Class A amplifier

[mhardy6647]

Welcome, despite being a hotbed for evangelical measurement fanaticism it can occasionally be pretty enjoyable here.
Keith

Best capsule review of this site I've seen to date!

At least:
1) there are smart folks here.
2) "they" review components that no one else does.
3) I get to see the guts of some modern, affordable components.

and, best of all...

4) It's a very active set of forums. The old ones have gotten pretty sleepy in the past five or so years (not to mention hyper-polarized and argumentative).

______________
Disclosure: On occasion, I use tubes, vinyl, tape, FM radio, and vintage horns... unapologetically.

 

[JSmith]

The AHB2 is a class A/B amplifier with feed-forward correction from a low powered class-A amplifier.

Just to confuse some people even more, the A/B amplifier functions inside of class-H tracking rails that are linear.

It's an ABAH amp... mamma mia.


JSmith

 

[mhardy6647]

Just to confuse some people even more, the A/B amplifier functions inside of class-H tracking rails that are linear.

It's an ABAH amp... mamma mia.


JSmith

Just the thing to use to listen to Genesis' album abacab, too, I'd posit.

 

[Deleted member 43441]

I have D-sonics Pascal based monoblock amplifiers, and I’ll tell you class D has arrived. I waited until it was perfected, and maybe it was perfected before I bought these. Nice and cool running, and excellent transparent sound. They just don’t do anything wrong in my opinion. As
a stark contrast I have a set of Classe audio monoblocks from back in 1993 I believe. I could never tell the difference between the two of them if I was blindfolded. Maybe the new ones have a little bit of less audible distortion? Maybe not. The ones from 1993 recently came back from the well-known repair place in upstate New York, because i listened to the chatter online, I thought they would have to be recapped after 30 years. I believe there were two capacitors out of spec, and they were in the standby path. Incredible build quality, and that’s what worries me today. Will our gear stand the test of time like our older gear?

 

[Deleted member 4708]

The AHB2 is a class A/B amplifier with feed-forward correction from a low powered class-A amplifier. It also uses feedback and a switching mode power supply. It claims to have negligible crossover distortion. I obviously like them

With music and HT, I frequently listen at levels that do not exceed 1 watt (measured using 0 dBFS signals and voltmeter). In reality, problably 1/10'th of a watt.

- Rich

Why do I keep making this mistake - calling Benchmark AHB2 class D?

 

[Goodman]

Clearly, your reference to "POWER" amps shows that you DO know the Marantz range - you are setting up your next get-out, because their reference and high end class D amps are integrated. You didn't specify power amps until this last post. No, you don't get out of your incorrect comments that way here. Bad luck.

Speaking of which, your attitude to PS Audio - you don't recommend MOSFET or class D amps, so I don't see how we agree, since in the right setup I would be happy to live with any of the PS Audio power amps, with another company's suitable preamps and DACs. You clearly don't recommend either MOSFET or Class D on principle, though, so you wouldn't. What's your point, that one amp you consider bad is better than another amp you consider bad?

And that brings me to your allegation. I'm class agnostic and believe in the use case. We have to start with the speaker/room interface, which will dominate the sound. Then choose an amp that will drive the speakers adequately. There's no reason in my opinion not to use a source that measures well, though I see no reason to only choose the "best" measuring. In fact, while I do, obviously, value decent measuring equipment, I actually believe that chasing "the best sounding" to the extreme is self-defeating. I happen to own the Marantz MA-10 - it has a bridged class D power stage that may not drive very low impedances (which I don't need). Does that make it a bad amp? It's a suitable amp for my use case.

As far as "weight" in the bass goes, I don't value it that greatly. I listen to early music (you might have guessed) and ensembles may have several different bass instruments playing. A good system allows me to hear what each of those instruments is doing. Is that what you mean by "lean"? My old AB amp was equally good at it. And I've heard far too many systems mess that up...

We are getting a bit side tracked.
A newbie solicited advice on power amps. He thanked me.
I said what I said, and you sort of jumped in (no problem) to say that my advice rubbish.
I only comment on gear I have actually owned or auditioned for many hours.
One exception to that, if Paul McGowan says his Class D amplifier is OK but not that great, I believe him.

 

[Galliardist]

We are getting a bit side tracked.
A newbie solicited advice on power amps. He thanked me.
I said what I said, and you sort of jumped in (no problem) to say that my advice rubbish.
I only comment on gear I have actually owned or auditioned for many hours.
One exception to that, if Paul McGowan says his Class D amplifier is OK but not that great, I believe him.

