Class A Amplifiers

[Teuton]

Hey folks,

Just curious if any of you use SS Class A amplification from the likes of Pass and Sugden?

What are your opinions of Class A?


Regards.

[Lorpuris]

I am using a Luxman L 590 A for the SHL-5's and a L 550 A for the P3ESR's. Both are conservatively rated and both sound better (to me) than the LFD. How better you might ask ? The bass is amazing for sure and the midrange is liquid and sweet.

Despite the ultra conservative power ratings, I have never run out of juice. These amps are well worth the price of admission.

[Teuton]

I am using a Luxman L 590 A for the SHL-5's and a L 550 A for the P3ESR's. Both are conservatively rated and both sound better (to me) than the LFD. How better you might ask ? The bass is amazing for sure and the midrange is liquid and sweet.

Despite the ultra conservative power ratings, I have never run out of juice. These amps are well worth the price of admission.

I've been doing a lot of reading on Nelson Pass's website--very pragmatic person, and one who doesn't perpetuate audio mythology.

He truly is an academic, and I am really considering purchasing one of his designs. I have only felt this way about a handful of companies--Harbeth being one of them, thanks to Alan Shaw.

For anyone interested, he has a list of articles regarding various subject matters such as audio cables, distortion, feedback, power supplies, etc. on his website.

[yeecn]

My complain about Class A amplifier is that it creates far too much heat.

What is your view relative to Class A vs. other more energy efficient amplifiers (Class AB for example)?

[KT88]

Hello, yeecn

One of my amps is a small clone of one of Nelson Pass' Class A Aleph designs, and it sounds wonderful driving my Monitor 30's. It makes about 12 watts per channel and so runs warm, but not objectionably hot-and yet, as Lorpuris stated earlier, it always seems to have enough drive. The sound is musically natural, yet very detailed.Some may say these amps are warm to the point of being colored, but I always hear right through this. My other amps are tubed, yet I found the sound of this little gem to be a revelation. Every session I have with it is a musical delight. If you listen to music rather than the sound of your stereo components, I think you would enjoy a Class A amp with your Harbeths.

I hope this is helpful.

Cheers!

Bob LaBarca
State College, PA
USA

[yeecn]

Thanks Bob for your input. I am very certain that 12W per channel is sufficient for most home listening. Afterall 120W is only twice as loud as 12W.

I am just wondering whether there is an absolute stand that Class A is 'better' than Class AB.

Cheers,
Yee

[Teuton]

Thanks Bob for your input. I am very certain that 12W per channel is sufficient for most home listening. Afterall 120W is only twice as loud as 12W.

I am just wondering whether there is an absolute stand that Class A is 'better' than Class AB.

Cheers,
Yee


http://www.passlabs.com/pdf/articles/seclassa.pdf

[Teuton]

My complain about Class A amplifier is that it creates far too much heat.

What is your view relative to Class A vs. other more energy efficient amplifiers (Class AB for example)?

While they are the least efficient forms of amplification, relative to other home 'electronics' they are not that bad. In fact, your desktop computer probably consumes more energy than a standard A21.

Of course you would want to shut the amplifier off after you are finished listening--there is no idle mode. The amp is essentially running at full output all the time.

What does this translate to on your monthly power bill? Tough to say in comparison to A/B amplifiers because they are usually much larger, and the listening habits might be different. Though I would guess maybe a couple dollars give or take.

[macraddy]

I run the Sugden mono blocks (inc. matching pre amp) and it?s extremely nice. I turn them on 15 minutes before use whereas previous A/B power amps have been left on permanently so I?d say I use less electricity now.

I think there?s little point listing all the amps I?ve heard and saying that I prefer the class A sounds as we?ve all heard lots of hi-fi and it?s subjective! When buying this amp the other contenders were the Naim 500 series which was also very nice but not as illuminated or to my taste, and the dreadful (IMO) Linn Klimax. I?d been a Linn devotee until this point so have no axe to grind. I maintain that the Kairn/Klout is still a very nice amp and now inexpensive too! (I had one for six years.)

To my ears the Sugden (inc. A21, A21SE & Masterclass Integrated) has a beautiful, liquid, warm midrange that is also detailed and correctly balanced. The overall sound is much closer to the real thing and the top end is illuminated and grain free. Bass is also natural. I think it?s sometimes called the three T?s ? Tone, Texture and Timbre. I?ve certainly agree!

[hifi_dave]

You really need to listen to a range of amps not concentrate on one philosophy. IMO

I've heard many 'Class-A' amps over the years and apart from some tube designs I have never been sufficiently impressed to buy any in. Now, this might not have anything to do with the Class-A circuitry, other things might come into play, I don't know.

I don't believe you can pick an amp because it is Class-A, Class-AB, Mosfet, tube, Class-D or whatever, it's what it sounds like in your system that matters.

[Teuton]

You really need to listen to a range of amps not concentrate on one philosophy. IMO

I've heard many 'Class-A' amps over the years and apart from some tube designs I have never been sufficiently impressed to buy any in. Now, this might not have anything to do with the Class-A circuitry, other things might come into play, I don't know.

I don't believe you can pick an amp because it is Class-A, Class-AB, Mosfet, tube, Class-D or whatever, it's what it sounds like in your system that matters.

I agree with you. However, there are only a small handful of companies that actually produce class A. Furthermore, most people are so bent on power ratings that class A is simply does not sell the way A/B does--especially on this side of the pond.

[honmanm]

I've used (and loved) a class A amp, but it was not the simple single-ended type... (this is a bit of a ramble, but hopefully something here will help you). Practicality of class A depends on budget, room size and character, speaker sensitivity... For a given budget, the class A amp will almost always run out of steam first - it depends how much you value smoothness vs. dynamics (if you have a small enough room, you probably can have it all!).

Every designer makes trade offs so as to produce a competitive product at an affordable price within a reasonable timescale (even in the case of NASA's Apollo project). And most of us have to get the best sound within a fixed budget! So to echo Dave, try as many as possible of the amps you can afford and find something that suits your taste in your system (and find an honest dealer who is able to spot what you like and guide you in the right direction).

The experience bit - my hi-fi iterations began in South Africa with a Quad 303 (class AB, but very likely out of spec), then to small Magneplanar speakers, then to a Sumo Nine (50W transistor class A) where I stuck for 15 years. At times I considered other amps (not as open/smooth/unfatiguing as the Nine) and speakers (fatiguing, coloured, sucked the life out of the amp).

