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AUDIO FORUMS >> General Discussion and Support >> A question on stereo to mono summing in the ZSB
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Message started by TomFrei on 05/13/16 at 13:30:22

Title: A question on stereo to mono summing in the ZSB
Post by TomFrei on 05/13/16 at 13:30:22

Couldn't find a section for the ZSB Switchbox, so I thought I would ask it here.

With the stereo/mono switch, how are the two stereo signals summed? I'm thinking of this with respect to this white paper:

http://www.rane.com/note109.html Which basically says that you need more than a simple "Y" cable to sum stereo to mono.

Title: Re: A question on stereo to mono summing in the ZSB
Post by Steve Deckert on 05/13/16 at 21:16:27

Hi TomFrei,

The paper you're referring to presents the source component with a 20K short to ground.

Our amplifiers have an input impedance of 100K so they will work with tube preamps and or tube output stages, so really the last thing you would want to do is load the signal path with a 20K resistor to ground because it would drop the input signal voltage which in turn would reduce the volume of the amplifier. Sonically it swamps transparency, and bogs down dynamics.

When stereo mono switches are installed in a ZSB, we don't present the source components with any additional load, we don't wan't you to hear the switch box! What we do is put a 10K precision resistor in series with the signal so rather than lowering the impedance of the amplifier it's connected to, it actually raises it. This also protects the source components from being shorted together by offering 20K of impedance between channels.

Thanks for asking!

Steve

Title: Re: A question on stereo to mono summing in the ZSB
Post by TomFrei on 05/14/16 at 02:56:27

Steve, I appreciate your answer. I'm in the deep end of the pool here, but I think I understand your approach. I'm going to order a ZSB and try everything out.

If I add a volume switch to the ZSB, does a full volume position = no volume switch at all? If it is passive, that should be the case, right?

By the way, I just received my zen amp a couple of days ago. I'm impressed on first listen. It drives my blumenstein orcas very well.

I appreciate your craftsmanship and engineering.

Title: Re: A question on stereo to mono summing in the ZSB
Post by Steve Deckert on 05/15/16 at 00:47:16

Hi Tomfrei,

Please let us know how that amp sounds in a couple weeks!

Thanks,

Steve