-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Mon, Jul 23, 2007 at 10:53:40PM -0400, Lee Revell wrote: USB audio interfaces seem to be pretty cheap and reliable. I'm using a FastTrack Pro now, and previously used a USB Audiophile, both of which obtained for less than US$100 each, and they sound great. I have an ASUS laptop; the hda-intel chip on-board is caca. It's also hardwired to the same interrupt as the video driver-- useless for low-latency audio. You could use firewire, but note that that some ASUS laptops (like mine) also have the dreaded Ricoh FireWire chipset, which, alas, does not have the "works" bit enabled. It's also hardwired to the same interrupt as the video and the hda-intel, doh. Firewire ExpressCards and PC Cards are cheap though, I got one with a TI chipset for US$60, and the ExpressCard slot shares an interrupt only with eth0. For live use, I have been using a self-powered FastTrack USB audio interface with: jackd -R -P70 -dalsa -r44100 -p128 -n3 -Phw:0,0 -Chw:0,1 The FastTrack is stuck at 44100 on Linux, for some reason, which is annoying but acceptable to me in a live situation. The Audiophile USB runs at 44100 or 48000 and beyond. - -ken

On Sat, 28 Jul 2007 15:07:44 -0700 "Thomas Vecchione" <seablaede(a)gmail.com> wrote: I would like to add a few comments here. Total isolation on the power side of a lot of equipment is now an economic prospect. I have a Sound Canvas that requires 9V at 1 amp and an SY35 that requires 0.8A at 12 V. What I have done is to put DC-DC converters in the dc power lines. That way the power bricks are correctly earthed but there is no earth loop on the other side (these converters are typically isolated to 2000V). You have the added advantage that the supply is now regulated and well filtered (where the power brick usually isn't). These modules are typically 30ukp. The only part of my system that has a direct earth is the computer itself, all other supplies are floated SAFELY. The amp I use for monitoring is relatively low powered and is plugged into a small safety isolating transformer. -- Will J Godfrey http://www.musically.me.uk

Try a different power strip? Shouldn't be the case, but just in case. Also make sure your outlet is running off the same circuit on the top and bottom, I have been some places where it hasn't always been the case. Couple quick questions, does varying any of the level controls on your interface make a difference in the volume of the buzz? Does it change at all when moving the mouse, or when your HD spins up, or you make your video card do work(Change desktops etc)? Does it exist when nothing is plugged into your interface, or when only certain things are plugged in to it, but not others? I have captured a sample of the buzz (normalized; it's nowhere near this To be honest, I am wondering if there aren't a couple of different things adding up in your case, most of the time a ground loop on a laptop, unlike in straight audio, will show up as digital noise that fluctuates as you move the mouse, or videoc ard starts going a bit harder, or your HD spins up. This sounds a bit more like standard interference, of the sort I would expect to find from a poorly shielded or isolated internal audio on the laptop. As such running through an external interface means that you should not have that problem. The audio wiring you were told is an internal problem on laptops, only applies to internal audio, it does not apply to external audio. Internal audio cards are prone for problems because they are poorly, if at all, shielded and pick up lots of interference from other devices, and the general signal flow on a laptop, both power and data, is generally not done for audio quality. I have been told that this is probably caused by the power distribution Again though see above, the problem you are referring to should only affect internal audio, not from an external interface. And to confirm, your USB interface is bus powered? I assume then you are running it without the power cable for it? Does this problem exist if you unplug your amp, but leave the settings(Gain etc) like you still have it plugged in to your interface(Meaning nothing is plugged in at all)? So far the only thing that works is to lift the ground on the power supply. A simple cheap DI box will do it fairly well in most cases. They usually have a ground lift switch on them for just such a purpose. If you make your own, a 1:1 transformer will do the trick. Seablade