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What's Your Experience with Digital Switching Amp?

The ICE class-D amplifier modules (with self-oscillating transistors) have started a new generation of digital switching amps (DSAs for short) for people interested in high-quality sound at affordable price. If you own one of these amps, I am very curious about how it performs in your home, how it compares to other solid-state and tube amps, and especially how it compares to other switching amps that are starting to appear out there. To start things off, I will go first with you my own—very positive—experience with the Velluto DSA (Analog Research-Technology; 500 wpc; $2800). I’d love to hear your experience with your own DSA in return.

A LITTLE BACKGROUND

I am not an electrical engineer so I hope you will forgive my errors in summarizing the inherent problems with the ICE modules. Out of the box, the frequency response of the ICE module is far from flat. Class-D modules are also very susceptible to RF that can make them sound awful. The ICE modules, like all class-D modules, emit EMI that can create havoc with the sound as well. Like many solid-state (ss) amplifiers, most DSAs have relatively low input impedance that makes them difficult to be driven by a tube preamp. How designers solved these problems affects the amp’s performance.

After a long search—there are quite a few suspicious DSAs in generic boxes out there!—I settled on the Velluto Digital Switching Amp from Analog Reseach-Technology, a firm located here in Dallas, for several reasons: 1) Living in Dallas, I can audition it exhaustively before purchasing; 2) I like previous products by Pat Digiacomo, the engineer who designs and builds these amps in-house with eyes toward great sound at a reasonable cost; 3) Unlike many DSAs that use off–the-shelf chassis and generic front panel, the Velluto comes in a custom chassis with a massive front panel finished in attractive brushed silver. I will skip the description of the amp’s looks, features, and circuitry—I can tell you about them later if you are interested—and go directly to the most important thing about this DSA: its sounds.

THE SOUND OF MY VELLUTO DIGITAL SWITCHING AMP

I have listened to the Analog Research Velluto for a few months now and the sound of this amp is quite unlike that of any other amp that I’ve ever owned, solid-state or tube. The Velluto’s sound is wonderful: silky, dynamic, and expansive. As I just recently RE-discovered Audiogon and read interesting threads about the H2O amps, which I believe uses the same ICE modules as the Velluto, I realize that I am not alone in my enthusiasm for the sound of a DSA. One thing I noticed immediately about the Velluto’s sound was the bass: tight, deep, dynamic, and abundant! Compared to the Velluto, my Rowland Model 7 monoblocks sounded anemic in the bass, which is hard to believe with 300 wpc of class AB power. The bass on my BAT VK-60 monoblocks was as dynamic as the Velluto’s, but with clearly less depth, tightness, and volume. Another thing that captivates me is the Velluto’s midrange. It is very smooth, but not liquid like my BAT’s midrange or neutral like my Rowland’s, or analytical like many SS amps I dislike. Rather, it is silky smooth. I have never heard such midrange before from any amp, tube or solid-state. It is quite an alluring sound, worthy of the amp’s name— I think Velluto means velvety in Italian. The highs are extended and detailed—that was expected from a frequency response that’s down less than 0.3dB at 20 KHz—but surprisingly without the dryness, or edginess of many ss amps.

But the one thing I love most about this amp is its soundstage: it is positively gargantuan. It extends so deep and so wide beyond the speakers that you feel like the walls of your room have dematerialized. The sound just seems to expand for ever beyond the speakers to fade away at a far distance. It is quite an uncanny effect. By comparison, the sound of my BATs is more intimate but bunched up in the middle with far less information around. It becomes obvious that the BATs, like many tube amps, is missing quite a bit of high-frequency information which, by subtraction, gives the illusion of a very focused and dynamic midrange. I now much prefer the panoramic sound of the Velluto, especially for orchestral music though the BATs still have their moment with intimate music.

THE FUTURE OF DIGITAL SWITCHING AMPS IN HIGH-END AUDIO

Without trying to be controversial, I feel that many manufacturers with great reputation based their own successful designs will not readily adopt these ICE modules in their new amps. The poor sound of traditional class-D amps will not help promote these new DSAs either. On the other hand, some well-known high-end manufacturers like Jeff Rowland have already started to offer many models based on the ICE modules. When designed right, these new DSAs can remove many limitations of older ss designs: excessive heat, large heatsink fins, cumbersome size, heavy chassis that strain backs and cost a fortune to ship, insufficient power and bass, analytical sound, edgy highs, or constricted soundstage. This is assuming that all the kinks in the DSAs are worked out properly. For example, these amps may have to be rolled off (!) a little more for tube lovers who just can’t get used to the additional information in the highs and the panoramic soundstage—I’m not one of them but some of my friends are. You also have to be extremely mindful of nasty RF and EMI gremlins still sneaking into the sound. The Velluto overcomes these hurdles successfully but I doubt that all DSAs out there have identical sounds.

