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Review and Measurements of Class D Audio CDA-250C Amp

Samoyed

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Did you see the NC400? Greats specs and sound.
The Panther likes Hypex!
FBEB2E0A-D0E1-43A1-808C-F5BF6355AE4D.jpeg
 

garbulky

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I wouldn't sell something you enjoy because it measured poorly. I use and appreciate Amir's measurements as a guide for buying and recommending new equipment, not as a guide for enjoying my existing gear. =)

These kinds of measurements are valuable from an engineering perspective, but their audibility under normal listening conditions is an open question particularly for speaker as opposed to headphones. The noise floor of a quiet room is 30-40dB, even with no music playing. And the loudspeaker and your room will add even more distortion. So you have to ask yourself if these issues are something you can hear. Or, better yet, get a hold of a better-measuring amp and do a A vs. B comparison yourself.
Yep: My emotiva XPA-1 gen 2 in class A mode measures between 76db to 86 db snr at lower power outputs. It has -90 db harmonics. Not terribly good right? I have zero regrets! Tons of enjoyment from the best piece of gear I've heard.
 

PappyBlue

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I wouldn't sell something you enjoy because it measured poorly. I use and appreciate Amir's measurements as a guide for buying and recommending new equipment, not as a guide for enjoying my existing gear. =)

These kinds of measurements are valuable from an engineering perspective, but their audibility under normal listening conditions is an open question particularly for speaker as opposed to headphones. The noise floor of a quiet room is 30-40dB, even with no music playing. And the loudspeaker and your room will add even more distortion. So you have to ask yourself if these issues are something you can hear. Or, better yet, get a hold of a better-measuring amp and do a A vs. B comparison yourself.

I was never impressed with the SDS-470C, it was a stop-gap solution. It just confirmed that I should buy the Bryston I've been wanting for a while
 

rkeman

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The Class D Audio SDS-470C has served as the amplifier driving a custom four subwoofer array in my home theater for about five years. Each channel powers two paralleled 8 ohm Acoustic Elegance SBP-15, each housed in sealed 6 cubic foot enclosures and equalized for flat in-room response to 16 Hz using Anthem Room Correction. The subwoofer has a mid-bass sensitivity of 92 dB when driven by 2.83 V. The variable gain offered by the SDS-470C allows the gain structure of the array to be optimized for lowest noise and maximal output. Self noise when idling is inaudible even from only a few inches from the drivers, the maximal output exceeds 115 dB at the principal listening position and the amplifier itself produces little heat and no mechanical noise even when driven to high levels for long periods. Distortion of the array at 105 dB, as measured by the Dayton Audio Omnimic, is below 3% at 20 Hz and less than 1% above 25 Hz. The subjective bass is smooth, powerful and clean.

So how does the SDS-470C do as a full-range amplifier? The four channel variant, the SDS-450C, has driven the Pi Speakers 6Pi cornerhorns, 3Pi two-ways, Jeff Bagby's Continuum monitor and a number of other high quality DIY designs with aplomb. With commercial designs (B&W CM8 Series 2, a GoldenEar Triton tower, and Magico S3, among others), it has proven sonically competitive with the likes of the Bryston 4B SST3, Audio Research Reference 75, and at least one very expensive (but very pretty) Mark Levinson.

Perhaps the Class D Audio SDS-470C is much better than the CDA-250C. Perhaps the SDS-470Cs balanced inputs, adjustable gain and ability to produce substantially more power yield significant auditory benefits. I have not had an opportunity to audition the CDA-250C, so I cannot comment with authority. Although elements of the measured performance of the CDA-250C appear to be inferior to the Hypex NC400, it still ranks toward the top of the amplifiers tested to date and has more than a few notable attributes (power output, relatively low cost, wide availability, efficiency, small form factor...). Despite the misgivings expressed about the CDA-250C, I would venture that it is capable of good performance in a wide variety of real-world audio applications, including high performance stereo and home theater systems.
 

Daverz

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I was never impressed with the SDS-470C, it was a stop-gap solution. It just confirmed that I should buy the Bryston I've been wanting for a while

Bryston publishes their own measurements and have been measured elsewhere, but it still may be interesting if Amir can borrow one of their amps just to have a reference measurement in the matrix.
 

phoenixdogfan

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Bryston publishes their own measurements and have been measured elsewhere, but it still may be interesting if Amir can borrow one of their amps just to have a reference measurement in the matrix.
Even better, Amir has some Levinson gear in his home system. Would see interesting to see how it Benchmarks against the other stuff that's sent in for review.
 