You actually gave a couple of pieces of "wrong" and overgeneralised information. I initially called you out on one part of that only, because it was something I was certain about. You clearly didn't "only comment on gear I have actually owned", as you put it now, either, on MOSFET or class D amps.

Much of the rest of what you said is opinion. You've actually been pretty clear some of the time, that you are taking subjective positions. People here may not like that either, but if it's a subjective claim, we can do what we want with it, and so can any later reader.

Had you said that you'd had negative experiences with MOSFET amplifiers, that would be OK by me. You didn't. You advised, as a blanket statement, to avoid MOSFET amps.

Had you said that "for the companies whose amplifiers I've used long term, that produce both class AB and class D amplifiers, the companies prefer their AB amplifiers" I might still have pointed to Marantz as a counter-example, but now we are just providing information to each other instead of setting off yet another argument about amplifier classes.

Many of us make mistakes on forums. I've made some real beauties in the past, and proceeded to dig myself into the occasional deep hole, as well, until I finally got what the other side was saying (or walked away to consider why people were getting angry with me). Even going that far isn't a bad thing, if you come willing to learn and can get there in the end.

On learning - have you ever tried a blind test? Apart from all too often being a humbling experience, it's fascinating when you realise that your results suddenly match up to what the more knowledgeable people (of which I'm not one) will relate from proper understanding of the science and the measurements.

 

[JSmith]

I believe him

JSmith

 

[MakeMineVinyl]

Most class D amplifiers use MOSFETs also in the output stage.

 

[Zog]

I was particular about the sealed box design, very much wanted that for a tight bass.. and the solid aluminum body. The frequency response does say it'll go down to 26Hz if I remember right. If the bass seems lacking I can always include the subs into the 2 channel stereo. Are you happy with the mid range and the highs? Do they ever give listening fatigue? I do have 5 band equalizer on the ma352 and 8 band equalizer on the C53 that I drive the MC462 with, so I can control the tone.. nice to hear from someone who owns these.. it was unfortunate when the set meant for my order came to the dealer, they noticed a hole in the package box and they refused to accept the shipment.. But I am glad they were looking out for me.. So I am waiting.. One other thing, how far apart are these speakers?

Mid range is good. My yardstick is a comparison of well recorded gear with actual instruments. Voice, brass, woodwind are superlative. Strings, eg piano, harp, and particularly the viol family are more obviously recorded music. I have no particular view of the tweeter - so I suppose that is a good thing.
I would counsel against a sub unless you get one that is very good, otherwise you will have muddy bass. If you do go for a sub then one that is powered with AB mosfets would match your A3s and likewise a sub that is a sealed box will also assist in integration.
Mine are 2.5 m apart. Clear soundstage between the boxes.

 

[Dclone]

I realise that the subject which were supposed to be discussed, class A amps (or only poweramps?) are a bit old. But. Well. I have some simple questions if someone have time to answer? I have a total of four 2 channels setups in my house (five total if TV surroundsystem is counted. But it’s not part of my question). My systems is built up solely with Krell pre and poweramps. Strictly class A (5 KSA-150, 2 MDA-300 and 3 FPBc and cx poweramps. Smallest ones is the KSA-150:s) The speakers I solely use is Infinity (IRS Epsilon, 2 pair of RS Kappa 9, RS Kappa 8 and 1 pair of Reneissance 80 driven by two Krell KST-100 monobridged poweramps.( I do not ask about that system, its A/B and in the kitchen.)

My systems gives a extremely lot of heat which is nice in Sweden during winter. But my problem is: Due to injuries and serious sickness I feel that, especially, my poweramps are to heavy (and cooling fins are razorsharp). To handle for me. I’ve tried Hypex class D which immediately shut down when i raised volume to normal, still conversation level. They were really cheap (as almost every class D are?). I think I bought theire strongest ones (approx 6-7 years ago). I tried to drive one of my Kappa 9 pairs. Did not work.

Question: Is there any reasonable weigthing, good sounding and has power enough to drive Kappa 9 class D poweramps (or other class) nowadays?

Tubeamps has no chance or Other class A products except the ones similar to Krell.

I am looking for a lightweigted (and less currentdrawing amps) meausuring good. The sound will be my subjektive part.

