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Is my Fireface UC working properly?

PostPosted: Sat Sep 07, 2019 12:10 pm
by JulianMoney-Kyrle
Has anybody had poor performance with the RME Fireface UC?

I've been spending the past few days upgrading my Hauptwerk system. Previously I was experiencing distortion which was most noticeable with Baroque-type sample sets (Freiberg, Velosovo, Zwolle, Kszrezcow - this one being particularly revealing) playing with full chorus. Adding mixtures makes the sound distinctly fuzzy, but I could hear it with 2' as well.

I thought the problem was that I was getting intermodulation distortion from not having enough speakers, and I have been spending the last few days adding more channels. I now have two pairs of Behringer Truth B3031A's, four pairs of B2031A's and a pair of Spirit by Soundcraft 4P's, which I use for the rear channel. Everything else is distributed between the Behringers, either with a stereo channel for each type of stop (foundations, upperwork, mixtures, reeds etc.) or else using using Hauptwerk's cycling algorithm to send everything to six stereo Behringer channels (the B2031A's and B3031A's sound very similar - more so than two speakers of the same model in slightly different parts of the room). I was previously using an RME Fireface UC as my audio interface, which gives 6 balanced output channels plus a "headphone" mix-down which I send to the subwoofer (SVS PC2000), and I have added a Behringer ADA 8200 digital-analogue converter to access the additional 8 ADAT channels.

While the new set-up clearly sounds a bit better than the old one, it hasn't really solved the problem.

While I was messing around with everything I realised that I could connect the digital output of one of my Sonos units to the SPDIF input of the Fireface UC. This was so that I could listen to the radio in the music room while waiting for samplesets to load etc., but I was struck by how bad the sound was compared to my HiFi (Sonos played through a Cambridge Audio amp and bit Tannoy speakers). Of course this cost ten times as much as a pair of Behringer monitors, but even compared to the Sonos speaker in the kitchen and the TV soundbar there was enough distortion that it was quite fatiguing to listen to.

So next I removed the Fireface UC from the organ and connected it up to the HiFi in the living room. The digital output from the Sonos unit went into the SPDIF input of the Fireface UC, and two of the analogue outputs from the Fireface UC went into the balanced XLR inputs of my Cambridge Audio amplifier. The analogue output of the Sonos unit went into an analogue input of the amplifier. After adjusting the level of the Fireface UC I could play the same music through the Sonos and switch between the two, effectively switching between the internal DAC of the Sonos unit and the DAC (and associated circuitry) of the Fireface UC.

Compared to the very clean sound of the HiFi, there was slight but noticeable distortion when listening to David Goode playing Bach on the Silbermann organ at Freiberg. With speech (BBC Radio 4) there was a little sibiliance with the Sonos DAC, but with the Fireface DAC the sibilance was quite marked, and very intrusive (I think speech is a good test of HiFi since we are all intimately familiar with it). I then tried a test recording of a sine wave sweeping upwards from below to above the limits of hearing. With the Sonos DAC I heard the expected rising tone. Playing the same track through the Fireface there were lots of other tones coming in and out at the higher end of the sweep. I am not a sound engineer, but clearly this shouldn't be there and I suppose it represents significant harmonic distortion (the test disc came with my in-car HiFi, and with that the sine sweep also sounds clean.

Now the Fireface UC is supposed to be a high-quality audio interface specifically recommended for use with Hauptwerk, so either it isn't as good as I had believed when I got it, or there is something wrong with my particular unit. Unfortunately it is a couple of years old and probably out of warranty now. I don't know if there is anybody who can test or repair it (I am in Southern England) or whether I should replace it, and if so with another Fireface or something else. I can't think of a solution which isn't expensive...

Re: Is my Fireface UC working properly?

PostPosted: Sat Sep 07, 2019 1:56 pm
by 1961TC4ME
There's about a million ways, well not quite, but close, to adjust the audio input between your soundcard and Hauptwerk, from what you describe I suspect that's where your problem is. You are able within Hauptwerk to individually adjust the db of each channel, mine usually set to zero, adjust the input using the input dba adjustment, mine usually set to -10 or so for each set. You can also observe the audio input in Hauptwerk. Is the meter going into the red? Then there's the control panel for your soundcard you can open and also see where things are set there. I'd suspect one of the mentioned settings is just too high causing the distortion. If you don't know where to look for these settings just ask, someone here will be happy to assist.


Re: Is my Fireface UC working properly?

PostPosted: Sat Sep 07, 2019 2:55 pm
by JulianMoney-Kyrle
Thank-you, Marc, for your reply. I don't think Hauptwerk output levels are to blame. With the Fireface mixer set at 0dB attenuation, I have to reduce the output of most of the organs I play by 15 - 20dB using the Trim function on the floating windows. This is still quite loud, and sometimes I have to use the volume slider in the same window. The meter is nowhere near the red, however, and even if I turn the volume down the distortion is still there. My monitors are capable of going very loud, much louder than I would ever want, so they are well within their comfort zone, too.

