Topic: HDSPe MADI with M-32DA - Buffer Induced Jitter?
I have the above on evaluation for my virtual pipe organ project http://theatreorgans.com/ianmclean/. The organ runs on an Apple MacPRO running 10.6.7. The engine is Hauptwerk V4. My sample set runs @ 24 bits/48khz and the entire organ loads from RAM.
Up until recently this project was using four Echo Audiofire 12's (AF12). Before that it ran with three AF12s and one Presonus Firebox. Two AF12s started to fail about a month ago. As I have also owned an RME FF400 which was my recording interface, and which has delivered excellent results, consequently I decided to try out the HDSPe MADI with M-32DA as a replacement.
At the beginning of this evaluation process my plan was to keep the audio configuration identical. That is 41 channels (consisting of 37 audio channels, plus four ambience system feeds) and to clock the remaining AF12 from the RME gear. Indeed, I had previously clocked the four AF12s with some success from my FF400. However, clocking either an Echo AF12 or the Presonus Firebox from the WC out on the M-32DA caused the entire sound to malfunction (collapse is the best word which comes to mind).
So, I spent several hours reconfiguring Hauptwerk to permit a 'pure' RME M-32DA outcome. At the beginning this was the best sound that I have ever had, even with less channels than usual. But, it didn't last. Progressively the sound would get brighter and brighter and channel relativity would change. Turn it all off and start again, and things would be fine, and then the process repeated itself.
In discussions with the very helpful and skilled RME importer, we came to the conclusion that this must be down to buffer induced jitter. I posed the question as to whether it would be a different outcome if I boot camped the MacPRO and installed Vista 64 (which I run the FF400 from, well also with XP32). He wasn't sure. I also then tried different buffer settings in Hauptwerk. Normally they have been set at 1024 frames or 21ms @ 48khz. Resetting to 9ms delivered a more consistent outcome, however, the balance between audio channels altered and the attack was compromised in several channels. Changing to 5ms brought on immediate brightness, changing back to 9ms and it was gone. This process could be repeated. So, it seems that this proved the buffer induced jitter case. Or does it? Is it something else altogether?
Available Haupterk buffer settings:
256 frames
384
512
768
1024
1152
Or, in ms @ 48khz
5/8/11/16/21/24
HDSPe MADI
8 available buffer sizes/latencies:0.7/1.5/3/6/12/23/46/93ms
So, it would seem that the timing differences would never match up even if I moved to Windows? So why did the Audiofires work? Because they weren't constrained by the frame by frame design of MADI? Is MADI the problem here? Or does Hauptwerk need to offer more variations in buffers?
Given that for the few minutes that the 'pure' RME solution functions correctly can be stunning, it would be great if there is a way to make this work for me.
Thanks,
Ian McLean