Good point. It had occurred to me that maybe there is ribbon cable running from the circuit boards to the DB25s inside the M-32DA. However, if there are, then they would be much shorter than the lengths in the BoBs, and any ribbon cable in the M-32DA is enclosed by its metal case.

"My reasoning" for "pseudo" balanced?

From here

http://www.rme-audio.de/en_products_m32da.php

Under "Features":

The units have separated driver stages for the TRS and D-sub outputs. The servo-balanced TRS jacks will work up to +21 dBu.

Under "Technical Specifications"

Output DA: 1/4" TRS jack servo balanced, up to +21 dBu. 25 pin D-sub, balanced, up to +24 dBu

Servo = resistive balanced = pseudo balanced.

There are more references in the M-32DA manual.

Cheers,

Ian

So, what you're saying is that the TRS outputs have three opamps in a cross coupled servo circuit? However, that should deliver the full balanced output voltage. So why is there a 5dBu difference between these outputs and the fully balanced DB25 outputs? IME, this lower output level is usually as a consequence of resistive balanced where the signal is connected between pins 1 and 2 only. A resistor equal to the output impedance of the op amp driving pin 2 is connected between pins 1 and 3.

And what about that BoB ribbon cable?

Cheers,

Ian

Well, I suppose what else could I have expected you to say? Which, of course, begs the question why did I even bother asking in this forum!? I was simply shocked.

I just hope that the combination of the sheathed connectors (DB25 and XLR), vs the TRS would provide me with a stable audio outcome when basically everything remains in the same connected state for months. My experience with TRS has been that they are not that suitable for long term connections. Better suited for old fashioned telephone switchboards and lots of volts and repeatedly plugged and unplugged. After all, the TRS tip was called, in those days, the 'magneto tip' for that's where many volts passed vs the relatively tiny volts in audio applications. But, I certainly comprehend the need for TRS in terms of the overall impact on the final form factor size of an audio device. I suppose my only question would be, than when dealing with a higher end device like the M-32DA, why weren't the SFF Lemo sheathed connectors used instead of TRS?

What I was also hoping for was a slight improvement in audio quality by undertaking this expense, and work. Not just a more stable audio output platform. The ribbon cable called that hope into serious question for me. The proof will be when it is all connected. The cables should arrive tomorrow, or Monday.

Cheers,

Ian

In terms of audio quality, and when using balanced connections in both cases, there will be no difference.

Follow up question. Are there any issues with running with not connecting Pin 1 at the amplifier end (all amps connected to AC ground in a star ground topology) using the servo balanced connections?

Cheers,

Ian

"My preferred method is to connect cable shields at equipment outputs and not at equipment inputs."  A quote from this article  http://www.soundonsound.com/sos/nov02/a … on1102.asp so, the writer there contends the reverse in terms of hum and buzzing. This is how my installation is wired - so quiet (no hum, buzzing or any noise) that it is almost 'black' (but only with XLRs at the amp ends TRS at both ends was very unsatisfactory). Been that way for years now. The only outcome that I don't like is sometimes (but not always) there can be a creeping brightness across all channels. That is what keeps me working on this. I seem to recall (from an article I can no longer find) that the servo balanced arrangement prefers to 'see' a connected Pin 1 at both ends but that this was not the situation for normal balanced connections. Based on this, would the Pin 1 lifted-at-the-amp-end wiring approach be a complete non issue with the DB25 balanced outputs?

Cheers,

Ian

Well, despite everything, I proceeded with the intellectually stimulating work of installing the BOBs, removing the TRS connectors, and soldering 32 Neutrik Gold XLRs onto the cables. It was worth it! There IS a difference, and it is NOT subtle. A much more natural sound, that possesses greater transparency. So, despite the more circuitous route for the signal (DBtoB25 then BOB [and their ribbon cables!], then XLR) compared to the TRS outputs, it seems that there are greater compromises in the combination of adaptive active balanced and TRS than there is in normal active balanced. Very happy.

Cheers,

Ian