[Vedder323]

Hi guys, I have been so impressed with my SDS-470 I have decided to share a review. Thanks. Let me know if you have any questions.

Class D Audio SDS-470
Class D Audio Power Amplifier Review
Ron Brenay

Squeezebox Touch>McCormack ALD-1>SDS-470>Gallo 3.1

Introduction:
There is a good possibility that Tom from www.Classdaudio.com might be out to save the world. I say this tongue in cheek but the truth is that after spending the last week with my SDS-470, I can’t help but wonder if this man knows something that other amplifier manufactures are not either divulging or willing to sacrifice. Tom told me in an early email leading up to the build of my amplifier “these amps are as good as or better than about anything on the market now and at any price. I'm not getting rich... just slowly building and growing a small business.” Was this mans “small business” going to be ranked with the many other companies that have over promised and under delivered?

Background:

Prior to the SDS-470, I owned the Melody SP3 integrated tube amplifier. For those that are familiar with the amp, you know it’s a far car fry from the last word in hi fidelity but at the same time, is nowhere near the bottom of the barrel. I would place it in the middle of the pack for (moderate powered A/B) tube amps and now that AV123 is long gone, one of the better bargains on the used market. I know the SP3’s sound like the back of my hand. I have owned it for 7 years and have seen speakers come and go but the amp has been the longest lasting piece of equipment I have ever owned ever since getting into this nutty hobby of ours. The SP3 is not a typical sounding tube amp, if anything it falls closer into the solid state sound signature. By all means, it’s not cold or sterile, but at the same time, it’s not incredibly warm either. It’s an amp that’s very balanced and brings out many of the details in music that solid state junkies typically look for. The SP3 is a fantastic tube amp that brought much of the strengths of a solid state amp to the table but also gave all the benefits of a warm, inviting sound of a valve amp.

The SDS-470 arrival

As I opened the card board box containing the 470, I kept feeling like I had made a mistake and was going to regret moving from my SP3 to the 470. I couldn’t believe and still can’t believe how light it is in comparison to my SP3 which weighed in close to 60 pounds. The 470 isn’t light enough to be considered “flimsy” but it sure didn’t come close to the hefty SP3. I couldn’t help but ask myself, where in the hell did he put all these watts he was rambling about (300/8ohms RMS 600/4ohms RMS)? I really was a skeptic as I flipped the rocker switch on the side of the little black box and sat down on my couch and grabbed my squeezebox remote…

Speaking of the design and function of the amp, it’s incredible. The amp is built with a careful approach to layout of inputs and outputs. Balanced Audio? No problem! RCA inputs? Check! Oh, you want a trim level thrown in as well? Piece of cake man, Toms got your back. The 470 reeks of quality, in and out. 2 little red led’s illuminate the front panel with a nice looking logo reading the company name and amp description written in white cursive. Classy.
Almost a ritual at this point, anytime I upgrade anything in my system, I start with Jack Johnson and friends “Curious George” soundtrack, track 1 Upside Down. The song is tough to get right and the opening has enough percussion going on that it’s pretty easy to hear how some amps smear the drums together, making it sound confusing and pudgy.  Within 6-8 seconds of the song, I pressed paused on my squeezebox and emailed Tom “Ummm…  WOW!”

I have heard this song so many times before and yet hearing it through the SDS-470 was different… it was a revelation, a new beginning, a new benchmark if you will…

As I continued listening, things went from “incredible” to “SHUT THE FRONT DOOR” good…  The bass line that cuts in the mix had the authority of nothing else I have ever heard come out of my system. The bass guitar notes were clear and trimmed around the edges. In other words, it popped from the mix and was separated in a way that gave the bass guitar its own voice, not just some background thud that’s easily lost. This kind of laser line precision and accuracy with the individual notes was easy enough to guide a blind man through rush hour traffic in New York! The Gallo 3.1s are known for being able to dig down deep but this was altogether different. There was a detail and definition in the mid-bass that I just haven’t heard prior to the 470.  I literally got out of my chair and just to make sure I didn’t pull a bone head move and left my Gallo SA amp on…  Nope. Nadda. This was the magic of the 470, all guts AND glory.

