ARX Audiobox USB DI VC - My Thoughts

[beancurdturtle]

Long, but hopefully not too boring. I hope it's informative for some of y'all.

 

First, here's my non-headphone listening setup: Lenovo Thinkpad T400, Vista Business, Foobar2000, DSP PPHS resample to 48000Hz, WASAPI out over USB (16 bit), ARX Audiobox USB DI VC, Yamaha HS 50M active near field monitors with a HS 10W powered subwoofer.

 

I think all the goods above are familiar to folks here, except the DAC and perhaps the Yamaha monitors. Brief description of the monitors. They want balanced XLR input. They are designed for flat response, precision, and excellent resolution. The monitors are bi-amplified and have basic controls with the purpose of tuning the output to the room, and controlling low/high cut with the matched subwoofer. The subwoofer has high/low cut controls and a level output to match it with the monitors. The objective is to be acoustically transparent - reproduce exactly what you drop through the XLR inputs, accurately, with no coloration. With good source - they are stunning.

http://www.yamaha.com/ca/productdetail.html?CNTID=59094&CTID=560502

 

I was running a Yamaha GO46 Firewire audio interface for the sound D to A conversion. I also used it as the interface to run a Digital Audio Workstation for recording. http://www.yamaha.com/yamahavgn/CDA/ContentDetail/ModelSeriesDetail.html?CNTID=64703&CTID=207900 The GO46 is ASIO compatible. So that's what I used for both recording and playback over firewire. The GO46 can go D to A, or A to D, 24 bits sampled at 32, 44.1, 48, 88.2, 96, and 192. Output is through TRS balanced phone jacks. The recording quality is phenomenal, and analog output from the DAW through the DAC is also pretty stunning, especially with good source. The problem comes from the usual sources - jitter, dropouts, and just plain childish arguments between the PC and the GO46. And the Vista driver is maddening - it comes with a warning something like "Don't touch your mouse or keyboard or your monitoring will be all screwy." So, I'm not doing much recording any more, I looked for a different "hop" between the PC and the Yamaha active near field monitors.

 

I'm a network engineer by profession. I manage the North American networks (global and local) for the sales offices of a major Japanese manufacturer. To move data and information I look for the most straightforward solution. The less mucking about you do from one point to another, the better off you are, and the cleaner your signal at the other end. So this lead me on a search for a DAC that Windows (or any USB compliant OS) recognises as a generic USB audio device, and pushes the end product out balanced XLR outs. I wanted something with gain control because I didn't want to add a hop through a preamp. What I found was US$600 or higher, had inputs and outputs I didn't need, and often no gain control. Again I want simple - USB in, balanced XLR out, with gain control. From my experience with data, the more extra circuits and stuff you put in a box - the less clean your output. After searching off and on a couple months I stumbled on the ARX Audiobox USB DI VC. I think I stumbled on it looking for Pro Audio DI (direct injection) boxes.

http://www.arxamerica.com/Series_Direct_Boxes.html

 

ARX is a Pro Audio company in Australia. That's all they do. If you work with Pro Audio, you know the need - make it work, make it easy, make it acoustically transparent, and it better not mess with my mix. The only complex thing you want to deal with is the music, the mixer, and the DAW. So my bias from being a data network professional, and a Pro Audio geek told me that I needed to try the ARX Audiobox USB DI VC.

 

What is it?:

A DAC, with standards based USB audio interface in, USB bus powered, ground lift for loop hum elimination if needed, two transformer balanced analog audio XLR Line out connectors, and gain control. Exactly what I wanted - nothing more, nothing less. Unfortunately the specs are a bit thin from the manufacturer - see the bottom of this page: http://www.arx.com.au/Australia/audibox_usb_vc.htm

 

Specs on the chips are here:

http://www.sonix.com.tw/sonix/product.do?p=SN11113

http://www.via.com.tw/en/products/audio/codecs/vt1612a/

http://www.datasheetcatalog.org/datasheet/philips/74HC_HCT20_CNV_2.pdf

Any feedback on the chips is welcomed.

 

Cabling up:

Balanced XLR interconnects from the back of the DAC to the Yamaha monitors. Turn the gain all the way down. Quality USB A to B cable from the Laptop to the front panel of the DAC. Idiot proof.

 

Configuration and driver installation:

None - well, none other than the usual hoop jumping needed for your media player and OS. The OS recognises the device as a standard USB audio interface. Idiot proof again.

