Class A amps with Klipsch Heritage

[PrestonTom]

Good Questions. Certainly you have the efficiency of the Heritage series that makes life easier (along with the fact that the impedance shown to the amp is not very low - so you do not need an amp capable of large amounts of current).

There was a review of the Klipschorn in Stereo Times that used a Monarchy amps - the review was favorable (sorry I do not have a link).

Nelson Pass has also made comments about testing his Class A designs with a La Scala (might want to check that out).

As an alternative (and a convenience) there are many A/B designs that will keep the amp in the Class A mode for at least the first couple of watts, the Parasound HCA series would be good example.

Good Luck,

-Tom

[NOSValves]

For my edification

does an amplifier exhibit the same charastic wether a 3,5,25 , watt ss or tube played in class "a" as

a 30, 50,125, tube or ss amplifier design for a/b played in class "a"

what would be the defficiences of the class a/b amp. please not trying to irritate or incite

seems to me that one is beign infered i'am looking for clarification.

The answers are just not that simple.... The differences have more to do with the designers personal voicing preferences in all respects. It's fairly simple no perfect amplifier, preamp, speaker, cable, CD player, Turn table exist. They are no absolutes in audio if that was the case then surely one of every component in an audio system would dominate the market. Well all have different wants, needs and above all ears. What sounds good to you is good. Taking any one persons opinion as fact is a recipe for failure in audio. Just too many variables.

Craig

[BS Button]

Monarchy SM-70 Pro! Class A zero feedback design, sound great on Klipsch heritage!

I know someone posted recently that they gave the Monarchy's (bridged as mono's) a try and didn't like them; I think that person was in the minority.

I had one, tremendous noise floor. Other than that, it sounded wonderful.

BS

[BS Button]

Monarchy SM-70 Pro! Class A zero feedback design, sound great on Klipsch heritage!

I know someone posted recently that they gave the Monarchy's (bridged as mono's) a try and didn't like them; I think that person was in the minority.

I had one, tremendous noise floor. Other than that, it sounded wonderful.

BS

Craig,

I love the looks or your VRD's, if I could only afford them. Even the baked on Gray enamel...Meagain is losing it..

[NOSValves]

I don't recall anyone saying the Pcat "couldn't handle it"..................... I do recall someone state they did not like the way amps of that topologies or description handled just about any music. Some confusion going on here......... All I know is every single review or comment I have heard to date makes me think SET type sound. Comments like sweet and smooth mid range (hanging notes), soft HF (meaning rolled off frequency extremes). Well sorry I have never listened to a SET amp that I preferred and it had very little to do with the power they produced. They just quickly want to make me yawn. Just like I mentioned above no absolutes exist in audio what I like the next guy could absolutely hate. You know what.... he would be 100% correct in doing so. What sounds good to the ear of the beholder is good simple as that.

I believe this is a discussion about Class A against amps of other topologies, tube, SS or whatever and I for the darned of me can not find one single direct derogatory word spoke in this thread about Pcats or any where else for that matter..............

Craig

[joshnich]

Hey Craig

You have not said a derogatory comment about the pCAT. What did say was that you had not heard an all triode amp that could handle more complicated music. Your quote from that thread is here...

"I've heard countless amplifiers from little vintage examples to 40
thousand dollar real triode heavy hitters both PP and SET with plenty
of power and the basic character is always the same. They sound great
at small 3 piece acoustics and Jazz but when ask to deliver some
complicated music like big band, rock, swing or even blues they just
simply congest up and everything seems to melt together. I find it very
telling that every time your enter a room at a show with these types of
amps the only music playing or even on hand is the type of music I'm
referencing. Hey maybe your amps are an exception to this but I would
have to hear it to believe it since I have never experienced it out of
that type of amplifier. Hey you have shocked me before! "

After I read this I realized that I couldnt respond, because i had not really listened to a lot of Rock on the pCATS. I certainly have not auditioned the number of amps that you have, and I certainly respect your ear, si I was thinking that there might be something to what you were saying. I now have spend a little time listening to Rock and Classical, and was saying that my experience with the pCATs is that the music does not congest and actually the opposite was the case. Thats all.

