How to build a simple balanced mono line mixer

[jandalo]

Hello All,

I would like to know if someone can help me, I need to build a very simple mixer, with two balanced inputs with phase switches and a balanced mono output. the purpose is to mix two signals from two mic preams before sending to tape as a mono signal. I would like this design to be very simple, since I'd like to keep the signal as clean as possible.

- Would it be possible for this mixer to be passive? (I understand that being balanced this might not be possible)

- Can I avoid the use of op-amps? (since I don't really need the signal to be amplified)


All help would be very much appreciated, I have been looking around but all I can find is unbalanced mixers. Thanks to all in advance.

 

[kmaier]

Suggest you consider a pair of Jensen line transformers. Will allow balanced in, unbalanced out, phase inversion via a switch and can do passive mixing on the secondaries using two potentiometers and summing resistors. Also provides complete isolation.

http://jensentransformers.com/datashts/11p1.pdf

Regards, KM

 

[jandalo]

Thanks KM, although I think that this is not exactly what I need, both I/P and O/P need to be balanced (needs to receive and transmit a balanced signal) also, would you recommend a passive design or would an active, more complex one be better?

Thank you!

 

[kmaier]

The transformers can easily provide a balanced output as well, so you still have that option. Passive should still work, but you lose overall gain. If you need unity gain or more you would be better off going active. You can also use a transformer for output which would allow a balanced output. It all gets down to how you prefer to do this. High quality transformers are not cheap, but if you're looking to preserve quality first, they are tough to beat. Poke around the Jensen site and examine some of their application notes, some great resource material.

Regards, KM

 

[jandalo]

I will have a look and let you know if I find something suitable. Thanks a lot.