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preamp mods

Discussion in 'Amps and Cabs [BG]' started by hrgiger, Apr 10, 2009.

  1. hrgiger


    Jan 11, 2009
    Anyone here ever (or know anyone that does) mod their preamp? Not the in-bass one but the in-rack one. I know that audiophiles like to tinker with their amps etc. (some making whole new input boards) and thought maybe some of the older preamps could benefit from some tweaking. I've read Passinwind's posts - have you done this at all? Take the Yamaha PB-1, is there anything that could be done with that to improve it? It's great the way it is, I was just wondering...
  2. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    The opamps are very old tech 4558s, so you might get some benefit from replacing a few in critical stages. Not sure about power supply or stability issues though, as I've never even seen or heard one of these Yammies.

    To answer the rest of your question though: have I ever not modded any of the preamps I've owned? Doubtful...:cool:
  3. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    Be advised that even if the op-amps are socketed and you find pin-compatible replacements, you can't just drop 'em in.

    Doing so runs the risk of ultrasonic oscillation, which can damage the preamp and power amp. You'd need to do some testing and possible component replacement to avoid this condition.
  4. I've done this with a mixer that used 741 op amps. Changing them out to more modern singles did not make all that much difference in noise levels. The active elements are only part of the story when it comes to noise.


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