Installed & wired up
Single core copper wire power cables made up from high grade CAT6a data cable. (23AWG)
For the I2S bus, mil-spec OFC silver plated, Teflon insulated cabling is used. (22AWG)
The USBtoI2S module is implemented in completely isolated mode with two independent low noise regulated power supplies for the USB side & re-clocking side which are fed by a potted toroidal transformer from two (2 x 5VA) separate secondary windings. This provides better noise immunity from the computer environment that's fed on the USB side allowing for a cleaner re-clocked I2S bus feeding into the TDA1541A.
Danny,
I have no interest in TDA1541 any more (or zenclock) so if I may make some suggestions:
If you are switching I2S between spdif receiver chip and USB bridge, the USB bridge will have way lower jitter, especially when it is isolated and will sound better IME.
As such I would be optimizing the setup for USB bridge as the spdif will never be as good. My recommendation is to mount the MUX chip close to the USB bridge
so you can get good grounds. Every cm of wire will make a difference.
You have specced 74HC157 for MUX (switching) but for lowest jitter 74ACT157 (AC logic) or possibly even better SN74LVC157A (LVC logic) is better.
If you check the data sheet the prop delay on ACT is less than 1/2 that of the HC and the LVC is even lower. LVC is recommended for 3.6V operation but
absolute max is 6.5V so should be OK at 5V.
I have found that these USB bridges are very finicky with sound so everything will matter.
As far as silver cable blah blah.... all the other stuff matters much more.
Now the last (and worst part) of the story:
The JLsounds USB bridge you have there is an old model which have since been updated.
The older model has discrete (Flip Flop) re clocking of all I2S signals which is really good. The newer on does I2S re-clocking inside
what looks like FPGA chip and only master clock OP comes directly from actual clock. This is OK for new Delta Sigma DAC's because they
use Mclk for timing reference.
Older multibit DACs like 1541 and 1704 use I2S bitclock for timing reference so I feel the newer USB bridge is possibly not as good for
old multi bit DACs.
I have 2 PDX DAC's on my bench ATM, both have been upgraded with JLsounds USB bridges. One has the older one (like yours)
and the other has a MK3 newer version. I have to say they definitely sound different. They newer one is cleaner and more clinical
and the older one is more musical and ultimately more listenable.
I'm currently playing with power supplies and other components etc etc to see if I can get the newer one to sound more musical
and engaging. It's very frustrating. The old JLsounds bridge was *Killer* and he went and changed it.
Anyway, good luck.
Terry