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TEAC UD-501 digital converter

TEAC UD-501 digital converter

The TEAC UD-501 is currently the cheapest DAC to support DSD replay across USB. It has fixed single-ended phono and balanced XLR outputs, and a volume control for the built-in headphone amplifier. There is no remote, but it does feature a range of filter options activated from a front panel menu button. 

This DAC is part of TEAC’s revamped Reference 500 series, a midi-sized but fully discrete range of components with silver ‘pro audio’ style side panels featuring integrated handles. The unit itself is available in an all-silver finish, or a contrasting matt black body with silver knobs, switches and side panels. Either way, the two-line display is an orange on black panel. 

Its two dials are not strongly resistive to the touch and both the menu button and the power on toggle should be more recognisably ‘thrown’ when engaged, but there is no play on any of the control surfaces. Overall, the metal-bodied DAC feels solid sitting on its four low feet. There is one odd ergonomic observation– the ¼” headphone jack is sited next to the power switch, while the volume control (which only works for headphones) is on the other side of the front panel. The logical panel order would be placing the headphone ‘group’ together, possibly on the right side of the front panel just after the display.

Its rear panel features a similarly odd choice of layout pattern. One part of the split digital input block itself splits the left and right analogue line level outputs. This relegates the two fibre-optic TOSlink inputs next to the IEC power inlet and a toggle switch to defeat the DAC’s power saving mode, while the two coaxial S/PDIF and USB digital inputs sit between the RCA and XLR sockets of the line out blocks. Fortunately, this is all clearly marked and covered in the comprehensive supplied manual, so this shouldn’t pose any functional concerns in everyday use. I used it single-ended exclusively.

 

Moving inside to the converter itself, the circuit is effectively a dual mono design, with everything from the two power transformers through to the separate output sections sharing only a common chassis. This includes one BurrBrown PCM1795 converter chip and a pair of made-for-hi-fi MUSES8920 operational amplifiers for each channel. The op-amps are connected in parallel with the RCA line-out terminals, acting as a buffer to ensure the signal arrives at the amplifier or preamplifier in good order. This levels the score somewhat between XLR and RCA on long cable runs.

The TEAC UD-501 supports PCM file playback through all its digital inputs; as standard through fibre-optic TOSlink, this is limited to 24bit, 96kHz files, while coaxial S/PDIF can support up to 24 bit, 192kHz files. The USB input takes this still further with a notional ceiling of 32 bit, 384kHz files (‘notional’ because no such files are currently commercially available). PCM files with a sample-rate below 192kHz can be upsampled to 192kHz, thereby allowing any data jitter to be folded into the signal itself. This can be switched off, however. There is also a three-setting digital filter for PCM: Slow, Sharp and Off. Both ‘Slow’ (gentle cutoff) and ‘Sharp’ (brickwall filter at half the sampling frequency) are standard options for the BurrBrown DAC, although unlike TEAC most implementations just use the Sharp option as standard.

The asynchronous transfer USB connector works to USB Audio 2.0 standard, meaning files beyond 24 bit, 96kHz PCM – or any DSD files – must be played through a compatible USB output from a computer. This comes as standard with any Mac computer running OS X 10.6.4 or later operating systems (you may need to adjust your computer’s Gatekeeper settings), but requires a driver for 32bit Windows XP or subsequent Microsoft Windows operating systems. As explained in the manual, this is downloadable from the TEAC website.

DSD over USB is a relatively new high-resolution pathway, an open standard developed across a range of platforms, but the notable partners include J River on the software side and dCS from the hardware manufacturers. The TEAC supports native DSD to 128x via ASIO 2.0 on Windows computers (with the software download) only and in DoP mode for Windows computers and Macs. DoP (DSD over PCM) ‘fools’ the USB controllers into thinking DSD files are PCM files. The TEAC is in on the deception and unpacks the file as true DSD. The TEAC UD-501 supports both ‘standard’ 2.8MHz and ‘double’ 5.6MHz DSD (DSD128) files, and these files can be downloaded from sites like Channel Classics, MA Recordings, Blue Coast, 2L, as well as a fascinating sampler from Opus 3 that comes in both 2.8MHz and 5.6Mhz file sizes. 

