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I pulled the preamp out of a broken guitar combo amp. The preamp has positive, negative, and ground leads for powering it at +/-25V. I would like to power the preamp with a dual channel benchtop power supply to see if it works. Is there any grounding or safety issue with plugging the DC-powered preamp into a power amp that is powered from an AC outlet?

With nothing connected to any power source, I verified that there is continuity from the preamp chassis all the way to the ground pin of the power amp's plug, so I think everything should be grounded safely. I also verified that the power supply's DC terminals are isolated. So everything seems correct, but I am still learning, so I wanted to double check before proceeding.

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  • \$\begingroup\$ What's the benchtop power supply's make and model? \$\endgroup\$
    – BobT
    Feb 7, 2020 at 4:29
  • \$\begingroup\$ It's a Topward 6603D. \$\endgroup\$
    – meanerelk
    Feb 7, 2020 at 5:15

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It should be fine. Just make sure that:

  1. You select a sensible current limit at the power supply based on the maximum current expected to be drawn by your preamp

  2. You connect one the terminal of each output channel together: -25 GND---GND +25. In a benchtop power supply each output channel is isolated from the others.

  3. Make sure not no mix up +25V and -25V :)

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  • \$\begingroup\$ Thanks for letting me know! I feel much better about attempting this now. The power supply has a serial tracking mode that shorts the - master terminal to the + slave terminal, so I shouldn't have to worry about manually connecting them. \$\endgroup\$
    – meanerelk
    Feb 7, 2020 at 14:35
  • \$\begingroup\$ I'm glad that I could be of assistance, please mark the answer as "accepted" if you found the info useful :) \$\endgroup\$
    – Ken Grimes
    Feb 7, 2020 at 15:52
  • \$\begingroup\$ Test successful! Now I need to build an appropriate power supply. \$\endgroup\$
    – meanerelk
    Feb 8, 2020 at 5:02
  • \$\begingroup\$ Happy to hear that :). Have fun! \$\endgroup\$
    – Ken Grimes
    Feb 8, 2020 at 11:49

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