Bass:

Hearing how well the 470 man handled the bass on the Jack Johnson cut made me pull out the big guns. I was done playing Susie Sissypants and it was time to really stretch the legs of the SDS. Next up was infamous Telarc recording of Tchaikovsky’s 1812 overture.  After settling in and relaxing myself, I grabbed my SPL meter and set the volume right around 85db with the opening chorus; I sat back and silently waited for the inevitable cannons near the end of the 15 minute song. Interestingly enough, I had NO desire to skip past the next 14 minutes leading up to the cannons. The detail in this amp was unreal; it took what the SP3 was able to do but carried the game to the finish line. Notes were controlled, quick and bloomed with cutting clearness that extended the sound stage well past my 7 foot listening gap between my Gallos. Depth with the horns reached front to back as far as I was able to imagine. Closing my eyes, I felt like I could throw a stone and hit some of individual musicians. This is hi fidelity at its best, folks. As 15 minutes rolled around and the first cannon blast played, I could hear my wife (who thinks us audiophiles are just a bunch of geeks) say “Holy $%it”. Now, to make it clear, she is the least interested person I know when it comes to this stuff. The cannons shook my entire room. Keep in mind though, this was not boomy, flabby or slow sounding bass. This was controlled, tight, gut wrenching and musical. If bass is what you look for in an amp. Stop right now and just order the SDS-470. No seriously, go. You will thank me later. 

Mids:

I have played guitar for 15 years and knowing how the electric guitar is supposed to sound is second nature. I tossed on Eric Clapton’s “tears in heaven” and followed it up with The Who’s “won’t get fooled again” just to hear how the 470 does with mid-range instruments and voices. As the guitar in tears in heaven rang through the Gallo’s, the sweet sound of Eric voice locked on just a smidge right of center stage. I could hear the chesty attack of the chorus and strain as he poured out his soul. Again, there was a sense of detail in the midrange that just simply wasn’t there with the SP3. The guitars had attack and a resolved a woody thump as he played used the back of his hand against the bridge. Detail freaks are gonna salivate with the 470, no doubt about it.

Moving on, the Who’s performance of “Won’t get fooled again” was both exhilarating and almost tense at times. There is something so natural and dynamic about the electric guitar in this song, it’s a great way to hear some real midrange dynamics. I loved hearing the grind of the tube amp and as Pete dug in deeper, so did the SDS-470. This creates tension… not a bad tension but a welcoming tension as the song climbs to its chorus and resolves. Localization of the instruments was spot on and again, sound stage was simply perfect. I couldn’t hear the speakers, only the music and the artists. Roger sounded incredibly clear and cut right through the mix and as he screams; you get the sense of real emotion with SDS-470. Toss boring right out the window, with the 470, boring needs not apply.  This amp is fun and dynamic, detailed and quick on its feet. Agility is the SDS-470s ace in the hole, no question.

Treble, Cymbals and the 470:

I have never owned a class D amp prior to the 470. In fact, I have never heard a class D amp prior to the 470. Apparently, there are many people that claim they just don’t resolve treble the way a good class A/B amp can. I have never done a comparison so I honestly can’t be sure. What I can say is that no matter what I threw at the 470, the cymbal crashes, high hats, and rides all sounded fantastically natural. Metallic? Not a chance. Tinny? Nope. I tried pushing the envelope with Jazz from the Pawnshop ranging to A perfect circle to see if there was ever a moment when percussion sounded off or odd. Sorry to disappoint, but I think the 470 not only resolved treble with grace, I think it does it just as good if not better than any class A/B amp I have ever heard. This includes amps that cost 15x more than 470.

Conclusion:

I will leave this review where I began. Tom is out to save the world. As far as I’m concerned, he does know something that other amplifier manufactures are not either divulging or willing to sacrifice. Tom knows how to build an amplifier that outperforms and exceeds all expectations that simply costs less money.
In closing, if the SP3 brought the strengths of a solid state amp to the table but also gave all the benefits of a warm, inviting sound of a valve amp, the SDS 470 brings all the strengths of a tube amp to the table, but also gives all the benefits of a refined, detailed, and dynamic solid state amplifier
 

[Rclark]

 Hey, nice review! Great read. I was inches away from one of these amps myself, but I decided to go with a Virtue Two.2 instead. Totally glad I did, subjectively, people have said Virtue edges out the Class D stuff in sound quality, but at the same time I don't have the big horsepower you do either.

 Recently the d class of amplifier has closed ranks. You should also look at the much more expensive Ncore that recently came available. There are reports of it besting $20,000 Accuphase amps, Pass Labs, and this is just the tip, looks like.
 
 ... Have you noticed all the big amps for sale lately?

 However, the designer of the Ncore would take issue with your comment about "strengths of a tube amp"; he would say these days there are no compelling reasons to choose tube amplification at all. And he started out as a young man designing them!

 Your review was very well written, I think someone like myself who is not an old hand in the hobby gets more out of these reviews than most.

