|   New to audio!!!! Class A and Class AB amplifiers | Skigull
Oct 25, 2003 10:37 PM | | I'm new to high end or should I say better audio. ( can't afford the real good stuff) What is class a amplifier and what is a class ab amplifier? Which is better? Also why do some not have classes? |
| re: New to audio!!!! Class A and Class AB amplifiers | RGA
Oct 26, 2003 1:11 AM | | They all have a class.
Class A - Many people feel that they sound the best. I tend to agree from what I have heard...though there are exceptions. http://home.no.net/andiha/articles/audio/claclassa.htm
One does not need to pay huge money for a class A amplifier. The Sugden A21a is around $1600.00US and IMO betters on a sound quality basis 10k spearates from Bryston and Krell. The problem is that there is only 25 watts with the A21a and if you are using a speaker that NEEDS more than this or is a tough 2-3ohm load...then the Sugden will get winded and sound pretty poor. With sich speakers the Krell and Brystons will sound better.
Why one would choose speakers that are inefficient is puzzling...now you have to spend a lot more on amplifiers that are generally worse because the designer of the speakers was an incompetant. http://www.audiosynergy.co.uk/a21arev.htm
A/B Typical in SS integrated amps such as Arcam, Roksan, Creek, other Sugden's, YBA, Rotel etc Can sound quite good
Advantages: Improved efficiency over Class A type amplifiers, excellent drive capability
Disadvantages: output not an exact linear reproduction of the input waveform, continuous current drain, efficiency not as good as other amplifier types.
REFERENCES
Gilbilisco, Stan, Ed. Encyclopedia of Electronics. TAB Books. PA: 1985
Gilbilisco, Stan, Ed. Amateur Radio Encyclopedia. TAB Books. PA: 1994
Then there is class B,C D etc. |
| re: New to audio!!!! Class A and Class AB amplifiers | Skigull
Oct 26, 2003 8:44 AM | | Thank you RGA for the info. If you can suggest anymore articals on amps. and how they work feel free. Again Thanks for taking the time!!!! |
| here... | RGA
Oct 26, 2003 10:51 PM | | Is one I found. http://www.win.net/audtatious/audio/ampclass.html
You should also be careful as the other poster noted about being seduced by technical terminolgy. many things are invented to increase profits because they can lower costs and essentially cheap out but rave about the superiority of technical aspects. Sometimes these merrits translate into superior sound, mostly they don't. Many of these higher end manufacturers even try to promote their new amp designs as sounding more tube like.
The issue of sound quality expands the gambit of opinions. ALL SS amps sound the same and on the other side very different. The former is silly of course because many SS amp makers build their amps to sound like tube amps...and tube amps do differ in all of these blind tests. But because very few CORRECT tests are ever done, we just get piles of pseudo science information simply out to fit an agenda. OTOH, one should not assume all amps sound wildly different, or even different at all. And then you have to consider whether the money involved to get the improvement is worth it.
The Sugden A21a has been sold since the 1960s. The design is the same as it was then but improved parts and integrating better heat handling materials has allowed that amp to have increased power. The A21a has been sold in current form since 1989. It's also had the benefit of 30+ years to be fine tuned to the hilt and using much better quality parts. There is nothing really in improved amplifier/speaker etc designs since then. They have been tweaking and improving parts of these old designs. That is why you see most of the highly regarded speakers like Quad,ML, Audio Note, and Magnepan and all of these tube amps for a start still using proven designs. They even get copied by the likes of Innersound, and Marantz has come out with their new STATEMENT amplifier...follows the Sugden Class A approach. Here is a perviable GIANT in home theater who knows where the "best" sound lies. It's actually quite inexpensive to boot.
Newer and more technically advanced(well technically different) amplifers/speakers have come and gone in all of these years and some very very expensive amplifiers/speakers can't touch the prowess of sound quality the A21a/above mentioned speakers incorporates. For instance you could get a louder more powerful sounding integrated from Krell for 3 times the money...you'll also see 300 times as many on the used market in 6 months because they annoy owners after a while.
You will need a 250watt amplifier to double the perceived volume level of the Sugden A21a(and that is assuming the speaker can handle and make use of the 250 watts). The vast majority of speakers are under 150watts max handling. The measly 25 watts is right at home driving an 87db 4 ohm Totem arro...even though this is supposed to be a nightmare kind of speaker for the A21a.
Quite simply, ignore the spec sheet that was invented by the accountants and marketing departments or crooked engineers trying to fudge their numbers.
I have heard 12 watt amps with speakers rattle walls where 100 watt recievers sounded lifeless and thin. Couldn't produce the scale or dynamic impact of the lesser amps. What I have noticed about most receivers is that I always want to put the volume up to hear the material clearly. Up and up and up - until I relaize the best position is off. Class B? - Other receivers are a lot better - Class A/B? Don't know(but the good receivers are prohibitively expensive and bang for buck goes right out the door. |
| also | RGA
Oct 26, 2003 10:57 PM | | http://www.soundentertainmentlighting.co.uk/en-us/dept_109.html |
| re: New to audio!!!! Class A and Class AB amplifiers | skeptic
Oct 26, 2003 8:06 PM | | I suggest that before you spend any money on any expensive audio equipment, you do a lot of shopping, listening, reading and questioning. Make your mind up to wait a considerable length of time before you plunk down your money or you will soon resign yourself to having made some expensive mistakes. If you are new to this, you are prime prey for everyone with something esoteric to sell. They will tell you that some particular arcane type of equipment is the magic bullet to audio nirvana. And there are a fistfull of them. You have entered a mine field. What are some of them? Class A amplifiers is a good place to start. Then you can proceed to the exotic audio cables of all types. How about worthless power conditioners. From there to other vacuum tube amplifiers and preamplifiers or the "preamplifierless" preamplifier sometimes called a passive preamplifier. Exotic cd players where the cd transport and digital to analog converter (D/A) can cost more than an entire sound system. For every manufacturer of every one of these products, there are a legion of people with testimonial stories about what a great improvement they made in their sound sytems and their sex lives.
