Playback formats on a TEAC UD-501 (TI PCM1795)
by, 08-25-2013 at 02:04 PM (5949 Views)
This is interesting DAC with a reasonable price tag, looks nice and high quality components.
Since it also offers bypass of the digital interpolation filters with direct 32-bit 352.8/384 PCM input as well as DSD128 support with good set of analog filters (conversion mappings), I wanted to study which would be best way to play back RedBook content on it.
I have excluded time-domain behavior inspections from this post, because going to that domain while keeping the frequency-domain behavior optimal at the same time is complex topic with too many variables to be discussed in a single blog post. (read: brickwall filters vs non-brickwall filters) So I cover only frequency-domain inspection of various ways to reproduce RedBook.
First set of measurements I perform is a 44.1/24 PCM with sweep from 0 - 20 kHz and measure this on a wide-band spectrum analyzer using "peak-hold" to expose both reconstruction properties and quality as well as see patterns of ultrasonic output since this seems to be a hot topic. Optimal output would have just the 0 - 20 kHz output and nothing else in the spectrum.
Second set of measurements I perform is intermodulation distortion test with 19+20 kHz tones. Optimal output would have just the 19+20 kHz tones visible and nothing else.
Since the UD-501 defaults to "NOS" settings, I first measured it in this mode.
NOS mode, sweep 0-20 kHz
NOS mode, IMD 19+20 kHz
Since the wide-band output of the IMD test looked quite extraordinary, I reproduce it here...
Next was time to test the most ordinary setting, with digital filter set to "SHARP".
SHARP mode, sweep 0-20 kHz
SHARP mode, IMD 19+20 kHz
Then was the filter type many find better sounding due to shorter pre-/post-ringing, filter set to "SLOW".
SLOW mode, sweep 0-20 kHz
SLOW mode, IMD 19+20 kHz
Since there is the digital filter bypass, I wanted to test HQPlayer with a "short" filter and 384/32 output (TPDF dither).
NOS mode, HQPlayer short@384/32, sweep 0-20 kHz
NOS mode, HQPlayer short@384/32, IMD 19+20 kHz
Then the part I was most interested in, testing upsampling to DSD128 using modulator "5.1". I used analog FIR setting 4 in this test, mostly because TI uses the same filter in their datasheet plots.
AFIR4 mode, HQPlayer short@DSD128, sweep 0-20 kHz
AFIR4 mode, HQPlayer short@DSD128, IMD 19+20 kHz
As a summary, at least on this DAC, DSD128 has most limited ultrasonic output and no strongly correlated elements visible at all. For those using HQPlayer, "5.1" is best modulator option for this DAC.