[Tyson]

A Return to 2 Channel Audio

When I moved to my current home, space considerations caused me to consolidate my HT system and my 2 channel system.  What this meant was a compromise that ended up giving me the worst aspects of both systems.  I had a 7 channel HT processor but only 2 speakers.  I kept the processor as a means of doing DD and DTS decoding, which it was OK at, but it was a very mediocre 2 channel music source.

After about 2 years I realized that I was not going to be going back to 7.1 or even 5.1 anytime soon, and my primary interest was in 2 channel music anyway.  So the HT processor had to go.

Searching for a new Solution

Let me state my preferences up front – I like tubes, but I find that I prefer Solid State, particularly in amps. 

I live in a high rise condo in downtown Denver, population density is very high, and emi/rfi and other grungy noise issues are particularly troublesome. 

I also have a short, but wide AV cabinet, leading to a need for longer IC's.  All of which means I'd like to have fully balanced equipment, if possible. 

Finally, my speakers (VMPS RM40's) are very, very difficult speakers to power.  They are full range, and need an amp with lots of power and control to drive the woofers properly.  On the other hand, the planar mids and ribbon tweeters are incredibly revealing, so an amp, preamp, or source that is even a little bit bright will be almost unbearable over the long term. 

Finally, I wanted a preamp that had full function remote capabilities – volume, mute, and source selection, since my wife would be using the system quite a bit for TV and movies.

Enter Audio-GD

I considered a few different options during my search.  Given my requirements and budget, I was looking very much at used Pass, Levinson, and Krell equipment.  The Pass “SuperSymetry” circuits and the Krell “CAST” technologies in particular piqued my interest. 

Researching CAST online and via local friends led me to another company called “Audio-GD” which also used “Current Audio Signal Transmission”.  Lucky for me, I had a chance to demo some non-CAST gear from this company locally, and I was very, very impressed with the sound quality and build quality.  Their website is:

http://www.audio-gd.com/En%20audio-gd.htm

So, I placed an order for the following gear:

DAC8 D/A converter

I already had an excellent music source in the shape of the fully modded Bolder Duet, so I was looking to get a DAC for use with my Blu Ray player (Sony PS3), and my HD DirecTv.  The DAC8 is fully balanced, dual mono, with separate power supplies for left/right channels, and separate power supply for the digital section.  8 D/A chips, 4 per channel, 2 in parallel feeding a second 2 in series, fully balanced signal coming straight off the DAC chips.

Pics with cover off:














C3 Preamp

Fully balanced, dual mono, with separate power supplies for left and right channels, and separate power supply for volume/mute/source switching.  Plus it's a dual box design, with the power supply stuff in one box, and the audio signal stuff in a separate box, very nice.  Accepts CAST, XLR, and RCA, and outputs either CAST or XLR/RCA via a switch on the back.  No global feedback, DC coupled, dual parallel power supplies, and very low distortion and noise measurements.  Real world measurements show ruler flat response from 10hz to 40khz, and the -3db point at 85khz.  THD is .01% at 1khz, and .022% at 10khz, both measured with 3V RMS output.  Part of this is no doubt a result of the optically controlled volume pot, which is designed so that there are never more than 2 resistors in the signal path, ever.

Pics:















C1 Amplifier

Starting to sound like a broken record here – fully balanced, dual mono, dual box affair, accepts CAST inputs or XLR inputs.  The “control” box does all the small signal handling and provides some gain, while the driver box (the “0db Module), provides some more gain and drives the speakers.  Output is 250 watts at 8 ohms, 500 watts at 4 ohms, and 1000 watts at 2 ohms.  It's biased into class A pretty heavily, a little over 40 watts pure class A at 8 ohms, 80 at 4 ohms, 160 at 2 ohms.  It also uses no global feedback and is DC coupled (like all the audio-gd gear).  Despite this, it actually has incredibly low distortion and noise measurements.  Real world measurements confirm it at .014% at 1khz, 1 watt into 8 ohms, and .3% at 10khz, 1 watt into 8 ohms.