Ilkless

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Even better, Amir has some Levinson gear in his home system. Would see interesting to see how it Benchmarks against the other stuff that's sent in for review.

Would prefer to see ATI stuff (be it their own class AB, their nCore multichannels, or their OEM models for Monoprice and Outlaw). Could offer much the same without the premium for esoteric hifi mystique. What limited measurements seem promising, but I think ATI needs an additional data point much more than Bryston does. Especially the nCore stuff, which is down to about $500/channel for their 8-channel amp (perfect for a 4-way with the Okto DAC8 as crossover I reckon).
 

Matias

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phoenixdogfan

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Would prefer to see ATI stuff (be it their own class AB, their nCore multichannels, or their OEM models for Monoprice and Outlaw). Could offer much the same without the premium for esoteric hifi mystique. What limited measurements seem promising, but I think ATI needs an additional data point much more than Bryston does. Especially the nCore stuff, which is down to about $500/channel for their 8-channel amp (perfect for a 4-way with the Okto DAC8 as crossover I reckon).
Thinking of building an LX-521 system?
 

Daverz

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Even better, Amir has some Levinson gear in his home system. Would see interesting to see how it Benchmarks against the other stuff that's sent in for review.

Yes, I forgot those big ML amp's in Amir's system. When I saw that pic I wondered why he hadn't measured them.
 
OP
amirm

amirm

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When I saw that pic I wondered why he hadn't measured them.
If your amps blow up during testing, it is one thing. If mine does, it is an entirely different matter! :D
 

decoRyder

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First time post, and I appreciate this site very, very much.

OK, so I ordered the SDS-400C from the same manufacturer. An hour after ordering the amp, I stumbled on this site, and the review of the CDA-250. Needless to say, I was really annoyed when I saw the measurements. I live in Phoenix, where it gets brutally hot, and I was looking for a cheap amp for my garage, to pair it with a cheap set of ELAC Debut 6 2.0's, since I was tired of once again putting my more expensive gear through yet another summer of 120F+ temperatures. My 'reference' amp is a restored and upgraded QUAD 303 built in 1970, and other than that I pretty much only listen to vintage gear; tube-amps, restored Sansui amps, restored Adcom amps and similar gear. I own Fostex horn speakers, Bowers and Wilkins speakers, Mordaunt Short Speakers, and a lot of DYI gear, and even though I don't consider myself an 'Audiophile' by any means, I will call myself an Engineer with a discerning taste born of 35+ years of experience in HiFi. I hope this gives you some idea about my background, and in case I've not made it implicitly clear, I do prefer the 'warm' sound of vintage gear, and tube amps.

The SDS-400 arrived a few days ago. Didn't expect much, just wanted something that wouldn't fry in the garage, and increase temperatures in there even further. Also, I'm extremely biased against Class D, I like analog just fine; in this case though I wanted something decent with lots of power, and cool running - and no - not some Crown amp, I've listened to those, and while they are loud, they sound clinical to me.

So? How does it sound? Well, it's now the best amp in a collection of 22 amps. I paired this with a halfway decent DYI chinese tube pre-amp, using matched Mullard 12AX7 tubes. What emerged from the combination of the amp, the tube pre-amp, and the cheap ELAC's blew me away. I have no other amplifier that sounds better; this combo sounds better than my reference system, using a tube pre-amp, the QUAD 303, and Bowers & Wilkins 684 floorstanders. I realize this is a completely subjective assessment, and in the not so near future I will buy another one of these amps, and send it for review to Amir, apparently the SDS amps have a better input stage, and some units have quality control issues to begin with. Maybe this one will measure better, maybe it won't; either case, it sounds phenomenal.
Meanwhile I'm somewhat ticked that the cheap 'garage system' now sounds better than anything else I can throw together.
 
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mikeburns

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Well this review caused me to stop lurking and actually join and post. Good work! I have a Class D Audio SDS470C myself driving Monitor Audio Silver 8 speakers (4 ohm, not particularly sensitive). I purchased the 470C after feeling my rotel power amp wasn't doing them justice and was potentially underpowering them. To say the 470C was revelatory would almost be an understatement. I am not kidding. Maybe my rotel was not working to spec. Who knows. But boy this SDS470C is great.

