300+ wpc, brand new: $420

[Feanor]

I've just comlete my first semi-DIY amplifier. It's working great! :)

I was/am very a happy with my Monarch Audio SM-70 Pro monoblocks, but I undertook this build with a few objectives in mind:

I wanted a fairly simple, first audio project to amuse me in my recent retirement.
I wanted more in depth exposure to a digital amplier. I want a comparision no only with the high-bias, low feedback Monarchys, above, but also with the Bel Canto eVo2i, Tripath-based I owned a few years ago, (based on my memory 'cause the Bel is long gone).
See if substantially more power would make much of difference in my usage, say 2.5x the 120 wpc @ 4 ohms of the Monarchys.What tempted me to this project specifically was the US-made, Class D Audio, (website here (http://classdaudio.com/index.php/)), amps. Their amps are based on commecially available "class D" chips, however the boards and circuitry are proprietary. I selected the SDS-258 (here (http://classdaudio.com/index.php/class-d-audio-amplifiers/home-and-pro-class-d-audio-amplifiers/sds-258.html)) model, actually the kit that includes a linear power supply, transformer, and gain pots for US$360, (here (http://classdaudio.com/index.php/class-d-amplifier-kits/home-kits/sds-258-kit.html)).

The biggest challenge wasn't the electronics, which are basically plug-ang-play, but the cabinet construction. This was something new to me and I made a dozen mistakes along the way, but fortunately none were show-stoppers; (first time I've owned or used a "step drill"). Class D Audio can also supply a case, but it was a little rich for me at $190; my own case included some 1/2" MDF, 1x4" pine, and a Hammond aluminum case botton: this stuff cost me about $20. Assorted hardware including Neutrik XLR connectors rounded up the price to about $420 plus shipping.

The SDS-258, according to CDA, is ingeniously designed for balanced input and that's the way I built it since my preamp has balanced output. (Single-ended is also supported.)

My first impressions of the sound is very possitive -- more to follow. Here's a pic ...

http://www.ody.ca/~wbailey/CDA_SDS-258_open(2).jpg

[Geoffcin]

Sweet!!!

[audio amateur]

Nice! Are those new speak cables you have there? Look like Nordost

[kexodusc]

Well done, Feanor...and thanks for the link...I'm gonna have to try one of those soon...

[Feanor]

Nice! Are those new speak cables you have there? Look like Nordost
Yes, they're Nordost Flatline Gold. But they're not new, I've had them for years.

[luvtolisten]

:thumbsup: Congratulations and nice job. Wiring looks professional, I can see it was well thought out.

[Feanor]

:thumbsup: Congratulations and nice job. Wiring looks professional, I can see it was well thought out.
Thanks. I did try to keep the cable runs short over all, especially the source inputs and speaker outs. The wiring to the gain pots -- the black things at the back between the speaker outs and XLR ins -- comes with the kit; perhaps I ougth to have shortened them, but things seem fine at this point.

I'll comment on the sound in a day or two. So far it's really good.

[poppachubby]

Looks fantastic. But where do the tubes go?

[dakatabg]

Looks cool, I would love to hear how it sounds but I will never have the chance, Feanor, you gotta tell us

[thekid]

F
Congrats on completing a very cool project!!
Should'nt there be runes on the front or at least a Silmaril embedded on the front?

[Feanor]

F
Congrats on completing a very cool project!!
Should'nt there be runes on the front or at least a Silmaril embedded on the front?
I like that suggestion!

How about Feanor's device, (as designed by Tolkien)?

http://www.ody.ca/~wbailey/feanor-device-120.jpg

[Feanor]

Looks fantastic. But where do the tubes go?
Toobs, eh, Pops? Well there are none in sight nor any prospect of them with this amp.

I feel it's still early to give a definitive review -- for one thing, I'd like at least one swap back and forrth with my Monarchys. However I offer a few tentative remarks.

