Class A/AB vs Class D speaker amps

[Dana reed]

Given the common bias against Class D in 2-channel audio, it would be interesting to see some comparisons between similarly priced Class AB and Class D power amps. Things like the Emotiva XPA series or the Red Dragon M500/M1000 come to mind. I currently have a pair of Schiit (gasp!) Vidars driving a pair of Magnepan 1.7i speakers. The setup sounds great, but given the low efficiency of Magnepans, more power would always be better sometimes. The Red dragon M1000 mono blocks are rated to 1100 W at 4 Ohm, but I've not seen too much in the way of user experience with them. I'd rather not start looking at megabucks McIntosh amps or the like in order to get from the ~600 W I'm getting at 4 Ohm now to being able to double that and have some headroom.

 

[Blumlein 88]

I don't think you'd benefit from more than 600 watts on the Maggies. They would have to play like more than 110 db loud to need more power.

So your running a pair of Vidars, which preamp are you using to get full power out of them?

I get that having some extra push with Maggies is good, but I don't think looking for more than you have is a fruitful path to take.

Nevertheless I'd like to see some amps measured too.

 

[Dana reed]

I was originally using a Jotunheim, but also trying a Freya to try out some tube sound. Given the good reviews of the RME ADI-2 DAC here and elsewhere I'd like to try that out as a DAC/pre as well. But I still would probably keep the Freya for analog sources like my old turntable, which I'd like to upgrade at some point and try some cartridges other than the old AT311EP.
Mostly, I like to listen to rock and metal, so super detail isn't as much of a concern, but I did fall in love with the Maggies in the local dealership listening to my favorite Dire Straits songs. That's how they ended up in my house instead of some easier to drive Klipsch or Tektons.
The Vidars can definitely push a good SPL to the Maggies with no audible distortion, but it's possible to push them into protection from either over temp, or over current prior to getting above 105 dB at my 10' listening position.

 

[Dana reed]

Falling in love with the Maggies when driven by a much more expensive Ayre power amp and a much much more expensive Audio Research tube preamp may have been a mistake given my not wanting to spend more on any other single component than the actual transducer. But I was probably swayed by the fact that Maggies are made only a few miles from my house and my overall desire to build a system out of as much US made equipment as possible. At this point, the Mac mini is the only non-US-made piece in the chain.

 

[Sir Sanders Zingmore]

I don’t think power is the main consideration with Electrostats in general and Maggies in particular.
The issue is more that they present a pig of a load to drive - from memory Maggies drop below 2 ohms and have quite a nasty phase angle.
So to drive them well you need a high current amp that is stable below 2ohms.

 

[andreasmaaan]

Hey @Dana reed,

What type of sound are you going for? The gear you're running at the moment sounds like it might be a bit "colourful", and the tube amp you auditioned the speakers with in the first place might also have added some euphony (the kind of harmonic distortion that people tend to like).

If your goal is transparency, then I'm sure many members here will have good suggestions within X budget.

But if you're looking for something more euphonic then the best advice is to try out as many amps (and/or preamps) as you can get your hands on and ultimately to go with your gut.

Don't know where you are in the world, but here (Germany) it's possible to return a product within a couple of weeks for a full refund without giving a reason. Perhaps you have similar laws where you are?

What is your total budget? And what source and preamp do you have in your system at the moment?

 

[DonH56]

Hmmm... I have never seen or measured a Maggie with a large phase angle but have not measured them all. My memory, which may well be faulty, is that phase angles were very low except through the crossover, and even there stayed low compared to conventional designs. ESLs are a different story (different design, though both are planar speakers). Planer dynamics (not ESLs) like Magnepans present a primarily resistive load though the crossover does introduce phase angles. IME the result is a fairly low phase angle around the crossover frequencies. The load is generally 4-5 ohms nominal and can approach 3 ohms or below at high frequencies, especially for models with the ribbon tweeter, but I have not observed high phase angles. Combining a center with a bass panel does push the impedance low around that crossover as well, can't recall offhand what was measured but I think it was also in the 3-4 ohm range or maybe a little below. They do have low sensitivity, offset somewhat by their more directional radiation pattern (less energy sent to the sides and above/below the speakers), so the combination of low impedance and low sensitivity does make them power-hungry. Low output impedance usually goes along with higher power and that helps control panel modes.

