Another possible contender, that is not like the
"typical" Class D Design; But is able to sit in, with
the Best of the Class A, AB, Designs ANY day. IMHO.
I have the PS Audio "Gain Cell" amplifiers, they are a
"Hybrid" Class D Design.
The GCA-500 is the 500wpc@8ohm and 1000wpc@4ohms
The GCA-250 is 250 wpc.@8ohms and 500wpc.@4ohms
Bass is "Natural", in other words, it is exactly
as the Recording captured it.
Not too deep, or "over-damped", but just right.
The mids. are as smooth as I have heard, with the highs,
not EVER "searing" I own Horn speakers, that are very
sensitive, so low level listening, is mostly how I listen.
These amplifiers, have the uncanny ability to deliver
that very 1st watt, with Authority!
We All, have our favorites, and what is "great" for one,
might be down right, "nasty" to another.
All I can say is that I enjoy Music at a Level I NEVER
thought possible.
Given a set-up that is really "tight", IMHO if you add
either one of the above amplifiers, whether, it it Music,
or Video, the PS Audio, delivers the goods.
*****Bass
*****Imaging
*****Soundstage
*****Pure Enjoyment
*****Forget the Electronics
*****Value
*****Ability to reach 120db.
*****Lack of Heat
From the PS Audio site...
The GCA 250 is a two channel, 250 watt per channel power amplifier that produces 500 watt per channel into 4 Ohms and drives down to <1.5 Ohms. It has a damping factor that exceeds 1000 and is the amplifier most people will want to own as its 500 watt per channel rating is more than enough for any loudspeaker system we know of, period. The GCA 250 has an input impedance of 47K Ohms, can be remotely turned on/off with a simple 12 volt trigger, is a fully balanced amplifier, and like the GCA 100, its ear in the tweeter to hear any hiss out of this amplifier. Distortion levels below 0.1%. The GCA 250 is the amp of choice for any system whether its a stereo or multi-channel application. This beauty can power anything.
The GCA 500 is a brute. This is one of the most powerful amplifiers available at any price from any manufacturer in the world. The GCA 500 is a no holds barred stereo, 500 watt per channel power amplifier that produces an incredible 1000 watt per channel, both channels driven into 4 Ohms and is drives down to <1.5 Ohms! It has a damping factor that exceeds 1000 and is the amplifier you will want to choose if you never want to worry about headroom or dynamic capabilities in your system ever again. The GCA 500 has an input impedance of 47K Ohms, can be remotely turned on/off with a simple 12 volt trigger, is a fully balanced amplifier, and like the GCA 100, its ear in the tweeter to hear any hiss out of this amplifier. Distortion levels below 0.1%.
The GCA 500 is unequalled in the world of audio amplification. The king, the biggest, baddest power amp around that can play the sweetest violin passage to the loudest rock and roll, dinosaur stomping audio experience this side of the galaxy. If youve never witnessed true audio power with limitless headroom and breath sucking performance, this is the one.
They do benefit from a good power cord.
Balanced Interconnects of the Best quality.
I Love Music! |
Afc - Ref1000 can drive 2ohm delivering 40A. Size of power supply has nothing to do with it since 2" toroidal transformer at 100kHz can pass as much power as 10" toroidal transformer at 60Hz. In addition voltage doesn't drop since it is line and load regulated. Traditional "linear supply" needs a lot of caps because of voltage drop and necessity to filter out 120Hz (difficult to filter out and audible) vs. SMPS high switching frequency (non-audible and easy to filter out). A lot of caps in parallel have a lot of inductance - not desirable since it is in series with the speaker. SMPS is in reality class D amp (origin of class D) and got bad rap only because of cheap computer power supply implementations.
"A Class D amplifier has one output stage fully "off" for half the cycle"
High efficiency of class D is not caused by switches being OFF. Speaker is always connected by Mosfet switches (there is no OFF) but direction of current changes. Icepower uses single supply and full Mosfet bridge reversing output while Hypex uses half bridge connecting output to positive and negative supply. Efficiency comes from the fact that Mosfets in ON state have very low resistance (in order of 20mohm).
Replacing in class D analog voltage with analog time (duty cycle) allows to get rid of nasty problem of output transistor nonlinearity that in class AB is corrected by deep negative feedback that causes transient intermodulation (TIM) and exaggeration of odd harmonics (unpleasant bright sound).