Moving to the UK changed the game (I brought the 303 as it is much more portable than the Nine, and it's easy to sell when we leave). The borrowed HL-P3s that we're using have forced me to reassess a lot of things I thought I knew about hi-fi. The quality of the combination (the 303 now serviced and with a new regulator board) comfortably beats my former system in most ways. When it comes to class A vs AB, my lesson has been that I would have been better off spending my money on speakers like Harbeths (or perhaps Quad ESLs) rather than the better class A amp (hindsight, isn't it wonderful!).

On the specific question of low-power ultra simple class A amps, I'm actually a bit worried by the pseudo-science in that Pass Labs article. Picking one example, the extrapolation of acoustics to electric currents! Anyone know of a speaker that doesn't hate DC? A single-ended amp needs a capacitor or transformer to remove the DC from its output - and what the speaker "sees" is a signal without DC offset, just like the output of an amp that has balanced + and - supplies (except that the component which removed the DC introduces some colouration).

Mark
(currently working out how many years it will take to save for a pair of C7s)

[Teuton]

On the specific question of low-power ultra simple class A amps, I'm actually a bit worried by the pseudo-science in that Pass Labs article. Picking one example, the extrapolation of acoustics to electric currents! Anyone know of a speaker that doesn't hate DC? A single-ended amp needs a capacitor or transformer to remove the DC from its output - and what the speaker "sees" is a signal without DC offset, just like the output of an amp that has balanced + and - supplies (except that the component which removed the DC introduces some colouration).



Can you please elaborate?

[A.S.]

This is very interesting indeed. I must agree with honmanm that if the power supply is 'single ended' i.e. + 35v and 0v then a blocking capacitor or transformer will be needed to isolate the speaker. This is because the amp will superimpose the music signal on a voltage half way between 35v and 0v (17.5v). This DC voltage must not be applied to the speaker coil or it will a) cause it to sit off from its at rest position b) cook the coil.

A 'split rail' power supply i.e. +35v..0v..35v doesn't need any DC blocking because if the amp is working normally the music signal is hovering about the 0v, central point. Of course, if the centre point shifts because of misalignment or component failure, then DC will be applied to the speaker with catastrophic effects. I guess that this unexpected and unwelcome DC output bias due to component failure is the primary failure problem with amplifiers, and the listener is lucky indeed if he can leap from his seat and switch-off the amp fast enough to save the poor speakers from DC destruction.

[Vlado]

This is very interesting indeed. I must agree with honmanm that if the power supply is 'single ended' i.e. + 35v and 0v then a blocking capacitor or transformer will be needed to isolate the speaker. This is because the amp will superimpose the music signal on a voltage half way between 35v and 0v (17.5v). This DC voltage must not be applied to the speaker coil or it will a) cause it to sit off from its at rest position b) cook the coil.

A 'split rail' power supply i.e. +35v..0v..35v doesn't need any DC blocking because if the amp is working normally the music signal is hovering about the 0v, central point. Of course, if the centre point shifts because of misalignment or component failure, then DC will be applied to the speaker with catastrophic effects. I guess that this unexpected and unwelcome DC output bias due to component failure is the primary failure problem with amplifiers, and the listener is lucky indeed if he can leap from his seat and switch-off the amp fast enough to save the poor speakers from DC destruction.

Every serious split rail amplifier have some protection circuit, the higher level, balanced amps are (mostly) DC coupled with circuits which are maintaining the DC offset.

[honmanm]

Can you please elaborate?

After Alan and Vlado's comment, not much more to add, really. Since the input signal varies around a centre "zero", the DC bias of a single-ended amp ensures that the negative half of the output stays above the power supply zero.

But after the DC has been removed you are back to exactly the same kind of push-pull output as an amp with bi-polar supply... it makes no difference. Even if there were an analogy between thermodynamics and electronics, it's not relevant here.

For some of the design thinking in single-ended class A amps see Rod Elliot's critique and reinvention of the Zen amp (http://sound.westhost.com/project36.htm).

BTW Mr Elliot is a big fan of active crossovers... reading his notes on crossover design side by side with Alan's makes for an interesting comparison.

Mark

[ryder]

I am using a Luxman L 590 A for the SHL-5's and a L 550 A for the P3ESR's. Both are conservatively rated and both sound better (to me) than the LFD. How better you might ask ? The bass is amazing for sure and the midrange is liquid and sweet.

Despite the ultra conservative power ratings, I have never run out of juice. These amps are well worth the price of admission.

A little bit out of topic.

Lorpuris, may I ask if you have experience with the L-505f? If yes, may I know how does the unit compare with the LFD in transparency, resolution and openness in the mids and highs?

In what aspects the Luxman L-590A and 550A sound better than the LFD? How does the bass performance compare between the two? I would appreciate if you can kindly elaborate. I am particularly interested in the transparency, resolution and airiness in the mids and highs between the two units.

Thanks.

[Lorpuris]

There is a lot debate on this subject so I will first say all of the aforementioned amps are in the highest percentile of quality.

I have limited experience with the 505 in that I used one for a few weeks when I decided to upgrade from the LFD. My immediate impression was that the musical presentation was superior in every way. The 505 was clearly more athletic in that it was never out of breath. The 505 has all the great qualities of the LFD but with sharper focus. If anything it seemed ever so slightly more forward in the soundstage but in no way harsh.

Since I had the 590 in the same time frame I had the rare opportunity to listen to them in the same room, same speakers !

The 590 is a bit of an enigma. It has a very conservative power rating so I was initially concerned about that. To begin with I am always ready to laugh when someone uses those metaphoric audiophile terms like " liquid midrange". That being said, that would likely be the exact term i would use to describe this amp. It has a sonic sophistication that defies any other description. The amp also has more real power than the LFD or the 505. The other amazing ability of this amp is the bass, Holy crap is it good ! While it will play much louder and cleaner than the other amps, I was really impressed at the low level detail. This is what really floored me, as I listen at lower volume levels 75 % of the time. The build quality is also much better than the other amps.

As far as the 550 goes: I like it almost as much as the 590. I do not think it has quite the bass performance of the 590 but everything else is spot on.

Anyway, I hope this helps !