Anyway it's all good

Josh

[woodsman]

Craig,

I have read nothing but praise for your VRD's as well. Only problem I read about was meagains and we all know how that turned out.

We just happen to be graced with some very talented amp designers and some very knowlegable people on this forum.

That's all I've got to say about that.

[jheis]

It might be beneficial (to me at least) if someone could give a (simple) explanation of different classes of amplifiers.

For example, my B&K amps "operate with a class A predriver and AB MOSFET power output stages." What does that mean?

James

[Guest " "]

jheis

"It might be beneficial (to me at least) if someone could explain the different classes of amplifiers"

http://en.wikipedia.org/wiki/Amplifier

Amplifier classes

Amplifiers are commonly classified by the conduction angle (sometimes known as 'angle of flow') of the input signal through the amplifying device; see electronic amplifier.

Class A

Where efficiency is not a consideration, most small signal linear amplifiers are designed as Class A, which means that the output devices are always in the conduction region. Class A amplifiers are typically more linear and less complex than other types, but are very inefficient. This type of amplifier is most commonly used in small-signal stages or for low-power applications (such as driving headphones).

Class B

In Class B, there are two output devices (or sets of output devices), each of which conducts alternately for exactly 180 deg (or half cycle) of the input signal.

Class AB

Class AB amplifiers are a compromise between Class A and B, which improves small signal output linearity; conduction angles vary from 180 degrees upwards, selected by the amplifier designer. Usually found in low frequency amplifiers (such as audio and hi-fi) owing to their relatively high efficiency, or other designs where both linearity and efficiency are important (cell phones, cell towers, TV transmitters).

Class C

Popular for high power RF amplifiers, Class C is defined by conduction for less than 180° of the input signal. Linearity is not good, but this is of no significance for single frequency power amplifiers. The signal is restored to near sinusoidal shape by a tuned circuit, and efficiency is much higher than A, AB, or B classes of amplification.

Class D

Class D amplifiers use switching to achieve a very high power efficiency (more than 90% in modern designs). By allowing each output device to be either fully on or off, losses are minimized. A simple approach such as pulse-width modulation is sometimes still used; however, high-performance switching amplifiers use digital techniques, such as sigma-delta modulation, to achieve superior performance. Formerly used only for subwoofers due to their limited bandwidth and relatively high distortion, the evolution of semiconductor devices has made possible the development of high fidelity, full audio range Class D amplifiers, with S/N and distortion levels similar to their linear counterparts.

Other classes

There are several other amplifier classes, although they are mainly variations of the previous classes. For example, Class H and Class G amplifiers are marked by variation of the supply rails (in discrete steps or in a continuous fashion, respectively) following the input signal. Wasted heat on the output devices can be reduced as excess voltage is kept to a minimum. The amplifier that is fed with these rails itself can be of any class. These kinds of amplifiers are more complex, and are mainly used for specialized applications, such as very high-power units. Also, Class E and Class F amplifiers are commonly described in literature for radio frequencies applications where efficiency of the traditional classes deviate substantially from their ideal values. These classes use harmonic tuning of their output networks to achieve higher efficiency and can be considered a subset of Class C due to their conduction angle characteristics.

[jheis]

Thanks fritz:

I checked wikipedia right after I posted & think I understand the differences between class A and AB and how they work.

I haven't found anything, however, on how a class A predriver works in conjunction with a class AB output stage. I'm guessing that this may mean that the amp is designed to operate as class A at low power (clean 1st watt?) and AB at higher power?

James

[J M O N]

....Well all have different wants, needs and above all ears. What sounds good to you is good. Taking any one persons opinion as fact is a recipe for failure in audio. Just too many variables.

I couldn't agree with you more.

[joshnich]

....Well all have different wants, needs and above all ears. What sounds good to you is good. Taking any one persons opinion as fact is a recipe for failure in audio. Just too many variables.

I couldn't agree with you more.

Don't think anyone would disagree with that. I do think that folks should take the opportunity to hear what they can before choosing and to disregard preconceived notions on what various topology's can and cannot do.

