combine stereo channels to mono

[scales11]

Hello, I am working on a small single speaker for a WiFi radio. I have a simple little mono amplifier:
Class AB 10W Mono Power Amplifier Kit TDA2030

and a soundcard:
http://www.ebay.com/itm/PCM2704-USB..._Audio_Amplifiers_Preamps&hash=item5d3bd8182a
-PCM2704 USB-DAC/ Sound card
-specification:
-voltage:5 V (USB interface),
-Distortion: THD+N: 0.006% (RL > 10 kω)
-Distortion: THD+N: 0.025% (RL = 32 ω)
-Signal-to-noise ratio: 98 dB
-Dynamic range: 98 dB
-Headphone output power: 12 mW (RL = 32 ω)
-Supports sampling rates: 16Bit 32k, 44.1k, 48k


which outputs in stereo. I need to connect the 3.5mm stereo to the mono input for the amp.

Can anyone recommend an easy way to do this?

Thanks!

 

[AndrewT]

just add the L to the R at the output of the source, then you can use a TS (mono) instead of a TRS (stereo/2channels) plug/socket.

But watch the source impedances. The source may object to monoing of the two signals.

If it has 200r to 1k output resistors, it will probably accept shorting the two signals together.

 

[AndrewT]

A more complicated way is to use a summing stage (an inverting opamp does this) to ADD the two outputs ready to feed into the mono amplifier.

 

[scales11]

Thanks for the advice!

I have updated the original post with the soundcard info (it links to an ebay page, but for now it does the job).

I will see if I can draw up the schematic and reply, just to be sure I understood.

 

[AndrewT]

Have you downloaded the 2030 datasheet and checked that is what you want/need?

The headphone output is designed for 32ohm drivers.

I would expect a USB powered headphone amp to use either no output resistors or very low value resistors to minimise the power loss out of the output stage.
Add a couple of 100r resistors for your monoed output.

 

[scales11]

No, not yet. I will start there!

 

[rayma]

soundcard outputs in stereo. I need to connect the 3.5mm stereo to the mono input for the amp.

Check Windows or the sound card data first. Otherwise a simple mixer, active or even passive with two resistors should work.

 

[DF96]

Has the forum search function stopped working? This question crops up at least once a month.

 

[scales11]

I am sorry to post it then. I did search and did not find an answer. Perhaps I searched for the wrong terms...