class d

I want to hear from people who has had experience with these that did not work out and why,all you hear is the positive.I'm not wanting to bash them whatsoever, its just there are people that dont like them,im curious why.Yes ive had a couple,they didnt actually sound bad,but they didnt draw me into the music at all either.
People whose systems were built around conventional tube or SS designs expect magic just by inserting class D amps. Hell,that can't be expected no matter what component is replaced!

I am still working on extracting their magic, but they ain't half bad now. PS Audio GCA 250 (level 2 Underwood mod) and Wyred4Sound SX 250 monoblocks

The bottom line is you have to work with them. I know this, they are VERY cable sensitive.

I heard my W4S on a mega system Scaena Loudspeakers ($50K), dCS Scarlati 3 piece digital ($70K), Nordost Odin speaker cables ($36K) and Tek Line Reference power cords (@$3K). The owner of the system was floored, and he is using the VTL Sigfried.
I've owned CI Audio D200, NuForce Ref9.02SE V2, Bel Canto Ref1000.

They each have strengths and weaknesses. The NuForce sounded most natural to my ears (unlike the God awful earlier NuForce amps), but they did not double power as impedance is halved, and therefore the sound they produced on my speakers was unbalanced. Bass was a bit shy.

The Bel Canto had great bass and balanced sound, but the top end was hot and tizzy.

The CI Audio did just about everything right, but they sounded flat and sterile.

I just didn't connect with any of them.
Much of the bad depends on how the output or recontruction filter is designed and what kind of capacitor is used in it and the higher voltage electolytic caps.

Just as SS or tube, there are better designs and their are worse.

Using the B&O IEC modules as is and inexpensive components throughout is what will produce 'sterile' sound from these amps.

Better desinged class D amps like the Spectron who deisgn their own IECs and ourput filters etc, sound much better and naturally cost more.
Hi Coffeey, as I have written abundantly elsewhere about what I have like in switching amps. . . I'll cover some of my less memorable experiences.

Heard the little Flying Mole monoblocks 2 years ago at RMAF. . . fuzzy, sterile, and forgettable, except for being extremely small and cute and inexpensive under $1K per pair.

Red Dragon -- heard at same show. Far too dark sounding for my particular preference.

JRDG 201 monos -- they are and older and a somewhat minimalistic design. sweet but a little cool, without the kind of subtle microdynamics that I like, nor with the dynamics that I want. They also can run out of steam and become glassy on louder passages unless the speakers are very sensitive. I heard the same problems driving Maggie 3.6, Vienna Beethoven Grands, Vienna Mahlers.

JRDG 501. Still an older design. Yet, you won't have authority problems with these. . . lots of authority in fact. . . I heard them on the same systems where I heard the 201s. Like the 201s they did not draw me into the music. While I would not call them sterile by any means, they do sound a little 'cool'. Perhaps more suited for Jazz ensambles than for female vocals or classical. JRDG has recently introduced an external PFC device called PC1 for the 501 and 201. This is said to bridge the performance of these amps much closer to that of the Continuum 500 and 312 amps. . . but I have no direct experience with PC1 in this application.

Channel Island monos -- heard last year at RMAF. . . sorry do not remember what model. Very nimble, but once again a little cool, and even a little tippy. On the other hand, these may not have been broken in, and switching amps are total bears to burn in. . . 1000 hrs or more in many cases.

The statement above about ICEPower based amps being inherently inexpensive poor performers is not quite correct. The issue is rather of how these power conversion modules are used. the same modules can be used in extremely basic and low cost devices, or can become part of much more sophisticated products costing upwards of $30K. Same as with transistors or tubes, really. And being the application of Switching modules rather new, the first design attempts were a little experimental and only moderately successful.
There was a really bad review of various class-D/T amps in TAS. It is available online now, BTW. Having heard/owned some of those amps, I can only say, that I fully agree with their conclusions.
"but they didnt draw me into the music at all either."

That would sum it up for me. I'm a big SET fan. The only one that has done it for me is the Red Wine Audio 30.2.

I don't play my music that loud so I get away with what I do. If I did, Class D would be a cheap way to get a lot of watts and some of them sound better than some marquis brand traditional amps.
"That would sum it up for me. I'm a big SET fan. The only one that has done it for me is the Red Wine Audio 30.2."