DSD replay has four FIR (finite impulse response) settings, which adjust the cutoff frequency and stage gain of the analogue filter. J River Media Center through a Windows 7 PC was used to support these files and the handling was almost as straightforward as any PCM file. These are massive files and downloading takes time even on fast fibre-optic broadband. Right now, I suspect few people have more than a couple of dozen DSD-based albums stored on a hard drive, but if the time comes where you have a couple of hundred such albums or more, you will have unwieldy terabytes of data to handle.

 

The TEAC UD-501’s menu system is remarkably comprehensive, for a DAC. It has a range of digital and FIR filter options and allows the automated PCM upconverter to be disabled. However, the TEAC UD-501 also includes options to dim or turn off the display, automatically power off the USB port when not in use, to allow the headphone socket to mute the line output, adjusting the ‘hot’ polarity of XLR, or even swapping between XLR and RCA.

The menu system controls filter options, and whoever had played with the filter options before me didn’t get them right. The PCM option sounded rolled off like a NOS DAC (because it was set to ‘off’) and FIR1 (cut-off of 185kHz, -6.6dB) sounded very slightly diffuse with a mildly exaggerated image size. Given the lower gain than other filter settings, this might be good for balanced operation. FIR2 (cut off at 90kHz and +0.3dB gain) performed more naturally, suggesting perhaps that the DSD stream passing unfiltered into an amplifier might not be a good thing! The other two FIR filter settings were indistinguishable from FIR2 in use. On PCM, I resorted to the Slow setting throughout.

Any DSD-supporting DAC needs to pass muster as a standard-resolution PCM DAC as well as making good with high-resolution PCM and DSD files. With the right filter settings, TEAC’s UD-501 did well in all three cases. I do not agree with the ‘all competent DACs sound the same’ ideology, but I think ‘all competent DACs converge on a similar sound’ and this DAC fits this profile well. I auditioned the converter with a range of musical samples, including acapella female vocals (‘Tom’s Diner’ from Solitude Standing by Suzanne Vega on 16/44.1 PCM) through to Big Band (‘You’re No Body Until Somebody Loves You’ on Sinatra Swings by Frank Sinatra in 24/192 PCM) to complex orchestral works (Beethoven’s 7th Symphony, Budapest Festival Orchestra, Channel Classics DSD download), and even Eric Bibb’s blues offerings in both DSD and DSD128 form on the Opus 3 sampler. In each case, the TEAC delivered a full, detailed and accurate rendition of the original recording, without any noticeable sins of omission or commission. At the extreme end (DSD128), the sound quality was extremely smooth and enticing in a manner normally reserved by vinyl-lovers for the best in LP. That being said, if you used this DAC with only 16/44.1 PCM files, you would be more than happy with its performance.

What applied to the line-level output also applied to the headphone socket, although I felt the UD-501 possibly could do with a touch more gain to enable it to drive the current crop of power hungry headphones. On my Sennheiser HD595s, it played to very loud levels indeed, but I have also used headphone amplifiers that aced this test with the volume knob less ‘cranked’.

The TEAC UD-501 is an extremely impressive DAC. It plays every audio file you could conceivably think of, and does so while cocking a rather large snook at companies that insist DSD replay is only possible at great expense. An integrated streamer aside, I can’t think why anyone would want anything more than this. Strongly recommended!

Technical Specifications

Digital audio inputs: 2x coaxial S/PDIF, 2x TOSlink fibre-optic S/PDIF, USB Type B (USB 2.0 compatible, asynchronous transfer mode)

Analogue audio outputs: RCA, XLR, ¼” headphone jack

Sampling frequencies supported: PCM (to 32 bit, 384kHz); DSD 2.8/5.6MHz

Upsampling: 192KHz

PCM digital filters: Slow/Sharp/Off

DSD Analogue filters: FIR1 (185kHz), FIR2 (90kHz), FIR3 (85kHz), FIR4 (94kHz)

Finishes: Black + Silver or Silver

Dimensions (WxHxD): 29×8.1×24.4cm

Weight: 4kg

Price: £699

Manufactured by: TEAC

URL: www.teac-audio.eu

Tel: +49 (0) 8142-4208-141

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