I don't understand mentioned output voltage offset of class D amps. It has as much offset voltage as any other class amp without output capacitor (it uses feedback/servo to zero output). Self zeroing is probably responsible in my Rowland for 5Hz (and not DC) bottom frequency range.
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According to R. Vandersteen, DC offset is only a problem in their speakers with a powered woofer (the 5,7, and quattro). Using the class d amps in their other speakers does not cause any concerns. I just spoke with him this afternoon about this. |
D amps also have much smaller power supplies, so some may lack in the ability to deliver a lot of current. Hence, despite high "power ratings," some may struggle with difficult to drive loads. |
reveiws are meaningless especially when it comes to these amps,only mag that had it close was hi fi critic |
To much bass could have been a side effect of the Legacy speakers, but i doubt it.Its more likely my amp has a more realistic creation of the sound ,where if its on the disc there will be plenty of it compared to class d where it kinda of overtook the end to the point of distraction. |
Regarding Class D application and DC offset...I discussed this with Richard personally, and just found a pertinent entry on the Vandersteen website...in the technical section. You have to wade through lots of entries, but you will find the DC offset entry there. It just might be easier to call Vandersteen and speak to him personally.....you will find him a knowledgeable, and fine person to talk to. I am running Ayre amps which have a protection circuit to turn off the amp if it senses any DC offset. |
"dont believe everything you hear EVEN from me "
EVEN from HIM !
Still, I love my Spectron amp, love its seductive musicality, love its effortless presentation.
Read professional reviews and amp owners reviews and then and only then ask for the amp. Spectron, for example, provides 30 days money back guarantee. I am sure many other manufcturers too.
All The Best |
Coffey,
Which one(s) did you try?
I think you are the first person I have heard allude to too much bass as a result of a Class D.
Mine are certainly not lacking in that department, though they sounded relatively lean in comparison to my prior non class D amp at first. I attribute that to the very high damping factor, which works well with my OHM speakers in particular to deliver tight clean and articulate yet powerful bass.
I could see where it might be considered too much in some cases like as a result of some bass heavy room acoustics maybe or other factors upstream that affect bass levels. |
Every single person will give you a different opin,One, dont believe everything you hear EVEN from me.but for me i couldnt stand them,way way to much bass,,after i listened for a few months , i cant pin it down in audiophile words ,,,but i could not stand them,was the amp system dependent i dont know,but they didnt work for me, |
DC offset can harm your tweeter, depending on the tweeter design and degree of DC Offset
DC offset present in class D amplifiers and all other amplifiers which do not use output capacitors e.g. Plinius.
Before you purchase your amplifier check the specs. Spectron' specs is 10 mV but as a rule its 3 - 4 mV and its all harmless e.g. drives very well Vandersteen speakers.
When discussing different class D amplifiers, my suggestion is to pay more attention to the power supplies which drive it. There are a number of factors influencing class D amp sound We have posted a paper on our web site which hopefully provides some light:
http://spectronaudio.com/tech1.htm
Good Luck,
Simon |
When I acquired my ref100ms used, the seller kindly obliged me and opened up the boxes to confirm the specific design. I f I were to pay a premium for that model, which I did, I wanted to be certain that the right guts were in there and not just rely on a model label on the rear casing.
Yes, the dc offset deal is news to me. Some explanation of what that is and why it might be an issue with some speakers and class D would be educational. |
Stringreen, please explain your statement. I don't see anywhere on the Vandersteen website or the user manual's where it's stated not to use class D amps. |
Readers please note that the BEl Canto ref1000 and ref1000m (or mkii as the ref100m has also been called)are two significantly different designs that reprotedly sound different and may work differently in different system configurations. Be sure you know exactly which design is being referred to.
When vendors change a design but only alter the model names slightly, things can be confusing. USing two different designations for the same design (re1000m and ref1000mkii) only makes thnings worse. |
I too have had Bel Canto's Ref 1000's in my system. IMO their power and overall presentation seem very well designed when paired with my Eidolon's. In the June / July issue of TAS Nelson Pass gives, what I consider, an experienced and gracious opinion of class D amplification. Unfortunately, like countless other opinions it generalizes these designs as well as assuming the goal of these designs is to achieve "the qualities of good class A amplifiers."