Why do people build and sell ineffieient loudspeakers? Are they just stupid? Do they just like wasting amplifier power? Of course not. The best of them obviously have something many audiophiles wanted in the way of sound or they wouldn't have succeeded so well in the market. Why do people build powerful AB amplifiers with transistors? Are they just cut corners, be able to advertise more horsepower, or is their performance valuable in real usable terms? What do you think? Hint, when you start to shop seriously, take your wife or significant other along to keep your feet on the ground. She may just help you stay away from overpriced, overhyped, oversold expensive mistakes. Even among serous audiophiles who advocate and prefer this arcane types of equipment, they usually agree that the improvements are relatively subtle.
Best advice, shop for loudspeakers first and foremost since that makes the most difference in the way a sound system will perform. Build your system around your favorite loudspeakers, not around an amplifier. And cavaet emptor, buyer beware. |
| re: New to audio!!!! Class A and Class AB amplifiers | rb122
Oct 27, 2003 11:24 AM | | The fact that there is a debate on whether efficient or inefficent speakers are best (I prefer high efficiency and lower power but I also like Magnepans which would be an opposite situation) makes this advice of yours the best:
b Build your system around your favorite loudspeakers, not around an amplifier.
So true. |
| re: New to audio!!!! Class A and Class AB amplifiers | skeptic
Oct 27, 2003 2:10 PM | | This is advice objective audio engineers have given audiophiles for decades and it is still sound advice IMO.
There are good and bad examples of high and low efficiency speakers of many different design concepts. However, to get the eqivalent low frequency capability out of a horn system, as out of an acoustic suspension system, the enclosure would have to be enormous, usually much too large for a pair in most modern homes. People who have restored AR3s and AR3a s continue to be amazed at the bass response of these 40 year old designs compared to most compact modern speakers whatever their other shortcomings are. Tests showed that within their loudness capability, their bass outperformed Altec A7 voice of the theater and that the original Bose 901 produced bass that within its loudness capabilities outperformed JBL Paragon, a horn design many dozens of times its volume. The price for this bass performance from small enclosures was efficiency. There is absolutely no correlation between efficiency and sound quality but people who insist on most vacuum tube class A amplifiers are restricted to having a very low power unit which limits their choices to high efficiency loudspeakers. Loudspeakers which are power hungry will not perform well when AB comparisons are made with more efficient models using these low power amplifiers and will almost always come out sounding second best when the switching equipment doesn't compensate for the difference in loudness even when more power is available. The louder speaker almost always sounds better in such tests. People partial to the sound of electrostatic, magneplanar, and other exotic types of inefficient speakers have the same experience at other frequencies ranges. For those systems, a powerful high quality low distortion signal from an excellent power amplifier is a necessity for realizing the full potential of their special qualities. That is why as I stated elsewhere, I am not a fan of puny expensive power amplifiers. |
| re: New to audio!!!! Class A and Class AB amplifiers | RGA
Oct 27, 2003 3:12 PM | | That is why as I stated elsewhere, I am not a fan of puny expensive power amplifiers.
The fact you always leave out is the QUALITY of sound from the amplifier. Of course you are 100% right in not wanting a 10 watt amp if you happen to own a 70DB 1watt 1 meter speaker that requires 500 watts to hear them at a medium level.
If you own a 95db speaker 8ohm and is pretty non dippy in the impedence then you don't need more than 10 watts to play at deafeningly loud levels.
High watt amps also have gains that make them sound truly TERRIBLE if mated to a very sensitive speaker. I had volume out of my Wharfedales when the volume was off or all the way down to zero. One slight turn and you're at a loud level - And this was a 75 amp.
It is critical that an amplifier sounds good. I like Bryston for a variety of speakers...but if you have heard them with a number I have heard them with you'd think they sounded truly awful...because they did. You have to get the right system match and listen to the sound especially at the frequency extremes. The Brystons do interesting things to woofers...works for some and thins out some speakers so much that it sounds like the low end response is completely gone. It almost sounds too fast if that makes sense.
And everyone buying the 3 watt tubes are not fools just because you hate anything that was not designed yesterday= with gimmicky designs over quality parts - today's 100 watt receivers sound gutless compared to that 25 watt Sugden...those 100 watt figures are obviously falsified or bent to because if that thin no bass gultless sound is 100 watts then the Sugden must have left of to zeros on the spec sheet.
Tube amps typically sound a lot louder than their numbers which was proven by stereophile a number of year back from an independant I believe.
Not that that means the SOUND is better of course...but type 2 harmonic distorion is ALWAYS better than type one from class B and A/B designs. Class A if done right is the most linear and CORRECT and Accurate amplifier design.
Engineers are simply lazy and cheap and would rather build high priced garbage and con us into thinking it's good. Yorx and Sanyo receivers at costco - whoah what great gear. Comparing them to high priced stuff garbage of the same design in tests reveals people can barely distinguish if at all.