I am keenly interested in hearing the impressions of other (I hope very happy) owners of DSA amps.

Justin_Time


My Audio System:

Speakers: Watts/Puppies 5
Amps (Balanced): Rowland Model 7s, BAT VK-60s
Preamps (Balanced); BAT VK5, Rowland Consumate w/ phono stage
Analog source (Balanced): SOTA Cosmos, Graham 2.2, Sumiko Geneis, Benz, Koetsu
Digital source: Sony DVP 9000ES (for SACD only)
Power cords: TaraLabs Prism AC Special and RSC; homemade hospital-grade PC
Speaker cables: OCOS Triple runs, MIT CVT, Straightwire Maestro
Interconnects: Onix GMR XLR, homemade XLR (Nutric connectors/microphone cables)
Miscellaneous cables: Audioquest phono cable; TaraLabs digital cable/special termination
justin_time
Post removed 
justin_time OP
100 posts
 
QUOTE: "Hey Justin time, I like the name. I was an early convert to ICE magic. I owned the eAR, loved it over any solid state amp I had owned. I sold it to Ramy, and later bought H2O signature monoblocks. The improvement was significant. The H2O has a robust power supply.

I know people who have crossed to H2O from great tube amps, and solid states, as well as class D amps suggested here, including Tripath's best."

Hello Muralman1,

I got the nickname from friends because I am a watch collector as well (Swiss automatics). I also have a penchant for arriving at meeting "just in time," not too late or too early.

Anyway, I am glad to hear that there is a difference in sound between digital switching amps based on the same ICE modules. Could you tell me more about the design of the H2O?

As you implied, a good power supply is important and a dual mono design like the H2O is best. Strictly speaking the Velluto DSA is not a true dual mono amp but, in actual operation, it is. Each channel has its own toroidal transformer for the low-voltage power supply. Though the output stage voltage is supplied by a common (oversize) toroidal transformer, each channel has its own winding. The designer, Pat Digiacomo, said that he did this to cut cost without cutting performance. His measurements showed that during normal operation, the channels did not modulate each other because the current to each module was actually supplied by the filter caps. For all practical purpose, the Velluto has a dual mono operation.

In addition to a robust, dual power supply, RF and EMI eliminations are very important to making a digital switching amp sound good. I would love to compare the solutions in H2O monoblocks with those in the Velluto.
danlib1
819 posts
 
I enjoyed my Bel Canto Tripath amp very much.

But I like my Cary SLI-80 Signature MUCH more. YMMV!
muralman1
1,527 posts
 
The H2O Sig monos have been reviewed by 6Moons

http://www.6moons.com/audioreviews/h2o/m250.html

You can see what they are made of there. I am not conversant in amp technology. I do know the power supply would do well for a class A solid state. All H2O amp components are chosen to bring out the best of the new technology.

I know the stereo H2O Signature has dual toroidals.

I did a search, and couldn't find the Velluto.

You are correct in your understanding of RF, and EMI problems. They are easily controlled if you use shielded power cords on not just the amps, but all components. I made my own using Belden wire, and Marinko plugs.

Now, here is a tip for you, Justin time. Ditch the MIT CVT. Frankly, for speaker cables, I have found nothing better than the absurdly cheap Speltz Anti-Cables.
justin_time OP
100 posts
 
Hey Muralman1,

Gee, I wished you hadn't said anything about the MIT CVT cables until I've sold them :-). I bought them because they were recommended for the Watts/Puppies (!). The Velluto revealed their flaws pretty ruthlessly. Surprise: the OCOS triple runs work well with my DSA amp & the Watts/Puppies perhaps because they are transmission lines but I have no technical understanding of that.

I have no trouble at all with RF and EMI with the Velluto. Each ICE module in the Velluto is encased inside a metal box and all leads in and out are treated with ferrite material to completely eliminate EMI. To stop RF, the Velluto uses coupling transformers at the inputs which also eliminate ground loops. This solution allows the use of either RCA or XLR inputs without adaptors.

Coincidence: my homemade cables are also shielde Belden! Where can I get the Marinko plugs?

Thanks for the review of the H2O. Sorry I forget to provide more background info about my amp in my thread. You can find out more about the Velluto at the following site:

http://home.att.net/~analog.research/main.html
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