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I am in the final stages of building a fully analog synthesizer. Instead of using +10V, GND and -10V, could I switch these voltages to +20V, +10V, and GND to save weight, bulk, and size of a power supply that has to generate -10V? Would a voltage change generally affect audio circuitry or affect output voltage and ruin other audio equipment?

schematic

simulate this circuit – Schematic created using CircuitLab

Basically, is it the relationship between voltages or amount of voltage in this case? And what's the best way to create +10V on the board, since the solution in the schematic most likely isn't very efficient?

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  • \$\begingroup\$ save weight, bulk, and size of a power supply ... why do you believe that is the case? \$\endgroup\$
    – jsotola
    Feb 15, 2020 at 22:55
  • \$\begingroup\$ What currents are required for each of the rails? \$\endgroup\$
    – hacktastical
    Feb 16, 2020 at 19:34
  • \$\begingroup\$ The whole unit draws 40W at full working load, so I wouldn't think I'd need anything more than 500mA. \$\endgroup\$
    – zvolk4
    Feb 16, 2020 at 22:57
  • \$\begingroup\$ @jsotola I am eventually selling the synths contained in a small metal enclosure. I'm trying to not add more weight to the unit, if I'm gonna be adding any weight I'd prefer to have it in an external power supply. \$\endgroup\$
    – zvolk4
    Feb 16, 2020 at 23:00

2 Answers 2

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It's not a good idea to replace the voltage levels that a system is expecting. Unless you're modding the synthesizer to accept your GND, 10V and 20V. Audio systems generally have a bipolar supply because it's necessary for the opamps inside to properly amplify an AC signal ( you can't amplify a negative voltage if your supply only has a positive rail).

Regarding your second question, yes a voltage divider is a terrible way to source a reduced voltage from. You'd need a buck converter to help you out there. Probably an adjustable one, never came across a fixed 10V buck converter. Be aware of he current rating on it as well.

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  • \$\begingroup\$ In an earlier question I was told that GND, -10V and -20V could be substituted for +10V, GND and -10V. Would this still hold up then? Or do I need to design a power supply with all those outputs? \$\endgroup\$
    – zvolk4
    Feb 15, 2020 at 21:25
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    \$\begingroup\$ @zvolk4 That completely depends on the circuits and power supply. If you have for example audio amp with say RCA connectors and a metal case, and a earthed/grounded power supply, obviously the RCA connector ground and metal casing should be at 0V/earth/ground level. If you replace the supply with 20V PSU, it must not be grounded itself, so you can use 10V level for the new reference voltage. \$\endgroup\$
    – Justme
    Feb 15, 2020 at 21:41
  • \$\begingroup\$ @SimeonR Also op-amps can perfectly work with AC audio signals, amplifying them, and have AC audio output, without a bipolar supply for op-amps. \$\endgroup\$
    – Justme
    Feb 15, 2020 at 21:43
  • \$\begingroup\$ @Justme I know, but does that extend to system that was originally designed with a bipolar supply? \$\endgroup\$
    – SRR
    Feb 15, 2020 at 22:19
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    \$\begingroup\$ @SimeonR Indeed it does not extend -- A circuit designed originally for bipolar supply (such as DC coupled amplifier) can't be powered with single supply. However we don't know what zvolk4 is powering, except for a small snippet from previous question - which is a AC coupled amplifier with ground referenced output, with 0V GND, and two negative supplies, -10V and -20V. \$\endgroup\$
    – Justme
    Feb 15, 2020 at 22:30
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If you don't need much current, it's not too difficult to make the -10 rail from the +10 one using a circuit called an inverting buck DCDC. That would be easier than trying to convert your bipolar design to single-ended, though that could be done as well.

EDIT: ok, 40W, so a good-sized supply. I suggest a pair of 12V switchers, with floating outputs, re-adjusted to 10V, wired head-to-tail to make a split +/-10V supply. Assuming equal loads, the supplies can each be 20W.

12V/20W is a popular LED supply, so you have an off-the-shelf solution, at least for prototyping. This type can also be had as an open-frame switcher, assuming you're willing to do the proper UL work to include it in your enclosure.

If space and cost was paramount and your volume justified it, a custom +/- 10V supply could be designed for your project. Cost in thousands could be less than $10. With some searching, there may be a suitable one already built.

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