Stereo and Mono from Stereo source
 

Hi,

I'm currently feeding a stereo line level signal to a 25w ST540 based Sparkfun stereo amplifier (running the main mid range drivers) and a 18w HA13118 based mono amp (powering a single bass driver).

At the moment I'm using a simple resister circuit to combine the left and right channels into a single mono feed for the mono amp, although this does work I do lose some volume and there is a noticeable drop in audio quality from the stereo circuit.

Is there a simple circuit or IC that will let me combine the stereo channels to mono but still feed the full, unaltered stereo signal to the stereo amplifier stage?

Basically, I need to run a pair of stereo speakers and a mono low frequency driver from a single stereo source.

Cheers,
John

i'd like to know how to do this too.

would it be better to use a crossover based around an op-amp or transistor, to isolate the mono bass signal from the stereo signal?

here's one that might work:
monoXover 2-way pre-amp audio crossover

jr

What resisor values are you using? If too low they will add too much load to the system. Something in the region of 1k-10k will probably be OK.

This is the Rane note on how to do it with resistors:
Why Not Wye?

I think that Rod Elliott has an active circuit.
DIY Audio Articles

fantastic!

here's another method, referenced elsewhere on this forum. I'm not sure if this is considered active or passive, since it's not powered, and does not use any transistors or op-amps. It uses an inductor, resistors, and capacitors:
monoXover 2-way pre-amp audio crossover

love that wye article, tho i'm confused about the resistors going from hot to ground. i thought the resistors are supposed to be series?

I think the resistor to ground is just to maintain DC bias when nothing is plugged in. May reduce clicks.