Amp/Preamp Asylum

Looking for a new Amp or Preamp? If you're after tubes, post over here.

Return to Amp/Preamp Asylum


Message Sort: Post Order or Asylum Reverse Threaded

Class ab and class a

65.92.231.166

Posted on March 29, 2022 at 07:31:08
itolduso1000timesb4
Audiophile

Posts: 190
Location: Canada
Joined: March 7, 2018
Would a very powerful high quality Class ab amp driving efficient speakers at high enough volume in a 30 ft. x 12 ft. X 8 ft. room remain in class a most of the time?

Please stay real and reasonable here.

Thanks.

 

Hide full thread outline!
    ...
RE: Class ab and class a, posted on March 29, 2022 at 08:47:29
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
That depends, we need more details such as efficiency of the speakers, and the Bias of the amp. ie how many watts it puts out before going from A to A/B. For example, in my room, 19 x 23 x 8 my Pass INT-60 (A first 30 watts) never went into A/B with my 100 db speakers. My CODA CSiB is biased for the first 18 watts to be class A. I doubt it goes into A/B very often, if at all for me. With other speakers it may be different.
Jack

 

RE: Class ab and class a, posted on March 29, 2022 at 08:57:23
Tre'
Industry Professional

Posts: 16105
Location: So. Cal.
Joined: February 9, 2002
A/B amplifiers operate in A/B, not A.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Class ab and class a, posted on March 29, 2022 at 09:32:03
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
Some (many?) can be biased so that the first few watts are in class A.
Jack

 

first few, posted on March 29, 2022 at 09:42:11
Story
Audiophile

Posts: 6239
Location: NJ
Joined: December 11, 2000
that's paltry and insignificant. You could say that most AB amps do that



 

RE: first few, posted on March 29, 2022 at 10:02:13
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
Again, it depends on how they are biased, as I said in my previous post.
The first few can be quite a few actually. Did you read my other response to the OP?
Jack

 

yes I did, posted on March 29, 2022 at 10:11:30
Story
Audiophile

Posts: 6239
Location: NJ
Joined: December 11, 2000
and ONLY if you have high efficiency speakers that only need a few watts will it make a difference - you may not even enter AB that way. I know this because I used to have horns. I now live with electrostats and I'm quite happy with them



 

I agree completely, posted on March 29, 2022 at 10:25:16
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
I am assuming the OP is inquiring about a similar situation.
FWIW, I went from electrostats to horns.
Jack

 

RE: Class ab and class a, posted on March 29, 2022 at 10:27:25
itolduso1000timesb4
Audiophile

Posts: 190
Location: Canada
Joined: March 7, 2018
So naim never existed I guess.

 

RE: I agree completely, posted on March 29, 2022 at 10:32:30
Story
Audiophile

Posts: 6239
Location: NJ
Joined: December 11, 2000
nice to meet you Jack, I had both for many years but eventually settled down with the love of almost a lifetime, my Uncle's Quad 57's



 

What speakers? (nt), posted on March 29, 2022 at 10:43:08
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
.

 

RE: What speakers? (nt), posted on March 29, 2022 at 10:47:55
itolduso1000timesb4
Audiophile

Posts: 190
Location: Canada
Joined: March 7, 2018
Rega RS 10.

 

RE: What speakers? (nt), posted on March 29, 2022 at 11:07:30
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
Deceptive specs.
Tweeter sensitivity = 88db. no other sensitivity given.
There's a good chance you'll be in A/B territory on any A A/B amp. Not that that's necessarily bad. If you want Class A, you will have to go A all the way.
Jack

 

RE: What speakers? (nt), posted on March 29, 2022 at 11:24:41
itolduso1000timesb4
Audiophile

Posts: 190
Location: Canada
Joined: March 7, 2018
Deceptive specs, a British trait I fear.

 

It depends on the amp manufacturer, posted on March 29, 2022 at 11:38:08
AbeCollins
Audiophile

Posts: 40808
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
...and it depends on your speakers.

One telltale sign of how an amp is biased is to measure its idle power consumption from the AC mains. Class AB amps that are more 'heavily biased' toward Class A will draw more power sitting there doing nothing vs an AB amp that is less biased toward Class A. And of course a true Class A amp might draw several hundred watts from the AC mains and run rather warm sitting idle.

