TOPIC: s/pdif digital input and volume control

My current configuration (3 way ) is:
CD-Player ( analog out ) - analog in pre-amplifier analog output A and B
Analog Output A (right channel) to PWR 125 BTL mode - Bass (<250 Hz)
Analog Output B (right channel) to PWR 250 SE mode - Midrange (250Hz-5000 Hz) - Tweeter (>5000Hz)
Analog Output A (left channel) to PWR 125 BTL mode - Bass
Analog Output B (left channel) to PWR 250 SE mode - Midrange - Tweeter
all is working perfect

New configuration: first try with digital output of the CD - Player : CD-Player digital S/PDIF output -- input digital PWR 125 (BTL mode) - bass (<250HZ) - This work perfect

Question one : I will try following configuration (not tested) Will this work ??
CD- Player S/PDIF out - input digital PWR 125 - (left channel bass) output digital to input digital PWR 250 (left channel midrange - tweeter) to digital PWR 125 (right channel bass) to digital PWR 250 (right channel - midrange - tweeter )
Will this configuration work with the asymmetric S/PDIF (all cables coaxial 75 Ohm, together not more than 3 meters) ? or only with a symmetric AES/EBU output (not available with my CD Player)?

Question two: if that configuration will work, i have a problem with the volume control:
I can control each channel and speaker (Bass, midrange , tweeter) with the digital input level .
For a master volume control i have to change all four (Master control) at the two PWR 125 and two PWR 250.
Is it possible to put these together in one. I think this master control (PWR 125/250) ) is a normal potentiometer, and is therefore is a analog part of the PWR, or not ? If these are a normal (e.g. 100 k or 10 K) potentiometers is it possible to control the master volume with with a four layer potentiometer (e.g.alps 100k). Are there some pins for that at the PWR ? (don´t care about the warranty)
Other ideas ?

Thanks Thomas

Between the amps, you would use XLR cables, there is no reason to use single ended there.

I assume that four amps chained will work but have not tried it myself (as I have only two).

On the first amp, you would need an SPDIF to AES/EBU transformer, some are made by Neutrik and Canare. BTW I haven't tried this either (see below).

You will need to do volume control digitally, before the first amp. With a computer-based source, this is easy, not so much with a CD player... one way to do it is use an OpenDRC-DI (or DDRC-DI). Not cheap for a volume control but then you can do FIR-based correction as well. Just an idea.

Hope that helps - ?

I try following setup:
CD SPDIF out to PWR 250 , and it is working without a SPDIF to AES/EBU tranformer.. Then XRL cable to the second PWR (all o.k.) then to the third PWR with XLR cable. This failed.
May be the characteristic wave impedance of the XRL cable is wrong. For the SPDIF it should be 75 ohm (output level 0,5 V) unbalanced and for AES/EBU 110 ohm balanced (output level 2-7 V)
May be i have to buy a SPDIF to AES transformer as you suggest !

Volume control: good but expensive idea. Will the OpenDRC-DI (or DDRC-DI) transform the SPDIF to an AES/EBU ?

Thanks a lot

Hm, interesting that it works to the first two and not the third. I don't know why that might be, it might be better to open a support ticket to ask before spending money (minidsp.desk.com).

The OpenDRC-DI/DDRC-DI has an "AES/EBU" output. I imagine that this is not a proper AES/EBU signal in terms of the protocol bits but for the purpose here it works fine.

@ Kunzmann

Sounds like a great setup! We look forward to seeing pics of this install.
I believe that most likely the daisy chaining (SPDIF to AES-EBU) is the issue here. Not 100% sure as we haven't tested with SPDIF linked to multiple units but I guess that it's indeed the issue. The easiest would certainly be to use AES-EBU level. i.e. level translator from 0.5V to 3-5V. That would really do the trick here. We'll ask the engineers in the mean time to see if they have some ideas/suggestions.

The OpenDRC will indeed do volume control and SPDIF to AES-EBU translation, together with overall room correction..

DevTeam

Sorry for the late reply
I realized following solution for the master control::
Cd Player digital output S/PDIF with a normal cable to a OpenDIRAC DI input S/PDIF:
Output AES/EBU (OpenDIRAC DI ) to Input AES/EBU PWR125 BTL mode (Bass left Channel)
Output PWR 125 AES/EBU to input PWR 250SE (Midrange and Tweeter left channel)
Output PWR 250SE AES/EBU to Input PWR125 BTL mode (Bass right) Channel)
Output PWR 125 AES/EBU to input PWR 250SE (Midrange and Tweeter right channel)

The master volume control is now possible with the OpenDirac DI (remote control or manual)
and work perfect.
The total cable length S/PDIF Cd-Player to OpenDIRAC DI is 1meter
The total cable length AES/EBU is app. 5 meter

Now i have FIR and IIR filters (OpenDIRAC DI) and IIR filters ( 4 PWRs)

Question:
As many other customers i have bought my four PWRs and the OpenDIRAC Di in Germany and i cannot find the new software for the PWR (IIR plus FIR filter) in my users download. Is it possible to download it from minidsp or from a german web-site ???

Hi Kunzmann

Woww great setup indeed! Do you happen to have some pics of your install? It would be great to share with the community! THanks!

For the PWR-ICE FIR plugin, we surely can help. Do you mind to please start a tech support (support.minidsp.com). We can take it from there to enable it for your user downloads.

DevTeam

Here a picture of my setup:
Tweeter: Fostex T825 > 5000 Hz
Midrange: Two Bohlender Graebener Neo8s planar-magnetic transducers with a short horn (self made) dipole 300 - 5000 Hz
Bass: Two Tang Band Woofer < 300 Hz (closed box)