5/30/99 AUDIO TESTING - REV 2 (now includes screen shots at end)
I have always noticed a frequency "dip" in the upper frequencies in
my 3200. The DtoD has never exhibited this problem. The 3200
has DDV S3.5 cards which lack the panning circuitry in the DDV S5 cards
(as in my DtoD). I have digitally lifted audio off an audio CD in
the CD-ROM drive in my Mac and used S/Link to transfer the audio to my
Synclavier and DtoD for accurate playback. The DtoD *always* sounded
better. This is partially due to the lack of Multichannel Distributor
and also there are only 4 tracks in my DtoD. Less voices mean a "hotter"
signal since less headroom is needed.
This is how to perform an unbiased audio test of the Synclavier's voice
cards. The actual test results are at the end of this
page. Feel free to submit your own. Just use (command)+(shift)+(the
number three) to save a screen shot. "Attach" the 'PICT' file to
an Email which includes your system configuration (PSMT vs. 9600, how many
outputs, etc.). I will post them on my page.
In SFM, create a few seconds of random noise. We'll create more
time than we need for measurement in order to allow time in the analog
sample for transient responses to decay into a steady state before we start
our spectral analysis. To do this, type the following:
CRE 3 /* This creates a three second sound file. */
ADD RAN /* This fills the file with pseudo-random numbers. */
SAV DIGITAL
Press the F2 key. This will run the RTP and place the sample "DIGITAL"
on the keyboard. Connect the output under consideration directly
to the STM input using a single cable and sample the signal. Before
saving the new sample, EXTRACT the three seconds containing signal using
a crossfade of 0. Save the sample as "ANALOG". Press the F4
key to return to SFM and type the following:
SET FFT 9000 /* This sets the FFT length to the maximum value
of 8192 samples */
SET LEN 1 /* This set the window length to the maximum value
of .16384 seconds (the equivalent at 50K of the FFT length) */
SET OFF .08192 /* This sets the offset time to half of the window
length. We do this because in order to cancel out random deviations;
we will average a series of running spectra. This value causes the
window of each spectrum to peak where the window of the previous spectrum
reached zero. */
You are now ready to perform a spectral analysis of these files.
If you want to be able to compare the original digital sample with the
analog sample, then obviously you'll need to analyze both. If you're
in a hurry and just want to see the analog frequency response, trusting
in the theoretical flatness of the digital sample, then by all means skip
the digital sample. To perform the analysis, type:
OLD DIGITAL /* or OLD ANALOG */
SPE 1 to 2 /* this should result in 11 spectra. You might
as well go get a snack unless you have the PowerPC hardware. */
When prompted with "Press RETURN for averaged spectrum" do so and type:
SAV DIG /* or SAV ANA */
This saves your spectrum so that you will be able to do quick comparisons
by typing REC ANA and REC DIG. You can zoom in to a frequency region
using SET ORI (origin in KHz) and SET RAN (range in KHz). |