Why doesn't every Class AB amp manufacturer bias their amps more toward Class A operations? Because it is expensive. The more the amp transistors remains in the conduction region the more power they draw while idle. The more continuous power these amps draw the larger the power transformer and heat sinks need to be in order to dissipate the extra (wasted) heat.

Some examples

My meager 30 wpc Pass Labs Aleph 3 amp drew nearly 250-watts from the AC mains not even playing music. It ran somewhat hot.

The Class AB 150 wpc Pass Labs X150.8 draws 370 watts from the AC mains at idle. That's a lot for an AB amp. On the other hand the Class AB 150 wpc Odyssey Stratos draws only 30 watts from the AC mains at idle. These are both "150 wpc amps" yet the Pass draws over 10x the power from the AC mains while sitting idle.

Specs above taken from each manufacturers webpages.

I've owned Class A, AB, C, and Class D amps. Class C was my RF amplifier for single sideband reduced carrier operation - Ham Radio stuff.

The link below shows a table of Pass Labs Class AB amps and approx how many Watts they produce in the Class A region vs Class AB.


 

The Pass Labs X600.5 runs 90 watts class A, posted on March 29, 2022 at 12:10:59
E-Stat
Audiophile

Posts: 33786
Joined: May 12, 2000
Contributor
  Since:
April 5, 2002
or almost one-seventh its rated AB output.

 

You could try the Pass INT-60, posted on March 29, 2022 at 12:22:09
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
As I said, 60 watts, the first 30 are class A.
You don't give a price range.
Jack

 

I have a pure class A SS, no chips, posted on March 29, 2022 at 12:40:07
Story
Audiophile

Posts: 6239
Location: NJ
Joined: December 11, 2000
it's a nary heard of Kinergetics KBA 75 and the E bills are climbing a bit more now and will get even worse. Believe it or not my Quad amp with the current dumping is dam close and the current draw is much less.



 

RE: Class ab and class a, posted on March 29, 2022 at 17:45:43
Tre'
Industry Professional

Posts: 16105
Location: So. Cal.
Joined: February 9, 2002
Unless it has sliding bias the output devices in a Class A/B are never "biased in the middle of the most linear part of the dynamic operating curve".

Since biasing in the middle of the most linear part of the dynamic operating curve is what gives Class A it's advantages (one being of the lack of generated harmonic distortion) I don't see how any of the power generated in a Class A/B amplifier can be called Class A.

The output devices in a Class A/B amplifier are idling (biased) and operating down in the non-linear "cutoff region". A region purposefully avoided in any good Class A design.

Class A/B is it's own thing. It is not a Class A amplifier that becomes a Class B amplifier when more power is needed. That would be an amplifier that uses sliding bias.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Parasound JC1+ has selectable bias, posted on March 29, 2022 at 19:42:20
voolston
Audiophile

Posts: 3146
Location: New Orleans
Joined: October 14, 1999
In the high setting, it's 25 watts of class A. As to the OP's question, I think the answer is yes - assuming the sensitivity of the speakers is high enough to allow it to happen. I do base my comment on believing some AB amps can output some watts in true class A.

The info you posted on the wattage draw of the Pass and the Odyssey is interesting. Is that Pass biased heavily into class A?

voolston - audiophile by day, music lover by night

 

RE: It depends on the amp manufacturer, posted on March 29, 2022 at 19:58:26
Utley1
Audiophile

Posts: 1535
Location: NYC
Joined: July 30, 2010
Very well explained ! Thank you! So there is no such thing as simply 'idling away' with a class A amp.

 

RE: Class ab and class a, posted on March 29, 2022 at 20:29:40
Tre'
Industry Professional

Posts: 16105
Location: So. Cal.
Joined: February 9, 2002
The output devices in a Class A/B amplifier are biased a little bit on. This is to prevent crossover distortion. Because of that there is a time, for the first few watts, that they don't reach cutoff.

That is not Class A operation. Class A operation is much more than just not reaching cutoff.

Again, a Class A/B amplifier operates in what is called Class A/B. Not A then B or A then A/B but A/B. A/B is it's own thing.

