Audiolics Anonymous Chapter 23
Two Years...
Smart Devices Inc.
2x150 VT Amplifier
Article By Bill Gaw

  Well, Who woulda thunk it! Two years of columns and still going strong. When Steven R. Rochlin asked me back then, when he started this rag (is that the correct term for a web-zine?), to write a column or two I thought he must be pretty desperate to have me. A gynecologist by vocation, to write about audio, my avocation. I figured what the hell (Steve sez: Glad to have you aboard Bill. Oh, and this e-zine is really called a bloody shambles haphazardly thrown together by Keebler Elves with the help of Gnomes and Power Puff Girl's Chemical X :-)   ). I have some spare time, and some knowledge about the do's and don'ts of this hobby after 20 years of listening and buying... and buying and selling and buying and selling, etc.. You notice how many more buying and sellings there are compared to listenings. Sign of an Audiolic to be sure. So maybe I could impart some of my hard earned and costly wisdom and prevent the new Audiolics from making some of the same mistakes I had. After all, I probably could have retired by now if I hadn't spent what I have on high end products. But then again, I probably wouldn't have gotten to the level of sound reproduction I've achieved.

Would I have been happier in my ignorance if I had stuck with that Spectro-Acoustics/Yamaha system? They say "ignorance is bliss", and my wife still notes that half the time I'm still not happy with my system even though every person who comes over and listens praises it. But what the hell, this is my hobby and I'm an Audiolic... and I know it. At least my wife knows now that its probably healthier and cheaper than chasing women, and is usually content now to let me disappear to my listening room for my evening alone with my baby.

Smart Devices Inc. 2X150 VT Stereo Amplifier

About a year ago I was looking for a way of getting the center back surround information off of my DTS 6.1 channel DVD's. Since I had sold all of my extra Dolby Pro-Logic decoders other than my EAD Theatermaster, and since I had heard several good things about the Smart Devices Cinema Surround unit that is a pro board used in most theaters doing DTS 6.1 decoding in a consumer type package (previously reviewed in Audiolics Anonymous Chapter 8). I purchased one and was highly enamored with the way it sounded. Unlike other decoders based on the Pro-logic system, which give a mono signal cut off at 7000 Hz, this unit will give either a stereo surround and front center signal from front stereo channels or a center surround signal from the rear channels of decoded Dolby Digital or DTS 5.1 or 6.1 tracks (depending on configuration) with full output to 20kHz. I found it far superior to any Dolby Pro-Logic surround decoder and at less than $300... a steal!

About three months ago I called them with a question on how to set up the unit and talked to the owner, a true gentleman named Norm Schneider and he immediately asked if I'd like to review his newest creation. Enter their Stradivarius MosFET based stereo amplifier. Sure I said, as I find MosFETs to be closer to my tube based feelings than other solid-state amps. A week later the unit arrived. I set it up using my center horn system and listened. Big Problem. There was a 60 Hz hum that was not ear shattering but loud enough to be heard under quiet passages. The unit does have a switch on the back to lift the ground but no matter what I did, including lifting the ground, reversing the AC phase, grounding the chassis to other equipment, etc., I couldn't lose it. So I gave them a call and Norm let me know that they had heard about this problem, which only occurred on pre-production models. They had a fix and I should return the unit, which I did. Then I waited several weeks for a new unit which finally arrived just before the EMAP Show.

At the show I met Norm and one of his associates to let him know that it would be a while before I could fit the review into my schedule. He graciously said I could take as long as I want. So Norm, I guess this is the preliminary review, and the final... as the return of the product may occur in four or five years. (Only kidding, Norm. I don't want to be responsible for your heart attack.) He then let me know that they will be producing a three channel amplifier in the Fall. Thus, one can buy one three channel unit for the front channels, run long interconnects and place either a two or three channel unit at the back of the room for the two or three channels of surrounds. This I find to be more intelligent than the five and six channel units out there where you have to run long lengths of speaker wire.

