$175 Class D amp--120 wpc

steve k · « **on:** 16 Jan 2010, 06:49 pm »

Being a tube guy, I've been leery over the years of the ability of Class D amps to come close to the best sonic aspects of tube amps. That was until a couple tube-lover friends of mine started using this Class D amp instead. They came from totally different backgrounds--one was using 2A3 monoblocks to drive Klipsch LaScalas. The other was using ASL monoblocks to drive Maggie MG 12's.

At the time I was biamping Maggie IIIA's with VTL monoblocks on the top/mids and a modified Hafler DH-500 on the bass panels. The VTL's were rated at 125 wpc into 4 ohms as is the Class D Audio amp at 120 wpc that my friends recommended. So I sprang for the kit just for kicks. After all, both these guys couldn't be crazy I thought. The kit consists of the amp board, the heavy duty power supply board and the toroid transformer--all for $175. I mounted them on a cutting board and fired it up.

Amazing is all I can say. The noise floor was much lower than the VTL's so I was getting a lot more low level detail. The mids were very warm and tubelike and the highs were much sweeter and less edgy than the VTL's were especially when driven hard. I was shocked! I'm only using this amp above 400Hz but my friends tell me the bass is really good too as they are using theirs full range. All I can say is I'm a believer. Class D amps have come a long way. I've since sold the VTL's and I'm using the Class D Audio amp exclusively on the mids/highs.

Lucky for me, my friends are both good wood workers and they made a case for me. Have fun with this!

http://classdaudio.com/index.php/

steve

JoshK · « **Reply #1 on:** 16 Jan 2010, 07:19 pm »

I think Class D amps do a lot of things right. They are not everyone's cup of tea, though. I think for those who don't like them it is an amalgamations of nitpicks, with prior biases partially to blame.

Class D amps have such a high dampening factor (low Zout) that they are unphased by woofer impedance variation and phase. That is to say that they have great bass, if maybe a bit dry with some speakers not optimized for such.

My understanding of Class D, which wouldn't fill a thimble, is that they essentially don't have crossover distortion, or rather it is so high in frequency and gets filtered out by the inductor that it is moot. I think that might be one key aspect in the tube vs SS debate. So to that point, Class D has characteristics closer to tube amps.

I don't know what the harmonic distortion profile looks like for a typically class d amp but I suspect it is closer to that of a decent tube amp too. Another plus in my book.

The most common complaint of class d is that the highs sound off. I don't know why that would be but I have my suspicions, and it has as much to do with what people are used to hearing.

TheChairGuy · « **Reply #2 on:** 16 Jan 2010, 07:47 pm »

Quote from: JoshK on 16 Jan 2010, 07:19 pm

The most common complaint of class d is that the highs sound off. I don't know why that would be but I have my suspicions, and it has as much to do with what people are used to hearing.

Yup, definitely my findings, Josh. Also the hiss issue for the ones I have heard are problematic, too. Tripath, JVC's hybrid and one or two others I've had here over the years.

Aside from the hiss, the overall noise floor is so low (much lower than tube amps) that the hiss is most bothersome I think. The low noise floor does make for spooky real image placement I've found...even if the treble sounds weird and the hiss bothersome.

So the higher noise floor of tube amps (only with voltage regulation so the bass is neatly tucked up and not flubby as most tube amps tends to sound to me) end up being preferred in the end, but not without appreciation of what Class D can do.

But, if you use Class D for (primarily) bass frequencies they can sound yummy.

John

TRADERXFAN · « **Reply #3 on:** 16 Jan 2010, 07:55 pm »

The ps audio c100 modded by cullen circuits, an "icepower" amp, had had no hiss/noise issue. The top end may have been a little softer, but noise was not an issue at all even on the Geddes speakers which are about 95db sensitivity. I liked it very much, very detailed (not everyone's "detailed" is the same so be careful making a judgment on that statement). I went with the redwine 30.2 because I could get even more transparency, and with no hiss/noise either.

Edit: Sorry. Didn't understand that "Class D" in this case was referring to a company's brand...

These amps I mentioed don't fit the cheap and cheerful hifi board either.
Sorry

-Tony

JoshK · « **Reply #4 on:** 16 Jan 2010, 08:01 pm »

I can't say I've noticed hiss with the Hypex modules. I've heard of the tripath hiss though.

steve k · « **Reply #5 on:** 16 Jan 2010, 08:02 pm »

I've had no hiss problems whatsoever. The highs are extended, smooth and natural sounding. My tube amps by comparison had a bit too much bite in the highs. I've heard several other ICE amps and several Bel Cantos and never warmed up to them. This little amp however is completely different sounding. I think the linear power supply makes a big difference but I'm beginning to see that Class D amps are all brewed a little differently. This amp does not use the ICE chip or the hypex BTW. Tripath is not a Class D amp it is Class T.
steve

JoshK · « **Reply #6 on:** 16 Jan 2010, 08:09 pm »

Quote from: steve k on 16 Jan 2010, 08:02 pm

... but I'm beginning to see that Class D amps are all brewed a little differently.