The original question should have been, "How many watts can I get from my A/B amplifier before the outputs start to reach cutoff". That would have been a proper question.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Class ab and class a, posted on March 30, 2022 at 04:28:08
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
Perhaps it is a sliding bias, I don't know. As I said, Nelson Pass claims the Int-60 puts out 60 watts, with the first being class A, before switching to A/B. You can take it up with him. No one said anything about class B. Other manufacturers do similar, though not as extreme.
Jack

 

There's a big difference, posted on March 30, 2022 at 06:33:15
airtime
Audiophile

Posts: 11135
Location: Arizona
Joined: February 4, 2003
The Pass INT-60 cost about $10k.

I think Tre knows what he's talking about. It would be more wise to pick his brain on the topic.

 

I was unaware price was involved. , posted on March 30, 2022 at 07:41:25
Jack G
Audiophile

Posts: 9522
Joined: September 24, 1999
And I do respect Tre.
Jack

 

RE: Parasound JC1+ has selectable bias, posted on March 30, 2022 at 09:17:21
AbeCollins
Audiophile

Posts: 40808
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
Yes, even though both the Pass and Odyssey are "150-wpc" amps, I find it interesting that the Pass draws 370-watts of power from the AC mains while idle whereas the Odyssey draws 30-watts. That tells me that the Pass is more 'heavily biased' toward Class A operation.

Anyone can do this little experiment with a home power meter. Measure the power draw of your amplifier while it's sitting idle not playing music.




 

RE: It depends on the amp manufacturer, posted on March 30, 2022 at 09:26:36
AbeCollins
Audiophile

Posts: 40808
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
In Class A operation the output transistor is biased in the middle of its load line and it is never driven into cut-off or saturation. It conducts current over the entire 360 degrees of the signal input cycle. The transistor is always ON and drawing a huge amount of power whether there is an input signal present or not.



 

Its not important!, posted on March 30, 2022 at 10:52:13
Ralph
Manufacturer

Posts: 4384
Location: Minnesota
Joined: April 24, 2002
The reason to run class A is to place the output devices in their most linear region, thus reducing distortion.

Its not really to eliminate crossover distortion, should the design be Push-pull. The reason is that as long as the amplifier is properly biased, there simply will be no crossover distortion; if there were, the amp would not be class AB but simply class B.

Transistors in particular (unless your amp uses Static Induction Transistors, also known as VFETs) are not all that linear, so unless you jump through some serious hoops to produce a zero feedback amp (such as Ayre) the amp will have feedback to improve linearity.

As soon as feedback is in the picture you have an entirely different can of worms! If feedback is used in insufficient amounts (less than 30dB-35dB) it will generate audible distortion of its own thru its application. If you look at the schematic of a tube or solid state amp using feedback you can see one reason why- the feedback point is applied to a device (such as one transistor of a differential amplifier) which has linearity issues of its own, meaning that the feedback signal isn't being seen by the amp in an undistorted way. This causes the generation of higher ordered harmonics thru bifurcation in the said device (which might also be a tube).

You may notice at this point that we are well off into the weeds- class A having little to do with it! It is helpful to have the amp make as little distortion as possible prior to the inclusion of the feedback though.

Put another way, this issue of feedback has to be solved if you really want to get down to the nub of it. To do that, the amp has to have two things:

1) a nice high Gain Bandwidth Product, such that the amp can support 35dB or more of feedback. If the amp does not have the GBP, the feedback will decrease as frequency rises, causing distortion to increase, thus contributing to brightness and harshness (since the ear assigns this tonality to the higher ordered harmonics)

2) The amp must have a lack of high frequency poles that cause phase shift; if it does not the feedback will be limited by something called the 'phase margin' of the amp where at some high frequency the phase (caused by those pesky poles I just mentioned) will become so shifted that the feedback is positive rather than negative- and that results in oscillation. This can and does limit how much feedback you can run!!

There are very few traditional solid state designs (meaning: not class D) that are capable of this and there are no tube amps whatsoever capable of this.

By this time you can see that the class of operation is still not a major player... unless the amp uses no feedback at all!

Class D offers a way around this, by allowing you to run so much feedback that the amp oscillates as soon as you turn it on, and then that oscillation is used as the switching frequency. In this way you can run 35dB of feedback and satisfy the requirements I laid out earlier.