[ryder]

Lorpuris, I cannot thank you more than enough. Your description on all 505 and 590 amps has achieved its intention in giving me a more accurate representation of the sonics of all amps concerned. I have been reading a lot of good comments from Luxman owners who seem to be extremely happy with their amps and it is good to note that you find the Luxman units to be better-sounding than the LFD. This doesn't come as a surprise as the Luxman, especially the Class A top-of-the-line L590AII integrated costs substantially more than the LFD, more than 2X the price if I am not mistaken.

The reason I asked you this question is because after comparing my Rega Elicit with the Leben CS600 and LFD, I find the Rega to fall short in terms of resolution and transparency in the mids and highs. The Rega is still a wonderful amp but little warm-sounding in comparison to the Leben and LFD. The Leben's transparency and airiness in the mids and highs are excellent and a notch above the LFD but I find bass slam and dynamics to be still slightly lacking compared to the LFD. I like the LFD but cannot seem to live without a remote, and that was the reason I am looking at the Luxman which seems to have nothing but good reviews on them.

After going through your comprehensive but precise assessment on the L505, L550 and L590AII, I believe the Luxman may be the one. Last question if you don't mind, is the L505 you listened to previously the L505f or L505u? Any substantial sonic difference between the two units? The L590AII costs a bomb(at least to me) and if I were to consider this unit I have to save up quite a bit.

Thanks again.

[A.S.]

I do wonder if we here should feel completely comfortable with the concept of single-rail PSU Class A amps these days.

To quote here ...


' There are losses everywhere, and it is essential that the amplifier builder has a reasonable knowledge of losses and dissipation requirements for an amplifier before starting construction. As many constructors have found, a Class-A amplifier is not a good option on a hot day if you don't have air-conditioning. The combination of a Class-A amp, a very hot day and air-conditioning will certainly get your electricity meter spinning too, and is definitely not an environmentally friendly option.' Source here (http://sound.westhost.com/efficiency.htm).

The problem with class A is that it is working at full output all the time, regardless of how loud or soft the music is. It is akin to driving a huge car at maximum revs, with your foot pressed almost fully down on the clutch so that only a fraction of the power is delivered where we need it: at the wheels or at the speaker.

From a related source here, the quote that ...


'Class-A Myth #2 Class-A amps give predominantly 2nd order distortion. They might, or they might not, depending entirely on the topology. A great many Class-A amps will produce distortion components that are almost identical to those produced by a Class-AB amp. This excludes clipping distortion, which should be avoided in any class of amplifier used for high quality audio'. Source here (http://sound.westhost.com/class-a.htm).

I can conceive of a situation within the next few years where class A amps will be outlawed on environmental grounds so buy now while you can!

[Thanos]

I do wonder if we here should feel completely comfortable with the concept of single-rail PSU Class A amps these days.

To quote here ...


' There are losses everywhere, and it is essential that the amplifier builder has a reasonable knowledge of losses and dissipation requirements for an amplifier before starting construction. As many constructors have found, a Class-A amplifier is not a good option on a hot day if you don't have air-conditioning. The combination of a Class-A amp, a very hot day and air-conditioning will certainly get your electricity meter spinning too, and is definitely not an environmentally friendly option.' Source here (http://sound.westhost.com/efficiency.htm).

The problem with class A is that it is working at full output all the time, regardless of how loud or soft the music is. It is akin to driving a huge car at maximum revs, with your foot pressed almost fully down on the clutch so that only a fraction of the power is delivered where we need it: at the wheels or at the speaker.

From a related source here, the quote that ...


'Class-A Myth #2 Class-A amps give predominantly 2nd order distortion. They might, or they might not, depending entirely on the topology. A great many Class-A amps will produce distortion components that are almost identical to those produced by a Class-AB amp. This excludes clipping distortion, which should be avoided in any class of amplifier used for high quality audio'. Source here (http://sound.westhost.com/class-a.htm).

I can conceive of a situation within the next few years where class A amps will be outlawed on environmental grounds so buy now while you can!

Gentlemen,

At about the same price point, we won't find huge differences between amps, especially with same topology. Heard McIntosh vs Krell, then Unison valves vs VTl and Iconaudio, then class A Accuphase vs Luxman (I've owned one) and just got messed up.

IMHO, it is speakers that is the critical factor. You'd better start up with speakers, listening your fav music through them with as many as different amps, then choose... Even the "best" amp will be heard as "rubbish" with bad speakers, while the opposite combo will get us thinking... I've lived this with my SHL5s. They sounded always beautifully with any decent amp, A or AB or valve.

But when we changed the 5s with some other standmounters from Germany (won't name them for obvious reasons- and about the same price), using the same two driving amps ( a Krell & a powerful Unico), then things changed like coming from a different planet.
So, if music is the center of gravity, does this amp discussion make a big issue?

Regards,
Thanos

[kittykat]

Tube amplifiers are notoriously inefficient as well. The amount of heat they give off is pretty wild. Good in winter, butnot especially useful over these few heat wave days we?ve been having down under. Switching on the aircon and a tube amp at the same time is not the most expensive form of entertainment, but pretty indulgent by any account, if not wasteful.

Lets not get started on the amount of iron and steel which goes into making those output transformers?

[Jmohd]

Should we all go into Class D amp?

Class D amplifiers, often achieving 90% to >95% efficiency. That means that of the power coming into the unit, most of it is converted into power to drive the speakers; so the amplifier itself will tend to run a lot cooler than more traditional designs.

As an example, Class A amps are around 30-40% efficient and A-B Class amplifiers about 55-65%. The means smaller power supplies and smaller cabinets for the Class D versions. Ultimately this should also result in cost savings once mass production starts and development costs are recovered.


Taken from: http://www.soundlabsgroup.com.au/c/Class-D-Amps/Class+D+Amps.html

[macraddy]

Ooo - have you heard a class D amplifier? Nasty!

[A.S.]

The commonly held view is that digital amplifiers as available today sound poor.

[keithwwk]

It may sound crazy to most of you, but to my ears, Class D amps sound is emotionless, musicless, and lacking human feelings ....or I should say they sing like robots...Another marketing hype.

[hifi_dave]

I hope you don't mind me chipping in but I would recommend that before spending any money, you have a listen to the new Rega Osiris. To my ears it is one of the best sounding amplifiers that money can buy and ideally suited to the Harbeth range.

[Lorpuris]

Ryder, The Luxman was a 505u I think... It was about 4 months old at the time.

