hardware device as audio analog to digital converter (ADC)

[spoRv]

My PC sound card is (still) the original integrated one; it’s a SigmaTel with the CXD9872RD chipset – not too bad to be an integrated sound card; plus, it has the ability to capture bit-perfect audio via the digital input – and that’s a VERY GOOD feature, when you must capture laserdisc PCM/AC3/DTS soundtracks.

However, the analog input/output, even if good, is not comparable with the best sound card around. The solution is simple: to buy a better sound card! Even if the solution is simple, I can’t afford the brand new sound card I’m dreaming of now, so I thougth about an alternative solution. Which one?

It’s possible to use an external device as ADC (Analog Digital Converter); just use an analog stereo cable to plug the output of your laserdisc player (or VHS, or another analog source) to the device analog input; then, use a digital cable to connect the device output to your PC sound card input (I used the TosLink optical connection, but a coaxial digital cable will do the same work; it depends from the device digital output and your PC sound card digital input).

The device’s own ADC could be better than your PC sound card or not; how could you discover which one is better? Well, some time ago I wrote into my hi-end audio capture card post about this wonderful tool, the RightMark Audio Analyzer – now version 6.0.3 is available, but I stick with the old 5.5 version, as the new one continue to crash my PC…

This tool simply analyze the input/output quality of your sound card; I used it to test not only it, but also the various path between the PC sound card and the other devices; they are two DVD recorder, a Pioneer DVR-320S and the Yukai DVD-R100A, plus a MiniDisc recorder, the Sony MDS-520.

Here you are the results; sampling mode: 16-bit, 48 kHz (except for MiniDisc, that is 44.1 kHz):

Code:

Test                         AN. OUT ->     AN. OUT ->     AN. OUT ->    AN. OUT ->    
                             Yukai DVDR     Pioneer DVDR   Sony MD       AN. IN
                             -> DIG. IN     -> DIG. IN     -> DIG. IN          
Frequency response
(from 40Hz to 15kHz), dB:   +0.35, -0.46   +0.21, -0.22   +0.16, -0.28   +0.35, -0.47
Noise level, dB (A):        -93.9          -92.3          -92.2          -93.8
Dynamic range, dB (A):       94.3           92.3           91.8           94.2
THD, %:                      0.020          0.0051         0.0020         0.0048
IMD + Noise, %:              0.019          0.0097         0.0082         0.0092
Stereo crosstalk, dB:       -94.8          -91.9          -92.9          -92.0

and another batch of tests I’ve done; CD and DVD are made using the RightMark test WAV file, burned and played with the Pioneer DVD recorder via digital optical cable; the digital in->digital out via digital optical cable; the analog out->analog in via stereo RCA cable – all 16bit:

Code:

Test                         CD             DVD            DIG. OUT ->    AN. OUT ->    
                             DIG. IN        DIG. IN        DIG. IN        AN. IN
                             44.1kHz        48kHz          48kHz          44.1kHz  
Frequency response
(from 40Hz to 15kHz), dB:   +0.00, -0.00   +0.00, -0.00   +0.00, -0.00   +0.34, -0.44
Noise level, dB (A):        -96.1          -98.2          -95.1          -92.9
Dynamic range, dB (A):       93.0           98.1           95.1           92.8
THD, %:                      0.0024         0.0003         0.0005         0.0056
IMD + Noise, %:              0.0063         0.0037         0.0052         0.012
Stereo crosstalk, dB:       -97.8          -99.5          -96.0          -93.2

Conclusions: I think my old sound card is not that bad, at the contrary, it’s slightly better than these external devices like DVD and MiniDisc recorders; even if the latter have sigma-delta converters, up to 24bit/96kHz, that, on the paper, are exceptional, actually the digital input of my old capture card support at best 16bit/48kHz, so this presumed superiority could not be taken in account.

So, at the end, I will continue to use the sound card that I have, until I could afford a brand new card. By the way, I just finished to do some test captures of the analog soundtracks of Halloween Criterion laserdisc; it has the commentary onto one analog track, and the isolated score onto the other; well, the channel separation is so good that is impossible to hear a channel “bleed” into another, and the overall sound quality is almost on par with the PCM soundtrack!

Hope this little test will help someone with a low quality sound card to find out how to use an external device to improve audio capture quality, or, at the contrary, to discover that this presumed low quality sound card has indeed a sound quality not so low… like I did! (^^,)