I agree pick your speaker first...but use a brain as to what you'll have to spend on an amp. ML is much better with Bryston than with Denon's expensive paperweights. But now your spending 30k on a speaker system. I think you can do better for half that with an alteration in the speaker selection and a lower to low powered amp. 50Watts from a gutsy amp can drive virtually every speaker made that requires one amp to drive.
the 11 watt Nuvista tube amp drove the N801 better than any other amp I have ever heard...more and better bass more and smoother highs and filled the room very well. It can't play as loud as a Bryston...but so what - buy a bigger Nu Vista. SOUND QUALITY not Garbage quantity. Bryston Monoblocks do both...but look at the price. |
| re: New to audio!!!! Class A and Class AB amplifiers | skeptic
Oct 27, 2003 5:12 PM | | "High watt amps also have gains that make them sound truly TERRIBLE if mated to a very sensitive speaker. I had volume out of my Wharfedales when the volume was off or all the way down to zero. One slight turn and you're at a loud level - And this was a 75 amp."
Sadly, this demonstrates a terrible lack of understanding about how audio power amplifiers and preamplifiers work. It is a beginner's illusion that if a slight turn of the volume control makes a speaker sound loud, this indicates a very powerful system. A great trick for people who want to fool you into thinking an amplifier is more powerful than it really is. The truth is that the gain of the preamplifier stage is independent of the power amplifier connected to it and most preamplifiers are compatable with most power amplifiers today. The goal is to match the sensitivity of the preamplifier with the available input signal and the requirements of the power amplfier so that it is easy to make critical adjustments readily allowing the user to achieve the loudness he desires from very soft to full output over the range of the control. A control which does not allow you to reduce the volume to inaudibility at the bottom of its range is most likely defective and needs to be replaced. It has nothing to do with the power capabilities of the connected power amplfier.
If you have a very specific application for driving a high efficiency loudspeaker that you do not expect to change, then available power may be a secondary or unimportant consideration and an amplifier of modest power may be perfectly acceptable especially if there are other audible considerations you believe exist and are important to you. But most audiophiles buying a power amplifier for general use with the speakers they have today, the ones they might buy tomorrow, and the ones they would like to try out from time to time should consider that a low power unit will impose severe restrictions and if they decide that they want a less efficient model at sometime in the future, they will have to replace the amplifier as well. Considering that most audio equipment loses value when it is sold used, this would impose an additional cost at some future time where a more powerful amplifier might well be kept at no further cost.
It is an absolute falacy that there is such a thing as a tube watt and a solid state watt. A watt is a scientifically precise definition for a rate of performing work. If vacuum tube amplifiers of a given rating sound subjectively louder than solid state amplifiers of the same rating, there are several plausible explanations for it. One is that given the generally higher distortion of vacuum tube amplifiers, they would sound louder. Another is that the frequency response of vacuum tube amplifiers is usually not nearly as flat as solid state amplfiers and a slight boost in the midrange relative to ss amps would make them sound louder. Because solid state amplfiers can be built with greater power bandwidth at low frequencies than vacuum tube amplfiers for the same cost due if nothing else to the series inductance of the output transformers, tube amplifiers of a specified power rating over a specified bandwidth may actually be able to deliver more power at midrange frequencies than ss amplifers. Said another way, a solid state amp at 50 watts per channel from 20hz to 20khz may also only produce 50 watts at 1khz but in order to specify a tube amp at 50 watts over the same range, it may actually have to be able to produce 70 watts at 1khz. It is also true that SOME vacuum tube amplifiers will not sound as awful when marginally overloaded into so called soft clipping as most solid state amplifiers. In no case should ANY amplifier be driven to clipping because it risks damage to the loudspeakers and the amplifier. One critical factor in designing a sound system meaning choosing speakers and amplfiers is to ascertain that they can work together to produced the loudest |
| re: New to audio!!!! Class A and Class AB amplifiers | RGA
Oct 27, 2003 10:05 PM | | "It is a beginner's illusion that if a slight turn of the volume control makes a speaker sound loud, this indicates a very powerful system. A great trick for people who want to fool you into thinking an amplifier is more powerful than it really is. The truth is that the gain of the preamplifier stage is independent of the power amplifier connected to it and most preamplifiers are compatable with most power amplifiers today."
I'm not a beginner and I understand full well about gain. many lower power amps set the gain too high purposely so that at the 9oclock position their 30 watt amp will sound luder than a 100 watt amps 10'oclock position. Nice try but that was ot what I was taling about and I think you know that.
I'm also not talking about power amplifers...I'm talking about integrated amplifiers.
"If you have a very specific application for driving a high efficiency loudspeaker that you do not expect to change, then available power may be a secondary or unimportant consideration and an amplifier of modest power may be perfectly acceptable especially if there are other audible considerations you believe exist and are important to you. But most audiophiles buying a power amplifier for general use with the speakers they have today, the ones they might buy tomorrow, and the ones they would like to try out from time to time should consider that a low power unit will impose severe restrictions and if they decide that they want a less efficient model at sometime in the future, they will have to replace the amplifier as well."
All of this I agree with and kinda stated it a bit below to your statement. No question high power amps offer, generally, more broad appeal. What I am merely saying is that WATTS is a big fat hairy overblown waste of space. My Pioneer Elite Receiver could play LOUDER than my Arcam Integrated...but the Arcam could play louder CLEARER. In other words I could crank the Arcam and get deafening levels with tight control of the bass no distortion. I could not be in the same room for long without getting a major headache. I never got the dial past 2O'clock because I was not sure of the amps gain and I didn't want to drive it to distortion. The Pioneer Elite (Flagship all discrete amps 125watts Continuous 20hz-20khz .00025%THD would get to 11 O'clock would be reasonably loud but had flabby boomy bass. Past eleven audible distortion and time to worry about blown speakers. Spec sheets are full of crap.
