recording/playback glitch at 24bit/192khz

[joebee53]

Hi Paul,
Picked up a new Focusrite Forte to record at 24/192. Connected via the mic preamps using the inverted RIAA/software RIAA. When I go to edit the tracks, the waveform looks fine but upon playback there is a second or two of high pitched noise then no audio although playback continues. I have recorded a few sides at 24/96 at the same settings with no problems. Any ideas?

[Paul Sanders (AlpineSoft)]

Hi,

Sounds like a hardware issue.  Can you try recording in Audacity (which is a free download) to see if you get the same problem please?

http://audacity.sourceforge.net/download/windows
http://audacity.sourceforge.net/download/mac

[joebee53]

Downloaded the latest version of Audacity 2.0.3 and tried recording at 24/192 and have the same issue. Have notified Focusrite tech support. Waiting on their reply.

[Paul Sanders (AlpineSoft)]

OK, thank you.  I will be interested in what they say.  Are you on PC or Mac?

One thing that might be relevant is that at 24/192 you will need a USB 2 port rather than a USB 1 port.  But they're all USB 2 these days, so it's probably not that.

[joebee53]

On a 2011 Mac mini 2.3ghz i5 with 8gb RAM, Mac OS 10.8.4, the Forte plugged straight into a usb 2 port on the mini recording to a thunderbolt raid one array. As of right now, have not received a reply from Focusrite tech support.

[matthew]

Hi,

I also own a Forte and have been using it for vinyl transfer with Pauls RIAA filters.
Superb results at 96/24 or 48/24!
The Forte preamps are very good indeed and give the vinyl transfers real tangibility.

I guess I've been through everything you are doing to create the best transfers possible.
I tried all sampling rates etc.
I do remember having an issue playing back in VS with 192 transfers through the Forte.
However the final ALAC 192/24 files created for ITunes played back fine.
The problem is specifically between the Forte driver and VS somewhere but only at 192.

However its not really a concern.
Download ABXer and try ripping at different sample rates then listening back through the Forte.
I will bet that you cant pick apart 48/88/96/176/192.
There does seem to be something I can pick out between 44 and 48.
I use 96 rather than 48 as its sometimes slightly better at declicking maybe Paul could shed some light on that?

For any recent high spec ADC this kind of behaviour would generally be expected as the old arguments about compromised filter design at 44/48 are long gone.
Do a spectral analysis in VS of rips at different sampling frequencies and you can see the sharp tailoff generally just above 20KHz.

Matthew

[Paul Sanders (AlpineSoft)]

> I use 96 rather than 48 as its sometimes slightly better at declicking maybe Paul could shed some light on that?

Not really.  We convert to 44 kHz to declick as the algorithms are tuned for that sample rate.  Note that this doesn't affect the sample rate of the final file.  It's just that the declicker scans at 44 kHz.

I would not expect VinylStudio to have problems playing at 192 kHz.  It certainly works here in testing.  Perhaps you could expand on the difficulties you encountered.

[matthew]

I remember when playing 192 tracks in the edit windows a high pitch whistle would occur for about 2 seconds and then silence on the forte output.

96,88,44,48 sample rates were ok.

However as mentioned playing back the 192 file in itunes was fine.

Maybe Im getting mixed up on the declick, would it be the riaa filters that are slightly better at 96 rather than 48?
If not then yet again it could be a figment of imagination and I need to ABX again!

[Paul Sanders (AlpineSoft)]

That sounds like a hardware problem.  It may be that iTunes is not playing back at 192 kHz - it certainly wouldn't surprise me if that were the case.  joebee (see below in this thread) reports the same problem, both in VinylStudio and Audacity.  I believe he plans to contact the manufacturer.

The RIAA filters should work equally well at all sample rates, although we do use a longer FFT at higher sample rates (because there are more samples to process, so it should cancel out).

[matthew]

Ok thanks.

I will wait to see what happens.

Could you post back JoeBee when you get a response?

Although as mentioned initially 48 sounds to be just as good as 192.
I cant pick them out in ABX.