pritch Posted May 20, 2006 Share Posted May 20, 2006 Possibly not the best place to be asking this, as it's a bit computery, but here goes... I've got a Phonic Helix Board 12 mixer. It's quite a nice little device, and hopefully is going to serve me well for the times when I'm pressed into doing sound. The board has a USB interface, so that you can record to / output from a computer. If I plug it into my laptop, then all's fine and dandy, fairly decent quality sound. If I plug it into my Mac, then the quality is awful, with white noise over the top of everything, whether I'm recording or playing sound. If I use my Griffin iMic (another USB sound device) with the Mac, then the quality is great again, so I know that the Mac handles USB audio with no problems. My hunch is that there's interference getting down the USB cable. But how do I clear it up? I've got it routed away from mains cables and everything. I look forward to your helpful advice and/or abuse. Link to comment Share on other sites More sharing options...
Andrew C Posted May 20, 2006 Share Posted May 20, 2006 There are all sorts of issues with laptops and sound. They are based around the architecture of the PSU. Try it on batteries. Does this help? I was under the impression that Macs are OK; my Acer is #####. I have to use isolating transformers on the outputs. Link to comment Share on other sites More sharing options...
Bobbsy Posted May 20, 2006 Share Posted May 20, 2006 The all-too-common issues with laptops and sound are more often to do with analogue inputs and the funny (or non-existant) earthing of the power supplies. Couple this with the noisy environment inside a typical laptop, and it's a miracle that you get any sound some times. However, with this being a USB feed, this shouldn't be the problem. Your board is outputting a stereo, 16 bit, 44.1 kHz sampling rate data feed via the USB port. Effectively, this is the same as a PCM .wav file. If you're hearing white noise instead of clean audio, my best guess is that your Mac is set up for something else...a different file format or possibly a different sample rate or bit depth. You don't mention the audio software you're using on your mac, but the settings on this would be my first port of call. Bob Link to comment Share on other sites More sharing options...
pritch Posted May 20, 2006 Author Share Posted May 20, 2006 Sorry, I should have been more clear. My Mac is actually a desktop machine, my notebook is a Windows machine, and it's fine whether it's running on mains or batteries. The Mac is fine with another USB audio device plugged in, but using this device kind of defeats the object of having a mixer with USB audio built in. I'm using Audacity to record. I also get the white noise when I play sounds though, through Audacity, iTunes or whatever. Regarding your point about earthing though, Bob... the Mac Mini that I'm using isn't earthed (mind you, neither is the laptop). Is that likely to cause a problem with noise going over USB? Cheers for the help so far, chaps. Link to comment Share on other sites More sharing options...
djw1981 Posted May 20, 2006 Share Posted May 20, 2006 my Acer is #####. I have to use isolating transformers on the outputs. OI ahve a DELL with same problem, where did you get your isolating transformers and which model etc as I just became rapidly confused when looking into this and just run laptop unplugged for duration on audio playback! Link to comment Share on other sites More sharing options...
WJProctor Posted May 20, 2006 Share Posted May 20, 2006 Yeah I had this problem with software on Laptops running it through a mixer. Unplugging the Power Supply worked fine on my dell. My new VIAO is fine though. Link to comment Share on other sites More sharing options...
Bobbsy Posted May 20, 2006 Share Posted May 20, 2006 Let me try to be more clear this time. Previous discussions of noise problems on laptops (or computers in general) probably do NOT apply this time. With analogue inputs, earthing is often a culprit, as is electrical noise inside the computer. However, that should NOT apply this time since USB is a data input so normal analogue noise and earth loops should not be a factor. Being a data input though, USB can carry whatever data format you want. In this case the Phonic mixer (according to the manual online) is outputting 16 bit, 44.1kHz sample rate stereo wave files. Wave is not the standard file format for sound production on Mac machines...and when you have data in the wrong format it often sounds like the white noise you describe. I know very little about Macs and their software, but from the symptoms you describe, the first thing I'd try is checking the software on you Mac and making sure it can handle...and is set to handle...the file format arriving from the Phonic. Failing that, I'd check the Phonic website and, if necessary, download updated drivers for your Mac. Hope this helps. Bob Link to comment Share on other sites More sharing options...
djw1981 Posted May 20, 2006 Share Posted May 20, 2006 Sorry :$ Link to comment Share on other sites More sharing options...
