Saturday, November 22, 2014

SRC using Analog loop back, a How to and description of my setup/workflow

By Tim Dolbear -

I talk about Sample Rate Conversion in 6 months into the 96k adventure.  Its a few blog entries down if you want to get caught up.

Well here is how I do it and some keys factors to note.

Sample Rate Convert by playback of a high resolution file and record or capture back at 44.1:

You need 2 different audio interfaces, 2 different brands, since one needs to run at 44.1 and the other at 88 or 96. Example I have a RME HDSP9652 and a HDSP 9632 but the ASIO driver sees its as 1 giant interface with 84 Ins/outs.

You also need 2 different audio software's to play and capture since they will be at different SR too.

Sequoia allows you to open 2 instances at the same time, one records from one setup of hardware, 1 feeds the the other for playback.

So I open up the Sequoia setup I named Playback, its using the Mytek 192DSD  D/A USB interface.  Its running at 96K and will play back my 96k stereo file. The Mytek is good for this setup since my RMEs are using 1 set of Digital inputs, and it also have a USB interface.  So I simply hit a button on the front to change from my normal recording everyday operation with my RMEs feeding it to USB input, so my Playback Sequoia can feed it.

I then open my main version of Sequoia which is always set to use the RME HDSP9652 +9632 interface. My Apogee is hooked to my RMEs. The setup is clocked from my A/D (Apogee AD16) and I switch it to record from my normal 96k to 44.1k. I open a session and arm a track to record stereo the input on my Apogee AD16 that is hooked to one of the 2 outputs on the Mytek 192DSD  D/A.

Playing back the Sequoia Playback instance, the file leaves the computer via the Mytek 192DSD  D/A and is captured back into the main Sequoia via the Apogee AD16. The recorded file is 44.1.

You can certainly add any hardware processing between the D/A and A/D, just make sure you address monitoring. In my setup I am listing to the Mytek which would be prior to any analog processing.