Connection of s/pdif source to 8240A's AES/EBU - Forum

Hello Heikki,

Thanks for your post and question. Genelec DSP loudspeakers digital inputs can be connected to AES/EBU signals. S/P-DIF and AES 3-id signals may be used with restrictions applying to impedance converters.

So, to use Genelec DSP loudspeakers with S/P-DIF input signals, you should use impedance-matching converters (available for example from Neutrik) and short cable lengths because the S/P-DIF link should not travel long distances. The Neutrik converter takes care of the fact that the terminating impedance of S/P-DIF is 75 ohms and that of AES/EBU is 110 ohms.

It is advisable to use the GLM software if you do this because GLM will then work as the volume control for the whole system (note that some source can control their S/P-DIF outputs and some cannot). This means a computer must be running somewhere with the GLM in it, and that GLM network cables must be connected to all loudspeakers and subwoofers.

Hope this is helpful.
Best regards,

Christophe,

Thank you for your answer! This helped a lot!

Heikki

Hi,

I work with the Mutec 1.1 for Sp/Diff --> Aes/EBU conversion 96Khz ... works also perfect ...

MC1.1 can even be used for getting back into your DAW dig at the same time ... works only with Single wire connections , no dual wire!!

www.mutec.de

have fun ...

Franky

So, to use Genelec DSP loudspeakers with S/P-DIF input signals, you should use impedance-matching converters (available for example from Neutrik) and short cable lengths because the S/P-DIF link should not travel long distances.

I believe this is because the S/P-DIF signals are much lower voltage than AES/EBU, and longer cables have larger resistance and increased noise floor, making the signal/noise ratio too large for the signal to be interpreted reliably at the speaker terminals, right?

But how exactly do you find out, if such a setup has short enough cables? How are the adverse effects of a bit too long S/P-DIF cable detected? Does the speaker have a led indicator that shows if the signal is fine, or does the GLM software report the input voltage levels, or something?

Basically, I'd like to build such a setup, and would try out with just S/P-DIF first, verify that it works and if yes, keep it, if not, then I'd need to get a sound card that has AES/EBU, which I'd rather skip if not necessary. Just need some reliable indicator / protocol of testing to know that it works, instead of forever wondering if it just almost works.

Hello,

Here are some comments on your questions:

I believe this is because the S/P-DIF signals are much lower voltage than AES/EBU, and longer cables have larger resistance and increased noise floor, making the signal/noise ratio too large for the signal to be interpreted reliably at the speaker terminals, right?

> The S/P-DIF signal voltage is a fraction of that in the AES/EBU. Also, S/P-DIF is not a differential transmission line, making it more prone to external disturbance. S/P-DIF has not been designed for long distances in the same ways as the AES/EBU link has.

But how exactly do you find out, if such a setup has short enough cables? How are the adverse effects of a bit too long S/P-DIF cable detected? Does the speaker have a led indicator that shows if the signal is fine, or does the GLM software report the input voltage levels, or something?

> There is no clear-cut rule because there are, in practise, so many variables that can affect the signal. However, the good news is that Genelec DSP monitors are carefully recovering the digital audio signal, and they either play it or refuse to make sound if the signal is not reliable. If you get audio, your cable is short enough.

Basically, I'd like to build such a setup, and would try out with just S/P-DIF first, verify that it works and if yes, keep it, if not, then I'd need to get a sound card that has AES/EBU, which I'd rather skip if not necessary. Just need some reliable indicator / protocol of testing to know that it works, instead of forever wondering if it just almost works.

> Build the setup and do a listening test. One way to gain additional assurance is to find cables that are somewhat longer, say 3 meters longer, and if the system works with those, then you have assurance that you have some margin in terms of the signal levels when using shorter cables.

Hope this is helpful.
Best regards,

I pick this thread up, as I struggle on another end of SP/DIF connection. I do use 3x 8240 (and 4x 1029APM as surrounds) in my home theater for left/center/right main channels and want to connect two home theater processors/pre-amplifiers to the 8240s. One system is my standard system via analogue XLR (works perfect and set up via GLM) and one new processor I have just bought that offers 8 SP/DIF channels (4 RCA SP/DIF outputs) and volume controll (which is perfect).

I started to hook up the processor with digital SP/DIF output and I do get sound. I tried stereo only. But I do not get the right channel, only left channel on both speakers. I tried to fiddle with AES/EBU switches on the back, made one A and one B, but no luck.

Speakers run in stored stand alone mode, as in home theater use, I cannot run a PC for noise reasons.

What could be a reason ?

I made a double check with a DVD palyer and it's SP/DIF output using GLM as a volume controll and still I struggle to get both channels on their correct speaker, just always on channel on both....

Could it be, that I need to tell GLM first "somehow", that "two systems" are run to the standalone speakers ?

Hello,

Thanks for your post. Following your detailed explanation, I assume that you have stored all acoustic settings with an analog setup. So, in that case the GLM software has not set the digital channel selection correctly (a default setting is used).

The channel selection is also stored together with all the acoustic settings in the System Setup file and recalled when using the stored settings. So, to solve the problem you describe, you should make a separate digital setup (with appropriate channel selection), run Autocal with it and store the acoustic settings again.

