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  1. PRR

    Help understanding cathode bypass capacitor

    Why would there be an "ideal" size, short of infinity? Why can't we have infinity? Are you asking single-ended or push-pull? If P-P, class pure-A or tipping into AB? These are very different cases. Are you asking for clean sound way less than clipping? Or a "nice" transition into and past...
  2. PRR

    suggestions for simple headphone amp (OPA1688 / 1622)

    For hearing-loss? Audiometers "usually" generate tone at high level, then a calibrated passive pad to reduce to headphone level. The reasons are also historical. But you should not need and do not want ANY gain to measure hearing thresholds. TDA2822 (and similar) run about 2uV and gain about...
  3. PRR

    Something to lighten the mood

    Did I already post this?
  4. PRR

    Examples of adjustable self bias 300b SE?

    But not stated here? I had to make it up. DigiKey: 91R1A-R16-A15L $6.36 91A1D-C24-A15L $7.45 91A1A-B28-A15L $8.19 91U1A-T22-A15L $8.19
  5. PRR

    LM386 Amp with Dual Inputs - need resistors or something?

    No volume- the LM386 does not have excess gain for e-guitar, the on-axe knob suffices. The LM386 inputs are nominally at zero VDC, "no pop". Yes, they float to a few mV but after a few hot licks at the blazing half-watt level, your ear is not bothered. Leo Fender or friend devised a...
  6. PRR

    Something to lighten the mood

    As they say in Boston, there is no U in harbor, but sometimes there is T.
  7. PRR

    Little Bear T12 schematic

    Gotta be a double-sided PC board, SMD on the other side.
  8. PRR

    Newbie wanting Bal/Vol control on an old TDA2003 bridged amp

    Yes.
  9. PRR

    Opinions on this headphone amp circuit? Is it worth it an external one?

    https://www.diyaudio.com/community/threads/opinions-on-this-headphone-amp-circuit-is-it-worth-it-an-external-one.396405/post-7282505 Yes, almost nobody needs +/-17V. My professional dreadnot hotboxes were closer to +/-11V output and I never clipped them even in the room recording a brass ensemble.
  10. PRR

    Something to lighten the mood

    Why can’t you hear a pterodactyl going to the bathroom? Because the “P” is silent!
  11. PRR

    And what did we buy today?

    Amazingly, still in business, still selling a near-identical tool (they turned the brandname around). https://www.abebooks.com/servlet/BookDetailsPL?bi=31435035960&cm_mmc=ggl-_-COM_Shopp_Rare-_-_-keyword= "..for over 100 years. With an extensive catalogue ....Moore & Wright continues to supply...
  12. PRR

    Something to lighten the mood

    I'm on the gin and tonic diet. So far I've lost 2 days!
  13. PRR

    OS Creating Keyboard Malware

    He is a long-time member. Maybe TOPS-10?
  14. PRR

    And what did we buy today?

    Dividers. Not compass. It does look like it has done a lot of scribing.
  15. PRR

    What are you Watching?

    Ah, I found a video which is disturbing but interesting. A Taxidermist stuffs and mounts a peregrine falcon. He skims lightly over stuffing insulation foam and wires up the limp bird skin, then spends much time grooming feathers and pose. This peregrine lived its whole life in captivity.
  16. PRR

    What are you Watching?

    Another big bird is the Peregrine Falcon. We killed them with DDT, oops, and re-introduced imported birds at Jordan Cliffs and The Precipice in Acadia National Park, above Bar Harbor, Maine, USA. Today (as in most years) they closed the trails around the nest site so the birds can breed in...
  17. PRR

    Op Amp gain calculation

    It is not just resistance. What is the Reactance of C4 10nFd? 160k ohms at 100Hz, 16k at 1kHz, 1,600 ohms at 10kHz. So just C4 and R2 define a gain of like 16,000/390 or 41 at 1kHz. I have grossly over-simplified but the trend is like EdGr says: sloping over the whole audio band with a wiggle...
  18. PRR

    Help with Distortion Measurements

    Jealous.
  19. PRR

    Question about power supply rectifiers heating

    Is it the same transformer? (Not that it matters-- we can never find the exact same part.) https://media.digikey.com/pdf/Data Sheets/AlfaMag Elect PDFs/L01_Series.pdf 15 VA Part Number = Secondary, No load voltage, Resistance 20°C L01-6354 ==== 2 x18V, 417mA 2 x22.2V, 2...
  20. PRR

    Audio Research phono stage

    Thank You for saying which "Audio Research phono stage". Link would be nice too: https://audioresearch.com/wp-content/uploads/2021/08/SP10_Manual_Schem.pdf Snippet: There is also a computer-drawn diagram but it seems to be copied from the 1982 hand-drawings. Yes, the lower heater is shown...
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