Class D Audio says ... "Our Super D Series amps provide more life-like imaging and sound stage, along with the beautiful smooth tube-like sound we're known for. These amps are powerful, clean, quiet , and transparent." Mostly true.
"Tube-like"? Well, there's a big variety of tube sound but I'd say not so much, especially if you mean "warm". There is some warmth in the 50-100 Hz bass region but the overall balance isn't especially warm. Vs. the Monarchys, there is some prominence at the top of the midrange, but then again the Monarchys are a little reticent in that area.
"Smooth"? Yes! The device, at least to my old and feeble ears, is basically free of solid state "nasties": no grain, no etching, no glare, and more generally, no harshness. This I say with the reservation that the CDA won't likey gloss over the shortcomings of up or downstream equipment.
"Powerful, clear, quiet"? Definitely.
"Transparent"? Yes, big time! Excellent resolution and "air" far exceeding anything I've heard in the price range; (kicks the heck out of Adcoms and NADs I've heard). Furthermore, the equal of the Monarchys and perhaps even my earlier Bel Canto eVo2i.In my system a noticeable quality is excellent brass and percussion sound from things like bells and cymbals, including cymbals struck with steel brush -- I believe the best I've heard in this particular regard (-- does that make it "tube-like"?). Bass generally seems a bit more powerful and punchy than the Monarchys (which aren't bad either). Is this the slight additional bass warmth? And/or is it the extra power??

[TheHills44060]

Wow that is so cool Feanor...great job!

Weird question but does that PS Audio power cable fit snugly in whatever IEC receptacle you used?

[Feanor]

Wow that is so cool Feanor...great job!

Weird question but does that PS Audio power cable fit snugly in whatever IEC receptacle you used?
Not so weird. It's bearly snug enough -- could be tighter or more positive. I don't like the excessive length of the PS Audio plugs either.

[GMichael]

Clean work Feanor. It looks great! Great review of how it sounds.

[theaudiohobby]

Feanor,

Congrats on completing your first DIY electronics project, :21:

[E-Stat]

I've just comlete my first semi-DIY amplifier. It's working great! :)
Really cool. That brings back fond memories of building Dyna kits when I was a teenager. The attenuator box I use with the main system is also DIY using components from DACT, Cardas, JPS Labs and Par-Metal.

rw

[thekid]

I like that suggestion!

How about Feanor's device, (as designed by Tolkien)?

http://www.ody.ca/~wbailey/feanor-device-120.jpg

We are probably enter geek territory but I think that device would actually look really cool. If not that device then a silver tree on one end and a gold tree on the other with the green background would look nice on your little "jewel". You could probably find an overlay at a craft store that you could use.

[Feanor]

We are probably enter geek territory but I think that device would actually look really cool. If not that device then a silver tree on one end and a gold tree on the other with the green background would look nice on your little "jewel". You could probably find an overlay at a craft store that you could use.
By the way, the reason the exterior is green is that that was the only paint I had around and I was too cheap to go buy another color. :arf:

[bobsticks]

Feanor, as a person that has ruined highschool shop projects I gotta tell ya I respect what yer doin'...further you're bringing me back to remembrances of my Grandfather who, in later life, took up model ship-building as hobby. The intricate workings and the detail are all very impressive.

I hope that the project not only proves itself a worthy investment of time in compare and contrast but gives you a seperate and equal level of joy as those magniificent Monarchys that you have...

Peace, Cheers, and thanks for sharing...

M

[harley .guy07]

I love when a fellow audiophile puts their ability to work and even though its a kit this is an excellent example of the kind of things that can make this hobby fun. And I am glad it sounds good.

[Feanor]

Feanor, as a person that has ruined highschool shop projects I gotta tell ya I respect what yer doin'...further you're bringing me back to remembrances of my Grandfather who, in later life, took up model ship-building as hobby. The intricate workings and the detail are all very impressive.

I hope that the project not only proves itself a worthy investment of time in compare and contrast but gives you a seperate and equal level of joy as those magniificent Monarchys that you have...

Peace, Cheers, and thanks for sharing...

M
Thanks, 'Sticks!

[Geoffcin]

I love when a fellow audiophile puts their ability to work.

Say that twice!

Back in the 'day, kits were nothing to sneeze at. From DYNACO to HeathKit, guys like Feanor were making quality gear back when the average guy could only get his hands on great gear if they made it themselves or sold their blood for cash. That same homemade gear STILL commands big bucks, and rightly so!

[Feanor]

Folks,

I posted a complete review over at AA; here it is ...

http://www.audioasylum.com/forums/amp/messages/15/157758.html

[thekid]

Folks,

I posted a complete review over at AA; here it is ...

http://www.audioasylum.com/forums/amp/messages/15/157758.html

Good read!!