That's exactlhy the problem Onemug. . . there is nothing to sum up. Like with every other technology, some class D amps will be of your liking, while others may be just. . . interesting. Some may be 'cheap' as you say, but some other ones are definitely not inexpensive. Yes, a Flying Mole and a few other ones at less than $1K are inexpensive. . . but a Nuforce at $5K? Spectron at about $8K for the stereo config and twice as much for a pair of monoblocks? JRDG Continuum 500 at $8800? or a JRDG 312 at $16K? or a JRDG 301 at $30K?

As you can see, like with SET, there are switching amps for all budgets, and for very diverse requirements. G.
had a bel canto s300...did not draw me in at all, actually sounded more like a decent hi-fi receiver than a decent high end power amp...I guess i was lazy and did not want to swap all cables and components in order to realize the possible potential of that i moved on. We can talk tech shop all day but at the end of it, if a piece does not move us...pull us in... what good is it?
for me this class of amplification has a long way to go to reach serious musicality.
just mho and really does not matter one iota. Embrace and listen for yourself..see where things are and be honest.
Dpac996, are you sure you are not generalizing a little prematurely? You have owned one switching amp which you did not like, and you're concluding that no switching amps can be of your liking? I have heard several amps that I disliked in class D, classic solid state amps that made me run away from the room, and tubes that put me right to sleep. . . should I conclude that the whole industry is immature and move to butterfly collecting? G.
Guidocorona what's with the 301 mono's and damping factor being so low and to get the watts up there I would need to order the 301's in Par configuration to get 850 watts at 8 ohms and 1150 watts at 4 ohms.

301 mono blocks $30K
8 ohms 400/850 (ser/par)
4 ohms 650/1150 watts (ser/par)
Damping Factor 60


312 stereo $16K
8 ohms 500 watts
4 ohms 1000 watts
Damping Factor 1000

Damping factor seems very low compared to the stereo 312 which is 1000. I was looking into getting a pair of these but I have to say I'm a little concerned wondering if they will have issues driving a heavy load, MBL 101E's and then the price of $30K WOW!. Looking at the power of the 312 Stereo the power in 8 ohms 312 is 500 but when you look at 4 ohms it produces 1000 not much less then the 301 mono blocks at 1150 watts.

Then I look at the Spectron mono blocks, scary power. I have never had any amps in my system with this type of power and only cost $14,400.

Description: Watts per channel, both channels driven
2,400 Watts at 8 Ohms
3,200 Watts at 4 Ohms
5,600 Watts at 2 Ohms
Staggering headroom of 7,000 watts over 500 msec

This is just unbelievable and would totally control my MBL's with no issues.

You seem to have some experience with both product lines so what's your take on this.

I still have the ARC REF3 pre that I would pair up with the Spectron's in Balanced configuration but I would also look into getting say the Einstein and a couple others to compare once they were broken-in.

Ralph Karsten posted a long explanation a while back regarding amplifier specifications with particular attention to power and damping factor.

Bottom line was most buyers place an unnecessary emphasis on damping factor specifications when considering an amplifier.
Hello Dev,

Simon Thacher from Spectron write that power in rms is almost irrelevant to the quality of the sound (it just defines the loudness) and he analyzes headroom in transistor, tube (regular and OTL) and switching amplifiers:

All The Best
P.S. Until I got 2nd Spectron amp to run in monoblocks I had no idea what my B&W 802D are capable of...
Hi Rafael, I was hoping that we would be able to move this side discussion to another thread so not to highjack this one, but it looks there are already a few answers to your post. . . so moving to a different venue is no longer as clean an option.

