Component Reviews

High Resolution Technologies DACs Music Streamer IIx & Music Streamer Pro

HRT offers a range of small inexpensive USB-powered DACs that can provide great sound quality from your hi-res digital files and standard CDs.

Published on June 10, 2011

High Resolution Technologies DACs
Music Streamer IIx & Music Streamer Pro

High Resolution Technologies DACs
Music Streamer IIx – SRP: $149.95
Music Streamer Pro – SRP $499.95


Specs – Music Streamer IIx:
Electrical =
Output 2.25 Volts RMS
Frequency Response: (20 Hz/20 kHz) 0dB /-.5 dB
Noise Floor: (DC to 30 kHz) 26 uV RMS
S/N Ratio: (DC to 30 kHz) 98 dB
THD+N: (1 kHz FS) 0.010%
USB to Audio output isolation: > 20M Ohm

Interface =
Data Rate up to 96kS/s
Bit Depth 16 or 24 bit
Transfer Protocol: asynchronous
USB type 1.1 or above
Power Requirements (USB buss): 200 mA
Dimensions: (LxWxH)  5.1 x 2.2 x .8 inches

Specs – Music Streamer Pro:

Electrical =
Output 4.5 Volts RMS (TiniQ XLR)
Output Impedance 200 + 200 ohms
Frequency Response (20 Hz / 20 kHz) * 0dB / -.6dB
Noise Floor (DC to 30 kHz) 9 uV RMS
Noise Floor (A-weighted) 8 uV RMS
S/N Ratio (DC to 30 kHz) 114 dB
S/N Ratio (A-weighted) 115 dB
THD+N (1 kHz FS) .004%
USB to Audio output isolation > 20MOhm

Interface =
Data Rate 32 kS/s to 96 kS/s in 5 steps & Mute with LED indicators
Bit Depth 16 to 24 bit
USB type 1.1 or above
Power Requirements (USB Buss) 350 mA
Dimensions (LxWxH) 5.6 x 2.1 x 1.2 inches


Intro
High Resolution Technologies (HRT) is a small audio firm founded by Kevin Halverson of Muse and Michael Hobson of Classic Records.  They are turning out a growing series of small USB DACs built here in the U.S. and achieving sonic improvements in the audio coming from computers far in excess of their reasonable cost.  Their hope is to get the computer-based, home audio system-uninterested younger generation to cop to the amazing sound quality they can get out of their computer devices with a really good inexpensive USB DAC.

I decided to ask for one of their entry-level DACs plus their recently-added Pro model, which as its name suggests is designed for the professional studio and recordist, but can be used by advanced audiophiles as well. I had thought if I was as impressed as some of the other audio reviewers have been with the HRT DACs I would purchase one for my home office.  I had forgotten that one of the several advantages we Mac users have over those of you in the PC majority is that while the only easy way to get a digital audio signal out of your computer is via a USB port, we can use the little 3.5mm Toslink optical output which is buried in the normal-looking headphone jack on the back of our Macs. So I picked up a 3.5mm plug to standard Toslink cable and moved my Benchmark DAC1 into my office, using it to compare with the sonic results using the two HRT USB DACs.

The Benchmark has two advantages in this case: a volume control and a built-in power supply.  The HRT DACs have neither. However, it’s much larger and costs over $1000, and in general I was amazed how close both HRT devices came to it  in fidelity.


Music Streamer IIx

This model is a brand new enhancement of the previous Music Streamer II. It is a much smaller and more compact case, less than an inch thick.  They have added a very useful display feature that is lacking on the Pro model at more than three times the price: five little LEDs on one end next to the USB socket and displaying  32K, 44.1K, 48K, 88.2K, 96K sample rates and Mute.  The device becomes an isolated pathway between your computer and your audio system – whether it is a simple little integrated amp and small monitor speakers (I have an AudioSource amp and stacked Paradigm Atom speakers in my home office), or a big home entertainment center. It takes all its power from the USB buss and has no wall wart, and it regenerates the power and clocking for all its internal circuits. It works with an asynchronous digital signal which is said to have advantages of over synchronous if the circuitry is handled right. The USB port is at one end and the RCA stereo jacks at the other end. The unit installs itself on your PC or Mac and is quickly ready to go. On my Mac I needed only to select it on the Sound Preferences and then select the sample rate of whatever I’m playing on my Mac’s SuperDirve – usually 44.1 of course. You can leave the word length setting at 24 if you wish and expect only to be changing the sample rate to 88.2 or 96K to play discs or downloads with those higher resolutions.

