|TEAC & Tascam combo with size differential. The E-MU 0404USB in the background to the left.|
In terms of the underlying hardware, the Tascam UH-7000 uses the Burr-Brown PCM4220 ADC compared to the E-MU's AKM AK5385A chip. On paper at least, the Burr-Brown should be significantly better with a rated SNR of 123dB compared to the AKM's 114dB. Of course, much of the final result depends on the circuitry built around the ADC such as quality of the pre-amplifiers feeding the input signal.
I. The Spectrum of SilenceTo start, let's have a look at what "silence" looks like through the Tascam UH-7000, with preamps set to minimum:
Impressive. With the ADC running at 24/96, we're seeing very low noise floor essentially flat down to -160dB across the spectrum (Note: I found an issue with this later on - see below).
Compared to the E-MU (sorry about the difference in scale!):
Clearly the old Creative unit is noisier with sporadic noise spikes reaching up to -140dB and a slight tendency for the noise floor to rise from about 35kHz and up.
So far, so good... The Tascam is doing well!
Let's now run a few RightMark tests to see how some of my DACs measure using both the Tascam and E-MU. I'll be looking at the AudioEngine D3 USB DAC as an example of a very capable but "lower tier" DAC in terms of resolution and the TEAC UD-501 as an example of a higher-end desktop DAC which would likely challenge the resolution of these ADCs. This will provide an opportunity to correlate the results between different "instruments". If the Tascam results closely follow what I've been seeing with the E-MU over the years, then at least it's suggesting that I'm on the right track with these measurements :-).
Windows 8.1 Surface Pro 3 --> 6' Shielded Belkin Gold USB --> DAC [AudioEngine D3 / TEAC UD-501] --> analogue cable (shielded RCA for D3 / XLR for TEAC) --> ADC device [Tascam / E-MU] --> shielded USB --> measurement Windows 7 laptop
Tascam latest Windows driver: 1.01
Tascam latest firmware: 1.07
ASIO (TEAC) or WASAPI (AudioEngine) drivers used for playback.
ASIO for all recording.
RightMark 6.3.0 used as measurement suite.
II. RightMark Comparisons
16/44:As usual, let us start with the most common audio resolution - good old CD-quality 16/44. Here is an overall score sheet:
A few graphs to consider:
|16/44 Frequency response: Essentially flat.|
|16/44 Noise floor: About the same across the board.|
|16/44 THD: Notice a bit more "skirting" at the base of the primary signal for the D3 suggesting more jitter as compared to the TEAC. Both Tascam and E-MU consistent in picking this up.|
|16/44 Stereo crosstalk: Interestingly, the AudioEngine has lower crosstalk than the TEAC despite the TEAC using XLR cables. Both Tascam and E-MU consistent also in this finding.|
24/96:Time to delve into the world of high-resolution with 24/96 then. Here's the summary:
|24/96 Noise floor: Not much difference really... TEAC slightly lower and this is consistent for both the Tascam and E-MU measurements.|
|24/96 THD: More evident than with the 16/44 measurement above, there's more "skirting" with the AudioEngine suggesting perhaps more jitter. But what's that peak at 30-40kHz showing up on the Tascam measurement?|
III. Dunn Jitter Test Comparisons:
IV. Tascam, we have a problem...
|Tascam UH-7000 24/96 "silence" at startup. Beautiful!|
|Tascam UH-7000 24/96 "silence" 15-minutes turned on. Couple little oddities.|
|Tascam UH-7000 24/96 "silence" 30-minutes turned on - LEFT channel. Huh? What's that?|
|Tascam UH-7000 24/96 "silence" 30-minutes turned on - RIGHT channel.|
|Tascam UH-7000 24/192 "silence" 30-minutes turned on - LEFT channel.|
I wonder whether this is noise from the switched-mode power supply (SMPS) given the close proximity to the audio circuits and whether this could be suppressed with better line filtering or RF shielding of the power supply. Well, here is demonstration of one piece of audio equipment where the audiophile practice of "warming up" the gear actually deteriorates performance.
Ultimately, the noise I found with the Tascam ADC once it warms up is of low-level and would not be audible in regular use (certainly not audible with LP needle drops, but high-resolution multitracking studios and those using effects processors might care) due to it being ultrasonic and down at below -100dB (a subjective reviewer would not have been able to pick this up). However, it is an unexpected finding which does show up when I do high samplerate measurements. If it were not for this, the unit would have stayed as a fixture on my audio equipment rack in the sound room.
Can anyone recommend to me a good ADC that is highly accurate, reasonably priced (maybe $500-600USD), stable Windows drivers, has good level controls, and provides good visual feedback of volume levels to avoid clipping? I'm certainly happy to purchase a Tascam unit like this one again in a few months and see if this issue is gone if by then I haven't found a better ADC.
I hope everyone had a wonderful Christmas and New Year time! Time to get back to a hectic work and family life... May your 2015 overflow with good music :-).