First foray into Class A amp -- recommendations


Thinking of checking out a Class A(or quasi) amp just to see if the sound is really better than a nice Class A/B amp. I want to buy a used amp and my budget is $2500-3000. My current class A/B amp is a McCormack DNA-1 Deluxe, rev. A.

I've been looking at a lot of amps here on A'gon and what I have come up with so far is the Krell KSA-200S, which, from what I read in reviews, operates largely in Class A into 8 ohm loads up to 200 wpc.

Considering that my McCormack is a pretty decent amp, do you expect that the Krell would offer a significant upgrade in my priority areas of bass slam and control, mid range transparency, and natural high frequencies? I also welcome any other suggestions or ideas. Thanks!
mtrot
I am a fan of Class A amps, preferably tube, but solid state as well. What speakers are you driving? Do you really need 200 wpc?

I would suspect that the Krell would offer a significant upgrade in bass slam and control, and a mild upgrade in the midrange, the natural upper frequencies may not be so much of an upgrade though, as that is where Steve McCormack's amps fair so well. If you go with the Krell, or any other older Class A amp, look into whether it has already been re-capped or not.

Krell is a big name, and an undisputed bass champ, but I prefer Class A designs from other designers better, namely Nelson Pass, either of Pass Labs or Threshold. Clayton Audio, CODA, and Plinius make some very good Class A amps too.
I just switched from Class A Claytons to a fully tricked out Class A/B McCormack DNA-2 LAE with SMc Audio's best current upgrade package including some of Jupiter's new copper foil caps and other neat upgrades.
On SQ alone, the move was mostly lateral with the win going to the SMc amp, which is more open sounding with better dimensionality and excellent tonality. Ergonomically, I like the SMc amp better since it can remain powered up all the time (standby circuit), doesn't generate the high heat, and is very quiet. IMO this amp is more musical than the DNA 500, which I also owned.
At your price range, I would look at the Clayton S100 or M100s and listen to whatever you plan to buy before spending any money.
I like the classic class A amps, Bedini 10/10 and 25/25, Classe DRA25, Levinson ML2, Rappaport Amp 1, etc.
08-28-14: Viridian
I like the classic class A amps, Bedini 10/10 and 25/25, Classe DRA25, Levinson ML2, Rappaport Amp 1, etc.

Threshold SA-1's. ;)
You'll hear the difference if you can listen to a pair of Parasound JC1 monoblocks, as you can up the class A from 10w to 25w while listening with a switch on the back.

And yes the 20w class a sounds much more "richer" compared to the lower setting.

Cheers George
Thanks for all the replies and info! Well, because of space constraints, I am mostly considering stereo amps, which is why I sort of landed on the Krell KSA-200S. I initially was thinking used Pass X250.5, but that runs ~$5000 used and is Class A/B above a certain output level. And, you cannot get any more than 30 wpc in a Pass class A stereo amp(maybe the X250.5 actually sounds better than the Krell KSA-200S, for all I know).

My current speakers are Legacy Audio Signature II which are rated ~93dB efficiency, but I don't want to base an amp decision on that because they are rather old and I may want to get new speakers before long.
Threshold SA-2 Class A Mono blocks up for sale on ebay.
@Mtrot, you might look into CODA amps since you are using Legacy speakers. Bill Duddleston is a big fan of CODA, in fact, he had them design and manufacture his Legacy line of amps and preamps. CODA also designed and built amps for Innersound. CODA is an offshoot of Threshold too, started by three former Threshold engineers.

I own a CODA Model 11 amp, a 100 wpc pure Class A design that weighs in at about 85 pounds. These can be had for under $2K on the used market. Currently I am using a tube amp, but I will hold onto the CODA amp because I don't think it can be beat for the $$$, and it makes for a nice change of pace. Do a little research and check out CODA Technologies.
I am looking at Accuphase Class A amps which have recently seen upgrades to their Amps A-36 and A-70 with 30 watts and 65 watts into 8 ohms respectively. Double that into 4 ohms and quadruple that into 1 ohm.

Does anyone have experience with Accuphase for the question here?
I would judge an amp by how good it sounds. Who cares what type of design it is?
I'm not as well versed as most here but I have a Burson integrated that's a Class A/B desing which operates in Class A (or so I was told) up to near it's maximum rating and there is something special about that Class A sound that is bequiling.

Having rather efficeint speakers, I've never had to run it full out and never exceeded 1/3 full volume to have as loud as I needed so maybe that explains why it was always so bewitching to listen to.

The upside to all of this is that it never got really hot.

