"Class A" solid state amps and integrateds: your recommendations & info. please

Ericus Rex · « **Reply #20 on:** 11 Feb 2012, 01:23 pm »

Others worth mentioning:

Forte (designed by Nelson Pass). Forte made both Class A and A/B so be careful of which one you're looking at.

Bedini 10/10, 25/25, 75/75, or 150/150. This company also changed the design shortly after production to run cooler. The hotter ones sound best. Transistors for this amp have been out of production for 20+ years but apparently John Bedini still has a stock of them. This amp (25/25) sounds very good and is quite inexpensive these days.

I found that the true Class A amps always sounded better to my ears than the onces that claim to be Class A for X number of watts then switch into A/B. Hot? Sure. Ineffecient? Sure. Better sounding than normal SS? ABSOLUTELY!!!!

sunnydaze · « **Reply #21 on:** 11 Feb 2012, 04:07 pm »

I have two pair of Class A monoblocks that I will be putting up FS:

Rawson Aleph clones
Monarchy SM70 pro

Both excellent condition. Both with SE and balanced inputs. Both about 70 wpc of pure Class A. Both run perfectly w no glitches, but very hot. I bought the Rawsons from a discerning audiophile judge in the Bahamas, and I think he may have had some factory upgrades/goodies done. Not 100% sure.

Do your research on all the great reviews out there, and get back to me if interested.

Thanks,
John

rodge827 · « **Reply #22 on:** 11 Feb 2012, 05:37 pm »

I have an ATC SIA2-150, I love this amp and felt it sounded better than the Pass Int 30A. Just my opinion

!

http://www.techradar.com/reviews/audio-visual/hi-fi-and-audio/amplifiers/atc-sia2-150-478483/review

http://www.whathifi.com/review/atc-sia-2-150

http://www.avguide.com/review/tas-194-atc-sia2-150-integrated-amplifier

http://www.witchdoctor.co.nz/index.php/2010/11/atc-sia2-150-integrated-amplifier-review/

Contact me through a PM if you are in, or live near NJ to stop by for a listen.

Chris

walkern · « **Reply #23 on:** 11 Feb 2012, 06:52 pm »

Cambridge Audio is currently updating their top of the line integrated amp (the 840A). They are available on close out from dealers for $1,000 (regularly $1,800 if memory serves) and use a sliding bias class A circuit that they have patented. They refer to the bias scheme as XD, but the amps use traditional power supplies and output stages (NOT Class D). I've listened to that amp a couple of times and found it to be very smooth and refined sounding. It does get hot in regular use, but not so hot you could fry an egg on it. Has plenty of control flexibility and even a remote control. If memory serves it is somewhere around 100 wpc. Might be just the ticket for a system that is a little bright or forward sounding.

srb · « **Reply #24 on:** 11 Feb 2012, 07:11 pm »

Quote from: walkern on 11 Feb 2012, 06:52 pm

Cambridge Audio is currently updating their top of the line integrated amp (the 840A). They are available on close out from dealers for $1,000 (regularly $1,800 if memory serves) and use a sliding bias class A circuit that they have patented. They refer to the bias scheme as XD, but the amps use traditional power supplies and output stages (NOT Class D). I've listened to that amp a couple of times and found it to be very smooth and refined sounding. It does get hot in regular use, but not so hot you could fry an egg on it. Has plenty of control flexibility and even a remote control. If memory serves it is somewhere around 100 wpc. Might be just the ticket for a system that is a little bright or forward sounding.

It is 120W/channel at 8 ohms and 200W/channel @ 4 ohms. The description of Class XD says: "This unique design gives pure Class A operation at low levels, moving smoothly into an enhanced version of Class B at higher levels. This system should not be confused with Class AB, which inherently generates greater distortion at high levels than a pure Class B design."

I had been looking at that particular closeout model (840A V2) as well, and appreciate several other features it offers such as HT Bypass input and adjustable trim level and input naming for each input. It is known to make a fair amount of relay clatter with the relay-controlled resistor ladder volume control, but I think I could live with that in light of the technical superiority over a potentiometer.

Steve

timind · « **Reply #25 on:** 11 Feb 2012, 09:09 pm »

Quote from: srb on 11 Feb 2012, 07:11 pm

It is 120W/channel at 8 ohms and 200W/channel @ 4 ohms. The description of Class XD says: "This unique design gives pure Class A operation at low levels, moving smoothly into an enhanced version of Class B at higher levels. This system should not be confused with Class AB, which inherently generates greater distortion at high levels than a pure Class B design."

I had been looking at that particular closeout model (840A V2) as well, and appreciate several other features it offers such as HT Bypass input and adjustable trim level and input naming for each input. It is known to make a fair amount of relay clatter with the relay-controlled resistor ladder volume control, but I think I could live with that in light of the technical superiority over a potentiometer.

