Sowter-based TVC

[leoduran]

[Speedskater]

When you re-drew the schematics, why didn't you correct the XLR pin #1 errors?

[leoduran]

Originally Posted by Speedskater

When you re-drew the schematics, why didn't you correct the XLR pin #1 errors?

Kevin,

I'm not sure I understand the "XLR Pin1" errors you're referring to.
Here's my intention (and hopefully the drawings reflect that):
1. Pin1 of inputs are tied together.

2. Pin1 of outputs are tied together.

3. Pin1 of outputs are ALWAYS tied to "Chassis Gnd".

4. Pin1 of inputs are conditionally tied to Pin1 of outputs.
That is, the DPDT-CO "LIFT" switch provides the option to:
(a) leave Pin1 of inputs floating (thus the name "LIFT")
(b) tie Pin1 of inputs directly to Pin1 of outputs (Hard Gnd)
(c) tie Pin1 of inputs via 1.5 resistor to Pin1 of outputs (Soft Gnd)

5. Pin1 of outputs is connected to Pin3 of outputs for single-ended ("RCA") output mode, as selected by the DPDT XLR/RCA switch.

6. And, lastly, for the single-ended (RCA) input case (AUX2 in the revised schematic), RCA common/ground of that input is connected to Pin1 of other input XLR's, and potentially to Pin1 of outputs (and "Chassis Gnd"), via the the LIFT switch.

Can you please explain what I missed?
Thanks.

[Speedskater]

XLR pins #1 should:
a] Be connected directly to the chassis as near as practicable to the connector.
b] Should NOT be connected to other connectors or other components (switches & resistors).
c] Should NOT be part of the audio circuit.

[Speedskater]

What I would do is:
a] Eliminate all the lift switches, all the 1.5K resistors and all the RCA phono connectors.
b] Correctly wire the XLR pins #1.
c] Modify balanced interconnects to gain the other features.

That is if you need an unbalanced input or output, put the correct connector on the far end of a balanced interconnect.
If you really want to dis-connect a balanced shield do it inside the cable connector.

[leoduran]

Originally Posted by Speedskater

What I would do is:
a] Eliminate all the lift switches, all the 1.5K resistors and all the RCA phono connectors.
b] Correctly wire the XLR pins #1.
c] Modify balanced interconnects to gain the other features.

OK, as revised, I did tie all pin1 inputs together, and removed LIFT switches, except for one (which does allow for tying pin1 of the outputs to the inputs; while providing the option to float the inputs... just my preference!).

Originally Posted by Speedskater

That is if you need an unbalanced input or output, put the correct connector on the far end of a balanced interconnect.
If you really want to dis-connect a balanced shield do it inside the cable connector.

Ummh... I do need unbalanced/RCA outputs, so if I used a converter cable (as you suggest), what would that cable do?: (1) tie XLR-pin2 to RCA-signal (2) tie XLR-pin3 & pin1 to RCA-common... which should be effectively what I've accomplished by having RCA outputs, coupled with the RCA/XLR switch (so, I chose to leave that as-is).

BTW, I've made all the changes (but kept AUX2 with XLR's for now), and it all sounds great!


Thanks for the feedback.

[Speedskater]

You might read some of Tony Waldron's papers on interconnects and EMI/RFI interference.

Tony Waldron's EMC ranting and ravings