All the best,
Nonoise
I think you're making a mistake getting another amp if you're also looking at getting new speakers sometime soon. I'd figure out the speakers first and then figure out which class A amp you want to play with. It may turn out that 30 class A Watts are more than enough depending on your speaker choice. That said, if I'm you I'd be very tempted to try the Pass XA 30.5 on sale here as it seems like it could drive your current speakers, and if you need more power in the future you could likely sell it for little loss. Best of luck.
The Belles SA-30 - from what I can tell a little-known poweramp, but going by its sound quality a regular thoroughbred the should play second fiddle to none, and therefore deserves much more recognition.

The specified 30 watts belies its actual capabilities; I've been told it driving a pair of S.P. Technology Revelation's with ease, and through my moderately sensitive speakers (93dB's) sounds completely effortless even with high SPL (100dB+ peak) Blu-ray playback.

The Sound Stage review appears to be a rather accurate representation of its sonic virtues:

http://www.soundstage.com/equipment/belles_sa30.htm
I used to own the Pass Labs XA 30.5 (now own XA 60.5 monos). The XA 30.5, which is in your price range, is a special amp if your speakers are efficient enough. Pass has recommendations on its website as to minimum efficiency and I think it is accurate based on my experience. It is really a lot more than 30 watts. I owned the McCormack DNA 0.5 for about 10 years and I remember it fondly as one of my best audio purchases, but the Pass IMO is better.
@Pnmeyer,

Well, yes, the McCormack is pretty good. I just thought I'd check out a nice used big class A amp and see how much difference, if any, I can discern. If not, I can just sell it. I will never know unless I check it out for myself.
I don't own Accuphase (yet) but have heard them at several consecutive CES shows. All I can say is they're the real deal. They are dynamic, transparent, and sublime. It's pretty damn realistic overall. With a great build and parts quality as well. To be on the safe side, I would partner the Class A amps with efficient speakers, but I've heard of good results with less efficient speakers too.
Yes the XA-30.5 looks to be a nice one and he's asking for offers, $2500 should be a nice price if he accepts.

http://app.audiogon.com/listings/solid-state-pass-labs-xa-30-5-class-a-power-amp-mint-condition-remaining-warranty-2014-08-20-amplifiers-30248-locust-grove-ga

Cheers George
<3k for a Class A amp doesn't leave you with many options. As always be careful buying used especially with an older(20+ years) amp. My suggestion would be a Krell KSA 80. It has been claimed by many to be one of the "best" sounding of the older Krell amps. A new option(slightly over budget) would be the Jungson JA-50 mono blocks($3800)from Grant Fidelity. I have not demoed this model but have heard other Jungson amps at AKFEST shows and was impressed with the build/sound/price ratio.
@Dave 72,

I actually have a close dealer who sells Accuphase, Krell, Pass, and ML, but, of course, then I am looking at new or demos, which are going to be more than I want to spend. I'd like to listen to his stuff, but I don't think it's right to take up his time if I am most likely going to buy used.

@ all,

I ran across a Krell FPB-300cx close to my price range, but upon investigation, I found that it does not have RCA inputs. It was suggested that I could use XLR to RCA adapters, but I did some reading on that and many caution against trying to do that. The statement was made that this could result in cutting the power output of the amp roughly in half. Does anybody have any experience with using XLR to RCA adapters with a big Krell amp like the FPB-300cx?

I wonder how much difference in sound quality there is between the FPB-300cx and the FPB-300, which DOES have analog inputs?
Most of the amps recommended here are in general good amps, however if you really want hear something special, check out the Symphonic Line Kraft amplifier. Even their slightly lower models like the RG7 would make most of the typical class A amps sound really ordinary. The Krells and Plinus-es dont even stand a chance. I have heard them and even owned couple of Plinius amps for extended periods at some time. I like them but Symphonic Line was way too superior to even compare.
Pani-Finding a used Symphonic RG7 could prove difficult. The current MK4 version sells for 8000 Euros, could a used RG7 even be had for under $3k?
I heard a Belles SA-30 driving a pair of $100K Focal in a massive room to unbelievable levels; couldn't believe it was 30 watts...
Does your local dealer take in trades? Ask him to keep his eye out for you. Then your not wasting time, and if they also have a service department, it's a lot easier to not have to ship a large power amp if repair is needed.

I picked up my pre amp, and amp this way.
Mtrot: That's cool, it's hard to find a dealer that carries all of those brands. Yeah I wouldn't do that either if you're going to buy used.
@No_money,

Yeah, I talked to him and was up front about my situation. He said he appreciated my doing that and that he rarely took in trades but would keep an eye out. He also said it was ok to come by sometime and listen a bit.

