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Daisy chaining pre/power via switched power out

Discussion in 'd.i.y.' started by booja30, May 22, 2020.

  1. booja30

    booja30 pfm Member

    I recently built a DiyAudio/Pass F5 class A amp that includes slow start and speaker protection/delay. It has a totally blank 10mm aluminum faceplate with no power switch (the switch is on the back next to the IEC inlet). I'd rather not put a switch on the front since I don't really love the little round thingies that are popular for DIY these days.

    I'm about to build a preamp (Salas DCG3) and was thinking about my old NAD 1600 tuner/pre and Quad 34 pre that both had switched main outs on the back so you could switch on/off an amp, CD, whatever, via the preamp power switch.

    On the preamp I would put the an opposite gendered (female?) IEC socket right next to the inlet (male?) socket. The IEC inlet ground would go to the chassis and also to the IEC switched out. The IEC inlet power in would go to the power switch (probably a Lorlin rotary DPDT) and then to the preamp transformers AND to the IEC switched out. Then I'd use a male to female IEC cable to power the amp.

    Since the amp already has slow start and ~5 second speaker delay, I don't think there should be a problem having them switch on at the same time via the preamp's power switch.

    Does this sound rational and sane? :)
  2. Michael J

    Michael J pfm Member

    Watch out for a ground loop... it's the reason for some switched outlets to be just two-pin live/neutral and the earth/ground connection is carried by the signal interconnect.
  3. booja30

    booja30 pfm Member

    Good thing to consider.

    When I think about it, is the situation that much different than when the amp and pre are plugged into the same power strip, for example? Either way there's a ground connection between the two via the mains, whether it's direct or through the power strip.

    Also, the amp has the PSU/audio ground 'lifted' from chassis ground via a CL60 thermistor and diode bridge in parallel. And I haven't even really thought about the preamp build yet but I think I might have read that its PSU/audio ground can be left floating so that it only shares signal ground with the amp and source?

    I'm too new at this to really know what I'm talking about. :)
  4. Michael J

    Michael J pfm Member

    Double-insulate everything... and draw a couple of squares one inside the other on the cases to look proper 'n' stuff.
    booja30 likes this.

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