In all fairness, I have not listened to the Rega or Leben. As with every amp I listen to, I find good qualities. In the case of the LFD, there was a lot of good, just not great for me. In the case of the Luxman 590, there was no good, only great. Everything I could ever want is there every time I listen. Yes, the Luxman 590 is expensive but when something makes that much difference I find real value there !

If something should come along that is better, I will report it and consider it. For the time being, the 590 really does it for me. It is sophisticated, musical, resolved, and has bass like none of the others.

[Vlado]

I hope you don't mind me chipping in but I would recommend that before spending any money, you have a listen to the new Rega Osiris. To my ears it is one of the best sounding amplifiers that money can buy and ideally suited to the Harbeth range.

Hi Dave,
how much is the ticket?

[hifi_dave]

In GB it is a touch under ?6000 which is a lot of money I know but it is a lot better than many far more expensive pre/powers I dare not mention.

[Vlado]

In GB it is a touch under ?6000 which is a lot of money I know but it is a lot better than many far more expensive pre/powers I dare not mention.

Indeed, a lot of cash, but looks impresive.

I wonder that nobody is mentioning here another British brand, the Musical Fidelity. I had a combo some 15 years back. The amp and the player name was Electra.

[A.S.]

Ummmm. I think that after-care is of great importance. Who will care when it fails? Maybe we should really investigate what we could do with a Harbeth badge on it. At an affordable price, approved technology and built to last.

Just a thought.

[Vlado]

Ummmm....... what we could do with a Harbeth badge on it. At an affordable price, approved technology and built to last.


Alan, some ideas?

[A.S.]

First I think you have to think about what our motivation could be. If I'm honest, it's depressingly wearisome to read the never ending anxiety about this amplifier or that amplifier. How much better? How much money? This issue of amplifier selection and the resulting 'audio nervosa' must be taking numbers of hi-fi enthusiasts to the very edge of pleasure, even sanity? 'Which amplifier?' emails and calls takes up an inordinate amount of office time, so much so that this week, we have had to draw the line and politely decline to correspond individually about this issue. Enquiries are directed to this User Group where we've said all there really is to say.

It's a subject that has almost nothing to do with musical enjoyment since I - and many like me - can perfectly enjoy music with good speakers and whatever amp we have kicking around whether it's class A, AB, D, solid state, tube or whatever providing that it's in-spec and if old, properly aligned and serviced. Personally, I don't have a favourite technology, because just like soft/metal domes tweeter choice, it's not the technology that's all-important, it's how the technology is applied by the careful designer.

The amp has an exceptionally easy job compared with the microphone and loudspeakers (both electro-mechanical devices) at the input and output of the audio chain. It should be possible to offer amplifier technology that meets all the basic criteria at a sensible price and which I would personally endorse with confidence. Of course, in a consumer's democracy users are welcome to buy whatever amp suites them, and Harbeth speakers will always be an 'easy load' but Harbeth's official position - and hence right to be aired in this forum, could be one approved amplifier solution. Other options can be discussed elsewhere. Then we could, once and for all, close the 'which amplifier is best' thread. That's our thinking.

What really matters is the music - not the gear.

P.S. Whatever sonic merits may or may not be generally attributed to Class A amplifiers, it's a socially unacceptable technology due to horrendous power wastage and not one that I now, in 2009, could personally endorse. I can think of no other device in the home - aside from the oven and kettle - which is so wasteful of energy. It would surely be cynical of me to be driving a diesel car for maximum energy efficiency and yet to be offering Class A amplifier technology.

[ryder]

Lorpuris, although you have not listened to the Leben or Rega, your experience with the LFD is enough to draw a conclusion. I have listened to all Leben, Rega and LFD so I know where each and every piece stands.

hifi_dave, may I know how does the Osiris flagship integrated compare with the Elicit? Does it share the same "warmish" house sound or take on a different sonic presentation with higher degree of transparency and airiness in the mids and highs with better bass performance? Just to let you know that our dealer doesn't take in the Osiris and Isis anymore after they manage to sell the one and only Isis CDP brought in from the UK sometime mid of this year. Due to the high price of the units they have adopted the "availability upon placement of order" policy which requires customers to commit to a purchase prior to listening to a piece.

Class A amps do emit a great amount of heat and send the electricity bills sky high. I once forgot to switch Class A to AB on my Plinius amp after a listening session and left it in Class A for a whole day. The next day I entered the room it was like a sauna, and at that point I knew the amp was running in Class A for 24 hours straight. When the electricity bill came there was a 20% hike. I couldn't imagine how much damage that could be done if the amp was left in Class A for the entire month. A catastrophy! Good for the winter though but I reckon a conventional heater may be a lot more cost-efficient than a Class A amp for this purpose.

[keithwwk]

The good old sound of Musical Fidelity was a history. The current production of MF is made in china or taiwan fully packed with high power rating and other tube/ss hybri old tricks...very good in term of advertisment and marketing purposes. There are many selling brands rather than sound quality.

[Gan CK]

I hope you don't mind me chipping in but I would recommend that before spending any money, you have a listen to the new Rega Osiris. To my ears it is one of the best sounding amplifiers that money can buy and ideally suited to the Harbeth range.

Any idea how would the Osiris compare to the LFD NCSE?

[Will]

In GB it is a touch under ?6000 which is a lot of money I know but it is a lot better than many far more expensive pre/powers I dare not mention.

If one had C7 or SHL5, would it make sense to spend ?6000 on this amp or better to take that money to fund the upgrade to M40.1?

I am struggling with this same decision myself... I think in the end I will end up going M40.1. As Thanos says, the speakers are everything.

[yeecn]

What really matters is the music - not the gear.I agreed completely. Since my passion for music is re-ignited some 5 months back, I have been listening to a large selection of music on my Harbeth, computer speakers, car stereo... The music continues even in the absence of audio equipments!

Really - learning about the music and the composers is much more interesting than endlessly pursuing the next bigger better sound. This is a different dimension of perception and experience altogether. Its origin is in the domain of human emotions in which physical sound is a secondary means of expression and representation.

It is the same with arts. I can related to you an experience during my student days. I used to hang a couple of van Gogh paintings and the Monet's "Lilly Pond" in my room. I got the posters because I knew the painters were famous - not because I knew how to appreciate the paintings.