The newer class D amplifiers from ATI and others have been praised in numerous reviews and would be worth trying out IMO. A lot of the issues with earlier class D amplifiers have been resolved.

FWIWFM - Don

 

[Thomas savage]

I would like us to test some amps , various class a/b vs class D would be of great intrest.

More intresting than yet another schiit dac.

 

[Fitzcaraldo215]

I don’t think power is the main consideration with Electrostats in general and Maggies in particular.
The issue is more that they present a pig of a load to drive - from memory Maggies drop below 2 ohms and have quite a nasty phase angle.
So to drive them well you need a high current amp that is stable below 2ohms.

You may not mean to imply, though you are, that Maggies are electrostats, which they are not. But, Maggies, like many 'stats, are dipoles.

I think it is also accepted that 'stats are generally a difficult load, but that Magies are not. I don't recall Maggies ever showing as dropping below 2ohms or having a difficult phase angle, but some 'stats definitely do, like mine. Maggie planar ribbon or quasi-ribbon drivers are relatively low in capacitance, unlike many 'stats, and also, I believe, relatively low in inductance, unlike many dynamic, voice coil drivers, though the passive crossovers may affect this in the Maggies.

I think raw power is often a consideration for dipoles of any kind due to their inevitable dipole cancellation in the bass, although raw power does not simply solve that, but it might help sometimes.

 

[Blumlein 88]

Yes, Maggies are almost purely resistive. Have a little phase around the crossover point, and not much of that. Pretty close to a 4 ohm resistor.

Planar Magnetics not ESLs. Row of bar magnets with wire on a mylar diaphragm with a ribbon tweeter these days. Funny, I purchased some 2nd hand Maggie 2.0s way back when. The owner also thought they were electrostats.

Electrostats rather than being resistive are almost like hanging a big capacitor on the amp.

 

[Xulonn]

My personal interest in the honesty of audio amplifier power ratings surfaced in the early 1980's when my Carver M400i Cube - rated at 200wpc - went into thermal shutdown while driving my ADS-L810 speakers during a party with a house full of people and the high-ceiling living room full of dancers. Bob Carver may have designed a lot of interesting and innovative products in his long audio career, but his "Magnetic Field" amplifiers, which lacked a capable and robust power supply, were not among his best ideas. Magnetic Field amps rank right up there with his "Sonic Holography" crap.

Based on my 50+ years of being an "audio hobbyist" I would be very cautious about choosing an amplifier for difficult loads based on the manufacturers published specs. On the positive side, Classe (and probably other old high-end amp makers like Ayre, Audio Research, etc.) appear to still be using the "old standard" RMS power ratings. However, Hypex , and perhaps other current Class D amp makers, appear to be follow in the footsteps of many "power rating" scams that audio marketers used in the past.

Even though I am a retired expat living in Panama on my Social Security pension, I considered purchasing a Hypex NC122MP-based "75wpc@8Ω" amplifier. I looked at the below spec sheet and realized that 75w is the "max" power, and the "continuous power is only 25wpc - and at what impedance is not listed. Is it logical to assume that if the "max power" rating at 4Ω is 125WPC, and the "continuous power" rating is only 25wpc (20% of max), that the 8Ω "max power' rating of 75wpc would correlate to "continuous power" rating of only 15 watts at 8Ω? Also, distortion ratings are at 1/2 of the power ratings.

Although I have not thoroughly researched current amplifier advertising vs reality, I did look at the specs for Classe's class D 2-channel amp offering - the CA-D200 ($2,200 at the Music Room), and they clearly state that output is 200wpc RMS @8Ω. (And to add to the confusion, RMS power output from amplifiers is not the same as RMS voltage measurements .)

I would really like to see Amir compare a "traditional" manufacturer's 200WPC amplifier with a Hypex or IcePower amp to see how measurements would compare. However, I realize that nearby WA owners would have to loan the gear to Amir for such testing to be possible. In the meantime, I suggest that anyone considering an amplifier from a newer company - especially Class D - do their homework, and perhaps discuss the issues here.

