Topic by forsterman

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  • forsterman
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Topic: USB VS Midi

Greetings,
I'm planning to get a digtial piano soon (Casio Px 350) and would like to use VST's for the sound. Pianoteq will likely be the first one tried. When setting up the pc, which scenario will give lower latency, piano to pc via usb then to audio interface via USB (UR22 or similar) then to preamp to amp to speakers. Is the output from the UR22 to preamp analog only?

Or would it be better to go Midi to UR22, USB from UR22 to pc, UR22 to pre/amp ect? When using this method, does the USB between the UR22 and PC talk both ways so that the midi signals get sent to pc then the Pianoteq sound gets sent back to the UR22?
thanks for your help

Last edited by forsterman (06-12-2014 16:39)

Reply by AKM

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Re: USB VS Midi

Also very interested in this topic. Some technical advanced people can tell this, the developers? I think one could test it just making 2 tracks in a sequencer getting a MIDI signal from a single keyboard to both of this tracks comparing the recorded MIDI tracks from a live play.

Last edited by AKM (06-12-2014 18:24)
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Reply by floyer

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Re: USB VS Midi

In both case, the latency caused by the USB link (between the PC and the MIDI-USB or directly the PX-350) would be the same. Around 1ms, since the device is pooled every 1ms (with USB, a device can't talk without a permission of the "host" - i.e. the PC. Then the host need to ask every 1ms if there is an event to be received). The 1ms period is the minimum that can be used at USB 1.0 "full speed"

The main effect of the MIDI link could be to add another milisecond (the MIDI link is a 31 250 bit/s link. With 30 bits per events, an event needs around 1ms to be sent.)

An other effect of the MIDI link could be to suppress ground loop (and an associated noise). But I have such a noise using at the same time the LINE-IN and the USB socket of my digital piano.

About the last question, USB device could be seen as multiple device (i.e. some USB key are seen as a CDROM and an hard-disk), then the PC could exchange with both subdevice with their specific protocol.

However, note that I have not done any measure...

Last edited by floyer (06-12-2014 18:51)

Reply by geert

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Re: USB VS Midi

Generally speaking, there is no noticable difference. After all, the Midi link, allbeit directly via USB, or via a Midi to USB interface, only has to transport note on/off messages and the Midi protocl is a serial communication-link at 31,25 kilobaud.  Also a direct USB link cannot trasport these items faster, as it is bound to the fixed Midi protocol.

This means that there is a very slight delay of around 1 millisecond.

This is all very much less than the latency that occurs in the process of audio processing and outputting the audio.

So forget Midi delay, and focus on audio latency. 

I use Pianoteq as a VST inside Reaper, and there I can have multiple instances of it, for example to playback a Piano Midi file, and on another instance of Pianoteq, play along with it in real time on a different instrument, let,s say vibraphone or so.  And I have no latency.
You can do whatever you like, latency most of the time is only generated by poor Audio devices and/or processors running on their toes.

I use a MOTU audio interface.

Reply by forsterman

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Re: USB VS Midi

geert, does running Pianoteq, or any VST, inside of Reaper provide for lower latency than just running pianoteq or others as a windows program?
thanks

Reply by stamkorg

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Re: USB VS Midi

forsterman wrote:

Greetings,
I'm planning to get a digtial piano soon (Casio Px 350) and would like to use VST's for the sound. Pianoteq will likely be the first one tried. When setting up the pc, which scenario will give lower latency, piano to pc via usb then to audio interface via USB (UR22 or similar) then to preamp to amp to speakers. Is the output from the UR22 to preamp analog only?

Or would it be better to go Midi to UR22, USB from UR22 to pc, UR22 to pre/amp ect? When using this method, does the USB between the UR22 and PC talk both ways so that the midi signals get sent to pc then the Pianoteq sound gets sent back to the UR22?
thanks for your help

I don't feel any difference in latency by using usb instead of midi.
But the usb connexion can generate or transmit some amount of electrical noises.
I recommand to use only a good midi cable to connect piano's midi out to your soundcard.

Reply by geert

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Re: USB VS Midi

I can agree with that.

But when you use a keyboard that does NOT need a separate AC power supply, like the Kawai VPC-1, or the Behringer UMX 610, etc etc, this is NOT the case.