Thanks for the info, but S/N ratio should not be your only concern. I've been looking at converters myself and more often than not it's what companies aren't specing that has me more concerned. You can have S/N ratio of 117db, Harmonic Distortion of 0.001%, but still have significant coloration of the sound. If the balanced input passes through a transformer, or capacitor, or if the analog logic is not well designed its possible for there to be distortion of frequency response and/or phase of the incoming signal.
For example, the Lucid AD2496 Users Guide, which has some pretty impressive specs says that frequency response of the converter is 20Hz-40Khz +/- 1db. That +/- 1db could mean there is a 1db drop in response at the extreeme frequencies, but it also leaves the door open for having a response curve is not completely flat. It could mean it has a 2db boost at 1 Khs for example. Most converters don't list clock jitter as a spec, they often don't qualify levels or frequencies at which the specs were measured, and the list of things not covered goes on.
One company that seem to be extreemely thorough in its specs is Apogee. The user guide for
the PSX-100 provides the following specs. I've even edited this down quite a bit:
Dynamic range:
–60 dB, Unweighted 116 dB –60 dB, A-weighted 119 dB
Relative THD+N:
-0.1 dBFS –110 dB (unweighted) –112 dB (A-weighted)
Frequency Response (10 Hz–20 kHz):
Gain ±0.025 dB
Phase < 0.01 degrees
Passband Ripple: ±0.001 dB
Channel Separation: Left/right 120 dB (worst case)
Crystal Oscillator accuracy ±50 ppm
Clock Jitter, 32kHz–106 kHz << 22 psec
----------
Compare that to MOTU who provides as little info as possible (its 24 bits what else do you need to know). You can't download user manuals for their stuff online. I went looking for 1296 information all I could find on their web site was A-weighted dynamic range of 117db. Thanks, but that doesn't tell me much.
-----
Lucid is not too bad (both in price/performance and in the specs they provide), they lie somewhere inbetween Apogee and MOTU. They provide the following in their AD2496 users manual.
Dynamic Range: > 115dB, A-weighted, 48kHz sampling rate
THD+Noise: < 0.002% (-1dBFS out, 1kHz)
Frequency Response:
For sample rates of 88.2kHz and 96kHz 20Hz - 40kHz (+/-1dB)
And for the DA2496:
Dynamic Range > 114dB, A-weighted
THD+Noise < 0.002% (-1dBFS in, 1kHz)
Frequency Response
For sample rates of 88.2kHz and 96kHz 20Hz - 40kHz (+/-1dB)
-----
M-Audio Delta 1010
Dynamic Range:
Outputs: 108dB (a-weighted),
Inputs: 109dB (a-weighted)
THD (at 0dBFS):
Outputs: less than 0.0015%,
Inputs: less than 0.001%
Frequency Response: 22Hz - 22kHz, -0.3,-0.2dB
-----
Aardvark Ark 24
Dynamic Range: 100 dB A/D; 110 dB D/A A-weighted
THD+N: .002%, 20Hz-22KHz, A-weighted
Frequency Response: 7Hz-22KHz, +/- .5 dB
-----
Aardvark Pro 24/96
Dynamic Range: D/A 110dB, A/D 100dB
THD+N: .002% @ 1 kHz
Frequency Response: 7Hz-44KHz, +/- .5 dB at 96 kHz
----
Here are a few high end converters for comparison...
For your drooling pleasure (most of us can't afford $8000 just for a sterio AD), the award for most rediculously high S/N ratio goes to...
db Technologies AD122-96. Their web page lists the specs as.
Noise (true 21-bit noise floor):
-127 dBFS (10Hz to 20kHz unweighted)
-129 dBFS (A weighted)
-123 dBFS (10Hz to 48kHz unweighted)
THD+N over 20Hz to 20kHz:
121 dBFS (.00005%) for -40dBFS or lower
108 dBFS (.0004%) for -20dBFS signals
100 dBFS (.001%) for full scale signals
Bandwidth: 43kHz at 96kHz sample rate
Channel Separation: 120 dB at 1kHz
Flatness Response: 0.05dB (0Hz to 20kHz)
Phase linearity: 0.1 degree (0Hz to 20kHz)
-----
Prism Sound Dream ADA-8
Transformerless electronically-balanced XLR inputs and outputs
Input Dynamic range:
112dB typical, rms unweighted, measured at -60dBFS
Input THD+n:
-105dB (0.0004%) typical, rms unweighted at -1.0dBFS
Over-killer function provides soft-knee limiting preventing converter overload
Output Dynamic range:
10dB typical, rms unweighted, measured at -60dBFS
Output THD+n:
-104dB (0.0004%) typical, rms unweighted at -1.0dBFS
-----
Mytek Digital 8x96
Dynamic Range: 120dB A-weighted, 117dB Total
THD+Noise: -105dB (<0.0005%)
Internal clock jitter: <10picoseconds
-----
Swissonic AD96
Frequency response
Passband: 2–22100 Hz (FS= 48 Khz)
passband scales with sample rate
Passband ripple: 0,01 dB
Group delay variation with freq: 0 linear phase
SNR & dynamic range: 115 dB (A-weighted)
THD+noise: -100 dB (@-1 dBFS)
THD: 0,003 % (@-1 dBFS)
Inter-chanel phase deviation: 0,1 degrees
Inter-channel isolation: -110 dB
-----
I've run out of time or I'd have included more, perhaps later....