To tell you the truth - I am an auditory person. I don't remember faces and I hardly notice anything about my surroundings. I pondered about the paintings once every so often, but I basically ignored the posters. After a couple of years of hanging the posters were already beginning to fade and the Blu-Tack were beginning to show through. Then one day while mindlessly gazing at the "Lilly Pond" my mind clicked - and I saw for the first time that the almost unrecognizable blotches of colors were not about forms - but about lights! I saw for the first time the reflection in the lilly ponds and I knew for the first time what the impressionist school of paintings was about.

It took me even longer to appreciate van Gogh - and the breakthrough moment was in a dream! It sounded bizarre, but it was during one of those vivid and colorful dream that I saw the dancing lights and colors portrayed in van Gogh paintings. I don't think it is a common mode of perception. For me it only happen once in a blue moon - mostly in dreams. But once it is brought to consciousness I knew that such mode of perception is there, just round the corner somewhere.

My involvements with music is much deeper and harder to put to words. But what I intend to convey is that arts and music encapsulates a rich world of human experience. It would be a pity to lost sight of that in technicalities and consumeristic pursuit.

[Will]

Ummmm. I think that after-care is of great importance. Who will care when it fails? Maybe we should really investigate what we could do with a Harbeth badge on it. At an affordable price, approved technology and built to last.

Just a thought.

Put me down for one! :)

[Jmohd]

If one had C7 or SHL5, would it make sense to spend ?6000 on this amp or better to take that money to fund the upgrade to M40.1?

I am struggling with this same decision myself... I think in the end I will end up going M40.1. As Thanos says, the speakers are everything.

Hi Will,

I had the same dilemma......I will go for the "King"... Now, I'm a happy cat :)

[Vlado]

Hi Will,

I had the same dilemma......I will go for the "King"... Now, I'm a happy cat :)


Guys, I think your decision is right, if my room were adequate, I would make the same decision.

Happy listening!

[A.S.]

Surely one of the most thought provoking posts in the Harbeth User Group. Thank you for taking the trouble to tell us of your experiences. I too share this experience of deeper and lasting awareness of reality during the sleep state.

[Thanos]

Guys, I think your decision is right, if my room were adequate, I would make the same decision.

Happy listening!Yes, Yes, Yes!

My room is also hardly 20m2, so my 5s are more than enough... Wish I had a LR of some 50m2..., then the 40.1 would become my new love.

Well, when my McIntosh MA6500 had a problem with its left VUmeter (wouldn't return to zero point at idle), I asked the local dealer what to do. They said I should re-pack the amp to send it in USA for check & possible repair... Don't want to mention the transportation cost...
So lucky I've been, that this electronic technician -friend of mine with low fees- is so gifted, that he perfectly fixed the amp (like it was never touched). He also serviced & repaired the same way a Meridian 507 player and the Nacamichi DR 10, all the money he got for these was less than half of the transportation fees for N.Y.!

Wish I was wiser to have some common well made and well supported European devices, so I wouldn't consider maintanance & repairs that much in the future, or struggling to find a good & responsible technician around...

Alan is very very right in this matter about long life, support and economy. So, I'm also a happy cat, not because I 'll change my 5s with the 40.1s, but because I have some hundreds of euros intact in my pocket. This money will be partially spent in ordering The series "Great voices of the 20th century" from Prima Voce (4 double cds with booklets), the excellent "Handel's famous arias" a 4cd pack from Harmonia Mundi, together with Harmonia's also excellent "Messiah" limited edition with William Christie conducting "Les Arts Florissants".
Isn't this better to spend part of the money to my local music store, instead of chasing the Holly Grail of amplification?

Best regards,
Thanos

[hifi_dave]

hifi_dave, may I know how does the Osiris flagship integrated compare with the Elicit? Does it share the same "warmish" house sound or take on a different sonic presentation with higher degree of transparency and airiness in the mids and highs with better bass performance? Just to let you know that our dealer doesn't take in the Osiris and Isis anymore after they manage to sell the one and only Isis CDP brought in from the UK sometime mid of this year. Due to the high price of the units they have adopted the "availability upon placement of order" policy which requires customers to commit to a purchase prior to listening to a piece..

When I posted about the Osiris, I knew I would get asked this one. All I can say is that the Osiris is far, far better than the Elicit which is already an excellent amplifier. As a dealer of many years, I have sold in the past, many of the US megabuck amps and I would say that the Osiris is well up with any of them at far less cost. It is a 'World class' amp.

I can't imagine any dealer, having sold their one and only Osiris/Isis combination, not wanting to stock it again. Why would they do that when they now know it sells ? As for price, it's not expensive by any means, so there is something else going on here I would suggest.

[hifi_dave]

If one had C7 or SHL5, would it make sense to spend ?6000 on this amp or better to take that money to fund the upgrade to M40.1?

I am struggling with this same decision myself... I think in the end I will end up going M40.1. As Thanos says, the speakers are everything.

I wouldn't agree that 'the speakers are everything' but I would say that you will get a bigger bang for your buck with the M40.1 than changing the electronics. When you have the speakers, you will better appreciate the amp.

[ryder]

hifi_dave, I have no idea why the dealer would choose not to import the Osiris and Isis in. I smell something fishy as well but that was exactly what I was informed.

[honmanm]

A quick note from the sub-?100 end of amplifier land.

Harbeth speakers are designed to work well at low levels, which is where crossover distortion is most objectionable (see second page of the ESP article that AS linked to) - this probably underlies the interest in using class A amps with them, perhaps also because they are often used to reproduce music that has large dynamic contrasts (i.e. with quiet passages where the distortion is clearly audible).

In that article Rod Elliott pointed out that the Quad current-dumping amps (405 606 etc.) are a clever compromise because conceptually they are a low-powered class A amp that "calls for help" from the class-C power transistors when needed. Might explain why old Quads are the "cheap amp" recommended for use with Harbeths.

[A.S.]

They are. The 405 Mk1 or Mk2 after a QUAD service (very affordable) are solid, reliable amplifiers. Not the last word in high fidelity, but good enough. The 606 is more powerful but much less reliable and not one of our recommendations.

[Stephen PG]

Harbeth speakers are designed to work well at low levels, which is where crossover distortion is most objectionable (see second page of the ESP article that AS linked to) - this probably underlies the interest in using class A amps with them, perhaps also because they are often used to reproduce music that has large dynamic contrasts (i.e. with quiet passages where the distortion is clearly audible).

