• Registered: 2011-01-30
  • Posts: 66

Topic: UFX - loopback vs direct DAW delay - Mainstage 2

I have done a test to check phase issues with loopack recording.

The test is done in Mainstage 2 (Logic 9.1.3 too), 44.1k sampling, firewire connection, OSX 10.6.6, fw driver version 2.89, 0.924 TotalMix:
My setting for "DSP EQ+D for Record" is off in Fireface Settings.
Mic channel 9 is routed in totalmix fx to submix AN1/2 with loopback on

Mainstage has 3 channels:
1 <- mic 9 ; pan: 100% left
2 <- input 1(from the loopback); pan: 100% right
3 -> sine sweep form test oscilator -> output 3/4 -> speaker -> mic connected to mic9 input on UFX

channels 1,2 go to output 11/12 which have a correlation meter and x/y stereo graph in insert path
there is a phase and level difference between the channels.

I have inserted sample delay on both channels to check which one is falling behind:
with 10 samples on ch 1 (8 with 96k sampling)
and  0 samples on ch 2
i've got my correlation aligned.

setting the routing in totalmix fx to mic9 = 0.0db, AN1/2 output = 3.0db made them equal by amplitude in DAW.

Setting the "DSP EQ+D for Record" to ON in Fireface Settings
made a difference. now:
with 6 samples on ch 1 (5 with 96k sampling)
and  0 samples on ch 2
made my channels align

Why is the loopback coming earlier then the mic input? why does setting the "DSP EQ+D for Record" to ON made the delay smaller?  Why are they not the same amplitude although the routing mic9->AN1/2 is set to 0.0db?

Fireface-UFX, Mac OSX 10.6, Logic 9, BCF2000, AC-7 user, vocalist, live sound recording
  • From: Germany
  • Registered: 2007-04-10
  • Posts: 9,557

Re: UFX - loopback vs direct DAW delay - Mainstage 2

Assuming I understand your setup correctly...

Zavieri wrote:

Why is the loopback coming earlier then the mic input?

Because the signal does not go through DA and AD conversion and through the air.

why does setting the "DSP EQ+D for Record" to ON made the delay smaller?

Because the DSP takes some time to process the signal.

Why are they not the same amplitude although the routing mic9->AN1/2 is set to 0.0db?

If one signal goes through DA, speakers, a mic, and AD again, how can the level be exactly the same as a digital loopback?


Regards
Daniel Fuchs
RME

Regards
Daniel Fuchs
RME

RME Support's Website

3 Reply by MC

  • MC
  • MC
  • Administrator
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 24,869

Re: UFX - loopback vs direct DAW delay - Mainstage 2

I think you indeed misunderstood his setup. Routing and DSP does add a delay of a few samples, and changing the DSP FX within the routing of course can change the amount of delay. The block diagram from all the routing between FPGA and DSP is so complicated that it makes no sense to show it (else I would have done in the manual).

The -3 dB sounds like it's caused by pan.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2011-01-30
  • Posts: 66

Re: UFX - loopback vs direct DAW delay - Mainstage 2

Daniel you misunderstood my setup.
Lets say I want to play an virtual amp modelling , what gives me less latency? This test shows that the signal comes faster to the daw when using the signal chain:
physical input -> ff UFX -> totalmix fx -> dsp -> output with loopback -> DAW
then
physical input -> ff UFX -> totalmix fx -> DAW

This seems strange to me so I would like RME to check if everything is working as intended. In latency critical applications every sample counts wink

Fireface-UFX, Mac OSX 10.6, Logic 9, BCF2000, AC-7 user, vocalist, live sound recording

5 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 24,869

Re: UFX - loopback vs direct DAW delay - Mainstage 2

Everything is working as intended. And I really don't want to discuss latency differences of a few samples, here equalling less than 0.2 ms while trying to play guitar...

Regards
Matthias Carstens
RME

MC's Website