There are actually two types of amps, the 2x150VT unit using a 6922 driver, with a list of $2,250 and the 2x150 using a FET, with a list of $2,050. Each has an Art Deco look chrome-black chassis with two sets of four LED's on the front to show power output from 0 to 150 watts in 50 watt increments. The tube unit, which I am reviewing being a tubaholic, has a front window through which one can see the driver tube glowing. On the rear is an IEC plug, three fuses, two sets of gold plated binding posts and RCA jacks, separated input volume pots, a ground lift switch, and a stereo-mono bridge switch.

Output is 150 watts/channel at 8 ohms and 240 watts at 4 ohms, at 0.02% distortion for the FET unit, and 0.9% for the tube unit, and 500 watts in mono bridged configuration. Damping factor and slew rate are very high yielding a frequency response of 2 to 160kHz. Each unit is burned in at the factory for five days. There are separate volume pots for each channel, so if you are using them in a biamp mode you can separately adjust the woofer to the mids, or you can run your CD player, etc. straight into the unit without pre-amplification as it has a 50 kOhm input impedance and full output with 1.95 volts input. Each comes with a graph showing distortion across the frequency band at full output for each channel.

The units are built to high end standards, using high grade parts, a large torroid power transformer, and only moderate local feedback. The company has used similar circuitry for years to build professional cinema amplifiers which have to be rugged and reliable. They are confidant enough in its indestructibility to offer a three year warranty. That's rare in the high end. In addition, at the end of the three years you can send the unit back, they will replace the tube, recalibrate the MosFETs, bring the unit back up to spec, and pay the postage back to you. See if any other company will do that.

I have now had the unit in my system for two months, primarily using it on my center front horns. One channel to run the woofer to 350 Hz and the other the mid-tweeter horn. This is actually a great way to evaluate an amplifier as the horns are very efficient and will show every problem in the amps first watt. The woofer, when played hard, will pick up any power supply problems as there is no crossover between the speaker and amplifier. Also, it is amazing how anomalies can be more easily picked up when listening to mono recordings as one is taking away much of the room masking that occurs with stereo playback. For the first three weeks, I only used the unit to listen to central channel information from DVD's, and except for one problem the unit sounded great.

That problem with low level 60 Hz hum, as mentioned above... I'm sure it has something to do with my system or electricity. I took the previous unit which had more hum to my friend Kwame's house, where he uses high-sensitivity Beauhorn loudspeakers and there the unit was dead quiet. Not a peep. And compared to his Korniff amplifier it was no slouch. Especially for a solid state vs. tube contest. Here in my home I've tried multiple different interconnects, speaker wire, etc., and have been able to lessen but not completely eradicate it. My speakers are about 6 dB more efficient than Kwami's so that could be the reason I'm hearing it here. So again, don't hold this against the Smart and in the normal 85-95 dB efficient system you probably won't hear it at all even with your head on the driver.

When I first got into high end audio, solid state was my choice of amplification. First with Class A/B FETs, then graduating to "Class A" push-pull units. As I became more sophisticated and my ears improved, I realizing that the 1980's solid-state stuff just didn't have that feeling of true music, I switched over to push-pull tube amps. These worked great with my VMPS Super Tower 2Ar speakers, bringing out their strengths. Though each amp I tried ended up destroying tubes and other parts such as taking out drivers. And in those days I didn't have the guts or intelligence to try to fix the things myself, so back they went to the factory for umpteen weeks. After a while I got fed up with that routine, bought a B&W 801 and began using Distech MosFET amps. These were based on the B&K 140 amps, were bullet proof, and sounded very good. They had some of the lushness of tubes and the some of the bass impact of solid-state, but lacked the ultimate of both. Plus they had the so-called MosFET hash, a grunge that floated with the image. I actually still have several of them and after 14 years of hard use they are seem to still be functioning to specification.

