Gearing up for measurements with REW -various issues I might need some help with.

[antcollinet]

So just got my Ultralite Mk5 and just learning how to use it. Note this is with a Mac.

For that purpose, I've looped SPDIF out to SPDIF in, and am using REW generator and realtime analyser to see what is going on.

This is working and I can generate signals and use the RTA to analyse them. Where I am stuck though is getting better than 16 bit performance, which with a fully digital loopback should be easy. As you can see for the 1kHz sine analysis, I'm only getting 96dB SNR, and ENOB = 16.

I'm assuming there must be something somewhere limiting the input our output (or both) bit depth, but can't find it.

• I can't find any bit depth settings in REW and it's status at the bottom of the page is showing 24 bit in and out.
• Cuemix doesn't seem to have any bit depth settings.
• The Mac Output settings (Midi and Audio) has it set to 32 bit float with no option to change.

Any ideas what I am doing wrong?

 

[staticV3]

See the "Use 64-bit FFT" section here:

RTA Window

I think the setting is under Distortion.

That may help a bit, but I don't think it's the smoking gun limiting you to 16-bit-esque performance.

Issues like these are why I prefer Windows

 

[mcdn]

Go and check in the audio midi settings app on your Mac. That’s where you set the bit depth and sample rate for the interface. Set to e.g. 96/24, restart REW and you should be fine,

 

[staticV3]

Go and check in the audio midi settings app on your Mac. That’s where you set the bit depth and sample rate for the interface. Set to e.g. 96/24, restart REW and you should be fine,

?

The Mac Output settings (Midi and Audio) has it set to 32 bit float with no option to change.

 

[antcollinet]

?

Exactly.

 

[antcollinet]

See the "Use 64-bit FFT" section here:

RTA Window

I think the setting is under Distortion.

That may help a bit, but I don't think it's the smoking gun limiting you to 16-bit-esque performance.

Issues like these are why I prefer Windows

Sadly made no difference.

 

[olieb]

Go and check in the audio midi settings app on your Mac. That’s where you set the bit depth and sample rate for the interface. Set to e.g. 96/24, restart REW and you should be fine,

I do not think that the settings in "Audio-Midi-Setup" (app on the Mac for configuring audio devices) is the reason for the problem (as anticollinet gets ENOB 16.1) But of course one has to check there first.

Exactly.

In the app you can configure the audio devices for the Mac: channels, bit-depth, sampling frequency ....
It is part of the Apple system app collection.
Maybe there is a config in the Ultralite?

 

[Blumlein 88]

Just as a check try the same thing using Audacity. Audacity does not suffer from the ASIO issues in MACOS.

 

[Rja4000]

Could you show us the REW generator and preference windows?

 

[antcollinet]

bit-depth

Which is locked to 32bit float. This is the output, but the input is the same.

Could you show us the REW generator and preference windows?

Yes...

 

[staticV3]

Which is locked to 32bit float. This is the output, but the input is the same.

View attachment 431073




Yes...

View attachment 431071View attachment 431072

16bit dither perhaps? There should be an option.

 

[olieb]

Which is locked to 32bit float. This is the output, but the input is the same.


Yes...

View attachment 431071

staticV3 might have found it.

REW looks a bit different for me

With 16bit dither I get a very similar result to yours.

 

[antcollinet]

Brilliant. That's fixed it. Thanks.

Don't know how I missed that. Wood for the trees I guess.


Now I know why - Screenshots above were from a Beta version. While you were providing me with the answer, I removed it and re-installed the standard version. That shows the bit depth of dither which the beta didn't have.

 

[AnalogSteph]

So you're on 5.31.3 now, instead of 5.40 beta something or other? Note that this still contains the "ENOB 0.5 bits too high" bug (fixed in 5.40 beta 57 after being discussed here on ASR). BTW, 5.40 beta 49 fixed a bug "Dither bit depth box was missing for tone generator", so is it possible you had a version preceding that?

 

[sam_adams]

Any ideas what I am doing wrong?

Did you install the drivers for the device?:

https://motu.com/en-us/download/#category=1&product=483

Make sure that your sample rates in Audio MIDI Setup.app match the sample rate in REW. I see that you created and loaded a calibration file for the device. Is that .cal file using the SPDIF digital loopback? if so, that's not going to help you if you are using the analog inputs/outputs to measure with for obvious reasons.

 

[antcollinet]

Did you install the drivers for the device?:

https://motu.com/en-us/download/#category=1&product=483

Make sure that your sample rates in Audio MIDI Setup.app match the sample rate in REW. I see that you created and loaded a calibration file for the device. Is that .cal file using the SPDIF digital loopback? if so, that's not going to help you if you are using the analog inputs/outputs to measure with for obvious reasons.

Yep, drivers installed. But all good now.

 

[antcollinet]

so is it possible you had a version preceding that?

Must have done - though I can't check now because it has gone, blasted into the infinite digital wasteland.

If the later betas are known to be more or less bug free, I'll probably go back to the latest.

 

[antcollinet]

OK - I'm back to playing with an SPDIF loop back to try to get a good understanding of all the REW settings. I'm currently trying a spectrum of white noise measurement.

This seems to be working fine, except that I can't get a spectrum to extend beyond 20kHz. I have a 96kHz sample rate setup for the Ultralite, and on the input and output settings in Sound/Midi (I'm on a Mac, remember.)

I've set the generator to output white noise with a 38kHz high end cut.

But the analyser is only showing a spectrum cut off at 20khz. Something is applying a 20kHz filter somewhere but I can't find it.

Any ideas or suggestions gratefully received (PS - I've not yet upgraded REW - so still on 5.31.3)

Screenshots as icons:

 

[olieb]

I can confirm that is not due to the REW version. I just tested V5.31.3 with an internal loop and I do get signals above 20kHz.
A filter setting in the Motu? Standard (dac) filter?
I did the internal loop with a little tool "Blackhole". There is a download (donation).

BlackHole: Route Audio Between Apps

Zero Latency. Perfect for Streamers, Podcasters, and Online Instructors.

existential.audio

So you can check whether the problem is internal or external.

 

[antcollinet]

I can confirm that is not due to the REW version. I just tested V5.31.3 with an internal loop and I do get signals above 20kHz.
A filter setting in the Motu? Standard (dac) filter?
I did the internal loop with a little tool "Blackhole". There is a download (donation).

BlackHole: Route Audio Between Apps

Zero Latency. Perfect for Streamers, Podcasters, and Online Instructors.

existential.audio

So you can check whether the problem is internal or external.

Thanks - my next step will be to try an analogue loop back.