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Audio driver problem


Not sure if this is the right sub-forum. I have an issue with the audio driver messing up every once in while. This is with the iCM4+. Here's the setup: A softsynth (let's say Animoog because it's rock solid) playing on my iPad, connected to the iCM4+ host jack 3; audio is being passed through to a Win10 laptop running Reaper and is received on a audio track there; there is another softsynth (let's say: Helm ) loaded in another track in Reaper; Reaper uses Asio4All aggregating (bridging) the iConnect audio driver as an input, and the ASIO driver from my Soundcraft desk as an output. All devices are set to run at 48k/24bits. The ASIO buffersizes of the individual drivers are all set to 256 samples in "safe" mode (that's way beyond the 64 samples the Soundcraft desk usually runs on). In the ASIO4ALL control panel though, the iConnect driver is set to 512. But whatever buffersize I use doesn't matter. When I start playing, I can play for half an hour without a glitch or a pop, and then all of a sudden the iPad sound heavily distorts (typical of a driver issue, losing the clock). It can go away by itself when I leave stuff idle for a while, or not.
-on the headphones of the iPad the Animoog sound remains perfect, so it's not the app.
-the Helm sound, running on the laptop, as heard on the mixer (via ASIO4All=>Soundcraft  USB driver=> mixing desk) remains perfect as well, so it's not the Soundcraft driver
-restarting the Animoog doesnt help
-restarting Reaper, thus closing and re-opening the drivers on the Windows side does help.
-In Windows, system sounds are disabled; onboard audio is disabled; laptop running in "airplane" mode;
-I tried various buffersizes to no avail (took me a day because this happens every 15 minutes or so)

This is rather annoying, a showstopper indeed. I am really enthousiastic about this AudioThrough feature, some plugins sound really amazing when using the Souncraft converters.
What can I do to debug this? (I'm quite computer-savvy, I have coded a series of VST plugins in C++ myself (but not active anymore), don't hesitate to suggest the difficult stuff) My iPad sure is an old one, but on the headphones the Animoog (and the other plugins I tried out, I don't use many) runs fine (it was developed initially when my iPad was current).




  • One more precision: the symptoms are: a huge amount of distortion, that remains for quite some time, but if I leave averything idling for a while, that distortion gradually fades away leaving some crackles. To get rid of this for 20 minutes or so, what works best is a reset of the iCM4+. I tried changing the number of buffered audioframes in the iConfig software but that doen't change anything. I don't know what the other setting ("sync factor value") does. I'd rather wait for your input before checking that out because it's extremely time-consuming to debug an event that happens only every 20 minutes.
  • Sounds like the digital clocks de-syncing in ASIO4ALL. Basically aggregating audio interfaces with ASIO4ALL is a hack, and if it works at all it's kind of a miracle. You could try playing with the sync factor value I suppose, but I very much doubt if this is fixable given your current setup.
  • Well, as I understood "sync factor" only reports the amount of latency compensation  the host should apply. So that's of not much help. There are a few clock settings in the iConnect application: we can sync audio to internal clock or one of the 3 USB device jacks. Does that mean attempting to sync to the host's high precision timer? Can't be syncing ASIO to midi, that doesn't work. I agree ASIO4ALL is quite a miracle. The overall latency when using ASIO4ALL is a bit on the high side for serious keybord playing, but it's acceptable for playing pads and atmospheric stuff, so i would suite me if only I could eliminate this risk. When rehearsing in private, it doesn't kill anyone but in live performance would be devastating. I'll do some more experimentations, in the meantime I'll use the headphone out of the iPad into a Radial DI specifically designed for that purpose and then into the desk. It's pretty decent, the Radial stuff is very well designed and sounds good. BTW I ran Latency Monitor on the laptop that hosts the ASIO4ALL driver to check DPC latency and other issues, when the iConnect driver desyncs everything remains normal (in fact, super-fine, this computer is nice and well configured for live-audio)
  • It used to be the case that you should always sync to one of the audio interfaces and the iPad would follow, but from what I gather iPads don't like that any more and prefer to be the sync master. I *think* - Apple change this kind of stuff all the time and rarely bother to explain it.
  • I still have an old iPad2, but was considering upgrading. There's no way I set an iPad to be a master clock in my set-up, so I'll reconsider. Thanks for the information.
  • edited October 2018
    It's not the model of iPad that counts, it's the version of iOS running on it. I think from iOS 10 or 11 the iPad likes to be the clock master.
  • edited October 2018
    Yes I understood, my iPad2 is limited to iOS 9, I wanted to upgrade because I want to run some the Moog Model D which doesn't run on iOS9

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