Could you describe this distortion?

[honmanm]

Could you describe this distortion?

For a technical description the Elliott articles will tell you everything you need to know. In brief, crossover distortion is a result of the transfer characteristic of transistors being non-linear near the point where they turn off. Subjectively, it's the "transistory" distortion you might hear on a "mini hi-fi" or when an amplifier is cold. Like most kinds of distortion, it is more noticeable by its absence - without it everything is suddenly clean and pure, less bright etc.

I've heard this while experimenting with a Quad 303 and a stepped attenuator as volume control. The amp was a bit overbiased, so that at the step just below normal listening levels it was able to operate in class A - sounded absolutely wonderful, rich smooth and natural. Step volume up by 3dB and suddenly there is an edge to the sound.

Makers of class AB amps have a number of techniques that minimise the effect of devices turning on and off. Careful bias setting helps a lot but (without compensation) bias current is temperature dependent and will vary with ambient temperature, program material, and average power level. Thus most amps are not at their best when cold.

[A.S.]

This is a very good explanation which I can clearly understand. I just wonder, how many of our reader here have any real conception of how an amplifier works? Could I ask you to take a step back and using your own words explain the concept of 'bias' and hence amplifier class? Keep it simple!

[Stephen PG]

I've not heard the slightest change in sound quality as my amp warms up (I leave it all off when not in use).

I use an Arcam pre-amp (C31) and an Avondale A260z power amp, which is based on the same RCA circuit as the original Naim amps.

http://avondaleaudio.com/high-end-audio/power-amplifiers-module/

[honmanm]

I've not heard the slightest change in sound quality as my amp warms up (I leave it all off when not in use).

I use an Arcam pre-amp (C31) and an Avondale A260z power amp, which is based on the same RCA circuit as the original Naim amps.[/URL]

Interesting - a friend with a Naim 32.5 preamp and 250 power amp has confirmed that the 250 sounds the same cold and warm (though he says the preamp takes about 4 minutes to warm up).

Oddly enough, that is a class A preamp and class AB power amp (which appears to have a modest bias - around to 36mA, about twice as much as the 303). It could be that the output transistors reach operating temperature quickly, maybe because they are attached to a small heatsink which then mounts to the case? It is likely (but I don't know enough to do more than guess) that the Naim power amp circuit operates in class A at normal listening levels.

Anyway, that's good news as one of my future amp options would be based around the Avondale NCC200 modules as used in your power amplifier.

[honmanm]

Could I ask you to take a step back and using your own words explain the concept of 'bias' and hence amplifier class? Keep it simple!

Well, that's a challenge... my understanding of analogue electronics is quite limited (though I'm trying hard to learn!).

Here's an analogy that might help explain the difference between class A, B, and AB (it's not perfect, but the best I could think of for now).

Imagine that bored (and fearless) game rangers entertain themselves by using their jeeps to wobble rhinos back and forth. (see attached diagram). The rhino, being unamused by the whole procedure, refuses to go anywhere.

In the single-ended system a single jeep pulls the rhino, and the force is balanced by a spring attached to a conveniently located wall. The jeep's engine must run continually, and the small movement of the driver's foot varies the engine's power so that the pull of the jeep is just a bit more (or less) than the pull of the spring. And so, the rhino wobbles.

That's a single-ended class A setup - a single power device, a driver device which varies its power, a load, and a decoupling device which blocks DC (prevents dragging of the rhino, which is against the rules). The power device runs continually, using energy and producing heat and the more "swing" you want in the load, the stronger the continuous pull needed (the reverse pull depends on how much tension there is in the spring).

The class B rhino-wobbler uses two jeeps, one either side of the rhino. In addition to the drivers there needs to be someone who coordinates their actions so that only one of the jeeps is pulling at any given time. This is much easier on the vehicles as neither of them is spinning its wheels or slipping the clutch, but not for the rhino which gets jerked around as the pull changes from one jeep to the other. Starting and stopping smoothly are about the hardest things to get right when learning to drive!

In a class AB arrangement, as the pulling jeep is about to stop the driver of the jeep on the other side starts to apply power so that the is no sudden change of "pull" from one side to the other. Not much wasted power, and smoother for all concerned. For small movements of the rhino, neither of the jeeps actually stops pulling.

If we wished the last arrangement could be used as a push-pull class A amplifier, with both jeeps running at an average of half their maximum power, and the two drivers taking it in turn to increase or reduce power (one reducing its pull as the other increases), giving the rhino a very smooth ride indeed.

In this analogy bias voltage is represented by the tension in the rope. Not a perfect analogy, I suspect. One of the weaknesses in this analogy is that "crossover" occurs at maximum displacement whereas in an amplifier it occurs at the equilibrium point. However a couple of other amplifier design features can be squeezed in. Specifically, if the drivers are sensitive to what is going on (a.k.a. feedback) the rhino will get a smoother ride, especially in class B. Less feedback is needed for class A, and in the single-ended case the system performance does not depend on a good match between the components providing "push" and "pull" - but is depdendent on the characteristics of the spring and wall.

[EricW]

It may sound crazy to most of you, but to my ears, Class D amps sound is emotionless, musicless, and lacking human feelings ....or I should say they sing like robots...Another marketing hype.

I haven't listened to any Class D amps, so I don't speak from experience, but I have noticed that a number of reputable brands of Class D amplifier have received quite decent reviews: Bel Canto, Channel Islands Audio, NuForce, Jeff Rowland, and Rotel are just a few of the ones that come to mind. There are certainly numerous others.

Now it may be possible that there are reviewers out there who are incompetent and deluded, but surely not that many (one hopes).

All I can say is (1) I would be very interested if Harbeth were to bring out an amplifier line: I'm sold on Harbeth speakers for life, and would look very seriously at an amplifier that embodied the same integrity of design, and was optimized for use with Harbeth speakers; and (2) I would hope that Harbeth - were it to do so - would at least take a serious look at Class D, as I think the efficiency/environmental benefits factor will become increasingly important in years to come.

[hifi_dave]

Beauty is in the eye of the beholder, one man's meat is another's poison etc, etc. Anyway, every Class-D amp I have heard sounds flat, cold, sterile and uncommunicative. That description applies to those you list (except Rowland which I haven't tried) plus others from Flying Mole, Aiwa and a Tube Tech prototype. Not very pleasant.