 

[DonH56]

Technically there is no such thing as "rms power". There is rms current, rms voltage, and their product is average power. I wish manufacturers would get that right...

 

[Wombat]

FWIW
https://www.ecfr.gov/cgi-bin/retrie...ty=HTML&h=L&r=PART&n=pt16.1.432#se16.1.432_12

 

[restorer-john]

My personal interest in the honesty of audio amplifier power ratings surfaced in the early 1980's when my Carver M400i Cube - rated at 200wpc - went into thermal shutdown while driving my ADS-L810 speakers during a party with a house full of people and the high-ceiling living room full of dancers. Bob Carver may have designed a lot of interesting and innovative products in his long audio career, but his "Magnetic Field" amplifiers, which lacked a capable and robust power supply, were not among his best ideas. Magnetic Field amps rank right up there with his "Sonic Holography" crap.

You are clearly still bearing the scars from that night aren't you? That dammed Carver!

I can visualize you poking around with the amp, several drinks under the belt, saying incredulously to the bewildered crowd, 'iss gone into thermal shuddown!' and watching as the dance floor rapidly clears, all those short skirted, long legged, shoulder-padded, stunning supermodels start milling out the front door and you're left alone with a smoking amp, several uneaten plates of hors d'oeuvres amidst still-burning cigarettes, dumped in various ashtrays.

Should have gone with a big-iron amp instead of that flashy box full of empty promises. Pick up a 1980s vintage Perreaux 2150B or an Adcom GFA-555- it'll outlast you and I, and never let you down at your next party...

 

[DonH56]

I'll refrain from commenting on the Cube (they are posted elsewhere). The Perreaux reference brought back memories of when the store I worked first acquired the line and the manufacturer's rep literally dropped off the first amp, loading height to concrete, to take it inside and prove it still worked fine. We did not sell many, but I do not recall ever having to work on one. The Adcom's ran hot as all get-out and I did see a few of them on my bench. Nice amps, though, and practically indestructible if the heat didn't kill something.

 

[Blumlein 88]

The 1st Maggies I owned, mentioned up thread, I also purchased the Carver Receiver the fellow had as I lacked a large amp. The almost purely resistive Maggies were probably a good choice for those. It actually played them loudly without difficulty. Sound quality wasn't great, but it didn't choke on the load.

Now awhile later I purchased my 1st ESLs, a pair of Acoustat Two's. Horridly inefficient and a tough load. The Carver had preamp outputs, and my plan was to use it as a pre feeding some other amp at least for the time being. I took it with me to try on the Acoustats. The owner laughed and said that isn't going to work. It was only an interim solution anyway until I purchased a suitable amp. He let me hook it up, and it played them just fine. Not unlimited power, but enough to do. The owner said, "WHOA! I can't believe that man". It also didn't sound the greatest, but it played them loud enough for 4 months or so. Never shut down or overheated or any other issues. So some of the Carver stuff was okay. It was rated 130 wpc I think. I seem to recall Audio tested it and it was more like 160 and into 4 ohms was near 300. I also remember it had a darn sensitive FM tuner in it.

 

[amirm]

I would like us to test some amps , various class a/b vs class D would be of great intrest.

A couple of class-d product measurements are coming but not of the kind you imagine .

I need to build a filter to test class-D amps better. So the capability is limited right now.

 

[DonH56]

Most of the Carver stuff I heard was great; the Cube was (IME) the exception, not the rule.

 

[restorer-john]

I need to build a filter to test class-D amps better.

My old AudioLab hardware simply refuses to sweep Class-D amps- the RF in the output actually locks up the micro in the unit and freezes the device and the program altogether. It's funny, she's old school. "don't bring those PWM amps near me she says".

The other problem is, it and most of my standalone test gear is single ended and most Class Ds are in essence, balanced outputs. Your AP is fully differential. Maybe the old AP is looking for a good home?

 

[amirm]

Maybe the old AP is looking for a good home?

Why, you are interested?