"One is that given the generally higher distortion of vacuum tube amplifiers, they would sound louder. Another is that the frequency response of vacuum tube amplifiers is usually not nearly as flat as solid state amplfiers and a slight boost in the midrange relative to ss amps would make them sound louder."
I apologise because I did mean to say the PERCEIVED loudness level which is not the same as the actual volume level. Just as the 10 times the power doubles the volume...it doesn't it doubles, roughly, the PERCEIVED volume level...but perception is all that counts here. Because tube amps have distortion that is more agreeable...then having a slightly elevated amount - and it's still small - just looks big versus SS, then more of the right kind of distortion is a helluva lot more agreeable than ANY of the lousy kind. Some SS amps are a lot better than others...and you seem to agree in that you backed Bryston and Krell not Yorx and Sanyo. Again I'm not attacking the technical prowess of "GREAT" SS amplifiers...provided you buy a great one. Because the Antique Sound Labs AQ1003DT, while it has its THD issues and roll-offs SOUNDS far better, especially for classical music, over solid state amps under a grand...Indeed, many SS amps are light in the loafers for bass= and have a nice helping of that grainy gritty sound...that is distortion no matter what the THD says.
Again I'm not telling people to BUY tube amps. I in fact was GOING to buy the AQ 1003DT and ended up buying |
| 2 and agree for a change | RGA
Oct 27, 2003 10:25 PM | | Again I'm not telling people to BUY tube amps. I in fact was GOING to buy the AQ 1003DT and ended up buying a SS amp. But these amps have come a very long way in the 20 years you've heard one. It very much depends on the tube amp you hear. The AQ1003DT for $800.00 weighs a ton, looks good, is well built and frankly, does not sound very much like a tube amp that I was expecting. In fact it sounds very much like a SS amp across the board. I would venture to bet that in a Blind test with the CDM 1NTs that I was using - you and anyone would be very hard pressed to tell it apart from many SS amps in the $1500-$3000.00 range. The point is that most of the tube amps today are far better just as SS amps are. Tube amps get to use all the best parts to extend and control both frquency extremes.
But then the speaker isn't full range - so the fact the amp can't hit 4hz doesn't matter much. Most Tube amps are in the 20-20khz range...and many new ones don't appeal to the older die hard tube fans. They look the part but they sound SS with a midrange(where 90% of the music lies) is more engaging and less gritty than most SS products).
Indeed, the AQ1003DT is rated 30 watts Class A 18hz - 25khz @ <1% HD and 20hz to 20khz at full power <3% HD Hardly numbers that say to me that there is no bass and no highs. Most people above the age of 30 can't hear past 15Khz or below 40hz anyway(and this was the frequency range not long ago - which leads me to believe that the vast majority of people aove 30 can't even hear at these frequencies. No matter the 1003 hits them anyway. The distortion is miniscule...not against the Pioneer I had...but the pioneer SOUNDS distorted. You had to crank the volume for it to sound clear and when you were starting to hear it clearer then the pendulum started to swing.
And I tried all the others, Marantz, Sony, Yamaha denon...all of which sounded the same or worse than the Pioneer.
And none of this even stats to get into the other pluses if you're so inclined with tubes, like the hobbyist aspects of rolling etc. I'm not so inclined because of the added expense of buying tubes and I really didn't want to lug the 32lb amp shoe-box size amp around and pay added heating bills. The sound however, is very good...better than the NAD C370 for example - especially if you listen to classical music. I like violins to have decay and not a grit and etch to everything. - Preamp section perhaps. |
| 2 and agree for a change | skeptic
Oct 28, 2003 1:31 AM | | I don't often quote myself but from another posting in this thread;
"There is no simple number or group of numbers you can read to completely understand or predict how an audio component will perform in actual use especially considering the number of aspects to it and the number of variables possible in the way it will be used."
There is a complex relationship between an audio power amplifier and a loudspeaker system and is unique for every pairing but here are some general rules;
The better the power supply, the better the amplifier. It doesn't matter what type of amplifier you are talking about. Many amplifiers must contend with loudspeakers with complex crossover networks which use equalization as part of their circuit to mitigate the limitations of using only two drivers each operating over a wide frequency range, or to try to time align, two, three, or more drivers. In short, many modern loudspeakers present very difficult reactive electrical loads (unfortunately for the beginner, using this highly technical term is the only way to accurately describe it.) Further equalization applied by exotic speaker wires adding large capacitance or inductance to the output load not only can confound amplifiers which performed very satisfactorily in earlier eras with speakers having less complex crossover networks and common zip cord wires, some amplifiers under some conditions can become unstable going into spontaneous oscillation. This is the price you pay for the absurd and wrong notion that equalization should be applied after the power amplifier stage instead of before it becasue of some false mythical concept of signal purity among audiophiles. To deny that a crossover network is an equalizer, a frequency selective circuit, is to fly in the face of fact. It is also a fact that with parts commonly available in an industry geared for solid state circuits which is the reality of the electronics industry today, it is much easier and cheaper to design a well regulated high quality power supply for 70.7 volts typical for powering solid state amplifiers output stages than at 480 volts needed for comparable tube circuits.
