balancing in an unbalanced world - 4 simple options but which one

[davidismynaim]

I am awaiting my delivery of a single Tortuga LDR v25 preamp board (I know it doesn’t amplify – before anyone picks up on the term preamp). I will be encasing it and wiring it up to input and out sockets. I opted for a single board rather than the balanced 2 board option for cost, size and complexity reasons. However, I would rather not use RCA phono connectors, because I am feeding from a DAC that has balanced out XLR. The pre will also output to my DBX Venu360 (also XLR) that does digital crossover into two sets of power amps (also XLR) to drive a pair of hybrid ESLs.
I like XLR plugs from an engineering standpoint and have all the necessary balanced quad core cables, so don’t really want to rip them apart to make balanced to RCA cables. Finally I also have some nice metal Neutrik male and female sockets waiting to be used.
So my plan is to wire the XLR sockets and plugs in the amp, but treat them as single ended, as if there were RCA phono sockets.
There are many views on how best to achieve a balanced out to unbalanced in and unbalanced out to balanced in. My research based on this https://crookwood.com/blog/dealing-w...in-the-studio/ site leads me to the following plan, though I have to confess the more I think about, this more confused I get. Especially as what I am doing is a little different, in that I am trying to preserve standard XLR cables and get the right result by correctly wiring up internally. The DAC is a Chord Hugo TT, metal chassis with wallwart DC power (not sure if that makes it a floating or mains earth, I am guessing floating) The DBX is a pro unit with earthed mains in, so I am assuming this is a mains earthed unit. It also has a pin lift that can help with earth loops)
Here are the choices, as I see it:
this is the same for DAC input or Output to DBX crossover

Note, both in and out XLR male/female mounted sockets on a plastic backplane.
Input or output option 1:
Pin2 (Hot) to the +ve input/output points on the amp. As if it is the middle pin of an RCA phono.
Pin 3 (cold) left disconnected
Pin 1 (shield) routed to the single start earth point in the pre. as close to the socket as possible.
Socket earth tag not connected to any metal
Option 2
As option 1, but tie Pin 1 and 3 together
Option 3
As option 1, but connect socket earth tag to pin 1
Option 4
As option 2, but connect socket earth tag to pin 1.

Please vote on the options or offer a better approach.

Thank you in advance for your collective wisdom

[Barry]

I would choose Option 1 for both input and output.

You could use Option 2 for input, but not for the output.

Taken from https://theartofsound.net/forum/show...dio-Connectors:


If XLR connectors are to be used in an unbalanced system, they are wired as follows (in the case of an unbalanced source connected to a balanced input):

1. ground or shield
2. line
3. connect to pin 1

However owing to some ambiguity over the use of pins 2 and 3 mentioned above, some unbalanced systems have the line connected to pin 3, and pin 2 is connected to pin 1.

There is an addition difference in convention between American (NAB) and European (CCIR) usage. The American convention is to use female XLR connectors for sources, whereas in Europe, male connectors are used.

In the case of a balanced source connected to an unbalanced input, the above wiring scheme will cause one half of the output to be shorted. In many cases this will not matter because a low value resistor (typically 10 - 100 Ohm) is wired in series with the output, but this is not always the case and should not be relied upon. The best course of action is to wire the centre pin (signal) of the RCA connector to pin 2, with the outer (return and screen) wired to pin 1.Thus:

1. return and shield
2. line
3. (not connected)

A full and comprehensive discussion of the various options available, as well as best way to avoid earth loops in a system of components using a mixture of signal connectors (both balanced and unbalanced) has been carried out by Rane Sound Systems, and is described in their technical note 110: http://rane.com/note110.html.