Andrew C Posted May 21, 2006 Share Posted May 21, 2006 Previous discussions of noise problems on laptops (or computers in general) probably do NOT apply this time. With analogue inputs, earthing is often a culprit, as is electrical noise inside the computer.Interesting. My first thought when I found that I had a problem was to use an Edirol USB interface; same problem. I accept that this probably not the OPs problem in this case. Link to comment Share on other sites More sharing options...
Tomo Posted May 21, 2006 Share Posted May 21, 2006 If I plug it into my Mac, then the quality is awful, with white noise over the top of everything, whether I'm recording or playing sound.Is the noise present only in the recording, or does it appear in the analogue outputs of the mixer as well? If the latter, than the fault is probably some form of interference along the ground line of the USB connector - uncertain how to deal with that as you can't lift the earth in the USB as power is used as a signalling system in the USB spec. If it's the former, then I'd guess you've got really bad OSX drivers for that particular device - your other USB soundcard obviously has good drivers. Link to comment Share on other sites More sharing options...
pritch Posted May 21, 2006 Author Share Posted May 21, 2006 Cheers Bob / Tomo. In response to your question, Tomo, the audio output from the mixer is unaffected, so I guess you're right there, it must just be that OSX doesn't like it. Which is a bit odd, as supposedly USB audio devices all conform to the same standard, and don't require drivers. I might drop Shure and/or Phonic an e-mail and see if they've enountered this before. Link to comment Share on other sites More sharing options...
Dmills Posted May 21, 2006 Share Posted May 21, 2006 Cheers Bob / Tomo. In response to your question, Tomo, the audio output from the mixer is unaffected, so I guess you're right there, it must just be that OSX doesn't like it. Which is a bit odd, as supposedly USB audio devices all conform to the same standard, and don't require drivers. I might drop Shure and/or Phonic an e-mail and see if they've enountered this before. OSX on what processor? It could be and endianness issue in the USB audio driver which would make it squarely an OSX bug. This would I suspect be more likely if running on a mactel box as the drivers may have been written assuming PPC and be missing the code to correctly handle the conversion. can you try it on a mac that uses the other processor architecture? Regards, Dan. Link to comment Share on other sites More sharing options...
pritch Posted May 21, 2006 Author Share Posted May 21, 2006 OSX on what processor? ... can you try it on a mac that uses the other processor architecture? Regards, Dan. It's PPC. As for trying it on another Mac, little chance of that unfortunately. I don't know anybody with a Mac, let alone anyone on Intel. Link to comment Share on other sites More sharing options...
jamesperrett Posted May 22, 2006 Share Posted May 22, 2006 Let me try to be more clear this time. Previous discussions of noise problems on laptops (or computers in general) probably do NOT apply this time. With analogue inputs, earthing is often a culprit, as is electrical noise inside the computer. However, that should NOT apply this time since USB is a data input so normal analogue noise and earth loops should not be a factor. I'm afraid that this isn't correct. The ground is still continued through the USB cable so any grounding issues with the computer's internal soundcard will also be present with most external USB soundcards. It would seem sensible, given all the problems that people have with noise, for someone to make a USB card with isolated grounds but all the USB devices that I know of use the computer's ground as their ground reference. So the USB device is just as susceptible to ground loops as the internal soundcard. Cheers James. Link to comment Share on other sites More sharing options...
Bobbsy Posted May 22, 2006 Share Posted May 22, 2006 That's only true if the internal sound card is connected to something (or, indeed, if the analogue ports on the USB source are in use). In this case, the OP is recording a USB output from his mixer and, as far as mentioned, not using the analogue card in his computer. If there was a ground loop involved in this scenario it would be at his phonic mixer and he's already mentioned at this side of things is "clean". In any case, a ground loop does not show up as white noise. That is some form of data fault. I agree that a USB cable...like any other electrical connection...could be the source of a ground loop problem in the analogue section of a computer's sound system. However, the USB data itself will not be susceptible to this and that, from all the evidence here, it where this fault lies...in a data signal, not an analogue signal. Bob Link to comment Share on other sites More sharing options...
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