 Pics would be cool too 

[steve k]

Hey Ron,
Thanks for sharing your thoughts with us. I agree with many of your points. I think the biggest difference I heard with Tom's amps compared to tube amps are just how quiet they are and how much lower the noise floor is. I was hearing quiet, subtle inner details of instruments in symphonic and jazz combo settings that I simply never heard before with my tube monoblocks. I heard more bloom with tubes but it started from a much higher noise floor. I hear much deeper into the music with Tom's amps. Hard to beat for the money.

steve

[Regalma]

I wonder which module your amp has in it. It is described as having 300 w/C into 8 ohms. That matches the TI-600 module.

I bought the kit based on his most expensive module, the SDS-258. Your description of your amp matches mine except for the bass. I noticed an immediate loss of upper bass/lower midrange impact compared to other amps I have run my speakers off of. The clarity and detail of everything else is fantastic. I can't go back to my old amp so I am working on boosting the impact below about 500 Hz. I moved my seat about a foot, that helped. But still tweaking. I may go to biamping.

[Nick77]

Great review, these amps also improve even futher with better caps and more capactitance in the power supply. Bass is even more impactful with increased overall dynamics and mico details.
Also dont forget they are responsive to power cords also. I have a Wywire Juice pc on mine and it was at least a 20% improvment.

[srb]

I wonder which module your amp has in it. It is described as having 300 w/C into 8 ohms. That matches the TI-600 module.

I thought the SDS-440C and SDS-470C complete amplifiers used new, more powerful SDS series amp modules that are not yet listed on the website?
 
I still think Tom could overall save precious time by adding the new module pages or for now at least adding the new module details to the already existing pages for the SDS-440C and SDS-470C complete amplifiers, rather than having to respond to the same email inquiries over and over.
 
Steve

[firedog]

Tom does weird things with the web site. And not to his advantage commercially.

Since the beginning of this thread the "more info" that is lacking on the web site has never appeared; the SDS 470 is apparently for sale, but goes in and out of the listings. The 440 seems similar in basic specs, but acc'd to Tom the 470 will play at 2,4, and 8 ohms - which is an important consideration for some - as not all of his boards will.

[roymail]

Vedder323

Thanks for the review which was insightful and well-written.  Thanks for taking the time, and I'm glad you are enjoying your amp.

What preamp are you using in front of it?

[Barry_NJ]

Vedder323

Thanks for the review which was insightful and well-written.  Thanks for taking the time, and I'm glad you are enjoying your amp.

What preamp are you using in front of it?

Squeezebox Touch>McCormack ALD-1>SDS-470>Gallo 3.1

[roymail]

Also, I'm wondering if you've had any heat related issues?  Sounds like you were pushing it pretty had on that 1812 piece.  Any problems there?  Thanks!

[Vedder323]

Also, I'm wondering if you've had any heat related issues?  Sounds like you were pushing it pretty had on that 1812 piece.  Any problems there?  Thanks!

No heat issues. I am having what seems to be a squeezebox issue from time to time. I always read that you need to keep the volume fixed at 100% but for some reason that just doesnt work well for me. If i run squeeze at 100 and the amp at 50% trim, ill kick the amp in protection when the cannons go off. Still trying to solve this issue without much luck.

[Lyndon]

Nice review.
I just joined the digital amp dark side.
I picked up a diy amp with the Hypex UcD 180 amp modules. I am very impressed with their sound. I am still in the honeymoon glow, but feel they will replace my Aleph 30 and Krell KSA-50.  I have it paired with the VanAlstine PAT-5 that I procured and repaired last fall (thank YOU, Frank, for all the help and the NOS power switch)
I will be heading up to my stereo mentor in Bountiful tomorrow.  Perhaps I can talk him into plugging his early version of Class D's modules and compare it to the Hypex.  But he has gone back to an integrated tube amp, so it is clear that the sound of any amp is not everybody's cup of cocoa.
All I can say is this little digital is making my ProAc's sing!

[Barry_NJ]

Nice review, thanks for sharing! I'm now that much closer to pulling the trigger on one of these...

[Rclark]

An Aleph and a Krell beaten. Take note people. Not a fad.

[Regalma]

Vedder323 - please tell us more about the protection kicking in. I am running my SDS based amp with my Squeezebox Touch. I am also having this problem. I keep the Touch output at 100%, feed the digital out to an external DAC, then through a preamp to the amp. I have the amp gain set at the mid point on the pots. When I try to output more than about 90dB at my listening spot the amp will shutdown for a moment at high volume points. I have had my VMPS speakers for years and have run them off many amps without ever experiencing this.

I am not tried to play with the Touch volume. I have tried changing the amp gain without success. ClassD says that this should not be happening, and he is sending me a new module. But maybe it is not the module. Though I can't imagine how the Touch could cause this. Its output is processed through the active stages of the DAC and the preamp.

I am curious if you have done any more experimenting. I'm going to have to try some myself.

