DC Coupled Preamp?

Discussion in 'Hi-Fi and General Audio' started by Rushkoff, Mar 21, 2024.

  1. Rushkoff


    Mar 21, 2024
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    I just bought a vintage PS Audio 5.0 preamp on eBay, to use with a newly retipped Denon moving coil cartridge.

    On searching the various forums for information on setting it up, I found this posted in 2005:

    "Also very important- this PS Audio 5.0 Preamp is a DC Coupled preamp designed to work only with an amp that has DC blocking caps, it will destroy your amp or speakers sending DC direct to your amp if it does not have them...realized his after measuring 8 - 12 vdc on pre outputs...I installed some high quality DC blocking caps so now good to go with amy amp with DC blocking input cap or not..."

    I'm using a Classe Cap151 amplifier, which has capacitors throughout its circuitry, but it doesn't have DC blocking caps, that I know of. I asked my cartridge re-tipper, and he thinks the above is likely myth.

    Has anyone else heard of this phenomenon in a pre-amp? I assume adding blocking capacitors would require me to modify the board and solder things in there?
    Rushkoff, Mar 21, 2024
  2. Rushkoff


    Mar 6, 2024
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    Whatever you do, never short/connect the output to earth/ground. It sounds like your preamp operates in Class A and the voltage at the output will be ~ 0 volt, when there is no signal. Under signal condition it swings +/- of this. However, this should drive your load, be it your power amplifier, or in the case of a Class A power amplifier, the loudspeakers. So it is important to make sure there are no connections to ground - directly.

    Look on the internet for the details of your preamp, or consult the handbook/manufacturer.
    Hodges, Mar 22, 2024
  3. Rushkoff

    Arkless Electronics

    Sep 7, 2016
    Likes Received:
    Anything with 8 - 12V on the outputs is faulty! The output would likely be saturated and no sound present with the DC. I wouldn't worry about it if all is working well.
    Almost all pre amps are class A so don't worry about that either;)
    Arkless Electronics, Mar 25, 2024
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