:thumbsup: :thumbsup:

[Feanor]

I've swapped out my Monarchy SM-70 Pros and will use the SDS-258 exclusively for a considerable while. Maybe a swap back the Monarchys in a month or two just to see if feel the say way.

The thing that persuades me about this Class D Audio amp is its ability to authentically reproduce the full harmonic signature of instruments, notably strings, brass, and persucussion such as cymbal. It simply beats other amps I've had in my system in this regard. It does have very sold, quick bass too, but that's not the biggy for me.

But maybe there is a price to pay: this amp is slightly on the bright side, at least in the lower treble region. To some people this would be insufferable and the CDA amps aren't an option to them. I won't argue that this brightness is truly more accurate or authentic but I will suggest that, at the very least, it doesn't detract from a highly authentic instrumental spectrum -- conceivably it's actually essential to it. Anyway, the CDA is for people who favor authenticity over sonic confection.

When I got the Monarchys to replace my previous, class D, Tripath-based Bel Canto amp, I said that Bel was the better amp with the best recordings but that the Monarchys were more enjoyable with the other 70%. Presently with the Class D Audio SDS-258 I'm reversing the ratio, i.e. that for enjoyment the CDA beats the Monarchy 70% of the time.

[luvtolisten]

Sounds like a good plan Feanor. It's hard to tell, unless you live with it for a while. I know with speakers I have to listen that way, for a month or so and go thru a variety of your favorite music, then go back to the original speakers and listen again. As they say, sometimes "you can't see the forest for the trees". I look forward to hearing your thoughts further down the road.In the meantime, enjoy!

[Feanor]

Sounds like a good plan Feanor. It's hard to tell, unless you live with it for a while. I know with speakers I have to listen that way, for a month or so and go thru a variety of your favorite music, then go back to the original speakers and listen again. As they say, sometimes "you can't see the forest for the trees". I look forward to hearing your thoughts further down the road.In the meantime, enjoy!
Thanks, Luv.

Note that I'm not a dogmatic dork like some people around AR Forums who who believe that they are infallibly correct and that their choice of equimpment is categorically better and, further, that any body who doesn't agree with them is an ignoramous who refused to be informed.

Not to name names, of course ...

[manlystanley]

My first impressions of the sound is very positive -- more to follow.


I am so jealous.... Why didn't I think of building my own power amp. Great job, please keep us informed of your testing.

Best Regards,
Stan

[Feanor]

I am so jealous.... Why didn't I think of building my own power amp. Great job, please keep us informed of your testing.

Best Regards,
Stan
I'm loving it, Stan.

See my review at AA that I linked above. The amp might not be for everyone: some might find it a bit bright & analytical, though it works great for me. But even for those people, it might work with a nice tube preamp.

My own preamp is tube, but is notoriously "solid state-ish".

[Geoffcin]

I'm loving it, Stan.

See my review at AA that I linked above. The amp might not be for everyone: some might find it a bit bright & analytical, though it works great for me. But even for those people, it might work with a nice tube preamp.

My own preamp is tube, but is notoriously "solid state-ish".

I like "bright". When you think about it, a signal that is attenuated is going to sound dark, or duller. "Bright" for the most part (unless the amp has an obvious lack of bass) means your amplifying ALL of the signal. I assume this 300WPC monster of yours doesn't lack in bass!

FWIW; I'm STILL using my PS Audio HCA-2 amp in my HT rig. I blew a channel in it (long story - my bad!) but turns out I needed a mono for my Magnepan CC3 center anyway. Class D amps and maggies go together like bees and honey!

[jrhymeammo]

Great looking amp, and thanks for sharing detailed info on the kit.
Zero Solder = Happy JRA.

Have you had a chance to switch back to your Monarchy?
I'll be interested to know the LT listenability of the amp.

BTW, Nic Pic!

JRA

[Feanor]

Great looking amp, and thanks for sharing detailed info on the kit.
Zero Solder = Happy JRA.

Have you had a chance to switch back to your Monarchy?
I'll be interested to know the LT listenability of the amp.

BTW, Nic Pic!

JRA
Thanks, JRA.

So far I've only switch back to the Monarcy the one time. This confirmed my initial impressions. However I will certainly switch one more time for doing anything drastic such as selling the Monarchys.