In answer to the damping factor of 60 on the 301 monos, I fear I do not have an answer. I do not know why their damping factor is low, nor I know if this issue would impact your MBLs. . . although I suspect it might. Those are questions for Jeff Rowland. Furthermore, I have never heard the 301s, so it is a little difficult for me to comment on their sonic characteristics. As you know I am very fond of both Spectron and JRDG 312. Unfortunately I have not had the opportunity of listening to both of them side by side on my system, nor I had the opportunity of hearing Spectron in mono configuration as yet. . . . and speculative audible comparisons are always a little. . . speculative in nature. But we have highjacked this thread long enough. . . how about now returning it to its intended purpose? G.
good point Guido. I too have heard similar sounds from other operating classes. Yes I may have been too hasty in my post. It seems to me, however that one may need to spend more dollars to have a class d based system exceed the musicality of a fairly high end class A/AB ss amp. Tube amps not really fair to address here, being totally different devices. A spectron, which represents the best of class d is what, 4 to 5 grand on the used market? I have not heard one and perhaps i shall someday. I wonder to those that have heard this, how would it compare to say a Pass Labs X350.5, or a higher end Ayre in the same setup?
After reading much hype on this particular amp (s300) i was really dissapointed. But this was after having owned a Pass X250.5, an ARC Vt100mkii, and a DNA 225. All of these amps were, in the same system, heads and tails beyond the sound with the s300. Not really fair though, I realize as price and target markets are different, but i lost all interest in pursuing say the bel canto ref1000's or nuforce. As I stated earlier, just mho, and not really worth anything in this subjective hobby to anyone but me.
Dpac996, you have compared 1 relatively inexpensive ($1400) switching amp with SS and tubed devices ranging in price between $5000 and $8000 and found the $1400 amp to be wanting--not an overwhelming surprise. You may have wanted to compare the fine amps you enjoyed with switching devices in the same price range. You may or may have not enjoyed the Spectrum, Nuforce, or JRDG Continuum 500, but at least you would have derived meaningful findings.
I love jeff Rowland's implementation of ICDPower in his 501, 312 and Continuum 500 integrated designs, all of which I've heard pretty extensively. I've had single-ended tubes, class AB tubes, class AB SS and now my new Continuum 500. I can't imagine anyone listening to my system and saying, "It doesn't draw me into the music."

I'm a trumpeter for fun, playing in several orchestras and bands and attending many more concerts as a listener. I look for real musical sound, without added bloom or mid-range euphonics. The Continuum 500 delivers dynamics, transparency and pure sound that sucks me in every time I turn it on.

I'm obtaining excellent results from a PS Audio HCA-2 amplifier driving Acoustat 2+2 electrostatic speakers.
I bought a pair of BC Ref1000s to have a listen to and ended up keeping them and selling the in use Pass x350 I was using at the time. (Meridian 861 and Revel Studios + treated room).

Wouldnt go back.
Hi Vikingboy, what did you like in the BC Ref 1000 over the Pass X350?
this is actually becoming quite funny...these threads in general about tubes vs ss, bias class A vs bias class xxx, cd vs vinyl, linestage A vs linestage B, tube damper 1 vs tube damper 2...the similarities between such discussions and those of a religious nature are quite striking indeed. Toss pride, envy, and greed in the mix and we have a very rich, although pointless, discourse. I have become quite bored with these discussions lately and I mean no offence to anyone but it's just that I would rather be listening to the stuff I have than trying to prove endless points to other obsessive types like myself. The answer to what is the best x-y-z chrome cadulator is, hold on to your butts: the one you are listening to NOW. Amen. Pass the egg nog.
Dpac996, Thought about unsubscribing perhaps? G.
as a newcomer, I would submit that there is some value to reading the debate. I am curious about class D and seeing that there are vaired points of view cements my decision to bring a couple home for a listen. From a practical standpoint, class D holds some attraction for me. The idea of small, non heat producing powerplants is an appealing one. We shall see...
08-01-08: Jimmy3993
I am curious about class D and seeing that there are vaired points of view cements my decision to bring a couple home for a listen.
That's what counts, and all that matters.
Hi Jimmy3993. Glad the lively debate stirred your interest. Please let us know what you decide to listen to. . . and of course let us know your impressions. Guido
i am auditioning a class d non digital switching amp.

the raptor amp is a serious reworking of the bang and olufsen ice power module.

it is a product from the glacier audio company, .

i generally prefer tube-based designs, but the raptor is an amp i could live with, if i were forced to give up tubes.

this amp has been reviewed by henry wilkenson, on .
Hi MRT, Raptor appears to be made by Gilmore, see:
At $5K it appears to be a direct competitor to the NuForce monos and the JRDG 501. May I ask what you particularly enjoied about the Raptor, and where you prefered other amps. Do you happen to know how many hrs of operation the Raptor monos had on them? ICEpower amps are notorious bears to break in. Finally, does anyone know if they will be shown at RMAF?
i generally prefer tube amps with planar speakers.

my friend auditioned the nuforce 9 and the raptor. he bought the raptor amps. i have heard the nuforce at ces.
based upon my friend's advice--he is a reviewewr, i decided to audition the raptor.