Loudspeakers which are designed to produce their best bass by using small heavy woofer cones in ported enclosures tuned to very low frequencies can present large undamped resonances which can to a degree be controlled by amplifiers having very low output impedences characteristic of solid state but not most vacuum tube amplifiers. This appears to reduce bass output in these speakers. Speaker designers who depend on such tuning for bass will recommend tube amplifiers because they generally have a much lower damping factor than solid state models. The speaker's inherent mechanical damping factor (meaning the speaker's internal damping in the enclosure) at resonance is not a specification you are likely to see from most speaker manufacturers. Reducing the bass output can alter the tonal balance making the treble sound exaggerated by comparison and giving the impression that solid state amplifiers sound bright and harsh. In fact, most solid state power amplifiers, even cheap ones, are far more linear with inherently much wider bandwidth, flatter frequency response and lower distortion than most vacuum tube models because of the inherent problems caused by the latter's output transformers. Vacuum tube amplifier manufacturers will NEVER talk about the output transformer eddy current losses or hysteresis losses of their cores or give you specifications for them. Solid state amplifiers do not have or need such transformers and direct coupled amplifiers don't even need an output blocking capacitor theoreticaly making flat response possible right down to zero hertz if the power supply and the rest of the circuit can deliver it. |
| 2 and agree for a change | RGA
Oct 28, 2003 2:20 PM | | Ok, but again I'm not talking to you about the technical merits of the amplifiers...which measures better - because everyone including die hard tube loving engineers agree with this. The issue is sound - and we can explain it to death as to why people prefer the sound of tubes and say there is a mid bass emphasis and a boost at 1khz or more power here and 2nd order HD and blah blah blah. The fact is many people, not all, like the sound of an good tube amp better. many of them add the fullness of a proper musical instrument that is lost for whatever reaosn with the SS kit.
I'm not saying tubes measure better, I honestly don't care...I care about results. And most people who own high end SS amps that then try tubes never ever go back...rearely does this happen the other way. Though a friend in the mid 80s went to SS and was quite happy...trying newer designed tubes instead of the junk in the 80s has made him go back. Better sound - saved money, worse measurements no doubt but better sound is what matters.
Again I'm not saying one is superior to the other. I agree with the points you make about speaker designs, crossovers the whole shabang. |
| re: New to audio!!!! Class A and Class AB amplifiers | rb122
Oct 28, 2003 3:37 PM | | But if your speakers are capable of 92 db/1 watt/1 meter, having a 100 watt amp is unnecessary. I use 25 tubed watts and although my amp doesn't have a power meter, I'm pretty sure I've never used more than 10 of those watts. And while my amp was pretty expensive when new, it was fairly inexpensive on the used market. Plus it has it's own built in preamp, since it's an integrated. If the day ever comes that I opt to replace my speakers with something that won't work with 25 watts, I'd imagine I could sell the amp for only slightly less than I paid for it. |
| re: New to audio!!!! Class A and Class AB amplifiers | RGA
Oct 28, 2003 4:40 PM | | And the chanes are when you go to other speakers you won't need to buy a new amp anyway. There are SOOOOOOOOO many speakers that offer 87db 8ohm with minimal serious dips that why would you deliberately buy a speaker that is very tough to drive? Odds are it won't sound any good unless you spend 10k on very high power heavy power supplied SS amplification anyway.
A good designer can make wonderous sound and still make it easy to drive. Thankfully, those designers have a CLUE and help the budget consious consumers who can buy nice lower powered better sounding amplifiers. Make it impossible to drive and then you always have an excuse..."Well if only you bought a more powerful high end amp from Krell - only THEN will you get the best from our speakers" The rest of the time they sound problematic.
Tube amps are perfectly fine...some aren't. It's a preference issue...but generally speaking you can buy a tube amp for significantly LESS money that has a better power supply, is far heavier and better built than SS amps. The ASL Aq1003DT is 2 channel, half the size of most any 5 channel gadget box receiver(with remote tuner and a bazillion chips) in all dimensions...and weighs two or 3 times as much...the power supply and being made of steel helps.
Some of the Audio Note amps are over 300lbs. |
| re: New to audio!!!! Class A and Class AB amplifiers | RGA
Oct 27, 2003 2:52 PM | | Build your system around your favorite loudspeakers, not around an amplifier
You can run most speakers with a class A or tube amp anyway.
You simply need to get a much higher power tube or class A amp that likes difficult impedences. It is very costly...but then it is very costly for good SS too. Class A has more ear friendly distortion for the most part.
Very good Class A/B amps are fine choices...whcih is what I have and probably what most audiophiles have. That said, I am big enough to admit tht as good as My high bias in A class A/B is it's beaten handedly by much of the better class A amps...probably some lousy class A amps too...so you need to be wary of the buzzwords and LISTEN to them. |
| re: New to audio!!!! Class A and Class AB amplifiers | DMK
Oct 27, 2003 7:30 PM | | When I bought my amplification a few years ago, I ended up purchasing tubed separates. My STRONG second choice would have been the Sugden A21A. I ended up spending about 3 times the price of a new Sugden on the used market but I felt the extra cost was worth it. On the other hand, the Sugden has been around for decades so if I ever decide to switch.... |
| re: New to audio!!!! Class A and Class AB amplifiers | RGA
Oct 27, 2003 10:34 PM | | And of course the Sugden has survived because it is one of the best sounding amplifiers at any cost ever made by anyone. And it will drive 95% of all speakers made. Basically if your speakers are 8ohm 87db or better you'll have ZERO problem using this amp to rattle your windows.
There is a reason that this amp survived and their class A/B designs have not...I have their A48b class A/B amp...more power as "Sugden frequently used MOSFETs rather than bipolar transistors, favoring their tube-like transconductance curves."
One reason I like the amp is that it sounded like tube amplifiers but had the oomph in the bass. You'll get that bass impact with costlier tube amps...but The AQ1003DT was not quite up to the level. And since the Sugden was 1/4 the price used and had a phono stage I needed then it was a pretty easy choice. |
| also | RGA
Oct 27, 2003 10:55 PM | | Just wanted to mention that I have heard the A21a and wished I could have happened on that one used(The A28b was next choice followed by the A48B) Intersting - as the power increases the quality decreases.