Additionally note also that in our DSP systems digital signals override analog signals. So if you want to use your analog source, then the digital source should not send any clock signal.

Hope this is helpful.
Best regards,

Thx Christophe for the reply. I struggled a bit with GLM (almost too powerful ), as I assume you mean I need to make something like two "groups" on the "same speakers", one for XLR analog and one for SP/DIF. I played around with "adding cables", but was not successful to find my way through, as such a "double use" is not really covered in the 8240 or GLM manual.

I will give it another try tonight and see how to make two "setups" for the same 3 speakers. I would have assumed, you can only measure the speaker "once" and then need to sort of activitate the two inputs....but maybe I'm thinking about it from the wrong perspective

Indeed, I will need to check, when the "digital processor" is in Standby, that is does not give any signal to let analogue XLR pass through. That I found in the manual right away

Indeed Christophe, I had to make a new setup, not group. That solved it

Now, what does that exactly mean to the three 8240s, will they recognize the individual measurement made with either analogue inputs, and the new measurement for the digital SP/Dif signal via AES/EBU input, in mind?

I was under the impression that only one setup can be stored, especially in standalone mode ? Sure the PC can load/ manage different setups at a time......but PC is off line due to noise.

Side note: yes, unfortunately the "digital" processor does trigger a signal in standby via SP/Dif and mutes the analogue inputs of the 8240s. So for that digital rig I will need a remote power socket to switch the processor fully off any power. Cumbersome but possible

Hello,

Correct, you had to make a new System Setup file, not a Group, which is another thing and for another type of use.

Now onto your next question: only one set of data is stored in each loudspeaker. So, when you load a new Setup File (for either the Analog or Digital source) using GLM software, all applied settings are set according to the loaded Setup file, and unless you activate 'Save settings into loudspeaker' again, the previously stored settings in the loudspeakers are active once you disconnect the network.

It should also be remembered that to activate the loudspeaker stored settings after a GLM use, all loudspeakers must be rebooted or stored settings switch toggled. This is needed if the stored settings vs the GLM settings are different.

In your case, the AutoCal calibration data with analog and digital source will be the same as you do not move the loudspeakers, but just change the audio input type. In that sense you do not need to 'Save settings into loudspeakers' each time.

In fact, it doesn’t matter which input is used during calibration, as the same settings are used for both inputs. Calibration results are not depended of the input selection. The only important thing to remember is to store settings with a digital setup to set the correct digital channel allocation.

Best regards,

The only important thing to remember is to store settings with a digital setup to set the correct digital channel allocation.

I see, ok, then it should all work out. Great

I leave the "store button" on the back alway "on" and usually reboot. I have all 3 speakers on one RF remote power socket, so that is an easy on/off via remote.

Thx again for the clarification.

Hello, I am using this setup:

MacBook Pro -> S/PDIF optical -> Mutec MC-1.1 -> AES/EBU -> 2 * Genelec 8250

No probem with that.

Recently I acquired a cheap Blu-ray player (Philips BDP2500). I connected the S/PDIF coax output of the BDP2500 to the S/PDIF coax input of the MC-1.1. But no sound arrives at the speakers, they just keep flashing the red LED. I tried all setting of the MC-1.1 and of the BDP2500 (Digital Audio = Auto/PCM/Bitstream, Downsampling = On/Off), but to no avail.

Any ideas anyone? Is it a matter of the cable? I tried a short cinch/RCA audio cable because I read somewhere that this should be good enough for S/PDIF connections. But maybe it isn't?

Markus

Hi Markus,

Your setup is very similar than mine.

I'm running Airport Expres -> optical -> Mutec MC1.1 -> AES/EBU -> 8250A AES/EBU IN -> AES/EBU THROUGH -> another 8250As AES/EBU IN.

It works just fine. Same with my PS3 slim and Windows laptop.

Have you tried to reload GLM .cal-file and reboot the speakers? And any other source is not sending any background audio at the same time?

I suppose you also have turned your bd-player to output stereo pcm audio? Mutec is only able to handle 2ch.

-Vili, Finland

Hello, I am using this setup:

MacBook Pro -> S/PDIF optical -> Mutec MC-1.1 -> AES/EBU -> 2 * Genelec 8250

No probem with that.

Recently I acquired a cheap Blu-ray player (Philips BDP2500). I connected the S/PDIF coax output of the BDP2500 to the S/PDIF coax input of the MC-1.1. But no sound arrives at the speakers, they just keep flashing the red LED. I tried all setting of the MC-1.1 and of the BDP2500 (Digital Audio = Auto/PCM/Bitstream, Downsampling = On/Off), but to no avail.

Any ideas anyone? Is it a matter of the cable? I tried a short cinch/RCA audio cable because I read somewhere that this should be good enough for S/PDIF connections. But maybe it isn't?

Markus

Hi Vili,

thanks for your answer. Yes, the Blu-ray player is set to output PCM. Restarting GLM does not help. There are no other sources apart from the MC-1.1.

Today I bought a dedicated digital (75 Ohm) audio cable. This did not change the situation.

Markus