I'm new to diyAudio, so I'm not even sure I'm posting in the right forum. I've come up with an op amp-based design for a 4 or 6 input microphone mixer, and I'm looking for any tips on the design. I'm attaching a schematic.
The mic input stages are differential amps with 40 dB gain, and these are combined in a summing stage with unity gain per channel. For the microphone level output, I'm planning to use a Jensen transformer, the same one that's used in DI boxes.
I didn't use any caps in the design. Should there be a blocking cap before the summing stage, or maybe before the transformer?
Is the overall gain appropriate for a mixer with mic-level output? Any ideas will be appreciated.
Thanks!
The mic input stages are differential amps with 40 dB gain, and these are combined in a summing stage with unity gain per channel. For the microphone level output, I'm planning to use a Jensen transformer, the same one that's used in DI boxes.
I didn't use any caps in the design. Should there be a blocking cap before the summing stage, or maybe before the transformer?
Is the overall gain appropriate for a mixer with mic-level output? Any ideas will be appreciated.
Thanks!
Attachments
Hi,
Your mixer or this :
Behringer Xenyx 502 Mixer at Gear4Music.com
What would you choose ?
or this :
or this for 4 balanced mic inputs :
rgds, sreten.
Yuor a lot better off buying and then modding if quality really matters.
Your mixer or this :
Behringer Xenyx 502 Mixer at Gear4Music.com
What would you choose ?

or this :

or this for 4 balanced mic inputs :

rgds, sreten.
Yuor a lot better off buying and then modding if quality really matters.
Last edited:
I would put a capacitor after r9 to r12 otherwise you will be amplifying any dc offsets.
I don't know about the inputs, it depends if the mic's give out any dc offset.
I have always put coupling capacitors on the inputs and outputs of my mixers.
I don't know about the inputs, it depends if the mic's give out any dc offset.
I have always put coupling capacitors on the inputs and outputs of my mixers.
Google 'differential amplifier'
Whoops sorry forgot to add about adding a resistor to make inputs differential.
Thanks Nigel. I see that I am missing the resistors from the non-inverting inputs to ground on the differential amps. I'll add those, and also appropriate capacitors to block the DC offsets.
optional
Could you take out the T1 and R15 to make it a "line" output mixer? also could this be hooked straight to a power amp?
Could you take out the T1 and R15 to make it a "line" output mixer? also could this be hooked straight to a power amp?
Could you take out the T1 and R15 to make it a "line" output mixer?
also could this be hooked straight to a power amp?
Hi,
Yes, but there is still a lot missing from the schematic.
Buy and mod if needed is my attitude.
rgds, sreten.
Thanks. I am simply working on something for a drummer to hear guitars and vocals. Loud and close to the touch for adjusting while playing. Sound quality is just not that important lol.
Thanks. I am simply working on something for a drummer to hear
guitars and vocals. Loud and close to the touch for adjusting while
playing. Sound quality is just not that important lol.
Hi,
You will need to give a lot more salient and accurate information
before anyone can work out the best approach to your problem.
Foldback is not a new problem and there are lots of approaches.
rgds, sreten.
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