A few days ago I replaced the Magneplanars' jumpers with the Magnepan-supplied resistors. These are 1 ohm resistors which, according to Magnepan, reduce the treble by 1-2 dB. Bear in mind that the MG 1.6 tweeter is actually a mid-tweeter carrying the sound above 700 Hz. So far I'm finding the sound less bright but retaining the excellent transparency and harmonic accuracy of the the SDS-258 amp. My next more will be to swap back to the jumpers, but meanwhile I think the mellower sound with the resistors would be closer to most people's liking (and to mine). Also, I will probably replace the Magnepan 10% resistors with high-spec Mills 1% resistors, perhaps 0.75 ohm rather than 1 ohm.

[Poultrygeist]

Feanor,

If you were forced to part with one amp would it be the Monarchs or the SDS?

Great job and enjoyed your review at AA.

[Feanor]

Feanor,

If you were forced to part with one amp would it be the Monarchs or the SDS?

Great job and enjoyed your review at AA.
Thanks, PG.

I think I would part with the Monarchys and might might list them on Audiogon in the near future.

[E-Stat]

I think I would part with the Monarchys and might might list them on Audiogon in the near future.
If you're still in the tinkering mood, I might suggest beefing up the power supply for either amp. That is an area where most amps can benefit given the size of the standard supply. I suspect the Monarchy amps would most have more punch and openness with a stiffer supply. Perhaps your new amp might also respond well to having more joules.

rw

[Feanor]

If you're still in the tinkering mood, I might suggest beefing up the power supply for either amp. That is an area where most amps can benefit given the size of the standard supply. I suspect the Monarchy amps would most have more punch and openness with a stiffer supply. Perhaps your new amp might also respond well to having more joules.

rw
Well, the Monarchys do have 60,000 uF per side and I don't imagine it would be safe up the voltage. In any case I'd be further ahead selling the Monarchys as-is since I pretty sure I like the Class-D-Audio better anyway.

The CDA SDS-258 is amenable to an upgrade and I know that some have done it. It will handle up to +-70 volts. I'm not sure what the current PS actually supplies since the transformer doesn't specify the DC output; maybe I could measure it with a multimeter. The capacitance is only 14,400 uF per side. One guy did up grade to this PS board from Connexelectronic (http://connexelectronic.com/product_info.php/products_id/89?osCsid=jaiasat3441bf6h4okgc4q5nt1) which will handle 71 VDC and has 6 x 18,000 uF (or 54,000 uF per side).

http://connexelectronic.com/images/PS18K71E.JPG

[E-Stat]

Well, the Monarchys do have 60,000 uF per side and I don't imagine it would be safe up the voltage.
No, I would only increase the capacitance given the design. Point to ponder: my thirty year old Stasis 3 runs 50,000 uF @ 65 volts while a pair of SM-70 Pros run 120,000 uF @ 30 volts. Which one has nearly twice the energy storage as the other?


I'm not sure what the current PS actually supplies since the transformer doesn't specify the DC output; maybe I could measure it with a multimeter.
It is quite easy to do. Measure across the positive and negative leads of the caps.


The capacitance is only 14,400 uF per side. One guy did up grade to this PS board...and has 6 x 18,000 uF (or 54,000 uF per side).
I would focus first on raising the rail voltage since energy storage goes up with the square of voltage. It may require using a different transformer.

rw

[Feanor]

...
It is quite easy to do. Measure across the positive and negative leads of the caps.

I would focus first on raising the rail voltage since energy storage goes up with the square of voltage. It may require using a different transformer.

rw
I will measure the rail voltages first.

[Ajani]

Nice Job, Feanor! It kind of makes me wish I had DIY skills...

Anyway, I'm anxious to hear your follow up comparison of the Class D versus the Monarchys... I've generally avoided Class D amps because of claims that they sound inferior to Class A/B and A amps... So I'm really pleased to see that you are preferring them for sonic reasons and not just efficiency or size...