[jseymour]

Vedder323
I have a SDS-470 and its protection will kick in if I have the volume up and I have my plasma TV on (same circuit of course).  I received my amp in January and still had my Xmas tree up with approx. 100 bubble lights on it.  This would cause the same condition.  If the amp volume is low, I can have the TV on.  I think it is a matter of the amp protection sensing an undervoltage or undercurrent condition.  I just have this single power circuit in my living room, so I eventually wil put in a dedicated power circuit for my audio gear.

Are there other loads present on your SDS-470 power circuit?

[Vedder323]

Sorry for the delay in a response. I have been busy. The amp is sounding great and I still feel the same as my initial review. No after honeymoon blues here. In regards to the amp cutting out, I have played around with it quite a great deal and still cant seem to be certain what the exact issue is. I have tried different outlets and tried with the squeezebox turned down but it will always kick in prot mode when the cannons go off around 90db. The 1812 overture is tough to deal with and im not knocking the amp for not delivering the goods on that specific track is playing that at song at 90 db comes few and far between. With this being said, im still open for other suggestions or ideas.

Thanks

[Gradofan]

Just received my SDS 470C and set it up driving my KEF LS50's, using my Monarchy M24 Tube DAC / Tube Line Stage and iPod Touch 4 w Pure i20 Dock. 

The sound quality is very much as you describe - pretty impressive in all respects... actually very impressive!  Perhaps the most impressive are the mids, soundstage and imaging.  The musicians just appear playing their music... and the speakers just disappear in a wall of sound.  And the mids are rich with great tone, tenure and texture. 

The highs are certainly not like I've seen described of class D amps (not to be confused with Class D Audio amps) - as being bright, brittle, or glassy.  Rather, they're very nicely balanced, refined and resolved.  They may even be a slight bit tempered, or recessed, rather than "up front" and prominent. 

The bass is rich and full - the LS50's don't sound like they need any sub at all, though the only extend down to about 47 Hz, with their effective range a bit higher than that. 

If I had some "nits" they would be the following - though, I don't know whether these are points re: the LS50's, or the SDS 470C.  But, I suspect they're related to the SDS 470C, since most of the reviews / comments re: the LS50's report their bass is well controlled and reserved, and their highs are bright, and extended.

1.  The bass seems very slightly over-ripe, and not quite as tight, fast, detailed and resolved as I expected - especially for a class D amp.  Based on the reviews and comments I've seen of class D amps, I expected the bass to be very tight, and well controlled - maybe even too much. 

2.  The highs are very slightly subdued, and not quite as bright as I expected - especially for a class D amp.    Based on the reviews and comments, I expected the highs to be somewhat bright, detailed - almost too much. 

The leading edges may be very slightly rounded and not quite as sharp as I expected. 

The LS50's sound is warm, rich and full for small monitors - not at all lean and bright.

Is this the sound of class d amps - warm, rich, full, with somewhat round leading edges???  Should I expect the sound to open up and brighten up, and become more crisp, more defined, with sharper leading edges as the amp burns in???  And if so... a lot... or... a little??? 

UPDATE:  Well I installed DSPeaker Anti-Mode 2.0 Dual Core... and... completed the analysis of the room acoustics and corrected it... and... voila... everything cleared up - the bass and treble are now more crisp, defined, clear, etc.  The sound is no longer as "laid back," and overly warm and rich.  Room acoustics make a huge difference in the sound of all equipment - the Anti-Mode is the simplest way to compensate for them - it really works!

[Gradofan]

Well... as I may have posted elsewhere...

The more the SDS-470C burns in with the KEF LS50's and KEF R400b sub... the better it gets!

Now using the Sony SCD-XA5400ES as the source, into the DSPeaker AntiMode 2.0, into a Grant Fidelity tube buffer, into the SDS-470C, into the speakers noted... and... the sound is superb in all respects.  Great bass, mids and highs, with excellent clarity and detail resolution, tone, tenor and texture, and very holographic soundstage and imaging.  A very rich, liquid sound with ambience and sparkle - very tube-like. 

The amp is great and the speakers are great.  The LS50's are the KEF "Mini-Blade" and are not desktop, or bookshelf, speakers.  They're very high-end stand-mount monitors, which must be placed well out in the room, away from walls to achieve their "real live" sound (very much like Maggies, except with greater dynamics, and a little lower stage).  Fortunately... they're easy enough to move out whenever you're ready to listen to them, and back against the wall, when not in use.

The sound will be improving for some time yet... since... I still have very few hours on this set up. 

Though not the "prettiest" set up... I'm increasingly confident the sound is as good as any hi-end set up out there at a virtual "pittance."

[charmerci]

 

I don't see how this stayed in Cheap n' Cheerful for so long.