The other cool thing about the C1 is the “control” box can be set up to drive 2 of the 0db modules, allowing you to biamp your speakers.  Of course I figured that the 500 watts I'd be getting into my 4 ohm speakers wasn't enough, so I ordered 2 of the 0db modules so I could have 1000 watts into 4 ohms.  Nothing exceeds like excess.










Order placed, and then....

I'd like to tell you that I placed my order and everything went smoothly.  Obviously I took a bit of a leap of faith, ordering from a small company halfway around the world. 

What's the worst thing you could imagine happening?  How about, audio-gd shipped my order in 4 boxes, and DHL only delivered one of them?  Yes, DHL confirms that all 4 boxes did in fact enter the country, but somewhere between LA and Denver, 3 of them got “Lost”, never to be found again.  Not a good start!

Luckily, Kingwa (the owner/operator of audio-gd), was very good to work with, and started building me replacements right away.  Since they have to build and test every unit from scratch, it took a while to get the replacements.  But they did come, and audio-gd took care of everything, replacing all the units, no questions asked.  Very nice!  I'd give them very, very high marks in the customer service department.  Kingwa does not speak English very well, but he is very fast in responding and is definitely understandable in his emails.  The main thing is that he is clearly committed to making things right if there are any problems, and this incident (for me), was high proof of that.

Everything installed, audio bliss?  Not exactly.

So, I get it all installed into my system, all hooked up together, and it starts making beautiful music, right?  Nope.  Not even close.  First, the 0db modules are running incredibly hot.  Far, far hotter than they should be.  And I'm getting very distorted sound out of my 40's.  After some panic, I arrange to have the amps tested by a friend locally, and Kingwa provided full schematics.  After opening it up and measuring it, Mike (mgalusha), confirmed his initial suspicion – that the bias was off.  Now, resetting the bias might seem like an easy thing to do, and on a non-balanced amp that might be true.  But on a fully balanced amp, it's a slow, iterative process.  Luckily Mike is extremely good, and after quite a bit of time and effort, we got the bias set properly and the DC offset at extremely low levels.  I've thanked him many times, but I will say it again – Thank You, Mike!

Get everything back home and hooked up again – amps don't run nearly as hot anymore – YES!  So it's all good now, right?  Not quite.  Less distortion, but some is still there.  I realize that the serial cables sent with the equipment, which is used to complete the power circuit between the two preamp boxes is pretty poor quality, and is not fully shielded, a big problem with my high EMI/RFI environment.  So, I replaced them with fully shielded cables of better quality bought locally.

Again, distortion drops, but is not completely eliminated.  I get the DAC and the preamp measured, but they measure perfectly and sound flawless in Mike's system.  The problem has to be elsewhere.  On a lark, I hook up an old Mondial MAGIC filter between my DirecTv HD reciever and the cable from the wall.  Presto, the vast majority of the noise is now gone.  Figuring ithe tiny bit that's left is noise from my AC, I pull out one of my old Monster power strips with filtration built in.  Ah, now we are talking!  The final step was switching from coax to optical cables from my cable box.  I also have a BPT 2.5 on the way, as my sledgehammer solution to a mosquito problem


(cont'd below)

[Tyson]

Finally Beautiful Music!

I thought that the balanced design of the equipment would make it less sensitive to noise and hash from the AC and the environment, but the DC coupled design with no global feedback and little-to-no current to voltage conversions seems to have made it actually much more sensitive than I would have ever thought.  But, once I got the source of the problems dealt with, I was able to finally hear how good the system actually is. 

As you might guess, the C1, C3, and DAC8 are uncommonly transparent.  With them in the line, you hear everything (and I mean everything) that your recordings have on them.  The level of detail and clarity is just insane, over the top, really.  When I was having the distortion problems, it made my system unlistenable.  But since I cleaned the sources and AC up, the sound is quite extraordinary. 

A friend of mine said that his first test of any equipment is “Does it make me want to turn the volume lower?”  If so, then it's a bad piece of equipment.  I agree with him.  But for me, I would add “Does it make me want to turn the volume up?”  If it does, then it's not for me, because it means that at lower levels there's not enough detail, not enough emotion, not enough involvement to make it really satisfying to listen to.  Very little equipment I've heard sounds involving no matter what level you play it at.  And that is the first major strength of the Audio-GD gear. 


