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Logic TDM lightpipe and bandwidth
Old 18th November 2009
Logic TDM lightpipe and bandwidth

I have been a logic TDM user for some time now, currently using an HD1 PT system with logic as a front end and working in core audio mode with a MOTU 828 as the CA interface, looping back through lightpipe into Logic's DAE mixer. I had taken a haitus and worked on a lot of projects in Protools and upon returning to logic feel like Native/softsynth material sounds TERRIBLE along with everything else originating from coreaudio! Like it has a bandpass filter and compressor on it. I also run stand alone Kontakt instances tied into the MOtu interface via a Soundflower/828 aggregate device. These too sound pinched and small and murky. everything clocks to my 192 as master. Is there a better way to do this? Master clock? AES interface, RME fireface. I have been of the opinion for a while that digital is digital is digital but maybe not. Is AES better sounding than ADAT? Is a different firewire interface better sounding than the motu 828 clocked from the same sourxce and used for solely digital sources? I am scratching my head here, and about to blame it on Logic and abandon the platform, any thoughts??
Old 18th November 2009
I have a similar setup: Logic 8.02, RME Fireface via ADAT into Pro Tools HD2 (7.4.6) with a 192, and it sounds fine. In fact I had done some null-tests to see if the playback of a stereo file in Core Audio via TDM, and one from DAE directly would null, and they did. In fact until a few weeks ago I used a Motu828 too for the same purpose, but it finally died, after about 8 years of service.

So I don't know via you have bad quality coming from core audio. How does it sound from the Motu 828 directly through the analog outputs, taking into account the slightly inferior convertors of the Motu?

btw I remember your name from the TDM Logic Users list - which is deserted in the meantime....
Old 18th November 2009
oh and just remembered - the one time I had quality issues was when I was working in 48kHz (I'm working in 44kHz currently). I had an slave PC running Gigastudio piping in through ADAT into ProTools. On piano and timpani sounds I noticed aliasing artifacts. I think it had to do with Gigastudio's realtime SRC being a bit dodgy. Changing to 44k solved the problem.
Old 18th November 2009
Thanks Crimson

Did you do your null test with a couple of instruments or many? what I hear sounds like a bandwidth issue with dense orchestra mixes especially. I am working at 48 k and I am running a gigasampler in my adat chain but with SRC applied to the adat ins of the 192. I also use Kontakt (X2) in standalone and have SRC checked in Soundflower. Maybe SRC is the culprit here So in changing to the RME interface your ADAT carried signals sound the same as the MOTU ADAT channels??
Old 19th November 2009
I did the null test with one stereo file, and also with about 6 of them mixed. I guess either wouldn't really make a difference as what you are looking at is not the summing of the core audio mixer but how the sum actually gets transmitted out via ADAT.

I could very well imagine that the realtime SRC is the culprit. I have never tried the 192s SRC. I always work at 44kHz and then convert my final mixes with Barbabatch to 48KHz (for film &TV delivery).

I noticed no difference in sound by going from the Motu828 to the RME FF400, again I'm only using its ADAT interface.
Old 19th November 2009
That's 2 lots of src?

Try running a test with everything at the same sample rate. That should confirm or rule it out.
Old 20th November 2009
yes removing sample rate conversion from both improved things. I think my old Logic PT Legacy rig I used for years didn't like 48k so I worked at 44.1 and set SOUNdflower to SCR because it was acting up otherwise. seems fine now. Thanks!
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