Put another way, don't sweat it.

 

So, what about Class ADH?, posted on March 30, 2022 at 18:30:54
Freo-1
Audiophile

Posts: 891
Location: Florida
Joined: June 14, 2008
This approach seems like the best of both worlds. The voltage is Class A, while the current is sourced via Class D. The measurements achieved with this approach are outstanding. It looks like a variation of the current dumping approach.

The DAC being integrated into the ADH amp also helps. No interconnects required. I'm surprised no one else has tried to emulate this topology.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)

 

RE: Class ab and class a, posted on March 31, 2022 at 04:23:47
cawson@onetel.com
Audiophile

Posts: 2060
Joined: September 27, 2004
I wonder why so many people seem obsessed with the technology their amplifier uses to meet the simple objective of recreating the sound as close to the original performance as possible.

I really don't care if my amp is powered by valves or transistors, is Class A or B or Z, or whether it uses feedback or whatever the individual designers see fit - I choose on how well it produces the music through my speakers - with a bias towards amps that are environmentally reasonably friendly.

As it happened when I decided to search for an SS amp to replace my earlier SETs, I home demo's a dozen amps of various technologies just by listening to the music they produced and comparing notes with others invited to comment. I ended up with a Purifi Eigentakt Class D amp, although I had expected others to "win", probably a Class A one.

 

If my amps ran...., posted on March 31, 2022 at 07:14:10
AbeCollins
Audiophile

Posts: 40808
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002

If my Class A amp didn't run hot as hell I'd want my money back !!

If my Class D amp ran hot as hell I'd want my money back !!

If my Op-Amps didn't have incredible GBP I'd want my money back !!





 

RE: Its not important!, posted on March 31, 2022 at 07:41:11
Tre'
Industry Professional

Posts: 16105
Location: So. Cal.
Joined: February 9, 2002
"The reason to run class A is to place the output devices in their most linear region, thus reducing distortion."

I don't disagree with the rest of what you said but putting all of that aside, a Class A/B amplifier never "places the output devices in their most linear region, thus reducing distortion" so none of the output power produced by a Class A/B amplifier can properly be called Class A.

And that was my only point.

My point was meant to be very narrow. Not a statement meant to predict how an amplifier might sound, etc.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

ADH isn't a class, like class A or D, its a marketing thing with a trademark, posted on March 31, 2022 at 09:11:51
Ralph
Manufacturer

Posts: 4384
Location: Minnesota
Joined: April 24, 2002
I took a look at the website where they push this idea.

There's a lot of misinformation. I'm guessing its written by the marketing department, by someone not having a grasp of the actual engineering.

The most obvious example is stating that a class D amp is digital and conflating the two. Class D amps are analog and employ switching. They are not digital; if there is a digital amplifier its not class D. Just so we're clear on that.

Its an interesting idea but one question coming to mind right away is since the class D is providing the current, it therefore has to be providing the voltage as well, so the class A portion would be doing nothing! So I have to assume that the explanation is simply incorrect.

 

Back in the old days, posted on March 31, 2022 at 09:14:08
Ralph
Manufacturer

Posts: 4384
Location: Minnesota
Joined: April 24, 2002
opamps didn't have all that much GBP, and so they had a 'sound' if you asked too much gain of them. So certain guitar effect pedals have these earlier opamps, and if you want them to sound right, you have to seek out those older semiconductors.

Totally FWIW dept...

 

RE: ADH isn't a class, like class A or D, its a marketing thing with a trademark, posted on March 31, 2022 at 09:25:16
Freo-1
Audiophile

Posts: 891
Location: Florida
Joined: June 14, 2008
I think it's more involved than that. I get the fact that Class D is analog, but when the engineers demonstrated the amp, they disconnected the Class D section, and just use the Class A portion. That only outputs a few watts. The claim is that the Class D provides the current, while the Class A supplies the voltage. It does seem like the Class A does switch the current source.

No other amp I'm aware of uses this approach. I can report that it sounds outstanding, and seems to have lots of power.

