• Registered: 2007-06-16
  • Posts: 214

Topic: FF800 gain anomaly

Some time ago I had some strange gain problem during the show. The day after I looked over it and at first it seemed like input stage problem on one of my fireface units.

Problem occurs when using two ff800 units; one as a master connected to the computer and second as a stand-alone AD-DA converter connected to master unit via adat optical connection (both ports for all 10 analog channels). Both units have analog I/O's set to +19dB. When feeding -3dB 1Khz test tone from analog 1 output of master unit to the analog 1 input of the second unit I got severly clipped signal back on adat 1 input of the master unit. With other channels I got approx 0.3dB lower return signal.

In fact signal returned back form ch 1 has approx 13dB more gain. Frequency analysis (with -20Db log swept sine) shows response simmilar to other channels - nearly perfect, only raised by 13 dB. Level meters in total mix shows the same also; when nothing connected to analog inputs they show about -108 to -109 dB silence only adat 1 on the master unit shows -95.

Detailed inspection of this problem discloses the following:

1. If I swap units the problem still persists.
2. If I use SPDIF for first 2 channels and adat for remaining 8, the problem still persists.
3. If I connect both units to the computer, synch secondary over adat the problem disappears.
4. If I independently test both units - feed analog outputs back to inputs of the same unit, I got approx 0.3dB lower singnal on input. This test confirms there is nothing wrong with input stages.

Anyone with the same problem?

HW revision 2.77, driver 3.014, win XP 32bit.

Regards, kasaudio

2 Reply by MC

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Re: FF800 gain anomaly

Hi, some more details please: You use unit 2 in stand-alone mode. It seems obvious that unit 1 works correctly and this is a stand-alone problem. When you exchanged the units did you flash mixer and clock settings to the same settings? Can you send me a screenshot of the clock settings and a preset file so I can fully reproduce the setup?

Regards
Matthias Carstens
RME

MC's Website

3 Reply by kasaudio (edited by kasaudio 2011-02-04 13:24:52)

  • Registered: 2007-06-16
  • Posts: 214

Re: FF800 gain anomaly

One unit was used as a stand alone (AD-DA over ADAT's) and the second connected to the computer over firewire.

It seems obvious that unit 1 works correctly and this is a stand-alone problem.

Correct, it seems a stand-alone problem, but if I swap units (master becomes a slave and slave a master) the problem still persists (on previous master). Master means the unit which is connected to the computer. So it is difficult to say, which unit works correct and which not. Will post screenshots, will try to obtain preset files but I'm not familiar with total-mix. I use it as little as possible (just to route inputs to outputs), flash the setting and that's all.

As far as I can remember, I never had issues in the past with the same setup (with lower version of HW revision). As full 20in-20out situation rarely occurs, it is difficult to say for shure. Screenshots follow.

  • Registered: 2007-06-16
  • Posts: 214

Re: FF800 gain anomaly

Here is a detailed description of gain problem:

To reproduce it with minimum effort, two computers are required. First fireface unit is "master" conected to one computer. Its mixer setting is the following:

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470242.jpg[/img]

Control panel setting is the following:

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470240.jpg[/img]

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470241.jpg[/img]

Second fireface unit is a "slave". It will operate as AD and DA converter over both ADAT input and output ports. To make things more transparent, it is connected to another computer. Mixer setting of the slave unit is the following:

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470246.jpg[/img]

Control panel of the slave unit is the following:

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470244.jpg[/img]

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470245.jpg[/img]

If I generate 1kHz -3dB test tone on output 1 of the master unit and connect it to the input 1 of the master unit I get the following.

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470235.jpg[/img]

Total mix shows 0.34 gain loss which seems correct.

If I then connect output 1 of the master unit to the input1 on the slave unit I get the following:

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470238.jpg[/img]

Meanwhile on the slave unit the TotalMix displays the following:

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470243.jpg[/img]

Till now everything is OK. Then I flash control panel and mixer settings on the slave unit, turn it off, disconect FW cable and turn it on. Slave unit now runs in standalone mode.

With nothing changed on master FF800 and computer I get the following:

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470236.jpg[/img]

Input 13 is severly clipped. To achieve the same level as in previous case, I had to reduce level of the oscilator by 12.1 dB to -15.10 dB

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470237.jpg[/img]

Frequency response of master output 1 connected to slave input 1 is obtained by -15.1 dB swept sine and is like it should be, only about 12 dB too hot.

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470247.jpg[/img]

Other channels work fine.

Even if I change system's setup and use SPDIF connection for the first 2 channels and 1 adat connection for remaining 8 the problem still persists as shown by the following picture:

[img align=c]http://s4.mojalbum.com/audio-foto_17376454_17428820_18470239.jpg[/img]

Oscilator's output is -15.10Db, output 1 and 2 of the master unit are connected to inputs 1 and 2 of the slave. Input 1 is 12.1 dB hotter.

If I swap the units problem is still there.

To reproduce this scenario with ease, I enclose TotalMix mixer presets. Preset 1 is for master unit, preset 2 is for the slave unit connected over both ADAT ports, preset 3 is for the slave unit connected over SPDIF and one ADAT io port.

KasAudio's FF800 presets

Regards, kasaudio

5 Reply by MC

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Re: FF800 gain anomaly

Thanks for all the details. The error is quite simple: there is a 12 dB gain in the first input channel, affecting any routing of the first (analog) input channel. This gain comes from the Limiter function. Set Limiter On in the Settings dialog, flash it, then everything works correctly. As you don't use the front input this setting can stay active with no problem.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2007-06-16
  • Posts: 214

Re: FF800 gain anomaly

Tnx for reply, will try that as soon as possible.

Are my units defect or is that an error of FF800's system (flash).
I have always had limiter turned off as from the pictures. As I understand turnig it on will cure my problems (by not using the front input).

kasaudio

7 Reply by MC

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Re: FF800 gain anomaly

We are checking where this error is, either driver or firmware, but not your units.

Regards
Matthias Carstens
RME

MC's Website

8 Reply by kasaudio (edited by kasaudio 2011-02-04 21:03:38)

  • Registered: 2007-06-16
  • Posts: 214

Re: FF800 gain anomaly

Tnx for your effort!

9 Reply by MC

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Re: FF800 gain anomaly

This error had been introduced in the 3.x versions of the Fireface Windows driver. A fix should be included in the next update.

Regards
Matthias Carstens
RME

MC's Website