[Feanor]

By popular demand I'm going to sum up my impression of the Class-D-Audio SDS-258 amplifier. My principal reference is my Monarchy Audio SM-70 Pro monoblocks.
Caveat: I am quite deaf above 10 kHz, so it is possible that I'm missing some high-frequency anomalies that other people can hear.Regarding class amps I've owned three of them:

Panasonic SA-XR25 audio-video receiver, which is still going strong after 6.5 years. The amp had an amazingly long burn-in, (so is my impression): about 400 hours, before which time it was pretty bright but now sounds neutral
Bel Canto eVo2i (integrated), (Tripath not ICEpower), which I owned for about 2.5 years. A totally neutral amp; very transparent, however I agree somewhat with critics who find it a bit "gray" or sterile in the mid-range.
The most recent Class-D-Audio SDS-258 which I've had for over a month and have listened to extensively.Monarchy SM-70 Pros I preferred to the Bel Canto on about 70% of recordings -- but note that this did not include the very best recordings. The Monarchys, (which I still own), are a tad warmer than the Bels and a tad "dark" in the upper mid / lower treble range. Tube fans, I suspect, would definitely prefer the Monarchys. The Monarchys have very good transparency but not quite as good as the Bel Canto.

At first I found the SDS-258 to be fairly "bright" (i.e. prominent) in the lower treble -- bright, but not harsh, grainy, or etched, (the latter being characteristics of that worst of all s/s amps I've owned, a Phase Linear 400). After the passage of 150 hours or so and -- more importantly I guess -- after installing 1 ohm, 5 watt, non-inductive Mills resistors ahead of the tweeters on my Magneplanar MG 1.6QR's, the brightness is gone.

My "final" conclusions are these for the Class-D-Audio SDS-258:

A neutral sounding amp. Not "warm" to be sure, but not bright, harsh, etched, or grainly. I personally don't hear any "grayness" to the mid range with this amp
Superb transparency and air, even better than the Bel Canto
Very solid, controlled bass. A bit more prominent in the 40-100 Hz range but ultimately more authentic than the Monarchy or Bel Canto in reproducing, e.g. large orchestral crescendos
Capable of very accurate, authentic instrument timbres -- better in this respect than any amp I've heard in my system. I don't hear any high-frequency anomalies that some critics report with class D amps in general, but see my caveat above.
Perhaps an amp more for lovers of accuracy versus euphony, but lacking any "nasties", IMO. The Monarchys are more forgiving of no-so-good recordings than the SDS, but I prefer the latter for 70+% of recordings, (the reverse vs. the Bel Canto), and these are the best recordings withal.

[Poultrygeist]

Feanor,

Excellent conclusions. You've got me interested but I'm looking at the lower power 224 versions. Do you think there's a significant difference between the CDA-224 and the SDS-224 kits?

[Feanor]

Feanor,

Excellent conclusions. You've got me interested but I'm looking at the lower power 224 versions. Do you think there's a significant difference between the CDA-224 and the SDS-224 kits?
The lower power, 224's and 254's have a really good rep. As for the CDA vs. SDS issue, the concensus is that the SDS has a small but significant sound advantage. The latter are also tuned for balanced input if that's something that matters to you; (it does to me because I have a fully balanced preamp). If my recollection is right, the SDS also has higher input impedance which is a good thing in general.

If you want a sub amp you'll probably would notice no CDA/SDS difference, but note that neither amp should used bridged into 4 ohms, and a lot of subwoofer drivers are 4 ohm. Actually, for sub amp, I'd go for their TI-300 or -600 amps that are fine bridged into 4 ohms. However according to Tom at Class-D-Audio the TI amps are not quite as nice sounding for full range use as either the CDA or the SDS amps.

For a lot of discussion of the CDA and SDS amps, see THIS (http://www.audiocircle.com/index.php?topic=76400.0) thread at AudioCircle.

[Ajani]

Feanor,

Did you have to do any soldering to assemble the amp?

Also, I'd love to see a picture of the rear of the amp (the inputs) as well as a final pic when you put the top on...

This looks like a project that might even be simple enough for me...

[Feanor]

Feanor,

Did you have to do any soldering to assemble the amp?

Also, I'd love to see a picture of the rear of the amp (the inputs) as well as a final pic when you put the top on...

This looks like a project that might even be simple enough for me...
Hi, Ajani,

Yeah, I'm sure you could manage it. The only things that really need to be soldered are the input connectors.

The boards have screw headers, so no soldering there. I used crimp connectors for the AC components and for the speaker terminals, so again, no soldering. Only the XLR connectors need to have the wires soldered to them.