All these DACs support iTunes and Windows Media Player, and of course any music subscription services you have on your computer can be streamed thru the DACs for a tremendous improvement in the data-reduced audio signal all the service provide. I hadn’t expected the weekly download I normally make of NPR’s “Wait, Wait, Don’t Tell Me” podcast would sound that much cleaner so that I missed less of the often hilarious dialogue, but it did. The tiny size of the Music Streamer IIx allows it to be placed almost anywhere near your computer.  You might like to orient it so that you can see the sample rate LEDs.

The Music Streamer Pro
The end of this much larger blue device opposite the USB port tells the story. It has a pair of special and very professional TiniQ mini-XPR jacks, and requires two Switchcraft mini-XLR to RCA adaptors to use it in most home systems. Also, with both DACs you need to make sure you have the proper USB connector cable – they need a squarish one at the DAC, rather than the tiny elongated ones found on many cameras, so your camera USB cable probably can’t be used.

The big enhancements on the Pro version are the XLR connectors, which point to the fact that the device is uses a fully-balanced differential output – more effective than the optional XLR outputs on many consumer receivers and preamps. And the much higher output level of 4.5 volts is better matched to professional equipment.  However, I actually heard little level difference between the two DACs when I switched between them. It has an even better S/N statistic than the Music Streamer IIx, but both devices were completely successful at maintaining a very low noise floor – unaffected by any stray signals bouncing around inside behind the thin screen of my 21.5” iMac.

All three of these DACs have circuitry that uses different techniques to achieve low jitter, which is an important consideration in converting the signal from your computer to a clean analog stereo signal – whether coming from an optical disc or digital files both on your hard drive or streaming online. HRT has also put their attention on other interferences and artifacts that can occur inside a computer.  The end result is to extract the highest possible quality from that digital signal in your PC or Mac.

Comparisons
I started by listening to some music from my Pandora stations. All three DACs did an excellent job of squeezing a bit more fidelity out of the data-reduced streaming audio.  The same went for any of the Internet radio stations, some of which use absurdly low sampling rates for music which would be more appropriate for speech only.

Then I moved to some 96K/24-bit discs. One of the 24/96 DADs released by Classic Records was “Dr. John Plays Mac Rebennack.”  I’m really familiar with this album since I once had it on a 15 ips double-track analog tape on a 10 ½-inch reel from Roumanis Recording.  That is, until the tape formulation failed totally and it became unplayable.  It was a pleasure to hear the 96K disc on my main audio system – gorgeous piano tone and Dr. John’s distinctive voice has great presence.  Thru the Benchmark, the results were almost as good as on my good speakers in my main listening area. Thru the Music Streamer Pro the piano sound was just a bit duller and Dr. John’s voice has a little less presence. But it was still most impressive. Switching to the Music Streamer IIx didn’t lower the quality much at all; it sounded almost exactly like the Pro version.

I next played a 96K/24-bit Classic Records DAD of one of the acclaimed Vox Turnabout recordings with the Dallas Symphony and Donald Johanos – Rachmaninoff’s Symphonic Dances. The impact and clarity of the music belied the higher sampling rate and it sounded fabulous on all three DACs. I felt the richness and wide range clarity to be just as good as the best 2-channel SACDs.  This time the Benchmark only had a very slight edge sonically.

I changed the iMac’s Audio Midi setting back to 44.1K and tried a number of standard CDs next. One was the new release from San Francisco’s Philharmonia Baroque – three Haydn symphonies. All three DACs made an immediately hearable improvement over the analog out signal directly from my iMac. Some years ago I had an Onkyo DAC which made a slight improvement on the audio from the iMac I had at the time. The last couple of iMacs seemed to have improved the analog audio out sonics and I was working without a DAC, but a DAC of the quality of all three of these puts some flesh and curves on the rather lean and bony quality of most digital recordings. With a good DAC like these it’s no wonder that more and more computers are becoming the basis of quality audio system.

I did find the Music Streamer IIx to have very slightly less muscle and deep bass support than the Pro version.  In fact, the differences between them seemed somewhat more pronounced with standard CDs than with hi-res sources, albeit extremely subtle.  However, the $150 DAC is still a terrific performer and I would be perfectly happy with it if only I had a remote control on my integrated amp, which I don’t.  If you have a remote you won’t be inconvenienced a bit by the lack of a volume control on either of the HRT USB DACs.  There are also some other HRT models positioned in between these two DACs, so you might find one even closer to your needs there.

Go right on to our second component review of Tom Gibb’s experiences with the Music Streamer IIx, which explore the area of using a PC as a music server and working with FLAC files and other hi-res downloads as well as digitized CDs.

 – John Sunier




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