Pentaconn is PH3/4, so follows the input as set in PH3/4 Settings page.

There‘s another option:

Get an cheapo DA-converter and connect it to Coax or Optical digital output, just for the VU-meter.
The block diagrams on manual, pages 40-46, show the digital outputs’ routing options for the various “modes”.

You can have an output independent from volume control.

Look at your country’s Amazon offerings.

Just make sure it has Coax or Optical input and can handle the max. sample rate you intend to throw at it.
192 kHz BTW is the SPDIF limit.

A level control might come handy to calibrate the VU if it doesn’t already have this.
If your VU’s are passive, a ‘phones output might be good to drive them.
Sound quality is of absolutely no concern in this application, of course.

Here’s an example, at 13 bucks:
https://www.amazon.de/Wandler-TEAMPD-Ko … amp;sr=8-9

This would be 6.5 V or +18.5 dBu for a 0 dBFS / full scale signal, or +4.5 dBu for your -14 dBFS reference sine wave.

Typically home hifi DAC‘s output 2 V / +8.2 dBu at 0 dBFS, so I wouldn‘t expect more than this.

In the Crookwood 2 VU’s user guide several calibration options (even the black ones at the back of the meters with quite some range) are mentioned, I guess it can be fitted.

From my practical experience a calibration of digital -6 dBFS = analog 0 VU fits quite well for having popmusic final masters show around 0 VU.

The Crockwood’s manual’s example of -14 dBFS = 0 VU is for tracking of instruments and vocals (more headroom), but I don’t find VUs very useful for tracking.
On tracking it’s the digital peak level that really matters.

HD 600´s drivers begin to clip about +18-20 dBu voltage -ballpark. So, no use for this "balanced" (it is BRIDGED in this context, actually) driving method for HD 600. ADI can whip it to its maximum output SPL-levels already in "unbalanced" driving mode.

P.S. Why even RME uses this audiophool bullshit term "balanced" regarding bridging of amplifier stages? Could be disregarded for some regular audiophoolery company, but the RME... engineer-Christ´s sake.

Using 'bridged' would cause a lot of confusion and takes away our time explaining this to customers, because nobody else uses it. Not to mention that from outside the unit you have no way to find out if this is 'balanced' or 'bridged' or whatever.

Also - did you read the manual?

This technique is mostly used in car audio, as the operating voltage is limited to 12 Volt, and balanced operation, here called bridging, delivers double the output voltage and four times the output power to the speaker.

Having a problem with this labeling is nitpicking, not 'Christ's sake'.

Thanks MC. It was worth it for me to just pay the €40 so I wouldn't have the pain of soldering up four tiny wires to a tiny Pentaconn jack!

Thanks all, I'll report back when the cable arrives and I've done some listening tests, it has shipped now!

There were many options, cheaper and more expensive, but this one seemed to have a good balance (pun intended...) of price vs. quality. I chose it with 3m length and of course the 4.4mm balanced Pentaconn connector:

https://www.aliexpress.com/item/1005004 … 1802uDnwoy

BTW the newer HD660S2 cans also come with a Pentaconn cable as standard, so you could probably order one direct from Sennheiser spare parts (I'm pretty sure they have the same connectors on the headphone end).

I‘ve NEVER seen any headphone amp in the world using “bridged” for balanced ‘phones out.

If RME started with it, people wouldn’t understand.

Technically the term balanced is correct, same “weight” with opposing directions on both branches of the signal wire.

It’s EXACTLY the same schematic like an active “balanced” line out, which no one would call “bridged” - a less correct term BTW - where is that “bridge”?

Balanced phones amps technically use “differential” signal out, like most of the line out variants below.
This is again no reason to use that label here.

Next - it’s not RME’s fault - and nobody else’s - that for signal transfer multiple variants of balanced outs are possible:

• Transformer balanced without ground reference.
• Transformer balanced with ground reference.
• Active electronically balanced with level compensation when connected to single ended destination.
• Active electronically balanced without level compensation when connected to single ended destination.
• Impedance balanced.

All the above without, and with source/destination impedance matching (for long distance and/or high frequency interconnects).

It’s a plus that RME mentions the used variants in the manual, even giving connection advice.
This information is important for proper use, in a complex recording studio environment e.g. it can make a difference.

Finally - in all cases the balanced noise suppression happens in the destination only BTW, by no means in the source.

Even more so as the 2/4 Pro has a completely balanced (differential) signal path from DA to Pentaconn, as explained in the manual.