[sdiy] USB/MIDI ground isolation?

[Seb Francis]

Colin f wrote:
>> -----Original Message-----
>> From: synth-diy-bounces at dropmix.xs4all.nl 
>> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of 
>> johnspeth at yahoo.com
>> Sent: 16 September 2009 23:18
>> To: SDIY
>> Subject: [sdiy] USB/MIDI ground isolation?
>>
>> We all know that the 5 pin DIN version of MIDI provides 
>> isolation between grounds by virtue of the optocoupler.  Can 
>> anyone tell me how they addressed the ground isolation 
>> problem with USB/MIDI?
>>     
>
> I think in a fair number of cases, the issue of grounding noise problems was
> resolved by the designers crossing their fingers and hoping all the end
> users would have laptops with double insulated PSUs.
>   

Are we talking here about 50Hz hum or high frequency whiny computer noise?

When developing digital audio projects via a USB ICD2 
programmer/debugger, you *really* hear the latter type of noise when you 
hook it up.  Maybe that's more to do with how the power supplies are 
getting coupled though rather than an earth loop?

Perhaps I've been lucky but I've never experienced either type of noise 
using the various USB-MIDI boxes I've had over the years.

Seb