the bit to de-burr the hole. I think the key is to keep the piece being drilled as anchored as possible along with the press. (I have a cheap tabletop) The bits are aggressive, especially larger one.
  8. When you mentioned 10 watt mono amplifiers, I thought you were referring to what I have. Those are parallel push-pull 6V6, (142AA?) each at 20 watts.
  9. I have some of them. I think Woody does a pretty good Freewheelin' Franklin. My apologies for throwing the thread all out of whack...
  10. Most my inspiration is with the likes of Mad Magazine artists like Bill Elder, or Freak Brothers Gilbert Shelton, or Robert Crumb. Or the CarToons comix artists...
  11. Breadboarding with a DC tube power supply is one way to build and test tube amplifier circuits. One is limited by voltage/current output of the supply, however.
  12. A different approach...
  13. While there is nothing wrong with PCBs, I think soldering point to point is something that should be encouraged. So maybe if one down the road wants to restore a vintage tube amplifier, they have the necessary skill to solder PTP with these older circuits.
  14. 6V6 push-pull could fall close to the 15-watt category, and could be possibly done on a budget...
  15. Working on this for a friend... Old school Dynaco ST-70, with cloth leaded OPTs, what appear to be the original EL-34 output tubes, and the VTA version II PCB.
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