Now considering mostly Krell and Pass used amps. Going to take a listen to a Krell FPB 300cx tomorrow.
Mtrot, I wouldn't get too hung up on Class A biasing to be honest, it is mostly marketing bs. For your budget, I would look around for a 2nd hand Modwright KWA-150SE. I saw one on the 'Gon last year in excellent condition asking $3300. The Modwright is warm and tube-like, has PLENTY of power and has amazing inner details. My two cents.
I have a Pass INT-30A, and love it. It's ain't going anywhere. But to some extent, I think watts is watts, and 30 ain't a ton (respectfully disagreeing with those who say the effective watts of the Pass 30s are a lot higher). I'd be hesitant about your Legacies; I have a bud who is a legacy nut, and they seem to want power (which is how Bill W. auditions them, at least when I was at the factory). I used to run the 92db Montana EPS2s, which I loved, but they Pass wasn't really up to it. (I now use 97db Vaughns, with powered bass, to better effect, though I'm not persuaded they are intrinsically better than the Montanyies.)

For all things Pass, check out Mark at Reno HiFi, who is super helpful and has good deals.
Getting a Class A amp doesn't guarantee any type of specific sound. Also, its very hard to isolate what portion of an amps sound quality is due to it being Class A, or some other factors. I know my answer won't be very popular because I'm not giving you recommendations on specific models that you can act upon right away, but if you do some listening, you'll probably find it to be truthful.
Hey, thanks for all the advice. Got to hear the Krell FPB 300cx yesterday, as well as a set of Pass XA-100.5, on the same speakers. With respect to authentic sound of instruments and voices, and a sense of depth and placement of the soundstage, it seemed to me Pass was clearly superior. Now, the Krell seemed a bit more dynamic, with more solid attack on percussive transients. I want the dynamics, but, dang, that true sound of the Pass is impressive. As I was told, however, the Pass SHOULD sound better, as you are talking about an $18,000 set of amps.
Getting a Class A amp doesn't guarantee any type of specific sound. Also, its very hard to isolate what portion of an amps sound quality is due to it being Class A, or some other factors. I know my answer won't be very popular because I'm not giving you recommendations on specific models that you can act upon right away, but if you do some listening, you'll probably find it to be truthful.
+1, Zd542 - I have found this to be exactly true, and based on his post above, the OP is finding this out too. The other lesson he will learn relates to the statement,
the Pass SHOULD sound better, as you are talking about an $18,000 set of amps.
Price and performance do not always correlate.

To Mtrot, if you want to run single-ended lines into balanced only amps, call Jensen or Lundahl transformers and purchase a set of input transformers for only a few hundred dollars. Assuming your amp's input impedance is sufficiently high, the transformers do a great job of single-ended to balanced conversion while also cutting down on noise.
response to Jdoris about his comment that the Pass int-30a's power isn't higher than 30 watts:

It switches to AB above 30 watts and clips at 130 watts at 8ohm, 190 watts 4 ohm. So it's not about "effective" watts, but about actual power you can measure. The xa30 and int 30 amps are actually 130watt @8ohm, 190 watt @ 4ohm amps. The first 30 watts are class A.
Melbguy --

Mtrot, I wouldn't get too hung up on Class A biasing to be honest, it is mostly marketing bs.

If the "marketing bs" regards how marketing itself misuses the term 'Class-A amplification' in its pure form (i.e.: disguised as high bias Class-A/B designs), Class-A in its strict sense is hardly to blame, nor is its sonic potential fully explored. By the same token marketing would have had its influence into making us fancy high power ratings, which in all practicality seems mutually exclusive with (true) Class-A designs.

Let's not forget what we're really fighting here: misleading marketing.
"09-12-14: Melbguy1
Mtrot, I wouldn't get too hung up on Class A biasing to be honest, it is mostly marketing bs."

Class A actually means something. Its an actual feature of the product. I wouldn't call it BS. Getting hung up in marketing, BS or not, is a choice. Sometimes learning about audio and selecting the right products is hard. And that's just the way it goes. But if you take the time to figure out what is right for you, and purchase accordingly, you'll be far happier in the end. If you don't, it never ends. lol.
09-15-14: Zd542
"09-12-14: Melbguy1
Mtrot, I wouldn't get too hung up on Class A biasing to be honest, it is mostly marketing bs."

Class A actually means something. Its an actual feature of the product. I wouldn't call it BS. Getting hung up in marketing, BS or not, is a choice. Sometimes learning about audio and selecting the right products is hard. And that's just the way it goes. But if you take the time to figure out what is right for you, and purchase accordingly, you'll be far happier in the end. If you don't, it never ends. lol.
You're right, what would I know...
Mtrot, if you go and audition a krell 400cx or 700cx, they will clearly out perform the pass labs amp you listened to, espeacially with high quality cables, my depth of the sound stage to me is endless,voices and instuments are incredible!
09-16-14: Audiolabyrinth
Mtrot, if you go and audition a krell 400cx or 700cx, they will clearly out perform the pass labs amp you listened to, espeacially with high quality cables, my depth of the sound stage to me is endless,voices and instuments are incredible!

