[LAU] On the fly bass downmixing to mono (mpd or alsa)?

[Ralf Mardorf]

On Mon, 2014-02-10 at 08:51 +0100, Ralf Mardorf wrote:
> On Mon, 2014-02-10 at 01:39 +0000, Fons Adriaensen wrote:
> > If you're a bit handy with a soldering iron, all it takes to
> > mix the DAC outputs to mono would be two resistors and some
> > short pieces of wire and connectors.
> 
> If the OP doesn't use tube amplifiers it should look like this:
> 
> http://1.bp.blogspot.com/_BGB-FuSV33o/S7qQlfl_1aI/AAAAAAAAAHY/QO2t7rZP5N0/s400/stereotomono.gif
> 
> When using tube amplifiers you might want to add transformers.

PS:

"Thanks for the useful post. I have one suggestion, though: I think it
might be better to use 1K resistors rather than 10K. The input impedance
of a typical amp should be in the region of 20K. At audio frequencies
(where impedance-matching doesn't matter) it is best if the input
impedance is at least x10 the output impedance. Assuming an output
impedance in the range 100-600 ohms (plausible for an MP3 player
headphone output), that would keep the total output impedance below 2K
which should result in more signal voltage across the amp's input." -
http://marcusmorris.blogspot.de/2010/04/stereo-to-mono-converter-how-to-do-it.html