it was obvious the basss response was benefitting from a 500 watt class d amp. there was greater extension, clarity and weight, than i experienced with the vtl deluxe 120, my reference tube amp. as expected, there seemed to be a bit more treble extension with this amp, compared to my tube amp.

i have about 20 hours of playing time. the designer alleges that a cintinuous signal of two hours is all that is necessary to render a reasonable assessment of the amp's capabilities. my friend disagrees. he suggests, well over 100 hours. in any case, i am pleased with what i hear, except for a bit of forwardness in the upper mid/lower treble. it is not too objectionable. considering that i enjoy listening to the magnepans with a solid state amp, after 10 hours of playing time, i would say the amp is worthy of audition by anyone seeking to purchase a non-tube amp.

there is a cable caveat here. i started with my reference ear to ear silver plated copper power cords and speaker cable. i heard the sound of silver and replaced them with element cable signature power cords and speaker cable. in addition,i removed the audience adept response 6 and replaced it with a ps audio ultimate outlet.

i would suggest copper cable interfacing this amp, before trying silver cable.

i think this is a very competently constructed product that won't disappoint. the amplifier has already been reviewed. i have no intention of reviewing it myself.

i hope this helps.
Guidocorona -

nuforce offers auditions via mail so that seems an easy place to start. I have the monos coming along with thier p-9 pre amp. My current amp is a mcintosh integrated and there is a jumper on the back that connects the pre to the power so I can pull that out and insert either the nuforce pre or the nuforce power or just run the nuforce combo together. Should keep me busy for a couple of weeks. But they will get sent back no matter what. This is only my first audition and there area few other things that I want to hear before I settle in.
Very nice MrT. Thank you.

That area of "fowardness" is where most of us hear the improvement with mucho burn-in.

Thank you MRT, much appreciated. . . both Gilmore and your friend are likely real optimist on break in time. . . As posted elsewhere, I suggest that about 1,000 hrs are a must for ICEpower switching amps fore they truly sing. Jimmy, you will have a lot of fun with the excellent Nuforce monos. Try to find out how many hrs of playing time they already have. . . . if you can, connect a tuner to them or a CDp on repeat, and let them play no stop for those 2 weeks. . . and only toward the end do some critical listening. Many people have dismissed switching amps prematurely because of simple lack of patience. If you could keep them around for one entire month, it would be best. . . . considering that they are probably partially already broken in, by the end you should truly be able to tell what they are capable of doing. G.
G - will do!
I will ask about playing time. they are dedicated audition amps so hopefully they will have some time on them already.
Have you heard the nuforce multichannel? I am looking for 3ch and talked to nuforce about 3 of the monos. They suggested the 7ch amp because it was less expensive that 3 monos and the SQ was the same.
Sorry Jimmy, I have no experience what so ever with multichannel gear. . . NuForce or otherwise. Guido
I dont think its funny at all its a legitimate ?I've listened to two different class d amps,and they didnt sound to bad,but just didnt pull me enough to pursue further so i sold them,it does seem they are quite promising.I'm still keeping a open mind on them.

At HE2007, I listened to two systems with Bel Canto REF1000 and S300 amps. The sound from both of these systems was a bit grainy on top. There was enough bottom slam, but it wasn't as clean and tight as some other tube and ss amps at the show. The systems were totally different for each amp, but these qualities were consistent for some reason. This finding was quite surprising to me as I was expecting the BC amps to sound clean, articulate and fast, based on impressions from reviewers and other users.

In the end, I ended up getting the Spectron M3 SE. After 5 or 6 months, I got another one and set them up in balanced mono-block configuration. I couldn't be happier with my choice.


Are there any Class D preamps? If not, are there likely to be any in the near future?
Never say "never", but I've not seen a Class D preamp and don't expect to. Class D is a method of producing high power with low heat, compact size and low weight. Since preampss are low power devices, the advantages of Class D are not really needed, at least in audiophile applications. Maybe in car audio, has anyone seen a Class D head in a car audio system?

08-03-08: Coffeey
... I've listened to two different class d amps,and they didnt sound to bad,but just didnt pull me enough to pursue further so i sold them,it does seem they are quite promising.
With the disclaimer that I've not auditioned class D amps in any formal manner, I've read a lot and gotten some sense of concensus. The only two class D amps I've come across that consistently collect favorable reviews, eliciting descriptions such as "smooth," "musical," and "involving" are the range of PS Audio amps and the modest little Onkyo A-9555 integrated amp.

