Some things to consider with interface quality are:
1. The pre-amp (how much gain it has) and the quality (how quiet it is)
-cheaper units are usually in the 50db gain range or less
better ones are in the 60-80db range
(A shure SM7B mic has an output of -59db) using this mic is best to have a pre in the 60-70db range !
Many have posted in forums that they cannot get enough gain to get proper recording levels with some of the cheaper units. If you have to run the pre-amp full volume you get more noise too!
(M audio profire 610= Adjustable Gain >53dB without pad)
(Presonus firestudio mobile=Gain Control Range (± 1 dB) –10 dB to 70 dB)
2. Pre amp Signal to noise ratio around 100db or higher is good too.
3. Phantom power needed for condenser mics
4. The other factor is the quality of the digital converter.
one of the specs to look for is Jitter. listed in Picoseconds
the higher the jitter number the lower the accuracy of
consistent sampling intervals (translates to loss of clarity.
Not all publish these specs in their documentation.
(Jet PLL Jitter Elimination Technology)
4. If using firewire you need Texas Instruments chipset on your PCI card or you will probably have problems.
5. Check manufacturer website for compatible driver for the operating system you are using on your puter.
Pre-amp specs most Interfaces under $600
Presonus Audio Box (USB)
Gain Control Range (± 1dB) 0 dB to 35 dB (WEAK)
S/N Ratio (Unity Gain, Ref. = +4 dBu, 20Hz to 22 kHz) > 95 dB
24 bit 44.1 or 48khz
Lexicon Alpha (USB)
+44db gain no phantom power
S/N ratio not listed
24 bit 44.1 or 48khz
Lexicon Lambda (USB)
+44db gain
S/N ratio not listed
24 bit 44.1 or 48khz
Lexicon Omega (USB)
+50db gain
S/N ratio not listed
24 bit 44.1 or 48khz
Presonus FireStudio Project (firewire in-out)
Gain Control Range (± 1dB) -4 dB to 50dB
S/N Ratio (Unity Gain, unwtd, Ref. = +4dBu, 20Hz to 22KHz) >101dB
24 bit 44.1, 48, 88.2, 96
M Audio Profire 610 /2626 (firewire)
Gain 53 db
S/N ratio -108 db (610) -109 db (2626)
24 bit 44.1-192khz
Mbox / Mbox Mini Gen3 (usb)
Gain range 54 db
S/N ratio -110 db(Mbox) -106 db (Mini)
24 bit up to 96k (Mbox) up to 48 kHz sample rates (mini)
Presonus FireStudio (firewire in-out)
Gain Control Range (+/-1dB) -6dB to 55dB
S/N Ratio (Unity Gain, unwtd, Ref. = +4dBu, 20Hz to 22KHz) >101dB
24 bit 44.1, 48, 88.2, 96
Lexicon I Onix U42S (USB)
+55 db gain
24 bit 44.1, 48, 88.2, or 96 kHz
Lexicon I Onix U82S (USB)
+55 db gain
24 bit 44.1, 48, 88.2, or 96 kHz
Lexicon I-Onix U22 (USB)
+58db gain
24 bit 44.1, 48, 88.2, or 96 kHz
Steinberg CI1/CI2/CI2+ (usb)
pre gain 60 db dynamic range 96db (does not specify if pre or converter spec)
24 bit 44.1 48khz
KONNEKT 6 (firewire)
pre -50 to+10 with boost on
mic boost 12 db
24 bit 44.1-192khz <42 ps jitter
EMU 0404 (usb)
pre gain 60 db
24 bit up to 192Khz
(A/D: 113dB SNR, D/A: 117dB SNR) <500 ps jitter
Motu Ultralite MK3 (firewire bus pwr/ usb2 w/external pwr)
60 dB of adjustment for the mic input and 32 dB for the TRS input
24 bit up to 192Khz
Onyx Blackjack USB 1.1
Onyx pre 60 db gain
24 bit 44.1or 48khz
Onyx Blackbird firewire
Onyx pre 60 db gain
24 bit 44.1-96khz
Cirrus converters 114 db dynamic range (rec/playback dyn range 111.5 db)
Presonus FireStudio mobile (firewire in-out)
Gain Control Range (± 1 dB) –10 dB to 70 dB
S/N Ratio >101 dB
24 bit 44.1, 48, 88.2, 96 kHz
Apogee Duet (firewire bus power) Mac only
Mic pre gain 10-75 db
24-bit/96kHz audio input and output
Line 6 UX series specs not listed
Tascam US122/us144 specs not listed
Most of the older M Audio Mobile pre and Fast Track models are in the 50 db gain range
Other specs / info about digital recording
16 bit = 6 db per bit dynamic range = 96db
24 bit = 6 db per bit dynamic range= 144 db
Even though burning to CD at 16 bits the increased dynamic range of 24 bit vice 16 bit increases headroom when recording.
Technology right now limits A/D converters and most can only produce a dynamic range of 100-120 db so you are limited by the converter when recording at 24 bit (dynamic range of 144 db) but its still better than 16 bit.
You end up realistically getting the equivalent of about 20 bit resolution in a few of the better units at this price point.
Having a unit that boasts 24 bit is not that meaningful if the dynamic range specs of the unit are down below 100db (barely above 16 bit spec of 96 db)
So bit rate determines dynamic range / headroom
Sample rate (44.1, 48, 88.2, 96 khz) determines Freq response and clarity.
The higher the sample rate the bigger the file size and CPU that is needed. (7200 rpm HD recommended)
Driver compatiblity for Windows:
http://rainrecording.com/windows-watch/
