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I'd like some suggestions for some passive differential to single-ended speaker audio level matching circuits for a particular situation where an external power source for an amplifier is not available. Ideally as little as possible attenutation from input to speaker, but essentially what is a common simple practice in the audio world that one might consider ?

The circuit below is what I had in mind, with the input from an external amplifier for driving a small speaker or a headset speaker. The actual speaker on the far-end is always ground-side connected. The input however could be differential or single-ended so having an option to short one of the 16 Ohms resistance with a MOSFET or a depletion mode analog switch would be great but not essential...

possible differential to single-ended passive match

Any thoughs would be greatly appreciated ... regards, Mike

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    \$\begingroup\$ Use an audio transformer. \$\endgroup\$ – Andy aka Jun 11 at 10:30
  • \$\begingroup\$ Do you have one signal source (one power amplifier), and you want to drive the speaker with it? Or do you have two signal sources, of opposite phase, and you want to drive the speaker? (this is normally called a bridge arrangement). \$\endgroup\$ – user69795 Jun 11 at 13:47
  • \$\begingroup\$ Hi, yes the amplifier has BTL outputs, and the SPK+ is tied to the load (could be from 8 - 32 Ohms depending on the headset, with < 200mW max output). \$\endgroup\$ – citizen Jun 12 at 12:00
  • \$\begingroup\$ I'd normally leave it like this, with the SPK- terminal to a dummy load. Sure half the power is wasted, but most headsets are already configured like this with one end tied to common ground. I though I'd revisit this to see if there may be a more clever/efficient way to do it ... \$\endgroup\$ – citizen Jun 12 at 12:03
  • \$\begingroup\$ And BTW, most available amplifiers < 1W that I found are mostly made to drive in BTL mode. Not much choice otherwise these days ... \$\endgroup\$ – citizen Jun 12 at 12:04
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Try removing the resistors and connect the ungrounded side of the speaker to SPK +.

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  • \$\begingroup\$ Hi, this is what I have now - SPK+ to speaker terminal, and SPK- going to a dummy load of 16Ohms. It's the most immediate way of doing it, but I was thinking there may be another way of doing the connections without the loss of half the signal ?!? If this is not the case then I need not worry about it as this would work out just fine. Thanks for the suggestion. \$\endgroup\$ – citizen Jun 11 at 12:14

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