My soundcard has a mixer app to control it, so I can readily adjust the input and output volume of each channel, as well as re-route them or mix them down (e.g. for the subwoofer).

I don't think the problem is as simple as an amplifier being overdriven. When I made my tests using my HiFi I completely removed the Fireface from the organ. The only input was from my Sonos:Connect, into the SPDIF socket, and the only output was a pair of balanced analogue channels going into a balanced XLR input on my HiFi amplifier. The Sonos:Connect also has an analogue output (normal HiFi-type line-level phono plugs) which I connected to another input on the amp so that I could easily switch between them. The distortion was still present, and indeed much more obvious when I had a decent system to compare it with.

In case you are unfamiliar with Sonos, it is essentially a networked music system that will stream music from the Internet or from other devices on the home network (LAN or WiFi). I have an NAS (network hard drive) with all 2,000 or so of my CD's stored as lossless FLAC files which I can play through the system, including a test disc with various files such as sine waves and pink noise. Sonos make self-contained players, TV Soundbars with satellite surround speakers, and also units which will play through a HiFi; with this the quality is very good and I would say comparable to a decent CD player. The Sonos:Connect is one such, and has an internal DAC to give an analogue output, and also a digital output in case you have an external DAC (my Cambridge Audio amplifier has one built in, but I can't hear the difference from the Sonos one). I would expect the Fireface DAC to be of comparable quality, but either it isn't, or there is something wrong with it. There are reasonably good cheap DAC's everywhere - smartphones, motherboards, bluetooth speakers etc., and I would have thought the Fireface would be noticeably better than those.

One thing is that there doesn't seem to be any difference in the sound between the various channels of the Fireface, which makes it harder to prove a definite fault.

With Best Wishes,

Re: Is my Fireface UC working properly?

PostPosted: Sat Sep 07, 2019 6:48 pm
by 1961TC4ME
Hi Julian,

I don't think it's a situation of an amplifier / amplifiers being overdriven either. For some reason you've got a rather 'hot' signal before the amplifiers and the signal is already distorted and the amplifiers are just playing what they're getting. A setting issue somewhere either in Hauptwerk or your soundcard seems to be proof as you report you have to drop the db of the set to -20 and you say it is still rather loud and distorted. At -20 things should be rather quiet. I'd also guess you probably notice as you pile on stops the distortion gets worse.

I know Martin and others here suggest setting the volume slider to 100, that has never worked for me and I use the volume slider daily and with every set I have. The way I have it set up, 75 is quite loud to bordering on getting out of hand, 35 to 45 is in the adequate ideal volume range for me (and the rest of the household occupants for that matter :lol: ). If I ramp it up over 75 the signal begins to clip and distort. Maybe take a close look there if you're sure everything else is set correctly?

A question: If you're able to listen through headphones, do you get the same results?


Re: Is my Fireface UC working properly?

PostPosted: Mon Sep 09, 2019 12:59 am
by orcoaffamato

I have a RME Digiface USB and in Totalmix I've set the output level of each channel at -18 dB in the Dim setting and I can switch it back to 0 dB turning off the Dim button (I never do that 'cause I don't want to blow my speakers).

Can you adjust the output levels on your speakers? Or are they fixed?

Did you measured the dB level in your listening position? I set mine at 85 dB using a pink noise wav file and a decibel meter mic.

Re: Is my Fireface UC working properly?

PostPosted: Mon Sep 09, 2019 2:32 pm
by JulianMoney-Kyrle
Hi Marc and Orcoaffamato,

I am using Behringer studio monitors with built-in amplification, but they don't have a volume control. I have some audio analysis software on my iPhone, and although it is no substitute for proper equipment, like many apps it is surprisingly useful (particularly for tuning the graphic equaliser in my car). When I play test files through my system I can easily reach over 100 dB without them being close to overdriven (I can't say the same for my ears).

Thanks for your tip about the Dim button, which I hadn't noticed previously, and while trying to figure it out I have discovered how group faders together (I think the technical term might be gang) so that I can change the levels of each channel together (you shift-click on the slider button of each fader and they go orange to tell you they are grouped). Indeed I have found it is well worth getting to know how Totalmix works as it is a powerful and easy way to control where everything is going while making tests.

Within Hauptwerk if I set the volume slider to 100 and the trim to 0 dB then the indicator in the same window starts to go into the red with full organ (and it is deafening unless I turn everything down in Totalmix). Depending on the organ, -18 dB in Hauptwerk and 0dB in Totalmix is about right; here the Hauptwerk meter stays well to the left of the green. If I set -10 in Hauptwerk and attenuate the signal in Totalmix then it is still well within the green, so I don't think anything is being overdriven in Hauptwerk itself.

I have tried fiddling with the levels as above, and it doesn't seem to make any difference to the sound whether I have it set loud in Hauptwerk and quiet in Totalmix, or the other way round, or somewhere in between. The distortion is less obvious if the sound is quieter but it is still there.

With headphones in the Fireface headphones socket, all the channels mixed down to the phones and the other outputs muted, I would say that the distortion is less, but still present.

