Sowter-based TVC

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Ummh...

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.
 
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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.
 
To the "XLR Pin1 police"...

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!).

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.
An externally hosted image should be here but it was not working when we last tested it.
 
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As shown in the updated schematic, I've added:
1) Input: Gain selector switch (0db/+6dB)
2) Output: RCA connectors & associated mode switch
3) Soft/Hard Grounding options (LIFT)
An externally hosted image should be here but it was not working when we last tested it.

Did you run any tests on this device? I'd be curious as to bandwidth, phase shift, distortion, noise, etc.
 
Jensen Transformers, at least, don't agree:
http://www.jensen-transformers.com/as/as035.pdf

Note the ground lift switch.

I must admit not being an expert on ground issues, and optimal ground wiring configurations (especially with respect to XLR input and output connectors, and combining that with single-ended RCA connections as well).

So if you, or anyone else on this thread, would like to propose an alternate wiring diagram, please do so (a picture of the updated diagram would be great)... I would certainly appreciate your contribution.
 
I must admit not being an expert on ground issues, and optimal ground wiring configurations (especially with respect to XLR input and output connectors, and combining that with single-ended RCA connections as well).

So if you, or anyone else on this thread, would like to propose an alternate wiring diagram, please do so (a picture of the updated diagram would be great)... I would certainly appreciate your contribution.

Generally, you should connect all XLR pin #1's to the chassis at the connector unless you need the feature of a ground lift. For the RCA connectors, they should not be connected to chassis ground at all. They get connected to the transformer in the same way as pins #2 and #3 of the XLR connectors.
 
It is best by far to use a very short wire directly from the XLR #1 pin to the chassis. An excess wire inside the chassis just acts as a noise antenna. Any hybrid or open shield connect at the receive end should be done in the cable connector.

This quick drawing is how I would do it.
Note: The unbalanced shield connections may not all be necessary.
 

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Ouch...you may run into ground-loops/hum-problems by connecting all pin-1/rca-shield to chassi. I would as a simple sollution use a 4,7-10 ohm resistor between all pin-1 and chassi(ground), just to "break" any loops. Same for RCA-shield. Have worked for me...

Arne K
 
Ouch...you may run into ground-loops/hum-problems by connecting all pin-1/rca-shield to chassi. I would as a simple sollution use a 4,7-10 ohm resistor between all pin-1 and chassi(ground), just to "break" any loops. Same for RCA-shield. Have worked for me...

Arne K

No, it's only a potential problem tying the RCA shield to chassis since balanced audio has zero current in the shield whereas single ended does have ground current. It's normal practice I believe to insulate the RCA jack from the chassis. Since there's a transformer in here, both the RCA hot and ground can be directly connected to the transformer in the same way that pins #2 and 3# from the XLR are connected, without touching any ground or chassis. Of course, the RCA ground is connected to a ground in the upstream equipment, and the RCA ground is also connected to a ground in the downstream equipment. Transformers are very useful for breaking ground circuits and preventing hum from ground loops.
 
schematic rca xlr

maybe this thread is too old....this the schematic I would like to use to have rca and xor input and rca and xlr output....something has already been tested....maybe someone is interested or can give his advise
 

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