Class D switching, digital, PCM, ICE, etc. amplifiers come in a variety of implementations. Many share some fundamental design features, still, most seem to have their own distinguishable presentation within class D. None of the class D amplifiers I've listened to at any length sounded like a push pull or SET tube, solid state, class A, AB despite others claims.
As a professional Bass player I often play raw digital pre production files as well as analog recorded tapes. What my switching amplifiers do for me is provide an unbelievably revealing and transparent presentation ( what could easily be termed as sterile ) and the most well defined bass. I've found their most unusual quality is their ability to preform at their full output capacity without becoming congested or fatiguing. It's as if they're passing current directly to the drivers. In short they sound like switching amplifiers and their presentation is not for everyone.
My suggestion is to do your own auditioning using robust copper interconnect, speaker, and power cable and an up to date dedicated and shielded AC circuit. Switching to a battery powered preamplifier took my system to another level altogether. |
Have owned several class D amps including tripath and ICE. I prefer the ICE module based amps. They have a natural sound to my ear.
Suggest you pick up a used amp and listen for yourself. The experience will be worth the investment. |
I'm a fan. But there are substantial differences from model to model and brand to brand. My Bel Canto Ref 1000s sounded good to me but a bit thin and dry. I switched to Kharma MP-150s and the improvement was dramatic. These amps sound very similar to my friends' tube amps. |
I have the Bel Canto ref1000 mkii monoblocks. They are the real deal and work very well with tube pre-amps which tend to have higher output impedance (not all Class Ds may be ideal matches for tube pre-amps), and all the speakers in my system, all of which tend to benefit from the high current delivery and damping factor.
For speakers that benefit from this (not all do), they are just what the doctor ordered in a small energy efficient package. For others that do not, well, I expect Class D to be competitive as well but there may also be a lot of viable competition. My amp hunt is over for the foreseeable future. |
Last year, I owned a pair of Bel Canto REF 1000 monoblocks. I very much wanted to like them,great looks, nice tidy size, low energy, but I gave up after 2 months. Weak bass, nowhere the rated power output - and essentially the midrange sounded as if it was in a tunnel. I am exagerating a bit of course, but the conclusion is that I could never see myself living with those. Life's too short to give another class D amp a second chance in this century. |
excessive DC offset can burn up some crossovers and/or built in amps. For a more technical explanation, contact Richard Vandersteen. Switching amps are verbotten on Vandersteen products. There are others out there that can be affected. Contact your speaker manufacturer to discuss their product's vulnerability to this problem. |
Hi Orpheus10. I have a Cary A306, not well known, but Class D. For me it's a keeper. Use to own the Wyred 4 Sound ST 1000 which is also quality. |
My experience mirrors that of Mrkoven. I have the ST500 and it's not quite tubes, but it also does not have the brittle crystaline quality of many transistor amps. I find the amp entertaining to listen to for hours without aural fatigue.
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Class D amps also generate lots of RF. At least they used to. That may have changed. |
Stringreen, can you explain that issue a bit more? |
another nod for spectron... great sounding amps (i came from atma-sphere) and a wonderful company to work with (simon is fantastic). |
..careful...you can ruin some speakers with some Class D amps. (DC offset) |
Class D amps are often referred to as "digital amplifiers," which is a misnomer. They are not digital. They are "switching amplifiers." They can be digitally controlled, but most are not.
In Class A amps, the output stages are "on" all the time. This creates a lot of heat, and the efficiency, well, it sucks. They can lose 70% of their output power in the form of heat, which is why you see huge heat sinks on those big Class A solid state amplifiers. Most of the weight is heat sinks. But they're the best in terms of the amplified signal- they introduce the least distortion, and generate an amplified signal of the input wave that most closely matches it.
Class B amplifiers have the output stages conducting 50% of the time- although the non-conducting stage is not actually turned "off" when it's not in cycle, so to speak. More efficient design, but subject to crossover distortion if the transition from one output element to the other is not perfect. Less heat generation, more distortion.
AB amps have the output stages on over 50% of the time. This lessens the crossover distortion, but you'll still get fairly rotten efficiency and a good bit of heat production. The output signal is not an exact replica of the input signal, especially at higher power, when some of the more sophisticated AB amps go from "pure Class A" mode to AB mode.
