Which circuit to choose to balance&unbalance in the console "Insert" section?

[Monte McGuire]

re SSM2412 - yes - I recall a tube / batch where the test kit measured the output THD+N at around -75dB instead of the usual -89.9dB

I have to point out that the -90dBV typical noise of a 2142 (and any of the ground cancelling drivers) is about 20dB more than what one gets with a simple buffer and inverter, so take that into account when considering the cost of these types of circuits. -90dBV isn't going to kill you, but it's an awful lot to throw away just to be able to wire a room up haphazardly and not have things go wrong. Is it that hard to wire up unbalanced gear sensibly and skip the pin 3 drive, or load it at the receiver with a matching resistor to ground?

 

[abbey road d enfer]

I have to point out that the -90dBV typical noise of a 2142 (and any of the ground cancelling drivers) is about 20dB more than what one gets with a simple buffer and inverter, so take that into account when considering the cost of these types of circuits.

THAT 1200 -105dBu.

Is it that hard to wire up unbalanced gear sensibly

It is if a longitudinal noise voltage is developed in the shield. No sensible unbalanced wiring can fix that.

  skip the pin 3 drive, or load it at the receiver with a matching resistor to ground?

If you can cope with the 6dB loss...

 

[Newmarket]

THAT 1200 -105dBu.
It is if a longitudinal noise voltage is developed in the shield. No sensible unbalanced wiring can fix that.
If you can cope with the 6dB loss...

THAT120x series are receivers so I guess you mean THAT160x Drivers ?
These state noise spec as:

Output Noise Onoise Balanced, 22Hz -20kHz -101 dBu

But note that 'Balanced' is stated.

 

[Newmarket]

I have to point out that the -90dBV typical noise of a 2142 (and any of the ground cancelling drivers) is about 20dB more than what one gets with a simple buffer and inverter, so take that into account when considering the cost of these types of circuits. -90dBV isn't going to kill you, but it's an awful lot to throw away just to be able to wire a room up haphazardly and not have things go wrong. Is it that hard to wire up unbalanced gear sensibly and skip the pin 3 drive, or load it at the receiver with a matching resistor to ground?

Just for clarity : The figures I quoted were the test set results (Neutrik A2 as it happens) of a DAC card and not simply a test of the SSM2142 itself. So I was pointing out the variability experienced rather than the absolute THD / N levels.
Basically we got 90dB before the SSM2142 and, typically, 89.9dB after it but had a batch at around 75dB.
Obviously with the results around 90dB I was pushing toward the limits of the test set (we had hired an AP2 earlier in the project but not to keep £££!!!) but it clearly showed the difference with the '75dB' parts.
All back in the last century and I'd probably look too use THAT160x now for the same function with minimum pcb area / parts count.
As it happens I have just put some THAT1606 on a few boards that I got done to implement a 'Ground Cancelling' output with options for invert / non invert and other options.
tbh I realised I had spare pcb area to put it on as an option so did that and fitted it to a few of the boards.
Bench tested with Sig Gen and Scope but not put audio through it yet.

 

[Newmarket]

Reading back to the OPs question on this I think the biggest issue may be that he has the typical insert configuration on a single TRS.
So how to get 'balanced' in and out (too many wires !) unless planning to modify the metalwork  if space permits.
assuming that the new pcb 'near the channel' is intended to be inside the desk...?

I'm using Trident MTA console which I would like to upgrade with "balanced" patchbay.
Every channel has "Insert" socket where tip is send, ring is return. What I would like to do is

Make a small pcb near each channel. From each channel I would like to balance signal (on that pcb) , send it to the patchbay, then from the patchbay balanced signal goes back to the pcb where I would  unbalance it and send back to the channel.

 

[abbey road d enfer]

Reading back to the OPs question on this I think the biggest issue may be that he has the typical insert configuration on a single TRS.
So how to get 'balanced' in and out (too many wires !) unless planning to modify the metalwork  if space permits.
assuming that the new pcb 'near the channel' is intended to be inside the desk...?

I would think the only easy solution to this non-existing problem would be to build the bal/debal circuits outside the mixer.

 

[abbey road d enfer]

THAT120x series are receivers so I guess you mean THAT160x Drivers ?
These state noise spec as:

Output Noise Onoise Balanced, 22Hz -20kHz -101 dBu

Correct; a respectable performance anyway.

 

[Newmarket]

Correct; a respectable performance anyway.

Definitely. And no trimmer to set 

 

[porkyc]

Similar to 2 replies back from AbbeyRoad...
External box, SSM 2142 feed, SSM 2143 returns. Job Done. Do not re-invent the wheel. For different reasons we did this at Twickenham Film Studios a few years ago.  This works fine. (Can you still get them?)
Incidentally, do not copy the use of the 2142 output circuit from your MTA manual: .... Homework, look elsewhere.
Harrison has the same problem on the 32/24 series; on the MR series consoles, they put the +10dB transformer O/P circuit in as the patch output feed with a standard -10dB diff input return. (Harrison ran 10dB down at that time). So each module has 2off 1:2 TXs on them.

In the real world, the benefits of line level balanced send and return will outweigh any of the 2142/43 technical reservations expressed here. Why has this taken 2 pages!?