USB Isolator

Can anyone recommend a USB isolator that I can place between the USB output of my PC and the input to my USB audio interface to reduce / eliminate the computer noise getting through.

Many thanks,

Peter

I haven't heard of any USB isolators needing to be used before. The midi standard typically has optoisolators at each end to make this kind of thing unneccessary. What is the problem that makes you think you need one? If it is noises in your speakers, a power conditioner is typically much more useful. Computers are usually pretty tightly regulated, and you shouldn't get any significant currents in their grounds unless they are coming from the wall. The power we get from the wall varies a lot. For instance if there's an arc furnace anywhere in your city, you can count on interference while it's being run. It was pricey, but I got a Furman PL8C, and the difference in noise in my monitors was amazing. All that being said, USB isolators can be cheap (I wouldn't get an expensive one, those are for, say running a laptop in a plant while the arc furnace is running). I just predict you'll be disappointed. There's probably way more unintended currents coming from the power cord.

The noise is nothing to do with midi. I have a USB link from my PC running Hauptwerk to my audio interface (and then to the main audio amplifier and on to the speakers). The noise I am referring to is noise from the PC which then gets into the audio interface and finds its way through the rest of the audio chain. I know it's PC noise as it varies as, for instance, the PC boots up and to keyboard keystrokes etc. It is not really a problem but is noticeable if the volume of the audio amplifier is turned up above my normal setting. A USB isolator would have opto-isolators which would greatly help remove the noise. I have tried one but had some issues with it so I am after any suggestions of one that other people have used and have had success with.

Peter

Well I guess you can keep on buying USB opto isolators hoping one will work. Don't be surprised if they don't work, or don't fix your problem though. There's a reason why no one here uses them.

Edit: I mean, I know you're an engineer and all, and you've been around longer than I have, I just don't understand why you think it's more likely the computer is sending a false current compared to the wiring in your building acting as an antenna picking up your computer. I can't imagine that audio going through USB is going to work well with anything interfering with the signal. So even if that were the problem, I don't think the optoisolator is going to work. All of the interference problems I've had have been related to the power.

Needless to say that the USB-signal itself, being digital, won't pick up disturbances from the PC power supply, but: What might be a potential cause could be a ground loop, and in that case a USB-isolator should indeed solve the problem, as long as it isolates all wires of the USB, not only the data. It also needs to isolate the USB power and ground for it to solve a ground-loop issue. And ground loops are to my knowledge one of the most common causes of intereference problem, but can also be the hardest to solve.

The likely problem would be running unbalanced cables from the audio interface to the amplifiers or powered speakers. It's normal to be able to test the audio interface and computer interface (USB-MIDI) and see 90db or better signal to noise ratios. Run balanced audio cables and keep all AC power coming from the same electrical circuit.

Although I have not used one with Hauptwerk, I did need to purchase one for my Pianoteq setup. I was getting background noise and tracked it to the USB MIDI connection. I bought a cheap “bare board” isolator on eBay and it solved the problem.

The first, and probably cheapest, thing I would try would be clip-on ferrite chokes on all the mains leads.

Nick