I'm shocked that some people seem to think you need mega watts to be able to drive most loudspeakers today - you don't. The only reason people think this is because there were so many atrocious amplifiers made that more power was going to fix it...and a host of BAD inefficient speakers. Time have changed. People consider 86db 8ohm tough to drive...it isn't.
The silly thing about all this is that A21a has survived 4 decades in various forms...and in blind listening sessions BEATS the crap out of all newcomers. Even What Hi Fi while awarding the 125Watts Roksan amplifer the winner in the last supertest noted that the the Sugden A21a was EASILY the best SOUNDING of the group. High praise for a 1960s designed amp.
The Sugden lost points because, being the same amp from 1989, has no remote control, doesn't have the aesthetics and features of the Roksan, and doesn't have the power making it harder for some speakers(like the 5% of speakers that require a mega amp - which of course the Roksan would not bea able to drive either so that was a stupid argument for What Hi FI to make) 125 watts versus 25 watts is audible - but it's going to be between very loud and rattling walls and windows and have you FEELING the sound in your cheast - versus a BIT more of that and then a less linear more fatiguing sound. No thanks I'll take the former.
I recently heard a set of PSB Stratus Gold speakers(not one I like) but it's a big realatively full range speaker - don't know the specs. It was connected to a 12 watt per channel amp. The VU meter never went past 9 and in a big room was vibrating the glass with a nice tight very deep bass response. Crystal clear and no audible distortion. The PSB is a 4ohm speaker and 88db sensitive.
Watts is BS...buying more is unecessary since they won't be used in 99.999999999999% of application. And they can sell their crap about Dynamic headroom all they want...just there because they have to grasp at straws.
Anyway, the rant is over.
What tube amp did you get over the Sugden. I have not heard a tone of tube amps - they're all sproting up all over because more and people listen to them and realize how bad their receivers truly are. |
| I agree with that, rb -- disagree who may! {nt} | Feanor
Oct 31, 2003 7:27 AM | | nt |
| It's bizarre that people will built a system around ... | Feanor
Oct 31, 2003 8:18 AM | | ... a 3 watt OTL SE Triode (or whatever). How limiting in terms of speaker choice! Yet quite few people seem to be on this track.
I've heard of some 100+db/watt speakers. Often they seem to be single driver or crossoverless. You would thing they'd be cheap if it weren't that the cabinets are complex. If they are so great, why aren't we all buying them? Then we'd fine with 3 watt amps, which ought to be cheaper too whether tube or SS. |
| It's bizarre that people will built a system around ... | skeptic
Oct 31, 2003 10:15 AM | | MikE is a prime example trying to build a system around his 7 or 10 wpc Moth amplifier.
Generally these efficient systems are horn loaded systems. They had great appeal in the early days of sound because you could use them to fill up a theater when only very small amplifiers were available. But to get bass down to about 40 hz, you had to have enormous enclosures. The Klipschorn was ingenius because when placed in a corner, it used the walls of the room as an extension of the horn itself. JBLs answer was the Hartsfield, a monster made with the best quality drivers. Altec had the A7 and Tannoy the Gold Monitor. Because of their size and cost, they were not very popular with ordinary homeowners or apartment dwellers and when stereo required two enclosures, the prospect was out of the question for most. Acoustic suspension systems pioneered by Acoustic Research and KLH offered high quality alternatives with bass response equal to or better than the best horn systems. The price was of course efficiency, a good 20 to 25 wpc necessary. In the early days of stereo, this was not necessarily cheap. JBL had an interesting answer, the Paragon and its smaller cousin the Metrogon, two three way full range horn systems in a single enclosure firing their midranges and tweeters at a single curved refecting panel. They predated Bose by about 10 years. They werent' cheap or small but at least they were only one unit.
A single full range driver suffers the same limitations that Bose 901 does. It cannot be both a high quality woofer and tweeter a the same time. We do not have materials that are both strong enough and light enough to make them so they wind up being a compromise. |
| It's bizarre that people will built a system around ... | DMK
Oct 31, 2003 12:08 PM | | b A single full range driver suffers the same limitations that Bose 901 does. It cannot be both a high quality woofer and tweeter a the same time. We do not have materials that are both strong enough and light enough to make them so they wind up being a compromise.
All speakers are compromises. It's a matter of what your priorities are. Because my hearing at age 46 isn't anything like it used to be, I'm more concerned with output under 14 khz. For all I know, my speakers (although they are quoted as going to 20 khz) may roll off sharply well below that. Bass is plentiful to 20 hz, although probably 3 db down. The midrange...well, I've said these things are as close to live music as I've found and I'm sticking with that characterization. |
| It's bizarre that people will built a system around ... | DMK
Oct 31, 2003 12:01 PM | | b I've heard of some 100+db/watt speakers.
Mine are rated at 103 db and they are "single driver" and crossoverless. Actually, there are two 6.5 inch drivers per cabinet. The cabinets aren't "complex" per se. They're made of Gibralter, a corian-like substance that is completely inert - at least how they are put on the speakers. I listened to hundreds of speakers before I bought these - pretty flat to 25 hz with usable output to 20 and (a guess) about 10 db down at 15 hz.
The interesting thing is that you'd think with my 25 watt amp, I'd be overpowered. However, I have not heard an amp of less than 18 watts that I'd pay two cents for. They may be out there but I've not heard one yet. OTOH, I stopped looking so who knows?
Anyone building a system around anything but speakers probably has a system you wouldn't want to be exposed to. |
| Ah-hah! Looks like we'd have case-in-point except ... | Feanor
Oct 31, 2003 1:54 PM | | ... by the sound of it, you sensibly subscribe to the speaker-first approach.