Smooth as glass, smooth as silk, a hot knife through butter

Yeah, you might say it's smooth.  No etch, no hardness, no glare, no unnatural emphasis on leading edge transients, this stuff is smooth.  Here's my acid test for smoothness – Billie Holiday.  Put on any of her recordings, they all have distortion and noise baked into the recording itself.  On average equipment, it seriously detracts from your ability to enjoy the music.  On very good equipment it does not.  The audio-gd gear passes this test without even breaking a sweat!  I listened to Billie for 4 hours straight this weekend, something I've never been able to do before with all-SS gear. 

What is the sound of one hand clapping?

That pretty much sums up what the sound of this equipment is – as close to “nothing” as possible.  That does not mean it is dull or boring in any way.  What it means is that I hear more of the actual flavors and colors of the recordings themselves.  Whether that's the studio trickery of a Nine Inch Nails album, the minimalist, angry young woman with a guitar vibe of Ani DiFranco, the large scale and drive of a Beethoven Symphony, the soulful wailing of Billie Holiday, or the dynamic, complex music of Queen or Dave Matthews Band, it all comes through as direct, unique, and separate musical events, each in it's own universe, laid bare for you to fully appreciate.  A very rare thing indeed. 

In the end, what does it sound like?  It sounds like your source.  And if your source is on the same level of quality, then it sounds like whatever the recording sounds like.

OK, so what does it not do?

It's not tubed gear.  It won't give you the sound of tubes, which means you won't get that magic that only tubes can impart.  If you want “bloom” in your mids, liquidity in your highs, and warm fuzzies in your bass, then look elsewhere.  Tube gear certainly has magic, but they also impose that flavor on every recording you play.  I like tubes.  I just don't want them for everything.  Which is why I'm contemplating getting a tube dac at some point, so I can flip between a tube source and an SS source at the touch of a button.  Many people get tube gear to combat the seemingly inherent nasties that are part of digital sources, especially when mated with SS preamps and amps.  I was one of those people.  But I now think that the best SS gear can also be non-fatiguing and enjoyable to listen to for hours on end. 

Put another way, great tube gear can transport the musicians directly into your listening room, with a palpability that is unmatched.  But, great SS gear can transport you to the recording venue, giving you a window into that precise universe, and simply putting less between you and the musical event.

Conclusion

Clearly I love the sound and capabilities of the audio-gd equipment.  It was a bit nerve wracking at first, and was not without issues, but once everything was addressed, the reward was truly world class music reproduction.  Effortless, powerful, clear, vibrant, it's all here.  Even factoring the cost of air-shipping these very heavy boxes, the price they charge is still far too little. 

[Tyson]

Postscript 1-17-2009
Since my name came up here, I wanted to update everyone on recent changes to my system. I made 2 discoveries about my speakers (VMPS RM40's) that made me realize that a change was necessary - 1st, the mid-panels have a small peak in the 2khz range that makes them slightly bright sounding with any amp that does not have a slightly "warm" sound. 2nd, I found that they sound MUCH better when actively biamped.

I got a modded DCX2496 to handle the active crossover duties and bought a VTL ST-85 to power the mids/highs.

So, now I've got the Bolder modded Duet feeding the DAC8, which feeds the C3 SE (turns out I do actually have the SE version), feeding the modded DCX, which splits the signal, sending bass to the C1 and sending mids/highs to the VTL.

The sound quality is amazing.

The DAC8 in particular has really only broken in during the last month or so. This equipment all takes a very long time to fully break in, and will not be as sweet or clear during the first couple of months of use. It will still sound good after a couple weeks burn in, but it will be a more "mid-fi" kind of good, the kind of good that makes you happy, but does not make you forget about other amps/dac's. After a few months, that changes (at least in my system w/the fully balanced stuff), I no longer think about other amps, preamps, or DAC's.