[harley .guy07]

I still keep coming back and looking at the circuitry of the unit you built. Very simple yet very clean. Very nice looking toroidal transformer and really clean wire work. I would not mind if you would give an update on how you are liking this amp compared to some of the pricier stuff you own. I am very big into studying digital amps since they are very efficient, light and seem to be the new thing out there now and am wondering if this is something to look into for a project to possibly have something I can put in place of my amp at times when I would like to show my handy work. I have studied circuit design and am going to attent a university for electrical engineering so having a project like this might be fun to do and if it sounds better than my present amp that will be all the better. I just am amazed on how clean that the circuits look and how much power it puts out with so little. The more I look at it the more I would not mind trying something like this.

[Feanor]

I still keep coming back and looking at the circuitry of the unit you built. Very simple yet very clean. Very nice looking toroidal transformer and really clean wire work. I would not mind if you would give an update on how you are liking this amp compared to some of the pricier stuff you own. I am very big into studying digital amps since they are very efficient, light and seem to be the new thing out there now and am wondering if this is something to look into for a project to possibly have something I can put in place of my amp at times when I would like to show my handy work. I have studied circuit design and am going to attent a university for electrical engineering so having a project like this might be fun to do and if it sounds better than my present amp that will be all the better. I just am amazed on how clean that the circuits look and how much power it puts out with so little. The more I look at it the more I would not mind trying something like this.
Harley, I'm still really enjoying the Class-D-Audio SDS-258 amp. The amp is exceptionally transparent, resolved, and neutral with excellent timbrel accuracy; the bass is solid and quick.

Any earlier reservations I had about "brightness" are now gone. I did install 1 ohm resistors ahead of the tweeters on my Magneplanars, but this is a Magnepan-sanctioned this tweak and they even supplies a pair of resistors for the purpose. Or maybe it was just burn-in or my accustomization, but in any case, no complaint about brightness from me.

Assembling the amp is a very easy. One needs no electrical knowledge, (good thing in my case), and the only necessary soldering is the leads to the supplied gain potentiometers and to the source inputs. I constucted my own case, and that was by far the hardest part for me.

Are you considering replacing your Adcom 545 amp? I've never really heard that model but I did own a 555II. The 555II was nice, powerful amp with a very pleasant rather dark or "earthy" sound. By contrast the SDS-258, (HERE (http://classdaudio.com/index.php/products/class-d-amplifiers/sds-258.html)), is very neutral -- something one might or might not prefer. However the 258 is far more resolved and transparent, with equal or better bass. I would have some reservation recommending the Class D Audio together with bright or harsh up- or downstream components, but it should sound great with neutral or warm-sounding equipment.

I suspect the SDS-258 would go well with most tube preamps. Note that the Class D Audio's SDS series amps' input impedance is 47k ohms, normal for solid state, whereas their CDA amps' impedance is lower, 20k ohms as I recall, which might be a problem with some preamps. The SDS series is tweaked for balanced input but single-ended is no problem. There is a lot of discussion of Class D Audio amps HERE (http://www.audiocircle.com/index.php?topic=76400.0).

[harley .guy07]

Yeah I really was not looking to replace my adcom just have a secondary amp to put in its place from time to time to get something different from my sound. I am a person that likes having options and don't mind having some fun swapping out components just for the sake of trying some newer classes of amps that are out there. the class D designs have hit huge in the pro sound market because of there weight and power. I play bass guitar as well and new newest bass head(amp) companies out there are really pushing there class d amps. I played through a mark Bass head the other day that had around 600 whats or so and only weighed a couple of pounds while my 700 watt head at home weighs around 60.

[Feanor]

Yeah I really was not looking to replace my adcom just have a secondary amp to put in its place from time to time to get something different from my sound. I am a person that likes having options and don't mind having some fun swapping out components just for the sake of trying some newer classes of amps that are out there. the class D designs have hit huge in the pro sound market because of there weight and power. I play bass guitar as well and new newest bass head(amp) companies out there are really pushing there class d amps. I played through a mark Bass head the other day that had around 600 whats or so and only weighed a couple of pounds while my 700 watt head at home weighs around 60. It'll do it for an occasional swap for your Adcom -- or you might find it trashes that unit. Either way, it's a nice option for a very reasonable price.

What 'pro' class Ds are you using?