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About JoaMat

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  • Birthday 12/26/1955

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  1. The ultimate DIY? A Stax SRM-T2!

    Two months have elapsed. The modifications work alright. Almost forgot what I’ve done. Schematic below shows the difference between the servos.
  2. Blue Hawaii BJT Build thread

    Of course offset servo is not needed with the Blue Hawaii. Blue Hawaii has been around for a long time. Manufactured and sold by HeadAmp Audio Electronics to many satisfied customers. Been given highest possible remarks by professional tester. As DIYer I do feel entitled to do any modifications to any amplifier I like. Doing so with a Blue Hawaii feels like a privilege. I’m very grateful for the Blue Hawaii and can’t thank you the designer enough.
  3. Blue Hawaii BJT Build thread

    I’ve used a couple of different offset servos with a Blue Hawaii. I found them very useful. If you like 45 volts drift you should avoid all kind of servos.
  4. KGSSHV Carbon Build Thread

    Nothing wrong with Servo 2 - the only servo you need.
  5. goldenreference low voltage power supply

    Just finished my morning coffee. Seems to be an interesting day. Thanks a lot Kerry.
  6. goldenreference low voltage power supply

    As I understand LT1021 is used in shunt mode in GRLV. From datasheet I get the impression that the 5 volts version of LT1021 is not meant to be used in shunt mode. As I recall one builder once tried a LT1021-5 in a KGSShvPSU without success.
  7. After a second thought I’m beginning to believe that it shouldn’t make any difference at all. After the diodes the “output” should be the same after swapping the leads from transformer, or?
  8. Thanks. This is a very long shot but what happens to the hum if you swap one of the AC from transformer to rectifier diodes (HV900). Will there be a change in hum if the AC to the two “rectifier bridges” are in 0 degree or 180 degree phase?
  9. Isn’t that an earlier PSU version with the long zener string?
  10. goldenreference low voltage power supply

    LTspice indicates a need of another 3 V unregulated. Plus more diode switching noise. Still a golden reference device or is it a silver line thing?
  11. goldenreference low voltage power supply

    Thinking loud. What if a simple CCS north of the 9 volt Zener as below? Will certainly make a tiny smd version layout looking cleaner.
  12. goldenreference low voltage power supply

    Milled this today – negative regulator. Shot by USB camera approximately magnitude 20. Using a 15th end mill, minimum clearance between pads, traces etc. is 16th. There are 5 vias 12th and they actually hit the bottom pads quite accurate. CNC machine is a fantastic gadget
  13. goldenreference low voltage power supply

    Did this today. Positive golden reference regulator. I managed to make a Kerry device in my kitchen but I think he is pushing the envelope now. I’ll try to make negative regulator as well and if this succeeds I’ll put them in a T2 PSU. Dark picture so you can see the small red LEDs on the board. Hope the small GRLV hit the market soon.
  14. goldenreference low voltage power supply

    Great work! Reason for KST42/92 replacing PBSS4140DPN? - need for higher collector-emitter voltage?
  15. Blue Hawaii BJT Build thread

    470R resistor, isn’t that the grid resistor? If so, is 2 W really necessary? From simulation I get some 2 – 4 mA through the resistor. In my Grounded Grid with mostly surface mounted devices I use 0805 chip as 470R - 1/8W and they seem to work.