Still it begs the question, if speakers of this ilk are so great, how come they aren't more popular?
BTW, I did spend a few miniutes one time checking out Fostex drivers and suggested cabinet designs -- kind of fascinating, but I don't have the time, money, or power tools to build a pair. |
| Ah-hah! Looks like we'd have case-in-point except ... | DMK
Oct 31, 2003 7:11 PM | | b Still it begs the question, if speakers of this ilk are so great, how come they aren't more popular?
Actually, they are - at least the concept is. The Brentworths I own are not popular because they are a small company with a limited (read as non-existant) advertising budget. Anyway, if you want to know about the concept and its popularity, check out www.lowtheramerica.com (I may have the website slightly incorrect but check google or audio asylum). Lowther makes single driver speakers (no tweeters) and they are most effective in horn designs. The fact that I personally have never heard a Lowther based system that sounded anything like real music doesn't mean others haven't and it doesn't mean I don't appreciate the concept because obviously I do. Lowther folks tend to hate Brentworths and vice versa. I guess they appreciate the peaky frequency response, lack of bass, megaphonish midrange and hot top end of the Lowthers rather than the neutrality of the Brentworths.
Heh, heh - that's another audio debate altogether! :) But the nifty thing about single driver speakers is low distortion and also no phase shifting at the crossover frequencies. Others disagree but I find speakers with too many drivers to sound incoherent as a rule - they detract from the "live" experience, to my ears. I'm always aware of treble, midrange and bass rather than a continuous musical whole.
The Brentworths (BSL's) are unabashedly neutral and will expose every single flaw in the system or the recording. Quite honestly, they are often too transparent - CD's generally fall apart although vinyl usually sounds excellent. Not to slam CD's altogether - the best recorded and mastered ones sound fantastic. I often lose myself in the music and the idea that I am at the recording venue happens more often than you'd think. Once I learned to appreciate these speakers, I could not do without them. One thing they taught me is that if you read a review that tells you the speakers under review excel at a particular type of music, skip the review. There must be horrible colorations with the speaker. The BSL's can play heavy metal, jazz, classical, whatever and, if well recorded, they all sound awesome. The only thing I hate about the speakers is that they weigh 150 pounds each! Optimal speaker placement comes with built in hernia! :) |
| It's bizarre that people will built a system around ... | RGA
Oct 31, 2003 7:18 PM | | If your speaker is rated 89db 8ohm and does not have badly designed bad habits...then an 8watt amp is more than enough to geenrate loud listening levels.
The term limiting is stupid since WAY more than half the speakers sold I would bet achieve the above rating.
90db is loud. You only need 1 watt to achieve loud. 8 watts gets you to 99. Now it would be better to have a 8W amp with a 100db speakers.
This would give you a max SPL of 109db.
Now you take your 120 watt Bryston and connect your 85db speaker
1=85
2=88
4=91
8=94
16=97
32=100
64=103
128=D'ohh too bad.
And all of this is just talking about power and loudness level. A good tube amp sounds better to most people. If all you want is loud then buy Cerwin Vega and an off the shelf reciever.
Those of us who care about classical music and want instruments to sound like instruments want quality amplification over a brittle sounding grainy beast. There are many a good SS amps...there are a many good tubes...get seduced by the SOUND not the numbers. |
| re: New to audio!!!! Class A and Class AB amplifiers | FLZapped
Oct 27, 2003 7:11 AM | | All amps have "classes". It refers to the conduction angle of the amplifer.
Class A is on all the time(360 degrees) and draw maximum power all the time. Runs hot. Will usually have the lowest achievable distortion.
Class B amplifiers conduct half the time(180 degrees) and usually have a push-pull stage to cover both halves of the waveform cycle. No very suitable for high quality audio since there is a deadband around the zero crossing as the halves of the push-pull circuitry switch on and off, which means distortion. But they run much cooler.
So then you have AB amplifiers, which overlap in the deadband area to help reduce the distorton caused by the push-pull stages switching on and off. They are a compromise between A and B so you get lower overall energy usage and better distortion numbers.
The majority of amplifers on the market ae AB designs. (It's essentially the defacto standard)
-Bruce |
| re: New to audio!!!! Class A and Class AB amplifiers | skeptic
Oct 27, 2003 9:12 AM | | It is unfortunate but a fact of the competitive marketplace in audio that even beginners are forced to jump into the thick of the battle over the merits of arcane audio equipment with very esoteric theories explaining their value. If they don't jump on the 100 mph trains from a standstill, they risk having their bank accounts run over by them.
Sorry I can't agree with everything Bruce said but here are some facts;
Neither vaccum tubes nor transistors are inherently perfectly linear distortion free devices. Both types of amplifying devices in their countless variants have inherent nonlinearities.
Push pull amplifiers were invented to replace class A single ended amplifiers long before transistors were invented because they represented an advance in the way to produce higher powered amplifiers that are practical, efficient, and cost effective.
Negative feedback was invented around the time of the second world war long before transistors existed, as a method for reducing distortion and extending frequency response at the expense of gain so amplifiers using negative feedback require more stages for the same amount of gain. Very complex to truely understand and use in design, when properly used, is is a godsend. When poorly used, it is a disaster.
In the 1960s the entire worldwide electronics industry began to abandon vacuum tube technology and replace it at enormous expense and difficulty with solid state electronics. With the exception of some very specialized areas and some small manufacturers of arcane equipment, vacuum tube technology, the protests of audiophiles notwithstanding, is effectively extinct. There were many reasons for this change but for audio amplifiers, it was a way to make very reliable, low cost, low distortion, high powered, high quality amplifiers that have an indefinite lifespan.