I have tried routing the output of Hauptwerk to my PC's onboard nVvidia chip and plugging the headphones directly into the PC. The sound overall is much more muddy and it is hard to say what is happening to the high-frequency distortion. I have also tried using different USB ports, using DirectSound drivers instead of ASIO (these introduced a different amount of delay for each channel makinig the organ almost impossible to play), updating the Fireface Windows drivers and updating the Fireface firmware.

I have also tried using a different digital source through the Fireface and Behringer monitors, by plugging my Sonos player into the SPDIF input. This sounds terrible through the Behringer monitors, and when I output it instead to my HiFi system it was better but not as good as using the HiFi's own digital input (Cambridge Audio amp and Tannoy speakers). I get the impression that the SPDIF input is worse that the virtual inputs coming through the USB port, but I don't use it for Hauptwerk in any case.

It does make a difference which temperament I am using. Playing an F-major chord with full organ on Velosovo using original organ temperament some of the upperwork is slightly out of tune, and switching to equal temperament the sound is cleaner and the distortion is less. Of course if there is intermodulation distortion present you would expect it to be worse if the various frequencies aren't harmonically related

I am getting so fed up with troubleshooting that I am going to try another interface. If that doesn't help then maybe the problem is my aging hearing (sensorineural deafness is often associated with a phenomenon known as recruitment, where moderately loud sounds are perceived as very loud and distorted - standard hearing tests only measure the threshold of hearing for different frequencies and don't assess the effect of damage to the auditory nerve, which can certainly affect intelligibility of speech).

Re: Is my Fireface UC working properly?

PostPosted: Mon Sep 09, 2019 3:26 pm
by orcoaffamato
How many channels are active on your Fireface UC? How many do you use?

You can disable the channels that you aren't using in the Fireface USB Settings Menu, under Options - WDM Devices (as written in the manual: Reduce the number of WDM devices to the ones really needed to improve performance of the operating system).

I saw that in the settings you can adjust the gain:

Line Out
Defines the reference level of the rear analog outputs 1-6. The available settings are -10 dBV, +4 dBu and HiGain.

And what about your Buffer Size and Sample Rate?

Re: Is my Fireface UC working properly?

PostPosted: Tue Sep 10, 2019 4:50 pm
by JulianMoney-Kyrle
I have just tried substituting the Fireface with a MOTU Ultralite Mk4. I had a rather frustrating time trying to get it all to work, until I realised that Hauptwerk was overworking the CPU because the buffer size was too small (it was set at 128). I increased it to 1024, which solved the problem, but the latency went up to 48ms, which is a little uncomfortable for fast playing, but 512 gives a latency of 24ms and the CPU load is well within the green. The MOTU controller lets you disable all the channels that you aren't using (in my case nearly all the inputs). The analogue outputs are at a higher level than the Fireface, which makes them louder than the ADAT ones going through a Behringer DAC, but eventually I worked out how to trim the outputs so that all the pipes sound at roughly the same volume.

The sound is definitely cleaner than it was before, so either there are some settings I have inadvertently changed which have solved the problem or else the Fireface really wasn't working properly. The MOTU also sounds better than the Fireface playing my Sonos system through the SPDIF input, though this makes it clear that the Behringer Truth monitors are markedly inferior to my HiFi system (not surprising as the HiFi amp and speakers cost ten times as much as a pair of the Behringers).

I have tried it so far with Velosovo and Freiberg - full organ still sounds a bit screechy with the Freiberg and I shall probably have to adjust the voicing of some of the mixtures. Silbermann was famed for the silvery sound of his organs (I expect he encouraged the pun on his name) and you can hear that on recordings of the Freiberg instrument (e.g. David Goode playing Bach). I expect if I want to reproduce that with my HW system I would need to use more expensive speakers and not sit so close to them, but that isn't really an option.

Anyway, it is certainly better to play, and I have found myself listening to how I am playing rather than being distracted by distortion, and the whole experience is more musical now.

Re: Is my Fireface UC working properly?

PostPosted: Tue Sep 10, 2019 5:27 pm
by brooke.benfield
JulianMoney-Kyrle wrote:
I am using Behringer studio monitors with built-in amplification, but they don't have a volume control.

Check out the back side of your Behringers and find the Input Trim potentiometer. It provides +/- 6dB of "volume" control. Not quite the same thing as a typical Volume Control on a stereo, but it does give a real world ~+/-50% change in volume from the 0dB position on silkscreened scale.

Re: Is my Fireface UC working properly?

PostPosted: Wed Sep 11, 2019 4:21 am
by JulianMoney-Kyrle
Thanks for the suggestion. I am already using the trim and other adjustments at the back of the Behringers in order to compensate for room position. I have them stacked on top of each other and the effect of this difference in position is quite audible. I am now using the trim facility on the MOTU to compensate for the ADAT and analogue outputs being at a different level.

Anyway, for whatever reason it is now sounding noticeably better than it did with the Fireface.