Josh

[joshnich]

The wonderful aspect of high effeceincy horns is that no real tangible reasons exist too limit your use to a pure Class A amplifier (except maybe to brag that your amp is pure class A). With well design A/B push pull amps you rarely ever going to push the amps out of Class A operation so why not take advantage of the benefits of the other classes of operation too improve efficiency, decrease size, increase power, or improve the life of output devices, or all three. When you have 60W or 100W or 300W it doesn't mean you have to use it!! So when you only need a dozen or so watts the other well designed topologies will deliver the Class A at a much lower cost of ownership with the side benefit that you can shake the walls down for those let your hair down moments. Why limit the versatility of your system??

Craig

I think the "tangible" reason is better sounding music at all listening levels.[]

Josh

Well Josh it wasn't all that long ago that you thought bridging a pair of stereo MC225 in mono of CLASS B per channel was the end all be all []

Dont know if I thought it was the end all but I certainly thought they sounded great . And no I am not selling my macs anytime soon!

Josh

[scott0527]

I believe this is a discussion about Class A against amps of other topologies, tube, SS or whatever and I for the darned of me can not find one single direct derogatory word spoke in this thread about Pcats or any where else for that matter..............

Craig

I did mention that they were rather large[]

[pauln]

"...With well design A/B push pull amps you rarely ever going to push the amps out of Class A operation..."

Craig

I know some A/B amps are specifically

designed to operate at low levels in class A, then move to A/B as

needed... but you're suggesting that A/B amps as a class do this? If

so, this does not match the general idea that A/B at low levels is more

prone to crossover distortion...?

[Deang]

http://www.aikenamps.com/ClassA.htm

[NOSValves]

Dean,

That article is kind of a "read between the lines" kind of thing. It could really confuse the novice. It was written from a guitar amplifier standpoint so while much of the information is transferable. If it was written from a Hi Fi audio amplifier standpoint it would read very differently because different objectives are in rule of the day. Guitar amplifiers are a different world all together.

Craig

[Deang]

I understand that, but it's still one of the better articles written that explains the principles of operation between the classes. As a novice myself as far as amps go, the question I asked after reading all that was: What real advantage is there in running Class A if you're still using a phase splitter? See, told you I was a novice.

[NOSValves]

"...With well design A/B push pull amps you rarely ever going to push the amps out of Class A operation..."

Craig

I know some A/B amps are specifically designed to operate at low levels in class A, then move to A/B as needed... but you're suggesting that A/B amps as a class do this? If so, this does not match the general idea that A/B at low levels is more prone to crossover distortion...?

Well that would depend on the amp and what the designer did with it. My amps for instance run in class too nearly 20 watts in ultra linear and about 10 in triode mode. Yes VRD's are biased on the class A side of the AB envelop. This is why I say us Klipsch users will just about never push them out of class A you would have to be a real head banger in the very large room.

My entire point in this thread is the difference in the sound of one amplifier to another can not be attributed solely on the class of operation, triode, ultra linear and so on. So many other variables to take into account and in the end its more the preference of the amps designer and him putting his personal touch to the voicing the amps.

The perfect amp for every listener does not exist. Some amps are clearly better then others in every respect. But by the same token some are just different then the next. Many wonderful sounding amps exist on the market and I'm absolutely sure the Pcat's would be considered one of them. Would the Pcat's float my boat? From what I have read so far I doubt it. Would I think they were horrible......absolutely not.

Josh obviously loves what he is hearing and I have no problem with that. But the great thing in this situation for me with Josh is I can get a very keen idea as to if I would like the sound. I have rebuilt some 5 or 6 different amps for Josh and garnished pretty detailed opinions and comparisons on them all. In just about all cases his opinion and ratings are the exact opposite of mine about which one he likes the best and why. So that would lead me to believe that he prefers a very different sound then I do. Is he wrong...... absolutely not. You can not be wrong in your preferences to what you like in audio it's literally impossible. I can sit back to myself and say that person is nuts and to me that person would be........but that is based on my preferences to the sound.

Craig

[NOSValves]

Dean,

Advantages and disavantage exist in every mode of operation. It's all about trade offs and limiting the effects. In the end no absolutes exist and it just gets down to personal preference.

Craig