Based strictly on laboratory measurements alone, manufacturers have never come close to approaching the performance of the best solid state amplifiers with vacuum tube technology in ANY measurement or combination of measurements including power, flatness and range of frequency response, low output impedence, non linear distortion, or noise. The measured performance of the best solid state amplifiers can challenge the limits of the best test equipment to measure their deviation from theoretical perfection. How this relates to actual listening is the subject for endless debate among audiophiles, however, there is no debate that among the limitations of vacuum tube amplifiers, it is the output transformer necessary to convert the inherently high impedence vacuum tube plate circuit output stage to a low impedence source capable of driving loudspeakers. There are very few products available that have overcome the need for this transformer. To what degree the limitations of this device contributes to the so called tube sound is also debatable.
Well designed, well manufactured products using high quality parts will always outperform a lesser product and give greater user satisfaction regardless of the design concepts of either. A $3000 McIntosh (40 year old) vacuum tube amplifier will easily outperform a $300 modern Panasonic solid state receiver. A $3000 modern Bryston solid state amplifier will easily outperform a $300 (40 year old) Panasonic vacuum tube receiver. Where the crossover point is, is a matter of debate. There is no simple number or group of numbers you can read to completely understand or predict how an audio component will perform in actual use especially considering the number of aspects to it and the number of variables possible in the way it will be used.
Almost anyone with something to sell or an emotional investment in one particular technology or another because they have invested their own money purchasing it will tell you that his answer is the only right answer. |
| re: New to audio!!!! Class A and Class AB amplifiers | RGA
Oct 27, 2003 3:23 PM | | "Well designed, well manufactured products using high quality parts will always outperform a lesser product and give greater user satisfaction regardless of the design concepts of either. A $3000 McIntosh (40 year old) vacuum tube amplifier will easily outperform a $300 modern Panasonic solid state receiver. A $3000 modern Bryston solid state amplifier will easily outperform a $300 (40 year old) Panasonic vacuum tube receiver. Where the crossover point is, is a matter of debate. There is no simple number or group of numbers you can read to completely understand or predict how an audio component will perform in actual use especially considering the number of aspects to it and the number of variables possible in the way it will be used. "
Now this makes sense. I am not saying Tubes are better than SS by the way...People on that wagon can stay on. There are good and bad in both designs.
You have to listen to the product with the speaker. Different speakers have wildly different sounds and requirements. I have heard Brystons and Tubes sound entirely different with different speakers. And the extra supposed advantage of lots of power does not mean that it wil play better ALWAYS. The extra power can handicap the overall sound with one speaker and blow the tube out the door with another.
Owners of the Khorn are highly irritated with high power SS amps...the sound is generally terrible with such set-ups. Now you may hate the speaker anyway so the point would be moot but if that is your beloeved speaker...then amplifier matching is more than just plunking your 5k down on Krell. The ASl Wave 8 monoblocks and AQ2004 preamp for $498.00 may actually WORK better even though the Krell is a better amp overall. |
| re: New to audio!!!! Class A and Class AB amplifiers | topspeed
Oct 27, 2003 5:52 PM | | Without getting to the arcane history of amps or the merits/demerits of ss vs. tube amps, FLZapped is right. The classes of amps has nothing to do with sound rankings (i.e. Class A's sound better than Class B which is superior to Class C etc.) It has to do with the design of the input and output stages. Many times amps will have a class A input stage and a class B output stage (hence Class A/B whereas the input stage is always on but the output stage isn't). There are also hybrid amps such as the Bel Canto Evo or PS Audio HCA2 (Hybrid Class A, get it?) that are either hybrid class A's or class D's (for digital) depending on who you ask. Digital amps such as these are a whole different ballgame from analog amps, whether ss or tube.
Bottom line, don't worry about what class it is. Just buy what sounds best to you in your system. It's your money.
Good luck |
| Skigull, a simple analogy of Class A and Class AB amplifiers | skeptic
Oct 30, 2003 9:38 AM | | Here is a simple if imprecise analogy of class A, B, and AB amplifiers.
Imagine a man with a short handsaw trying to cut down a tree all by himself. He saws back and forth with relatively short strokesbut has complete control over the motion of the saw. That's analogous to class A. Now imagine two men cutting the same tree with a saw twice as long and a handle at each end. Imagine that each man only does half the work. One man pulls the saw in his direction cutting the tree while the other simply goes along for the ride so he can be in position to take over when its his turn to go back in the other direction. That's analogous to class B. But let's say that there's a problem. Let's say that when the saw stops and just as the other man is about to start, the saw snags the tree and has to be pulled with a jerk to get it started again. Now let's assume that just as this is happening, the man who is about to stop can give just enough help in the opposite direction to keep the saw from snagging so that the motion changes direction smoothly. That's analogous to Class AB. Imprecise but easy to understand.
It is in this transition from positive to negative going voltage that the class AB amplifier shows some of its strengths or weaknesses. If the transition isn't perfect, the result is a kind of nasty harmonic distortion called "crossover notch distortion" because viewed on an oscilloscope, you can see a small notch where the voltage crosses over from positive to negative or visa versa. Engineers trick....listen to class AB amplifiers at very low volume preferably with high efficiency loudspeakers. This will exaggerate the effect of this distortion if it is present. Class A, B and AB amplifiers can be built from either transistors or vacuum tubes. It was somewhat easier to design and adjust AB amplifiers without crossover notch distortion using vacuum tubes than transistors in the early days. Some engineers still don't get it. Look for amplifiers which state words to the effect that harmonic distortion decreases with decreasing power output. |
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