One thing I should mention is that the voltage gain and output buffers for all of the equipment is modular and can be replaced.  This is good from a support/repair standpoint, as it is a lot easier to pull and replace a module compared to replacing an entire board.  They also offer modules with different circuits, which will change the sound a bit.  So, if utterly neutral is not to your taste, you have the option of tailoring it to your preferences, very cool.

I am running all XLR cabling (Bolder Cables, naturally), as I found I liked the sound with the Bolder XLR cables over the audio-gd provided CAST cables.  That might be a result of the CAST cables not being as good as the Bolder cables in an absolute sense, or it might mean that I simply prefer the sound of the balanced output over the CAST output.  Impossible to say without getting Bolder to custom make a couple pair of CAST cables for me, but that's not in the budget right now.

[richidoo]

Awesome review Tyson. I have been waiting to hear about your new gear, but had no idea your journey was so colorful. Thanks for hangin in there all the way through and reporting so eloquently. I especially appreciated your final comments about tube v ss:

Put another way, great tube gear can transport the musicians directly into your listening room, with a palpability that is unmatched.  But, great SS gear can transport you to the recording venue, giving you a window into that precise universe, and simply putting less between you and the musical event.

Of most concern to me was that the amps arrived out of bias. Did Audio-GD offer explanation or assurance that it couldn't happen again?

Thanks
Rich

[Tyson]

No explanation from audio-gd, but I suspect it might be because they are building it on a 220V and 50hz based electrical grid, while we're on 120v and 60hz.  I might be wrong about that, but if they were using a converter that didn't track perfectly to our voltage and frequency, it might cause the issue I saw.  Since I had Mike locally I didn't worry too much about it once we set a date to measure and adjust them. 

On another note, one thing I really like about the audio-gd gear is they really do things right from an engineering standpoint - good quality parts, immaculate board work and build quality, completely separate power supplies for each major function, separate boxes for the power supplies and the audio signal processing, dual parallel power supplies, great volume control and source switching, and lots of iron - 200,000 microfarads of capacitance in each 0db module, 48 output devices per 0db module, and not crappy ones either, the really good toshibas.  Every circuit is fully differential throughout, unlike some other companies that have a single ended circuit and stick a transformer on the output to make it "balanced", no this is all fully balanced circuitry throughout.  No feedback AND low distortion AND great bass AND incredible midrange purity (usually you have to pick one and sacrifice the others). 

Only downside is they take fooooorrrreeeevvvveeeeerrrrr to break in fully.  There's a LOT of transformer, caps, resistors, and output devices to flow electrons through.  Man, I thought the Odyssey gear took a long time to break in, but it's got nothing on this stuff.

Back on topic - I think their engineering choices are really, really solid and I cannot see any place that they skimped or tried to cut costs.  Build quality, circuit design, execution, parts quality, all are very good.  Clearly that results in some very good measurements, and in this case also results in outstanding sound quality.

[Tyson]

Updated with pictures added to the first post.

[jules]

Great review Tyson!

It sounds as though your audio-gd combination achieves all the accuracy and detail one could ever dream of.

I also salute your patience and would like to confirm all you have said about the customer service given by kingwa ... exceptional!

For those who are interested in other audio-gd products, here's another one ... the SA100, 100W per channel amp.



As Tyson has already said ... the quality of the boards is excellent, double sided, heavy foil flash gold plated. This amp uses a pair of 650W trafos and again a very generous bank of power supply caps.

At the moment this is a collection of parts in a box for me but I'll report back when it's all assembled.

Thanks again Tyson.

Jules

[Tyson]

Surprised there's not more interest in this, maybe I lost all my audiophile cred, after being away for so long

[JP78]

tyson, thanks for the entertaining read . i wouldn't feel bad about the lack of response...things seem a bit slow around here lately.

i looked but i didn't see any ballpark for price? also is air freight a requirement or did you upgrade to expedite? i suppose some of us could wait for the slow boat from china (sorry couldn't resist!)  .

jp

[jules]

pricelist:

http://www.audio-gd.com/enweb/Pricelist.htm

most of the larger products weigh about 35kg so postage/freight is quite expensive. On the other hand, the price of the various products is quite exceptional [as in LOW]!

jules

[Tyson]

The C3 was 1260, the C1 was 2200, and the DAC8 was 1260.  Plus, I wanted an additional 0db module with the C1, that was an extra $1k.  Shipping was not included in the price, so the cost shipping 260lbs of equipment in 4 boxes was a little over $300 total.  Total cost was still incredibly low, bang for the buck is off the charts, IMO.

