VSTiBoard interfaces

A project log for VSTiBox

VSTiBox is a synthesizer for hosting VST software synths.

Jan BertJan Bert 10/17/2018 at 21:090 Comments

In my latest mechanical design I am using two black Arturia Beatsteps. The size of the Beatsteps causes the overall size of the synth to increase a bit. But this doesn't bother me. Because the Beatsteps have so many buttons and encoders, I am thinking of using the right Beatstep as menu interface instead of the 8 RGB buttons and menu encoder that is currently on the VSTiBox. 

The increased width also creates a perfect space for the pitchbend and expression wheels.

The space above the right Beatstep can be used to fit an audio interface and mixer. The problem with my current VSTiBox is that I do not have enough audio input and output channels. I currently do not have a MIC input for vocoder stuff, and I'm using the onboard soundcard + an additional 2 channel USB interface for a clicktrack and backingtrack output. The clicktrack and backingtrack outputs are not ASIO and that gives some time sync issues when starting the track. I have addressed this issue by manually adding some milliseconds delay in the VST host code, but this is not a pretty solution. I'd like to have have an audio interface that handles all input and output channels on the same asio buffer update handler. 

My new requirements are:

I have drawn a schematic that shows the functional design of my ideal audio interface. The input and output channels have a visual indication on the audio levels. The MIC input and headhone output have a dedicated volume knob. All the other black virtual volume knobs can be controlled by a single big encoder, and some buttons to select the correct virtual volume knob. 

To achieve this kind of functionality I’m considering two options:

  1. Buy a multichannel PCIExpress audio interface like an SERAPH 8 MWX or RME HDSPe AIO PCIe plus a separate MIC preamp and headphone amp. This is an expensive but time saving route.  
  2. DIY custom audio interface. In this way I can have the audio level indicators and volume control exactly the way I want it, and a formfactor which fits the VSTiBoard perfectly.

At the moment I haven't decided yet what it’ll be, but I was recently inspired by freedsp. I have been in contact with one of the contributors and was gifted a bare PCB of the Infinitas. Awesome! The Infinitas is a working prototype of a USB audio interface with up to 32 in- and outputs. I've got the prototype with 2x freeDSPx-BAL-IO-x8 (also on Tindie). 

For low latency audio I do not want to use USB, but Ethernet. A latency of less than 0.1ms with UDP over Ethernet is very possible on a Windows machine. I could build an Ethernet controller board with the volume encoders and display options exactly the way I want it. Then use the Infinitas DAC&ADC stage and add a separate MIC preamp and headhone amp. For the controller I'd choose an iMX RT1052 or SAM E70 Cortex M7.