Passive and balanced monitor switch. Impedance match with my equipment

[Piscolabis]

Hi!

Im just building a passive and balanced monitor switch with relays and headphone amp.
But Im not sure of the value of the stereo volume pot to match with my actual system:

Interface output impedance 100R
Speaker input impedance: 20K

A Pot as a U-pad with two input resistors may work?

I don´t have to much space for rotary stepped attenuator

Any help could be helpful,
;D

Nacho

 

[Piscolabis]

:'( I am thinking on use a 1k dual log potentiometer for de volume.

Could that work?

please some Help!

 

[emrr]

1K would bridge the source Z sufficiently, standard voltage divider is fine, balancing may or may not matter.

 

[joaquins]

It will work, please do not connect the center of R2 to ground, it just harm the CMRR and noise performance and do nothing good for the signal, it's already referenced to some ground...

JS

 

[ruffrecords]

Here are a couple of designs for balanced attenuators. The right hand one can be used with a 2 gang 1K pot to make a low cost stereo balanced level control.

https://drive.google.com/file/d/0B_n67A1hN3qtV2xnOHpLc1pUNEU/view?usp=sharing

Cheers

Ian

 

[Piscolabis]

Thanks a lot for the answers! 8)

Do you know some place to buy a proper 1kA dual  potentiometer?

I find this Alps of 10kA http://www.ebay.com/itm/271946040284.

Cheers!!

 

[ruffrecords]

BY 1KA I assume you mean log or audio taper. Please note there is no universal meaning for A, B and C suffixes to pots. To some manufacturers A means linear and B is log and vice versa.

http://uk.farnell.com/vishay-sfernice/p9a2r100fisx1102ml/pot-log-dual-1k/dp/8791376

Cheers

Ian

 

[Piscolabis]

Thanks a lot for the A B pot info ,Ian ;D

I will find some dealer near from my country to buy a precission potentiometer.

Cheers

Nacho