 

Test Tracks:

I use a few different sources to judge accuracy. A couple recordings of me playing an Irish whistle - this because a whistle has a specific sound called "chiff" that will give away any inaccuracies in the high end, and I know exactly what my instruments sound like. A track from a Japanese release of Bryan Adams Anthology, a live recording that really tests sound stage width and instrument isolation well. A couple tracks from Buena Vista Social Club, which really tests the ability to recreate environmental acoustic ambiance, and sound stage depth. A couple tracks from Prince's Emancipation set, tests detail that usually only pops when you use something like my AKG K70 cans. Something from Jake Shimabukuro's (ukulele) Gently Weeps disc, to test the subtle details and natural representation of and un-amplified instrument. Stevie Ray Vaughan playing Little Wing, because it rocks and it's fraught with "flaws" like guitar cord crackle and ground hum that I just love. And a few more.

 

My impressions:

Very accurate lows, mids, and highs - across the board. Breath and voice of wind instruments are clean, sizzle without inaccurate sibilance. String pluck and fret sounds are precise and natural. Bass (acoustic, electronic, and amplified) is tight and controlled - acoustic bass is warm and natural. Soundstage is wide and deep, with great isolation both in width and depth. Environmental acoustic ambiance is accurately rendered.

 

Short story:

It's in/out and functions suit my specific need very well - which means it will not be suited to everyone. Sonically it works, very well - no jitter, stutter, dropouts or artifacts even pushing my system with several other programs running concurrently. It's easy. It adds no color to my music. Simply very accurate. Compared to the GO46, cleaner and tighter from low to high. Altogether, I'm very pleased with it and the price vs. performance value.

 

Answering Alberto:

"this dac, if I've well understood, has a passive output stage: two transformers and therefore no opamps, then low gain. This approach has positive aspects on the sound; natural mids, no dry highs but the bass loses impact and energy. I don't know if your hi-fi system has big woofers or not, but what you have to pay attention above all is the bass impact."

As you said my Yamaha monitors render "natural mids, no dry highs". And the bass is very tight and accurate. I didn't notice any loss of impact. In fact, I had to dial down the level on the subwoofer to balance with the monitors in reference to what is recommended in the Yamaha documentation, and compared to using it with the GO64. I'd say the bass is not colored or negatively impacted by a passive output stage (if it is in fact passive) at all.

 

Photos are here:

Jazzy box!

 

 

The goods.

 

 

 

I guess thay have kangaroos for Quality Control.

 

 

Front.

 

 

Top.

 

 

Back.

 

 

Bottom.

 

 

Innards.

 

 

Chip PCB.

 

 

 

[beancurdturtle]

I said "AKG K70", I actually have AKG 701s. Big difference.

 

[memphiskat]

Thanks for the review. Very interesting box. The link you provided to the ARX page shows a box configured a little different. The one on the web page has the audio outs and the volume control on the front/usb on back. It also doesn't have a ground lift. Doesn't really matter just thought I'd mention it.

 

Karl

 

[beancurdturtle]

Well, the photo on the manufacturer's site is right - even if the US distributor has it wrong.

http://www.arx.com.au/Australia/audibox_usb_vc.htm

 

[One and a half]

the DAC, a sampling rate specificiation wouldn't go astray from the manufacturer especially on USB. Noise rejection may not be that great since the application notes recommend to use a laptop without the mains powered power supply. first time I have heard this from a DAC manufacturer. Can't quite make out the chip top left corner wonder what it is.

What's the price, AUD400?

 

[beancurdturtle]

I believe its a Philips PLL chip. I'll crack it open and get a legible photo tomorrow.

 

I also was wondering why the specs were so thin from the manufacturer.

 

I'm thinking the recommendation to use a laptop battery powered is from the same abundance of caution attitude that motivates them to have a ground lift. It's Pro Audio think. I don't know for sure without specs or a schematic showing the regulators or whatever is cleaning up the power over the USB bus.

 

I can tell you my Thinkpad is docked, power goes into the dock, and the USB connection is from a port on the laptop, and I haven't picked up on any unwanted noise. Though if I was driving my AKG 701s with it instead of the Yamaha Monitors - I could be more discerning.

 

Thanks for the feedback,

 

[beancurdturtle]

Here it is...

 

 

Data Sheet: http://datasheet.digchip.com/364/364-22667-0-74HCT4046A.pdf