I'm not sure how it actually works, but it sure sounds better than most any setup I've come across. I agree the write up is likely written by marketing, but I think the approach is unique, to be sure.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)

 

Not contesting that the amp works, but go look at their website; you'll see it is indeed a trademark, posted on March 31, 2022 at 10:02:48
Ralph
Manufacturer

Posts: 4384
Location: Minnesota
Joined: April 24, 2002
and not an actual class of operation.

Here is the power formula (which is an extraction of Ohm's Law):

1 Watt= 1 Volt times 1 Amp

From this you can see that if you have a voltage, you also have an amperage. The two cannot be separated, else you cause a new branch of physics!

So if you are driving an 8 Ohm speaker with 10 watts (solving for current first):

10 = 8 times the current squared.

Thus the current is about 1.12 Amps. That means the voltage is about 8.93 Volts. Quite literally you can't have one without the other. I don't know what those 'engineers' did but they didn't switch back and forth between just current and just voltage.

Again, I'm not contesting how the amp sounds nor that it works. I am contesting the explanations I've seen, which fly in the face of basic electrical laws.

 

"which fly in the face of basic electrical laws." Yup! nt, posted on March 31, 2022 at 10:31:18
Tre'
Industry Professional

Posts: 16105
Location: So. Cal.
Joined: February 9, 2002
.
Have Fun and Enjoy the Music
"Still Working the Problem"

 

This sounds like a variation of the QUAD "current dumping" amp topology, posted on March 31, 2022 at 10:41:06
Steve O
Audiophile

Posts: 11255
Location: SE MI
Joined: September 6, 2001
There are two amps: a high power but lower accuracy amp and a low power but very hi accuracy amp. The low power amp is driven with a correction signal and it's output is added to the output of the high power amp such that the combined output is as precise as that of the low power amp alone. Or something like that. I've heard it described as a form of feed-forward.

 

current dumping, posted on March 31, 2022 at 12:07:56
Story
Audiophile

Posts: 6239
Location: NJ
Joined: December 11, 2000
Peter Walker must have been born on another planet. I have Quad 57's and a current dumping amp for the quads as well as a few different amps.

I remember something like the low power amp is class A driving 2 class C amps, one + the other - , and the waveform put together to then drive the speaker. That's a lousy explanation and I forget how it's done exactly but it sounds quite good. If I also remember correctly, he also invented tertiary windings on output transformers that was later used by McIntosh but received no credit for that.

I once mailed Quad across the pond for help restoring my Uncle's 1957 57's and he personally mailed me guidance and original picture manual of the Quads and how to update them. Back then at 21 Y.O. I didn't recognize the significance of that, what can I say.

edit - I was wrong, it's 2 class B sections not class C



 

RE: Not contesting that the amp works, but go look at their website; you'll see it is indeed a trademark, posted on March 31, 2022 at 14:20:23
Freo-1
Audiophile

Posts: 891
Location: Florida
Joined: June 14, 2008
Understand your point. They are not very clear on how it actually works.

I think Steve O is onto something with the current dumping/feed forward concept. I had read that one of the Devialet engineers at a demonstration initially played a track with only the Class A amp, then connected the Class D stage.

However it actually works, can't argue with the results. Would have thought by now some other manufacturers would have come up with a similar approach. Maybe it's because it's trademarked?
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)

 

RE: Back in the old days, posted on March 31, 2022 at 17:32:51
AbeCollins
Audiophile

Posts: 40808
Location: USA
Joined: June 22, 2001
Contributor
  Since:
February 2, 2002
That's interesting about guitar pedals. My first IC op-amp experiments as a hobbyist was with the Fairchild uA741 which was probably the most popular of all time.

I still have a few books on the topic and some are probably classics in the field but I was just a hobbyist [ham radio and related] so who knows.

IC op-amp Cookbook by Walter G. Jung, 1974.

Active Filter Cookbook by Don Lancaster, 1975.

Op-Amp Handbook 2nd Edition by Fredrick W. Hughes, 1986.

Transducer Interfacing Handbook by Analog Devices, 1981 [about transducers, signal conditioning and IC op-amp instrumentation amplifiers].

Forest Mims III had a series of "Engineer's Notebooks" and other short topic books on various practical projects. I think Don Lancaster had a CMOS Cookbook. I lost all of those during a move.