Now after reading the specs/test I am a little concerned that maybe what I prefer in this amp is actually noise? I can't tell, it just now amplifies music in a way that makes it warmer yet more detailed. Its like my speakers now provide more tone. I ABed the two amps as best I could and every time the Class D just brought something special that the rotel didn't. I would love to see the SDS470C tested but I live in NZ so that is not happening. I kind of doubt it will measure any better after seeing the CDA go down in distortion flames =). I agree the lack of real technical specs via ClassDAudio is pretty questionable.

One question. At what point does distortion become audible? Is what the CDA produces as noise and distortion audible? I get that any hifi enthisiast wants the least amount of distortion but what is the minimum of noise that would actually be noticeable? It seems that the distortion mentioned in the test would not be regarded as euphonic or anything? I wonder why mine sounds so good? Is the spec of less than 0.02% distortion appropriate for the hifi world? It certainly sounds like it is.

Keep up the good work. I really hope we can get another Class D Audio amp checked out. If nothing but to soothe my rather OCD personality =)
 

decoRyder

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Now after reading the specs/test I am a little concerned that maybe what I prefer in this amp is actually noise? I can't tell, it just now amplifies music in a way that makes it warmer yet more detailed. Its like my speakers now provide more tone. I ABed the two amps as best I could and every time the Class D just brought something special that the rotel didn't. I would love to see the SDS470C tested but I live in NZ so that is not happening. I kind of doubt it will measure any better after seeing the CDA go down in distortion flames =). I agree the lack of real technical specs via ClassDAudio is pretty questionable.
)

Yeah, I can not reconcile the bad measurements, and how this thing actually performs (I have the SDS-400). After reading the review, I half expected this amp to blow my speakers, and set the house on fire. Tonight, my wife, who habitually rolls her eyes about my obsession with Audio, actually listened to it when she walked into the garage. Her comment: "Oh wow - that sounds good... how much did THAT cost?!". First time ever my wife said anything positive about any audio gear:)

I will buy another amp, probably the upgraded SDS-470C, and send that to Amir in the foreseeable future - hopefully he will find the time to measure it, AND listen to it.

2yh3xb.jpg
 
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D

Deleted member 15871

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Why are you selling? Does it sound worse to you now or you didn't really like the sound in the first place?

Ok. I get it. You guys love measurements. Don't get upset with me... I prefer how's it sounds and what makes me happy.
You liked the sound? Ok then.
Sorry
 
D

Deleted member 15871

Guest
Well this review caused me to stop lurking and actually join and post. Good work! I have a Class D Audio SDS470C myself driving Monitor Audio Silver 8 speakers (4 ohm, not particularly sensitive). I purchased the 470C after feeling my rotel power amp wasn't doing them justice and was potentially underpowering them. To say the 470C was revelatory would almost be an understatement. I am not kidding. Maybe my rotel was not working to spec. Who knows. But boy this SDS470C is great.

Now after reading the specs/test I am a little concerned that maybe what I prefer in this amp is actually noise? I can't tell, it just now amplifies music in a way that makes it warmer yet more detailed. Its like my speakers now provide more tone. I ABed the two amps as best I could and every time the Class D just brought something special that the rotel didn't. I would love to see the SDS470C tested but I live in NZ so that is not happening. I kind of doubt it will measure any better after seeing the CDA go down in distortion flames =). I agree the lack of real technical specs via ClassDAudio is pretty questionable.

One question. At what point does distortion become audible? Is what the CDA produces as noise and distortion audible? I get that any hifi enthisiast wants the least amount of distortion but what is the minimum of noise that would actually be noticeable? It seems that the distortion mentioned in the test would not be regarded as euphonic or anything? I wonder why mine sounds so good? Is the spec of less than 0.02% distortion appropriate for the hifi world? It certainly sounds like it is.

Keep up the good work. I really hope we can get another Class D Audio amp checked out. If nothing but to soothe my rather OCD personality =)

I just ordered the newest SDS250C with the regular large power supply. I won't get it until September or October due to my location 13 hrs ahead of NYC.
Tom said this amp matches well with Magnepan SMGa's. If it doesn't, oh well, I'm stuck. Live and learn.

Where do you set the adjustable gain controllers, 9 O'clock? 12? 3? All the way?
Thanks,
Joe
 
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