The reason I have discussed this is that the Smart amps have all but eliminated these problems. Gone is the grunge and hash. In their place is a nice deep clear sound stage. The mono Mercs and RCA's that I've played display great depth with a solid image. The hum completely disappears and without the tube rush of my SET's, I am able to hear further into the stage (which is very important with mono recordings where depth is the only dimension). While they don't have quite the mid-range musicality of my 2A3 SET's, what does? What they do have in spades is a deep solid bass. I was even able to turn off the subwoofer, adjust the digital graphic equalizer for a 12 dB/octave boost from 80 Hz down to counter the natural drop-off of the horns, and hear really tight deep bass which was at least equivalent to what I get on my main horns with my Plinius 50's in "Class A" mode. Plus the impact of the Telarc bass drum (you know the one) was the strongest yet from speakers in my room. And they are considerably cheaper than the Plinius' with more power output, although not all of it "Class A". The highs go on forever, or at least as high as these 54 year old ears can hear, and are sweet. Not the typical solid-state bleeding ears variety.

So what have I learned. First, solid-state still does not beat SET's for mid range musicality. Second, at least this new MosFET amplifier, it beats both the best of the MosFETS from 12 years ago and present day comparably priced FETS for mid range. Third, this amp beats the FETs and SET's I've heard for highs.

Would I buy this unit? If I were going back to standard low to mid efficiency speakers, yes. They give good value for the money, are attractive and built like a "Brick Outhouse". Therefore it should give good service over the long term. I think one of their three channel units in the front and a two or three channel unit in the rear channels would make a great surround home theater speaker system. How do they compare to other MosFET amps in their price range? I don't know, but I may start trying to find out considering the price to value ratio of these. How do they compare to their all solid state brothers? Again I don't know, but if you aren't into tubes, at least try them on the rear channels and save a few bucks. Would I buy them? With my setup now, no. But if I were to build a separate home theater system, the yes i would buy them. A good value for the money.

Where can you get them? Norm says he has several distributors now and the three channel units should be in stores in the next month or two. Contact them at info@smartdev.com, or peruse their web page at www.smartdev.com.

Next month, I'll probably be reviewing some updates from Lloyd Walker for my turntable, and some other tweaks he's sent my way.

Specifications

Power Rating: Greater than 150 Watts per channel into 8 ohms at less than 0.02 % THD 20-20 kHz with both channels driven.

Tube version: Greater than 150 Watts per channel into 8 ohms at less than 0.25 % THD 20-20 kHz with both channels driven.

240 Watts per channel into 4 ohms at less that 0.04% THD from 20-20 kHz with both channels driven.

500 Watts into 8 ohms at less than 0.04% THD from 20 to 20 kHz in monophonic bridged operation.

IM distortion at 150 Watts into 8 ohms: less than 0.25%

Frequency response into 8 ohms: -3dB, 2 Hz to 160 kHz at 1 Watt, -3 dB 6Hz -100 kHz at 150 Watts.

Signal to noise ratio, unweighted: Exceeds 100 dB referenced to full output into 8 ohms over a frequency bandwidth of 22 Hz.-22 kHz.

Input Impedance: 25k ohms. Vacuum tube version: 50k ohms

Input sensitivity: 1.85 volts RMS for 150 Watts into 8 ohms.

Rise time: 10 kHz, 60 volts p/p square wave, 10% to 90%: 2.5 microseconds

Slew Rate: 10 kHz, 60 volts p/p square wave: 30V per microsecond

Damping factor: 
300 @1 kHz into 8 ohms.
60 @ 10 kHz into 8 ohms.

Size: 5.8" high, 15.8” wide, x 10.1" deep.

Net weight: 23 lbs. (10.44 kilograms)

Company Information

SMART Devices, Inc.
5945 Peachtree Corners East
Norcross Georgia 30071

Voice: (770) 449-6698
Fax: (770) 449-6728
Website: www.smartdev.com/smartht.html