One other item that really intrigued me is the FBI500, which is basically the C3 and C1 put into a single Chassis.  That's only $1470, and still has the full current audio signal circuit internally, from input to output, and still does 250w at 8ohms, 500@4, and 1000@2.  I was very, very tempted to get that, but I knew that I would always wonder how much better the 5 box solution of the C3 and C1 would sound over the 1 box solution of the FBI500, and the separates were in my budget anyway, so that's the route I took.

[zybar]

Tyson,

It was a well written review and I definitely enjoyed reading it.

For me personally, I am a little concerned with buying from China (not for political reasons) due to logistical issues.

How do you handle warranty work or technical issues?   

I would also be very concerned with resale value.

Glad this has worked out for you and been such a positive experience.

George

[saisunil]

Nice write-up

There is mention of Mark Levinson here and there - any design / performance relationship.

Cheers

[Tyson]

George,
Yep, definitely a concern, one I was willing to live with.  For work on it, you can send it back to the factory (not cheap), or get a local tech to work on it (audio-gd will provide full schematics).  The cool thing about the design is that most of the circuits are modular, which means they can be pulled and replaced by a new module, a very smart approach to dealing with damage/repair issues.

You are right though, if I decide to resell it, I would no doubt take a big hit.  That was part of the risk in ordering it, I didn't even know if I would like the sound, or if it would be as good as it turned out to be.  Big, big risk.  But, looking at the build quality and the design choices, I felt that even if it was not "amazing" out of the box, that they got the basics right, and it would make a good platform for upgrades/mods to get it to a high level.  Lucky for me, I don't think it needs any mods, it's performing at such an incredibly high level already. 

saisunil,
I can't speak for Kingwa, because I never discussed this topic with him directly.  But I can speculate a bit - I think what he does is study designs of other high end equipment to try to figure out from an engineering standpoint, what makes them better?  What do they do different that improves over the run of the mill amp/preamp/dac designs?  Then he uses those concepts when designing the gear.  For example, one thing that levinson does is use 2 stage power supplies as a means of dealing with AC fluctuations.  It's expensive and complicated, but it's pretty solid in dealing with the issue, so all of the equipment (at least the ones I bought), use this 2 stage power supply.  Same with the volume control - levinson uses an advanced control circuit which allows the use of a remote (with memory function), but still keeps only 2 resistors in the signal path at any given time.  The C3 uses the same approach.  Same thing with the Krell CAST, it's expensive, complicated, and difficult to implement, but has some real benefits from a signal purity standpoint.  Again, solid engineering.  I do think that the use of the Krell name is just for marketing/name recognition, because current based circuits have been around since the 50's, and the specific circuit he is using is based on a publicly available Japanese design.  But, what sounds better?  Krell CAST, or Japanese style Current Audio Circuit? 

Again, that's primarily my take based on what's on the website.

[mgalusha]

I missed this the other day. Nice write up and you're welcome, I am enjoying the Springbank 15 as well.

The amps were biased at about double the level specified in the schematic and as such they were very hot - 165* F at idle in my very cool basement. Because each channel is fully differential there are four amplifier modules per channel and getting them adjusted to the proper bias level and keeping them balanced against each other to generate minimal DC offset took a lot of time. Part of this was learning what the reaction of the circuit was to adjustment and how long it took to settle and waiting for thermal stabilization after making changes. Many hours of adjustments, waiting and measuring.

