USB/Firewire Notebook Meeting Recording PreAmp

2 replies [Last post]
Joined: 06/30/2005

With a couple of M-Audio USB Mobile Pre's, four good condenser mics and a notebook, I have a system that provides excellent multi-channel playback meeting recording (NCH Swiftsound's MSRS software) anywhere but for the timing issue between the Pre's, creating echo, most times, between them of the order of 0.1 secs.

A search for a real solution has turned up nothing viable. A 19-inch preamp is not portable. I want a small(ish) 4- or (better) 6-ch XLR phantom-powered input pre-amp connecting to my notebook by USB or firewire (or SPDIF?), and portable. Am I asking too much? Should I be considering an anologue output pre-amp to a GigaPort AG converter to USB? Or finding some sort of SPDIF to cardbus adaptor to take SPDIF output from a digital preamp?

And I don't want to spend an arm and a leg on this gear.

It's surprising there just doesn't seem to be and one-box solution to this simple requirement, so I am sure I'm missing something. Any suggestions?

Malcolm :|

Joined: 02/12/2009

Your problem lies in mismatched clock. Multiple interfaces need to be clocked together or their timing will be off. The mismatch would be heard either subtly (as smearing/phasing) or drastically (as an audible echo/delay).

The Mobile Pre has no word clock input, so you don't have the option of using an external clock generator (via word clock). And it has no digital input, so you don't have the option of clocking via SPDIF etc. So you can really only use one at a time.

Some other units are designed to be daisy-chained, routing their clock via software drivers which allow you to select which unit is the clock master (such as all the MOTU interfaces).

For portable multichannel recording in your situation (4-8 channels), I recommend the MOTU Traveler. Here's the Traveler's deets from my Guide to FireWire and USB Audio Interfaces:

Quote:FireWire, 24 bit/192k, 8 analog in (4 XLR mic, 4 TRS), 8 analog out (TRS), 8 ch ADAT I/O, AES I/O and S/PDIF I/O. Has 4 mic preamps, ADAT sync, word clock I/O, MIDI I/O, headphone out, more. Bus-powered off FireWire for portable field recording, or with external battery pack, or with wall AC. Zero-latency monitoring of multiple sources. Works as stand-alone mixer. Comes with AudioDesk software (Digital Performer w/o MIDI).

There's a switch on the side of the Traveler to select whether it is powered off of the wall AC or FireWire. (Read this MOTU tech note and this one.)

I've been using the Traveler for a month or two and I'm a big fan. Note that officially it does not come with an AC power pack, but my particular unit did (I bought it from zZounds). Some other users have gotten AC packs, some have not. Perhaps MOTU is in the process of changing their stock one way or the other?

Joined: 06/30/2005

Thank you, Sir, for your extremely helpful lead on the problem. I had a feeling I was in the right place to ask!

I'd read about "word" clock and hadn't a clue what its role was. Obviously, I need to sign up for Digital Audio 101!