Twisted Pear 4:1 Mux Demux Switch

[juancho]

Hi,
I'm having problems with a TW 4:1 mux /demux switch and hope someone can help! I'm using the switch to switch between Optical, SPDIF and AES.

Everything works perfectly until I connect the AES input. Then the output from the AES input comes out whatever source position is selected and any other source does not come out.

I'm using an impedance /voltage converter circuit for the AES input but I get the same problem when using a Canare conversion transformer.

I tried connecting the AES input to another input position and the same thing happens. Anybody any clues as to what's happening?
Thanks
David

 

[BrianDonegan]

Can you sketch out a diagram of the AES connection? AES is usually differential, so would require two lines, but I assume you are converting to a single-ended signal with the transformer. Typically, problems arise when signals are not sharing a ground into the MUX chip.

 

[juancho]

Hi,
Thanks for the reply. I have used both a resistor output /impedance adapter and a Canare transformer adapter with the same results. In fact, I checked yesterday and the same thing is happening with SPDIF input as well.
David

 

[BrianDonegan]

A quick sketch would be helpful

 

[juancho]

Here's the resistor version. The Canare transformer is a transformer solution

 

[BrianDonegan]

And you are connecting the output GND to a shared ground (including power) on the MUX board?

 

[juancho]

In terms of grounds:
1. The MUX power ground is shared with the TW optical board
2. SPDIF output ground connects to the Buffalo 11se Pro DAC Board spdif input
3. AES, SPDIF and Optical grounds connect to the respective input grounds on the MUX Board
Thanks