Cheers from still cold Sweden

Mikael

 

[Doodski]

Some details on the RS 9 Kappa speakers that brought the older class D amp to it's knees. I suspect it might not be a good class D variant and the class D technology has improved. I don't know if the RS 9 Kappa can be well served with a high power class D amp or not. I do remember the 8 and 9 as both being power hungry and bringing 200W/ch class AB amps to what was apparently max output. Add in some tone controls and variable loudness and voila a pair of pounders. Great speakers. I miss them because they where always fun to operate.

 

[dpturner]

0.8 ohm at 32 hz, 0.9 at 7100

 

[Axo1989]

Yes, that's a load.

You've likely thought of this but are the current (post-D'Agostino) fan-cooled sliding bias Krells light enough? Looks like ~30 kg for XD monoblocs in (nominal) 375 or 575 watt flavours, similar for 300 Duo. They'll also run cooler and be considerably more energy-efficient. You may still have to ask about < 2Ω as the tech specs don't say. Depends on your perspective: they are lightweights compared to classic Krell, but they dwarf Hypex/Purifi class D (in kilos and kroner) so maybe not what you are after.

 

[Mart68]

0.8 ohm at 32 hz, 0.9 at 7100

Blimey.

I'd stick with Krell. Yes they are heavy and the heatsinks are razor sharp but on the plus side if thieves break in that will prevent them stealing them.

Seems to me even the best Hypex implementation will not handle loads below 2 ohm but willing to be disabused of that notion.

 

[Dclone]

Yes, that's a load.

You've likely thought of this but are the current (post-D'Agostino) fan-cooled sliding bias Krells light enough? Looks like ~30 kg for XD monoblocs in (nominal) 375 or 575 watt flavours, similar for 300 Duo. They'll also run cooler and be considerably more energy-efficient. You may still have to ask about < 2Ω as the tech specs don't say. Depends on your perspective: they are lightweights compared to classic Krell, but they dwarf Hypex/Purifi class D (in kilos and kroner) so maybe not what you are after.

I have tried the 375 and they were nice but did not had enough power. Have not been able to test the 575 due to lack of distributors in Sweden. The 300 duo like the Evolution serie does not deliver current enough for the 9:s. Ok for the 8:s though. Epsilons design demands a minimum of two poweramps so maybe two Duos will work but it would be a step down from today. (I think…)

I was hoping for some lightweighted class D power amps. Maybe if I bi amp? Two, four or more of them?

Thanks all for taking time answering. And btw, as You can see above the Kappa 9 are really beautiful and sound fantastic. I am lucky enough to have my little Infinity collection in Santos wood.

If I find an alternative I let You know.

Cheers from Sweden

 

[JSmith]

1ET400A - PURIFI

Single-channel, analog-input Class D amplifier module Negligible THD and IMD Extraordinary low noise Load-invariant response Exceptionally clean clipping Low losses & high efficiency Easy to integrate Designed in Denmark KEY SPECIFICATIONS

purifi-audio.com

JSmith

 

[voodooless]

I’m pressure the class A amp will have quite elevated distortion driving these loads.

Moral of the story: get decently designed speakers.

 

[SIY]

Some details on the RS 9 Kappa speakers that brought the older class D amp to it's knees. I suspect it might not be a good class D variant and the class D technology has improved. I don't know if the RS 9 Kappa can be well served with a high power class D amp or not. I do remember the 8 and 9 as both being power hungry and bringing 200W/ch class AB amps to what was apparently max output. Add in some tone controls and variable loudness and voila a pair of pounders. Great speakers. I miss them because they where always fun to operate. View attachment 191346
View attachment 191347
View attachment 191348

Is there another measurement published elsewhere of the impedance curve? There's a lot of odd features to that IF it's actually the magnitude plot rather than phase.

 

[Doodski]

Is there another measurement published elsewhere of the impedance curve? There's a lot of odd features to that IF it's actually the magnitude plot rather than phase.

I googled extensively and that impedance plot is the only plot for the RS 9 Kappa. They can be bi-amp'd from the rear panel. Here is some sort of promo pic or something like that showing the crossovers and the rear panel. I ran the RS 9 Kappa off a Yamaha MX1000, a Luxman M03 and a mid 1980's HK Citation 200W/ch power amp. They all operated well with the RS 9 Kappa but they where at the limits even without the protection circuitry engaging. They presented a difficult load to the amp although it was not amp blowing impedance.