Absolutely. I've only heard a couple class d amps, and they don't sound the same. I have Hypex modules, so that is what I commented on. I've never cared for the ICE based amps I've heard. I think Bel Canto uses ICE. I also have a Sharp mini system with a 15w class D amp, I think it is tripath based, but not sure.

TRADERXFAN · « **Reply #7 on:** 16 Jan 2010, 08:35 pm »

Well going from this, there isn't much difference
"A Class T amplifier is an audio amplifier product. Rather than being a separate "class" of amplifier, Class T is a registered trademark for Tripath's amplifier technologies. It is an implementation of Class D amplifiers, but improves the control scheme to create more efficient and higher quality audio amplification. "

http://en.wikipedia.org/wiki/Class_T_amplifier

steve k · « **Reply #8 on:** 16 Jan 2010, 08:37 pm »

I stand corrected.

TRADERXFAN · « **Reply #9 on:** 16 Jan 2010, 08:48 pm »

Well don't feel bad... its marketing's job to confuse the crap out of everyone and make distinctions that are insignificant -and if they are able to put a meaningless trademark on it, even better

Charles Calkins · « **Reply #10 on:** 16 Jan 2010, 08:55 pm »

Tony:

Did you buy their kit?

Cheers
Charlie

bummrush · « **Reply #11 on:** 16 Jan 2010, 09:10 pm »

did 175 buy all shown in pic?Also does the company sell the transformers as a package?Or does the company just sell the modules? I think ive looked at this site before and cant really make heads nor tails, on just what the heck is needed to make a complete amp.

TRADERXFAN · « **Reply #12 on:** 16 Jan 2010, 09:12 pm »

I think Steve did. I didn't.

steve k · « **Reply #13 on:** 16 Jan 2010, 09:17 pm »

Quote

did 175 buy all shown in pic?Also does the company sell the transformers as a package?Or does the company just sell the modules? I think ive looked at this site before and cant really make heads nor tails, on just what the heck is needed to make a complete amp.

$175 kit buys the amp board, the power supply board and the transformer. All you need to do is wire the 3 together and run a power cord to the transformer. The website shows the amps and the kits. This is the kit I bought:

http://classdaudio.com/index.php/120w-x-2-240w-x-1-amp-power-supply-transformer.html

Tom threw in the heavy duty power supply board at no additional cost.

steve

mr_bill · « **Reply #14 on:** 16 Jan 2010, 09:18 pm »

Quote from: steve k on 16 Jan 2010, 08:02 pm

I've had no hiss problems whatsoever. The highs are extended, smooth and natural sounding. My tube amps by comparison had a bit too much bite in the highs. I've heard several other ICE amps and several Bel Cantos and never warmed up to them. This little amp however is completely different sounding. I think the linear power supply makes a big difference but I'm beginning to see that Class D amps are all brewed a little differently. This amp does not use the ICE chip or the hypex BTW. Tripath is not a Class D amp it is Class T.
steve

Steve,
Could you explain the audio/performance difference between the class d amps you built and the Bel Canto for example?
Thanks,
Bill

macrojack · « **Reply #15 on:** 16 Jan 2010, 09:25 pm »

This kit looks like something I could do which makes me very suspicious. Could it really be that cheap, that good and that easy?

I'm currently using a Jeff Rowland Design Group 102 amplifier with his PC-1 power factor correction unit. It's hiss free, dead silent, in fact, and rather user friendly and refined. However, if I can achieve similar results for under $200, sign me up.

This prospect is very exciting.

mr_bill · « **Reply #16 on:** 16 Jan 2010, 09:27 pm »

Macrojack - exactly what I'm thinking.

I hope Steve will share more.

jtwrace · « **Reply #17 on:** 16 Jan 2010, 09:31 pm »

Yep. This is so crazy I think I need to try it. Anyone have a promo code for ordering????

steve k · « **Reply #18 on:** 16 Jan 2010, 09:41 pm »

Macro, I understand your skepticism. I was skeptical too and just tried this experiment for kicks. Little did I know, I'd be selling my tube monoblocks once I heard it.

(there was a time when I was biamping with two pairs of tube monoblocks). I should add that I'm still using a tube linestage. I recently heard the Bel Canto 1000 monoblocks and while the bass was fantastic, the mids and highs were a bit dry and unviting IMO. I like a liquid, tubey sound. The Class D Audio delivers just that in my system--a big warm sound with a full midrange and smooth, liquid highs without any stridence or edginess.

The one thing the tube amps did better in my system was creating a 3 dimensional soundstage. I've recently added a Museatex Bitstream DAC to my system which brought back a lot of the 3 dimensional imaging in spades but that's another subject. As always in audio there are tradeoffs and the 3D thing is one of them with this amp. However, it is dead quiet, detailed without being analytical, and very warm and involving.

It may not be everyone's cup of tea but if you like tubelike sound, this is the closest I've heard a Class D amp come to it and at a bargain. I understand Tom is developing a case for his amps so he will soon have a prodect more marketable to a larger audience.

steve

poseidonsvoice · « **Reply #19 on:** 16 Jan 2010, 09:47 pm »

Steve,

Fantastic post. Can you also mention it at the Lab? A lot of diyers would be interested as well.

Thanks.
Anand.