As Tyson mentioned, the equipment is very nicely made, clean layout with high quality parts. Once the amps were biased we tried them in my system. My system is actively bi-amplified so this involved resetting the gain settings in my crossover (modified DCX2496) to match the Audio-GD to my other amp. We ran these on the top end with the little Rotel 1080 on the woofers. While it sounded good it wasn't what I thought it should be. We then configured the system with both Audio-GD amps so they were feeding both the low and high sections of the speakers. To do this we had to remove the C1 (I think) module so we only had 6dB of gain from the amps thus limiting our volume but the resulting sound was exceptional. Both of us were pretty stunned, particularly on the bass. The little Rotel can manage 400W into a 4R load but it sounded positively anemic compared to the depth and control of the Audio-GD amps driving the woofers. It necessitated me making some tweaks to the Rotel the next week.

It was dead quiet in my system but my environment is vastly different than Tyson's. I live in the country with no industry for miles and pretty good power and my listening room has a dedicated 100A branch and multiple 20A circuits for the audio gear and several balanced power conditioners. It sounds like Tyson has gotten this under control as the gear itself was very quiet and well behaved on the test bench.

Very nice stuff if you can live with the somewhat distant support for China. 

mike

[Jon L]

You are right though, if I decide to resell it, I would no doubt take a big hit. 

I should be able to afford them after the "big hit" the way my stocks are going.  aa

They do look to be built very nicely, though I do wonder if one will get the tube itch after a year or so.  Truth be known, I haven't been able to live without some tubes in there somewhere long term...

[Tyson]

Mike,
You should hear them now!  I thought they were still a bit green in your setup.  Bass was VERY nice, but the mids and highs left a lot to be desired, 'specially compared to your massive tube amp.  But, they are much further along in the break in process now and the mids have filled in very nicely and the highs recessed a bit and smoothed out considerably.  The big surprise is how harmonically rich the mids sound.  Still not quite in tube amp territory, but running into class A pretty heavily seems to be paying off nicely.  I'm listening to the DSD remaster of Beethoven's Symphony 9 performed by Szell and the Cleveland Orchestra right now and it's just intoxicating all the colors and richness.  Hard to believe it was recorded more than 40 years ago. 

Jon,
I plan on converting my Duet to a tubed output circuit (courtesy of Wayne at Bolder Cables), so I agree, it's hard to live without tubes.  The SS DAC8 is fully class A, so it's far from sterile sounding, in fact it's quite rich and beautiful, but tubes are tubes and there's no substitute.  So.... a tubed source is in the works.  I thought about doing a tubed amp or preamp, but I think that would be a case of over-egging the pudding, at least for my tastes and preferences.

[satfrat]

Sweet writeup Tyson, loved the pictures. Doesn't sound like you have the BP2.5 in play yet but I'll be curious to read what you have to say about your system once you have it. It also sounds like all that gear still needs to settle,,, maybe you haven't heard the best from it yet? I am most interested in your thoughts about the BPT, mostly as I have a BP2.5 and I know how silent the ground noise got once I connected everything into it.

I'll also state that after all the years I've spent reading your great post reviews and with all the gear you've gone thru(on Hamonic Distortion), it surprises me that you would gamble on a (made in china) unknown company. After reading all the issues you had, I can't imagine anyone would really want to go thru all this. Afterall, most of us don't have a Mike Galusha in our back pocket to fall back on. You're very fortunate indeed. Tyson (or Mike), do you feel that further tweaking of the bias will be needed as you gain some hours on this system or is fluctuation on nonissue? Just curious.

I'm looking forward to future followups Tyson as you gain some milage and especially after you've gained this milage with the BPT in play.

Cheers,
Robin

[Tyson]

Thanks Robin,
I'm totally stoked to get the 2.5.  I think I'll eventually get the custom z-sleeve for it, and the ERS material as well.  For now I'm just incredibly excited to hear what it can do in my system. 

[mgalusha]

Tyson (or Mike), do you feel that further tweaking of the bias will be needed as you gain some hours on this system or is fluctuation on nonissue? Just curious.

Robin, I think it will be pretty stable. They used 15 turn pots, so I was able to set it very precisely but things do change over time and it will drift but I suspect that will not occur for a while, at least I hope so as those amps are pretty awful to move around.