 

FWIW etc, posted on March 31, 2022 at 20:39:23
Steve O
Audiophile

Posts: 11255
Location: SE MI
Joined: September 6, 2001
Best sound I ever got out of my partially refurbed 57s was with a passive attenuator driving a pair of completely refurbed Quad II tube amps. Never seriously tried them with anything solid state.

 

Highly informative, thanks -nt, posted on April 1, 2022 at 04:56:30
Feanor
Audiophile

Posts: 7760
Location: London, Ontario
Joined: June 17, 2003
Contributor
  Since:
March 12, 2004
nt



Dmitri Shostakovich

 

RE: FWIW etc, posted on April 1, 2022 at 07:03:06
Story
Audiophile

Posts: 6239
Location: NJ
Joined: December 11, 2000
over the last 40 years of playing music thru them with different amps, they can be extremely revealing. Back then I tried a Phase Linear 400 through them and that was bad. The usual import receiver with loads of feedback was bad. I don't know anybody local with Quad tube amps, my Uncle had a Dynaco Stereo 70 and I have a few different including Mark III's.

Quads have euphonic qualities, at least the 57's. They also throw a wide spacious soundstage beyond the left and right and have a good sense of depth. You can't tell where the mid/tweeter panel is, even with my plain speaker cloth and metal screen long gone. Revealing of sources, yes, so much so that deficiencies in recordings are plainly evident. My quest is over except for music where the money should go.



 

Bet that sounded great!, posted on April 1, 2022 at 07:36:22
Freo-1
Audiophile

Posts: 891
Location: Florida
Joined: June 14, 2008
NT
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)

 

RE: It depends on the amp manufacturer, posted on April 1, 2022 at 12:17:49
itolduso1000timesb4
Audiophile

Posts: 190
Location: Canada
Joined: March 7, 2018
Thanks! I will have to read that again taking my time to take in all that information.

 

RE: You could try the Pass INT-60, posted on April 1, 2022 at 12:28:12
itolduso1000timesb4
Audiophile

Posts: 190
Location: Canada
Joined: March 7, 2018
That was a typo. Someone brought to my attention that the booklet with the product correctly states the efficiency of the speakers is 88 db.

 

RE: Class ab and class a, posted on April 2, 2022 at 21:02:09
LtMandella
Audiophile

Posts: 2074
Location: CA
Joined: May 27, 2019
well said.
Good luck though convincing 99% of the audiophile world though :)

Don't wrestle with pigs. You both get dirty and the pig likes it.
Mark Twain

 

Thanks, it's called the "dumbing down". Even the websites..., posted on April 3, 2022 at 10:43:33
Tre'
Industry Professional

Posts: 16105
Location: So. Cal.
Joined: February 9, 2002
that talk about the so called "Class A" part of AB operation then turn around and say this,

"Notice how the current fluctuations in a proper Class A amplifier are always centered around the mid-point, that 50% of maximum which is the same as the idle current."


Someone needs to put 2 and 2 together.

"In Class A, the current swings are always centered around that mid-point idle current which is 50% of maximum. This is called "biased around the mid-point of the linear region". That's vital for low distortion. The other classes of operation, Class B and Class AB are definitely not biased anywhere near that mid-point "

That is correct, AB is biased in the non-linear cutoff region.

Or this website that first says

"As we said above, the Class AB Amplifier is a combination of Classes A and B in that for small power outputs the amplifier operates as a class A amplifier but changes to a class B amplifier for larger current outputs."

And then says

"For Class A amplifier operation the switching transistors Q-point is located near to the centre of the output characteristic load line of the transistor and within the linear region."

Sorry but you can't have it both ways. Class A amps never operate in the non-linear cutoff region unless they are being over driven, Class AB amplifiers can't help but operate in the non-linear cutoff region because the output devices are idling (biased) there.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Thanks Ralph., posted on April 16, 2022 at 05:21:06
jusbe
Audiophile

Posts: 5925
Location: North Island
Joined: April 4, 2000
Nice explanation, neatly put.

I always enjoyed zero-feedback SET amps (which I hope to try again soonish) and am now hugely enjoying my Class D Marantz Reference PM-10 a great deal.


Big J

"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."


 

Page processed in 0.038 seconds.