Steve

That clicking noise was a definite turn off for me. Mine was the original version so I can't comment on the sound of the v.2. Can only say I hope it is improved.

audiobat · « **Reply #26 on:** 14 Feb 2012, 10:58 pm »

I tend to gravitate to the Luxman piece indicated above. Every time I have heard Luxman at a show it was just fantastic.
There are also some neat features on them like tone controls or you can bypass it for a direct signal path.
VU meters look cool too.
Some have internal phono preamps that have been well reviewed.

I an going with more main stream products in contrast to the small unknown manufacturers I hear about on this site. I have some equipment that I can no longer get support for because the manufacturer is out of business. I know we like to look for a "deal" or the holy grail in performance vs price, I have done it too and I have been burnt twice for about $8000! I don't have money to loose so from now on, if they have no track record I ain't betting on that horse, I AM DONE! I don't care about what kind of hype I read on the web or what kind of stupid buzz reverberates around a forum or blog, $8000 is allot of money.

Sorry I had to vent I guess...

vegasdave · « **Reply #27 on:** 20 May 2012, 04:23 am »

FM Acoustics.

http://www.fmacoustics.com

jdoris · « **Reply #28 on:** 20 May 2012, 12:57 pm »

"I have an ATC SIA2-150, I love this amp and felt it sounded better than the Pass Int 30A."

The ATC is AB right? A more direct comparison might be the Pass INT-150, which is 150 wpc AB, as opposed to the INT -30A at 20 wpc A. What did you prefer about the ATC?

John

Freo-1 · « **Reply #29 on:** 20 May 2012, 01:05 pm »

I’ll also throw in the Pass Labs XA 30.5 as a solid recommendation. It is easily one of the best sounding amplifiers on the market, and has something along the lines of 6 db of headroom. The build quality is first rate, and reliability top notch.
There is a discussion on another forum about measurements vs. what is actually heard. A gent who has designed amps for many years had some great insights about Class A amps, so I thought I would share them:

“ Class A does not have the crossover distortion of AB. Designers use feedback (local or global) to eliminate that form of distortion - but since feedback takes some time in order to come into effect - you get some "open loop" crossover distortion in a transient that a simple measurement won't appear - but may be very apparent in the time domain. The sound will be DE-sweetened vs a class A. That is a rather large effect.There are other effects surrounding things like device parameters (input capacitances, diode effects, etc. depending upon the device used) that behave much better with class A than AB.Also there are a couple of ways of handling the bias of class A. If the bias is "open loop" then on peaks it can break into AB (though the gain can drop a bit unless you wrap feedback around it and play games with bias level) which can affect the sound. You can also force a particular bias on a transistor "come Hell or high water" which I personally prefer - but it has its own problems, too - but this will affect the sound of Class A and whcy some class A stuff doens't sound like others.Another BIG factor is how the power supply is bypassed. This is a dirty little secret on how electronics manufacturers get their "house sound" - the amount and value of capacitors on the power supply lines will have a huge impact on the sound.Nelson Pass does it one way, David Belles does it another way. When you measure using static tones you will see they all measure the same, but in the time domain you will see very small differences at different frequencies that give a particular amp a "warm" or "cold" or even "detailed" vs "musical" ... all good stuff!”
He also went on to state that that the objective audio point of view only takes a subset of measurements into account, and often do not take the time domain aspect (which will cause its own set of distortions) into consideration.
The above provides some reasons why Class A amps (subjectively) often sound better than other topologies.

richidoo · « **Reply #30 on:** 20 May 2012, 03:30 pm »

I didn't see what speakers you use after rollo asked... but here are two options that are not mentioned yet.

Parallel SET tube amp like 845 if you can live with 50W and have easy to drive speakers. The best I've heard is Mastersound 845 Evolution $16000, but there are other brands that cost much less, like Melody. Or even diy SET like SimpleSE <$1000.

My fav SS class A is Parasound JC1 with 25W class A and 800W of A/B waiting in the wings if when you need it. A supremely authoritative and musical amplifier. $8000 new

Another that always sounds good when I've heard it is Pass XA30.5. $6000 new.

Class A doesn't necessarily sound "better" than other topologies, nor necessarily have lower distortion. It's the design that matters, and synergy with the speakers and room. Several golden ears on AC have recently dumped their class A amps for class D. Class AB can also be made to have extremely low crossing distortion so that is not an issue if you seek out quality AB amps. Class A does have a sound that is unmistakable, usually heavy on 2nd or 3rd order harmonic distortion, which most people like. 2nd order is predominant on the single ended class A designs, while 3rd order distortion is predominant on push pull class A designs. But the single ended designs often have a special magic of their own that makes up for their extra fatness in the mids. I think it is the glow of 2nd order harmonic distortion on the high frequencies which makes treble like spatial cues, brass, cymbals and vocals very special indeed!! It is another type of machine flavoring added to music, and you must decide whether that is right for you. I have run parallel SET 300B and decided that it did not serve the music well enough for me, although it was a very beautiful and intoxicating sound.

werd · « **Reply #31 on:** 20 May 2012, 05:05 pm »

I think you can get about 10 or 15 watts of class A out of most big Amps before they switch into A/B in solid state.

srb · « **Reply #32 on:** 20 May 2012, 05:53 pm »

Some amps, like the Parasound Halo JC 1 monoblocks, have a rear panel switch to select between low (10W @ 8ohm) or high (25W @ 8ohm) Class A bias.