A Class D amplifier has one output stage fully "off" for half the cycle. This makes for a very efficient amplifier- only about 10% of generated power is lost as heat. These amps use pulse width modulation to take the input signal and generate a square wave analog signal. This is in contrast to the typical sine wave generated by a Class A amplifier. The square wave contains spectral inaccuracies, which is rectified by running this signal through a low pass filter. The resulting signal is a near perfect sine wave amplification of the original input signal.
The result is much higher efficiency. The switching elements are off half the time, so they generate less heat and suck less power than they would in a linear (on all the time) mode.
MOSFETS used to be used as the switching elements, but many of the newer D amps use integrated chip assemblies to act as the switching elements. They are more efficient switching devices than are MOSFETS.
The result? A powerhouse amplifier in a tiny package. You can get a 500 wpc D amp that weighs about 20 pounds. A similar Class A power amp would weigh in somewhere between 60-100 pounds, have huge heat sinks and have to be placed somewhere that they can freely ventilate. The Class D amps generate almost no heat whatsoever, and are designed to be left on all the time. At idle, they draw practically no current at all, so there's no need to power off after you're done listening. Heat dissipation is not an issue, so you get a relatively tiny package that can be placed anywhere you like. They don't need to "breathe."
They sound pretty darn good, too. I prefer tubes, but the Class D amp I own (Rowland 102) is no slouch. It sounds quite good. Weighs about seven pounds. No heat sinks. Minimal hassles. 100 wpc into 8 ohms.
If you're looking for a tiny amp with a huge bang that generates practically zero heat, the Class D amps are for you. Purists may bitch that they're jacking around with the input signal (and they are), which means that somewhere in the path, you have to introduce signal inaccuracies. However, as the technology improves, those inaccuracies are becoming less and less. Run 'em side by side with a Class A solid state amp or a tube amp, and you might find a difference, but it's not much. They don't sound processed or mechanical to my ears. In fact, to me, they sound quite a bit like a tube amp. Not quite as good, but when the 845 amp is heating up to 200+ degrees this summer, and I'm sweating like a pig with the AC on full blast, I may very well switch over to the Rowland and stay cool without sacrificing as much sonic quality as I once thought. I've been using the Rowland more and more lately, and it's getting more difficult to find a huge difference between it and the MastersounD tube amp I use most of the time. Make no mistake, the difference is there, but it's subtle, and something I could definitely live with in the name of comfort. If you live in the northeast or midwest, where air conditioners are more of a luxury that a necessity (as they are here in the deep south), yeah, I can see myself easily switching over to the Rowland during the dog days of summer. |
I'm a fan of Class D for sure. It can be done very well, but not all are created equal. Definitely add Chapter Audio to the list of incredible sounding Class D. It's one of the Class D brands not as well known in North America. Disclosure: I'm a dealer for both Chapter Audio and Bel Canto, so you can take my post with a grain of salt if you wish. |
Orpheus10 - I have Rowland Model 102 based on the same Icepower modules as mentioned Bel Canto S300 (and M300). It is very smooth and transparent (nice liquid midrange) but also very revealing. With new speakers (Hyperion HPS-938) I can finally hear smooth natural sounding sibilants. Rowland makes very nice preamp - Capri in the same case, designed as a set.
Here is review of the set: http://www.audioenz.co.nz/2007/rowland_capri-102.shtml |
I have a Spectron and it it sits inside a cabinet...and stays very cool. Previously had a Bryston...which I was told was a cooler running S/S and the Spectron is way cooler. As far as sound Spectron is the best I have had...but then again I have only had the two. |
Krell _man and others, I want you to know that I appreciate your rapid response. I need something that runs cool in the bedroom for the summer. |
They're awesome. I wasn't a believer until I heard them for myself (Bel Canto S300 & Wyred4Sound ST500). I always thought class D would sound very shrill/digital/thin, but that's not the case. They are very powerful, transparent, and smooth. |
I agree with Krell man. The Spectron more than likely is the best sounding switching amp on the planet! |
I think my Spectron sounds fantastic!
For what it's worth, I've been an audiophile for 38 years and the Spectron Musician III Mk2 is my first Class 'D' amp.
Chuck |