Perhaps the technology will improve with age but I hope that Harbeth don't go with it just yet !!!

[Vlado]

Beauty is in the eye of the beholder, one man's meat is another's poison etc, etc. Anyway, every Class-D amp I have heard sounds flat, cold, sterile and uncommunicative. That description applies to those you list (except Rowland which I haven't tried) plus others from Flying Mole, Aiwa and a Tube Tech prototype. Not very pleasant.

Perhaps the technology will improve with age but I hope that Harbeth don't go with it just yet !!!

Some D class amps are now ready for the primetime. The older share Dave's description.
Check this active speakers with class D amplification, praised by Jean Marie Geijsen of
Polyhymnia International:

http://www.audioresolution.eu/en/products/audio-resolution-ellipse/

[davidlovel]

I changed from a Sumo 9 plus class A amp in the late 1990s to a class D amp and have never looked back.
See my earlier post for my experiences with my Super HL5s:


My choice of amplifier
When I auditioned the Super HL5s the dealer used Audio Research pre- and power-amps that enabled me to decide that the Harbeth speakers were what I was looking for (see my first post at: http://www.harbeth.co.uk/usergroup/s...=4493#post4493)

At the time the amplification in my system comprised a Bel Canto DAC / Pre-amp driving an Alner-Hamblin SA400 stereo power amp (class D, 300 watts into 8 ohms). The increased transparency of the HL5's caused me to think about improving the power amp. My son has had an LFD integrated for 19 years and Stereophile had just given it an A rating, so I auditioned the latest LFD Integrated Zero LE (60 watts into 8 ohms) against my Alner-Hamblin SA400 stereo amp, via Harbeth Compact 7ES-3 speakers.

The amps were certainly different but I found it hard to say which I preferred: the LFD had a more airy top, the SA400 better-defined bass. The mid-range transparency was similar. I took the LFD home on approval to audition in my system before reaching a decision.
Initially this was just as inconclusive: I liked both but with no strong preference.

I have a subsidiary hi-fi system which I use in conjunction with my computer for the playback and recording of LPs. I had a second SA400 amp in this system so I took the opportunity to set both to bridged mode (1100 watts into 8 ohms), and used these mono-block amps to drive the HL5s in the main system. I did not have high expectations for further improvements as the review in the January 2006 issue of Hi-Fi News referred to gaining more of the same (sound-stage width, layering, more air), but in my system the mono-blocks sounded like a different amplifier. The noise floor seemed lower, resolution was much improved and the top sweeter. Most striking however was the improvement in "musicality" by which I mean the emotion conveyed; the music made a lot more sense than before - rhythm, dynamics (micro as well as macro) etc. etc. I wondered whether this was a 'honeymoon" effect and would disappear after a few days but no, I continued to get a renewed buzz from whatever music I played.

So I now use the SA400 mono-blocks to drive the HL5s. (I bought the LFD integrated Zero LE to use in the subsidiary system.)

My experience confirms how important it is to listen to potential new components in one's home system. 60 LFD watts sounded very good, 300 SA400 watts was already far more than enough power; what extra could 1100 possibly add? As noted elsewhere the HL5s are a benign load. One possibility is that the effect of the low-pass filter in the class D output could alter the frequency response in the change to bridged mode, but the filter is set to give a flat frequency response for a 6 ohm load i.e. close to the impedance of the HL5s at these high frequencies, so there can be very little effect.

David

[Vlado]

I changed from a Sumo 9 plus class A amp in the late 1990s to a class D amp and have never looked back.
See my earlier post for my experiences with my Super HL5s:



David

Such sonic difference is related to "control" not to absolute power. I think.

[Alexander]

can i write something about my experience with Class A? I discover a really bargain with MF A1 and MF CD Pro, the amplifier has no much power but this combination give me thrills of joy while i'am listening to the music. And i buy my equipment only because of that it sould be entertain me.

[coredump]

can i write something about my experience with Class A? I discover a really bargain with MF A1 and MF CD Pro, the amplifier has no much power but this combination give me thrills of joy while i'am listening to the music. And i buy my equipment only because of that it sould be entertain me.

Thanks for the recommendation. it was one of my favourite amplifier in my wish list. btw, does this amplifier runs hot? reckon that this MF model is like the Sugden 21A. is it the new MF A1 WITH USB INPUT ?

a link here
http://www.mhennessy1.f9.co.uk/mf_a1/introduction.htm#history

[ryder]

I have listened to an old Musical Fidelity A1 Class A integrated last year. If I am not mistaken it's a 30W amp and runs hot. Excellent amp for vocals and slow-paced music but fails to match the LFD and the Naims when it comes to speed, dynamics and bass slam when music gets complex. For select types of music the MF A1 can be a gem indeed.

[ryder]

Thanks for the recommendation. it was one of my favourite amplifier in my wish list. btw, does this amplifier runs hot? reckon that this MF model is like the Sugden 21A. is it the new MF A1 WITH USB INPUT ?

a link here
http://www.mhennessy1.f9.co.uk/mf_a1/introduction.htm#history
This is the amp I have listened to in my system. It is a vintage amp and runs very hot which reminds me of my Plinius SA-100Mk3 in Class A mode. The description in the link has been spot on in that the top cover will be too hot to touch once it gets hot. Not too sure if the current production of MF A1 has USB connections. Anyway I don't think the classic A1's are still in production after Musical Fidelity stopped producing them in the early 90's?