Steve

Freo-1 · « **Reply #33 on:** 20 May 2012, 10:33 pm »

It’s safe to say that all amplifier topologies other than Class A exhibit some sort of crossover distortion, the physics behind the design cannot be cheated. It’s also known that as the efficiency of the amplifier increases, the amount of signal switching (and associated distortions) also increase. It is an open debate as to how much of the distortions are audible during playback, BUT, most basic measurements listed during amplifier reviews do not take the time domain aspect of a complex music signal into account. Class A amplifiers do not exhibit the time domain distortions that switching or feedback methods employed by other topologies employ.

While some golden ears have embraced the latest set of Class D amps released, there are other golden ears that do not care for the Class D amp sound. Given how Class D has both extensive filtering at the output, as well as a lot of negative feedback to get the distortion levels down, it’s not surprising some people do not care for it. It will be interesting to see if the latest Class D offerings hold up over time as long term reference units, or if the next set of offerings supplants the current offerings.

Who’s right? Who’s wrong? No one is wrong or right. It’s a matter of personal preference.

werd · « **Reply #34 on:** 20 May 2012, 11:10 pm »

Quote from: srb on 20 May 2012, 05:53 pm

Some amps, like the Parasound Halo JC 1 monoblocks, have a rear panel switch to select between low (10W @ 8ohm) or high (25W @ 8ohm) Class A bias.

Steve

That's interesting thanks

SlushPuppy · « **Reply #35 on:** 20 May 2012, 11:35 pm »

Quote from: werd on 20 May 2012, 05:05 pm

I think you can get about 10 or 15 watts of class A out of most big Amps before they switch into A/B in solid state.

The Consonance Calaf MKII integrated amplifier does 40 before switching:

"The first 40 watts of the Calaf is pure Class A."

Link

jerryleefish · « **Reply #36 on:** 21 May 2012, 01:18 am »

A few days ago I decided to dust off a class A amp that I bought ions ago. I even forgot who made it, closer inspection revealed Pioneer M22. As I recall
its most notable feature was heat also it weighs a ton. I now wish to give it another whirl but a little shaky about an initial start up. Instinct dictates applying power gradually using a Variac while standing back. If the lights don't flicker repeat this proceedure a few times until my courge is fully restored.I plan to hook it up to horns which is against conventional thinking. The wags say horns and tube amps go together like champagne and grits. At this point I'm not expecting angelic sonority only a reminder of a Wirlitzer.

saisunil · « **Reply #37 on:** 21 May 2012, 01:34 am »

Not to take it off topic but I would highly recommend the OP to look into tube amps - one can some of the goodness from tubes what one gets from class A ... yes they are apples and oranges ... but if sonics are what matters then you can get that from a tube amp in $1000 range that one would be hard pressed to find in class A solid state design at same price point ...

Just a perspective ...

Cheers

rodge827 · « **Reply #38 on:** 21 May 2012, 01:47 am »

Quote from: jdoris on 20 May 2012, 12:57 pm

"I have an ATC SIA2-150, I love this amp and felt it sounded better than the Pass Int 30A."

The ATC is AB right? A more direct comparison might be the Pass INT-150, which is 150 wpc AB, as opposed to the INT -30A at 20 wpc A. What did you prefer about the ATC?

John

John,

The ATC runs in Class A for the first 15w (called ATC in the UK to verify) and moves to A/B as needed. I directly compared it to the Int 30A since I was in the market for a Class A integrated.
For my system the ATC was the one to buy. The Luxman 590A II was the clear winner, but the cost was prohibitive at the time.

The ATC had better speed, tonal quality and musical presence than the Int30A. Musicians were more in the room and better defined. At the time I could easily afford either piece and went with the ATC and had the added benefit of pocketing a couple of grand.

As with all opinions they are just that OPINIONS! Your findings may be different and something different may suit your system better.

Due to the wonderful economic situation

, I had to sell the ATC a short while back and hope to someday repurchase this great sounding instrument.

Rodge

BruceSB · « **Reply #39 on:** 21 May 2012, 11:55 pm »

If you are really serious about class A you should have a listen to a Sugdan.
They have been around forever and a day.
I think they produced one of the very first class A transistor amps.
As I considered my next upgrade I would have gone for two of the Masterclass monos (165 watts) to drive a pair of big-ish SoundLabs electrostats if I was going "stereo". Instead I looked to 5.2 surround and the Sugdans are just not practical for my small listening room.
Follow them up, here is the link.
http://www.sugdenaudio.com
It is my opinion that nothing beats a big class A amp, but the realities of life prevent me from fulfilling that with five electrostats in a 152 inch by 121 inch (by 94 inch) room!
Enjoy your quest.
Regards
Bruce