• rvlt
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Topic: [Solved] Fireface800 + ADI8-DS: different analog voltage levels?

Hello,

I recently changed my setup from two older Multifaces (the second used as an ADAT converter in disconnect mode for a total of 16 channels) to a Fireface 800 + ADI8-DS.

I noticed that the analog voltage levels are different on the FF800 and the ADI8. The ADI8 has almost 3dB more output than the FF800 and less input gain:

When I use a loopback cable to send a test signal from Output > Input on the same unit, the I/O levels match (minus the small headroom margin), but when I cross-patch between the FF800 <> ADI8, I get different levels.

Both manuals state that the output level is the same on both units (0dBFS @ +4dBu = +13dBu).

When I used the same setup with my Multifaces, the levels where spot on.
I temporarily connected a FF400 and the levels where the same as on the FF800.

Shouldn't be the levels on both units the same? What am I missing here?


Setup:
- both units set to +4dBu I/O levels
- when both units set to -10dBV, I get the same level difference
- test signal 1kHz sine wave @ -12dB on output
- TotalMix fully reset, all faders on 0dB
- used a balanced, known good cable directly on the back of the units (to rule out problems with the console, patchbay or multicore cables)
- all 8 channels on both units behave the same
- ADI8: Process=off, Clock=Input, Combine=off, Copy Mode=off
- Mac Pro 2012, MacOS 10.14


(Of course I can compensate at least the output level difference by lowering the ADAT Outs in TotalMix, but still curious to know if this level difference is to be expected)

Best regards
Lars

2 Reply by MC

  • MC
  • MC
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Re: [Solved] Fireface800 + ADI8-DS: different analog voltage levels?

The most easy way to solve this is to get a cheap multimeter and measure the output voltage of all units and channels directly. Did you use the same balanced TRS cable to connect MF output to ADI input? And vice versa? 3 dB difference sounds more like unbalanced connection error.

Regards
Matthias Carstens
RME

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  • rvlt
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Re: [Solved] Fireface800 + ADI8-DS: different analog voltage levels?

Yes, the same balanced cable used for all the test connections. An error with balanced / unbalanced connection was also my first thought, but that seems not be the case here.

I did measure the output with a Picoscope, using a 1k sine @ -12dB from my DAW (TotalMix also shows -12dB on all outputs), scope probe connected to +hot and -cold.

Vrms results:

FF800: 0,854 Volt
FF400: 0,865 Volt
ADI8:  1,182 Volt

These levels were on all outputs (minus a few millivolts deviation). That's probably by no means a professional measurement here, but since the same test setup was used for all units, at least I can see the difference in output levels.

Hm.. really puzzled now. There aren't any internal jumpers/trimmers to adjust the levels, are they?

4 Reply by MC

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Re: [Solved] Fireface800 + ADI8-DS: different analog voltage levels?

Vrms results:

FF800: 0,854 Volt = +0.85 dBu = +12.85 dBu = Ok
FF400: 0,865 Volt = +0.96 dBu = +12.96 dBu = Ok
ADI8:  1,182 Volt = +3.67 dBu = +15.67 dBu = error

A multimeter would have been better, though. The Picoscope does not measure ground-free, so the results might be invalid.

You might want to repeat the measurements using a mono / TS cable. That gives definitely valid results with PS and would be interesting to see.

You should also do a quick check that the level is the same at 100 Hz and 10 kHz, to rule out defective capacitors at the I/O.

Regards
Matthias Carstens
RME

MC's Website

  • rvlt
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Re: [Solved] Fireface800 + ADI8-DS: different analog voltage levels?

Ok, I used a TS<>TS cable on the outputs and measured again. With the Picoscope (1st value) and an older Multimeter, just to be sure (2nd value).

I also checked each output at 100Hz and 10kHz and there was no difference.


FF400        0,860 Vrms        0,84Vac

FF800        0,848 Vrms        0,83Vac

ADI8-1        1,150 Vrms        1,12Vac
ADI8-2        1,150 Vrms        1,13Vac
ADI8-3        1,128 Vrms        1,10Vac
ADI8-4        1,141 Vrms            1,12Vac           
ADI8-5        1,151 Vrms         1,13Vac
ADI8-6        1,156 Vrms        1,13Vac
ADI8-7        1,151 Vrms         1,13Vac
ADI8-8        1,149 Vrms        1,13Vac

The weird thing is that all ADI8 channels are affected... are the I/O levels set by a firmware that wasn't calibrated, maybe?

6 Reply by MC

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Re: [Solved] Fireface800 + ADI8-DS: different analog voltage levels?

No, not possible. I don't know how these increased output levels are generated, but it is not correct, so something is broken in the unit that needs repair.

BTW, you should check the other output ref levels of the ADI as well. It might be that some work correctly.

What makes this completely non-understandable (from a technical side) is that you claimed that doing a loopback at the ADI the levels match. I can't believe that the inputs are also off to work at +15 dBu instead of +13.

Regards
Matthias Carstens
RME

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  • rvlt
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Re: [Solved] Fireface800 + ADI8-DS: different analog voltage levels?

Ok, I will take the unit home and double check everything with my home setup. Will also check the other ref levels. If the levels are still too high/too low, I will contact support then.

Thanks for taking the time!

  • rvlt
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Re: [Solved] Fireface800 + ADI8-DS: different analog voltage levels?

Mystery solved: my ADI-8 is a broadcast version with a reference level of +6dBu instead +4dBu. Therefore higher output, lower input levels. Took a while to find out ...