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denimboy 4th February 2013 01:13 PM

How can I split a mixer bus?
Here's what I'm working with

3 Stereo Input Channels

1 Stereo Master Output

1 Stereo Headphone Output

Originally, all 3 channels are wired to a bus that feeds Main Output circuit and Headphone Output circuit simultaneously.

I want to modify the circuit so Channel #3 feeds Master Output but NOT Headphone Output.

I'm trying a configuration with switches but in the end, Channel #3 signal reaches Headphone Output through Master Output bus->Channel #1 path->Headphone Output.

I'm trying to be as clear as possible. I have a schematic but it's a pdf.

gmphadte 5th February 2013 06:27 AM

You will have to connect headphone input to the mix of ch1 and2 and then feed ch3 to the master.

I don't know how useful is my suggestion.

Gajanan Phadte

denimboy 5th February 2013 10:59 AM

Yes, that's what I'm trying to do. Are you suggesting I make a mix of 1 and 2 through a buffer and feed the buffer output to Master input where I add channel #3 ? Would that block signal from channel #3 to reach channel 1 and 2 path (to headphones)?

If that makes any sense...

sofaspud 5th February 2013 11:09 AM

You can use Adobe Reader to Take a Snapshot (from the Edit pulldown menu) to save as a graphic file. Or use Ghostscript to save the page as a graphic file.

denimboy 5th February 2013 11:47 AM

sofaspud 5th February 2013 09:06 PM

Your post #3 is the only answer I'm aware of. 1 and 2 go to the Headphone Out and to a buffer. 3 gets added after the buffer and 1-2-3 go to Master Out.

denimboy 6th February 2013 12:15 PM

The idea behind this is to use Headphone Output as an Aux Send for channels 1-2 and use channel 3 as a Return.

denimboy 11th February 2013 11:47 AM

I know this is ultra basic stuff but I haven't use op amps in awhile and I must make sure I get it right.

I will use the same 4560 as the original design. The only thing I'm not sure is should I use an input resistor (like figure B) and which value to keep everything flowing properly?

FYI, the buffer will be connected between Channels ouput (Ch.1 = R5 for Right and R10 for Left) and Master input (R40 for Right and R37 for Left). See schematic I posted before.

denimboy 11th February 2013 05:52 PM

Here's the modified schematic. Now I've having a hard time figuring out if the op amp buffers need bias resistors, in/out capacitors, etc.
All I want is a 1/1 reproduction of the signal. No amplification.

cbdb 11th February 2013 06:08 PM

you dont need the extra buffers, the summing amps are all you need, you just have to rewire the inputs to the summing amps, omitting channel 3 from the head phone amp. Are you sure the section wth the discrete transistors is not the HP amp?

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