The Onkyo lists at $700 but is easy to find under $500. Both Stereophile and The Abso!ute Sound gave it enthusiastically favorable reviews. The only thing that has caused me to hesitate buying one is that it has no pre-outs, and I might like to bi-amp. The reviews of the Onkyo also mentioned that it had excellent bass extension, tight bass control, and excellent yet musical clarity throughout. Yet its damping factor is a mere 25.

This PS Audio overview of their GCA power amp series mentions that their first-gen HCA-series amps of this topology only managed a damping factor of 25-30 as well. So that makes me wonder if switching amps manage to assert tight control without a measurably high damping factor. Still, the overview also mentions that for their new GCA line they figured out how to up the damping factor considerably.
Despite what one may read, Onkyo and PS-A are not in the elite class of ICEPower or Class D. They're good value for the money, but not really top contenders. PS and Onkyo have significant marketing budgets that garner them many reviews vs. the boutique makers with little or no budget.

08-08-08: Dcstep
Despite what one may read, Onkyo and PS-A are not in the elite class of ICEPower or Class D. They're good value for the money, but not really top contenders. PS and Onkyo have significant marketing budgets that garner them many reviews vs. the boutique makers with little or no budget.
Neither PS Audio nor Onkyo use the ICE module, but rather have engineered and patented their own approaches. I do find it interesting that both Abso!ute Sound and Stereophile both reviewed a well-built but mid-fi priced audio product from Onkyo. There's an awful lot of Onkyo and Denon gear that these two mags *don't* review, or only obliquely rather than formally.
I just got a p9 and a pair of v2se's from nuforce to listen to for a couple of weeks. The are demo samples and according to the company are plenty worn in. I was told to let them run for 20 hrs or so and they should be ready.
I snuck a quick listen to make sure that everything was working and didnt like what I heard. I wont bother to describe till I do what the rep suggested and give them a day.
Will post my 2cents once I have spent a little time with them. Very helpful company to deal with so far. I called the number on the web site, talked to someone for a while and they sent everything out. Pretty simple.
Yeap, Nuforce amps sure do not like travelling, may take a week of real playing time before they forget how much they disliked the airplane's cargo hold. . . until such time, they'll keep reminding you about how unhappy you have made them! [smiles!]
I just purchased a Spectron Musician III (not the SE mk ii version), and should receive it in about a week. Am looking forward to trying it with my inefficient MBL 121 monitors. I've already dabbled with Class D - a pair of the older Nuforce 9.02 . I didn't like what I heard with those amps but based on what I've ready about the Spectron, I have high hopes that it will win me around. I will likely upgrade it to the SE mk ii later on, as funds allow, assuming I enjoy what I hear with the basic version. I'll update folks on my findings.
I have posted a review of the Gilmore Raven, the stereo version of the Raptor, in comparison to the Nuforce, in the reviews section of this website. This amp still amazes me months later.
Jimmy -

If you have access to a tubed pre give it a listen with the V2SE's. I've heard that the P-9 with the V2's can be too much of a good thing. IMO switching amps really need to be paired with a good tubed pre.
i sent the raptors back. i listened to a recording of the tchaikovsky violin concerto on the chesky label. i compared the raptors to my vtl deluxe 120 in triode mode.

using the vtl the violin was more full bodied. i heard the strings and the wood body. wit the raptors, the balance favored the strings and the sound of the wood, was barely evident.
I have the PS Audio GCC250 driving Magnepan 1.6s.
They play well together and have stunning dynamics.
Ruthless exposure of mediocre source means I ended up having to do a pretty substantial upgrade there, as well.
Now that's over, I wouldn't change a thing.
any idea why they need to run for a while after travel? Not that I doubt it, just that I dont understand it. And you would think that the rep who sent them to me would want to show them in the best light and tell me to wait a week. But that wouldnt be the first time that a vendor said a component would sound optimal right out of the box either...
strange hobby.
Outlier, I will really be looking forward to hearing how the Spectron matches up with the MBL's.

Is the Spectron brand new? If so, I can tell you from personal experience that the first 100-150 hundred hours of a new Spectron can be cruel to your ears. Do not play too loud or you will really strain your ears. After 100-150 hours the sound starts to smooth out with continuing and notable improvement as you pass each 100 hour mark with close to full break-in at about 1000 hours. To expedite break-in try keeping a source continually playing through the speakers 24/7 even at low volumes. Good luck and have fun.