Why would he want one of those problematic amps? I've heard they have microprocessor boards controlling the bias, and the boards are always screwing up so bad that even their own Krell technicians can't fix them.
Keep it simple!! Besides, I don't think those amps will be in his $2K-$3K price range.

Go ahead AL, get some practice using the markup tags on this reply. ;^)

Cheers,
John
09-16-14: Jmcgrogan2
Go ahead AL, get some practice using the markup tags on this reply. ;^)


See how easy that is??? LOL!!
Fair enough. Skkotb.

But I stand by my comment: If you have moderate or lower efficiency speakers, there's considerable risk the Pass 30s won't be showing their best. (Which, I suppose, is part of why Pass sells many more powerful, and expensive! ;), amps.

If the OP is after "Class A" sound, his issue may not be how the 30s measure in A/B.

Of course, YMMV.

Cheers,

J
I had a pair of xa60.8s and can't recommend them enough. they rock

(but I moved and had to sell due to space issues...)
@audiolabyrinth, who wrote:

"if you go and audition a krell 400cx or 700cx, they will clearly out perform the pass labs amp you listened to, espeacially with high quality cables"

That much difference between the 300cx and 400cx? I thought the 300cx was a bit more dynamic than the Pass XA100.5s, but it wasn't a huge difference.

Now, the speakers being used in the comparison were Magnepan 3.7, which are apparently not the most dynamic speakers out there. But, there was no question that the Pass were better in sound stage and fidelity to the actual sound of instruments and voices.
"You're right, what would I know..."

I wasn't trying to be negative with you or say that you don't know what you are talking about. Its just that your post was vague and may unfairly lump together all class a amps with bs marketing. If you could point out specific examples, that would help a lot. And you may be right. Maybe the rest of us overlooked issues that you did not.
Mtrot, Hi, I own the 700cx modded, There is a huge substantial difference between this and the 300cx you are looking at, if my amp was not modded, there would still be a big difference, for one, the 300cx is the bottom of the cx line, and the 700cx is the top of the stereo line, which esentially is mono blocks in one chassis, where the 400cx and 300cx is not!, hope this helps, Happy listening.
If you have cold winters, than KSA200 is able to provide heat to the whole room.
@Zd, fair enough. I certainly wasn't criticizing Class A power as my Vitus runs in pure class A up to 25 watts true rms and can be manually switched to class A/B mode which delivers 100 watts true rms and is great for home theater duties. In Kl.A mode the Vitus can change to Kl.A/B mode at very high volume levels or under extreme load, but does so instantly without switching. That is what I meant by pure Kl.A. The Krell fanbois endlessly claim that their amps are pure Kl.A, when in fact they use a sliding bias scheme as confirmed by John Atkinson. Only a few pure class A amps have been built, including the Threshold T800 but they were prone to failure.

What I meant is, most customers want the marketing bs and claim they do not. Amps like Boulder and Rowland market Class A amps which in reality are highly biased class A/B amps. Vitus do not change the bias based on input signal amplitude – that has nothing to do with real kl. A. It's just a marketing gimmick. What Vitus's research has shown is that when the transistors they use has a core temperature of about 70degrees C then the music becomes REAL Liquid – listenable for hours – not the usual competitor “bleeding” ears after 30min. Some call it dynamics, “air” in the high freq – I call it a headache.

Moreover a lot of manufacturers routinely quote peak power figures, or don't quote "true RMS" power just to impress people. Vitus quote their power figures in "true RMS" which is a correct, but less impressive spec. Also, Vitus is using in-house designed UI-core transformers which are much more efficient than typical toroids used by most manufacturers and loses max 1.5v tested. That is another reason why specs on paper mean very little.
If you really want to discover Class A amps, the Krell KSA amps might not be optimal. They're very good amps IMO and I owned a KSA 50s for many years, however these were sliding bias designs that went to A/B operation when necessary. That's not a bad thing per se, but its not an ideal choice if you're looking for a pure Class A amp. OTOH.......

A pair of used Clayton M100s would be worth considering if a pair pops up. The last ones I recall seeing on Audiogon went for $3k ish - some time ago - so they should be near your price point. Their small, deep chassis might make it easier for you to accommodate mono amps, too. The Clayton amps were real Class A monsters and could roast meat as well as handle tough speaker loads. IIRC, the M100 was the smallest mono amp Clayton sold and put out 100+ watts in Class A.

I'm not sure how much benefit Class A amps provide into any given speaker, but this one will allow you to find out.