[Alexander]

This is the amp I have listened to in my system. It is a vintage amp and runs very hot which reminds me of my Plinius SA-100Mk3 in Class A mode. The description in the link has been spot on in that the top cover will be too hot to touch once it gets hot. Not too sure if the current production of MF A1 has USB connections. Anyway I don't think the classic A1's are still in production after Musical Fidelity stopped producing them in the early 90's?

don't know exactly, but i bougth one of them 1 week ago, produced 2008 with a36 months warranty ,import from the official german distributer. I learnd ,that MF will not continue the production, but this amps don't fits in the spirit of the age, but for only listening music in normal volume(that means for me U2 "Rattle an Hum" so loud hearing , that my neighbour was friendly wringing on my door;.) is it a good choice, even you have a look on the price, cann i tell in the forum about price? or is it forbidden because of compliance here? I have a interesting link, se here.....sorry ni german. By the way yes, my youngest son (6 years old) was pretty amused about heating, but yes it will be warm a little but in compliance with the EU CEC Norm, so fo me it's ok, but the amp needs a little more costs of electricity, but compare that with the Glow Lamp Sales in the EU , they shines brighter , warmer but the need to much power against the new energy safer Lamps and this kind of lamp make a cold brightness like in the emergency operating room...i hope most of you could understand me and my bad english
take look here http://www.stereo.de/index.php?id=474 , i forgot...yes MF A 1 has an USB Input, so i took my Laptop on the Amp and go in the internet to hear my favorite internetradio

[ryder]

Good to hear you are enjoying the sound from your new Musical Fidelity A1 integrated. I can imagine the warm glowing sound of the MF A1 which sounds a lot like tubes with no grain. Very smooth and liquid sounding amp which brings out the best in vocals from the Harbeth. I had the opportunity to listen to the old generation of the MF A1 when my friend brought the amp over to my place sometime last year. Very nice sounding amp indeed. Needs about 2 hours to warm-up and you are ready to go. Thanks for the link to the German review of the new MF A1. the internals of the amp look quite impressive. The extra convenience of the USB input is certainly a welcome note for those who have their music collection in the hard drive.

Enjoy~

[Labarum]

Ummmm. I think that after-care is of great importance. Who will care when it fails? Maybe we should really investigate what we could do with a Harbeth badge on it. At an affordable price, approved technology and built to last.


What a good idea. A well built no nonsense amp.

Current Dumping is now out of copyright now, I believe, and there are Quad 405 clone boards available. I have read, however, that components are now so much better than years ago that the advantages of current dumping over ordinary class AB are not so great.

But, as I said, a straightforward no-nonsense workmanlike amp would be great.

And these days I only need a power amp - my straightforward no-nonsense workmanlike DAC doubles as a pre-amp.

[Alexander]

i think, i have the warranty for 36 months from a serios distributer and dealer, who is over 20 years located in the city.I have bought them as new and with original packaging, but only bought it because of the sound and not of the Money....extra value for the money was an additional

[keithwwk]

http://www.mhennessy1.f9.co.uk/mf_a1/introduction.htm#history

This is the one I bought many yrs back. I started my hifi journey with this sweet sounding amp together with my Kef Coda 7 speakers. 20watt, run very hot, nice black color....a lot of fun and memories whenever I see it.. :)

[audio39]

In 1984 I first heard the Luxman M-05 pure Class 'A' amplifier...I am now on my thrid M-05, I continue to get caught by the upgrade bug, but always return to this amp.

I have owned amps and pre's from all of the big names...Classe, Bryston, Mark Levinson, Krell, Pass, Accuphase and Simaudio...although some of the amps have been Class A in operation, none have sounded as musical or as sweet as the M-05.

Very recently I had the chance to spend some time with the new Luxman M800a, it wasn't a surprise to me that the sonic signature of the new amp was near to my beloved M-05.

So is it the Class 'A' operation? I think partly. But in the case of Luxman I think it's also the many years of data compilation that can be relied upon by anyone performing design work in that organization.

So I personally prefer Class A amps...but I definitely prefer Luxman to all else.

Rick.

[carlo]

Just curious if any of you use SS Class A amplification from the likes of Pass and Sugden? What are your opinions of Class A?Regards.

I'm using a pair of Pass XA100. With such amplifiers, that run in pure class A without switching to A/B class, and that are, by project, limited in current output, a choice of speaker with easy impedance load (never too low) is mandatory. To me, Harbeth has been the first choice.

As for the sound, class A, to my ears, offers a very "speaking" rendering of the sound, that means extremely correct sense of proportions especially of instruments tone, with the right amount of harmonics and a vivid presentation of the material the instrument is made of (it seems stupid, but it is not so expected that when you hear a violin you hear something in wood and when you hear a flute you hear a metallic alloy... things become more confused when you hear a Korg keyboard, but let's assume the general concept...).

With my Pass I also feel a generally indulgent treatment of bad recordings: even poorly recorded music remains highly enjoyable... I say that because before the Pass I owned a full Spectral system (pre DMC30SL, power DMA100S, cabling MIT/Spectral reference ULII 350 and 770) with a Wadia CDP, and such a combination/set-up was ruthless with less than acceptable recordings. Every imbalance was ruthlessly focused and moved forward... on the other hand, with very high-end and over-engineered recordings, thing were astonishing, but that was working on 1 or 2 recordings on 10.

So I would say that the biggest sound advantage of class A remains its intrinsic musicality and naturalness: more music than simple sounds. I have as a reference only my Pass XA100 and a comparison made between my XA100 and the new XA100.5, that are units (based on the same basic project) that switch to A/B class when you need more current ... well, with the A/B class you can feel that everything tends to become more rigid and cold, less liquid and breathing...

With Harbeth, that by themselves tend to sound natural and musical, I think that Pass amplifiers make a very special synergy, both in terms of good electrical matching and musical attitudes.

Cheers
C

[MrAcoustat]

I have listened to an old Musical Fidelity A1 Class A integrated last year. If I am not mistaken it's a 30W amp and runs hot. Excellent amp for vocals and slow-paced music but fails to match the LFD and the Naims when it comes to speed, dynamics and bass slam when music gets complex. For select types of music the MF A1 can be a gem indeed.

Musical Fidelity is a 25watts per channel Integrated Amplifier, and please keep away from children because it's really really hot, sounds great with efficient speakers 90db plus.

[Sebastien]

... Your description on all 505 and 590 amps has achieved its intention in giving me a more accurate representation of the sonics of all amps concerned...

Here's an hard one. Hope someone can help me because I haven't found anything on the web on this: is there any phono stage differences (quality, sound, caracteristic) between Luxman's L-505u and L-590? Or any at all in Luxman's integrated amplifiers range? Or is it all the same phono stage if it's a $3500 US or a $8000 US unit?

Sebastien

[Sebastien]

After going through your comprehensive but precise assessment on the L505, L550 and L590AII, I believe the Luxman may be the one...

Lorpuris! I need you to remind the best possible comparison between Luxman's L-505u (which I own) and L-550AII (which I like to own). I'm interest in every comments, especially about the bass and dynamic. I don't want a sideway move where I will lost these caracteristics from the 505u (what I felt if I'd go with a Sugden A21al).

Please, tell me everything you remind about the L-505u and L-550AII.

Sebastien