class A sound

mhardy6647

FTGV wrote: »

heiney9 wrote: »

When someone describes an amp as A/B is does NOT mean it's biased to run in Class A to a point then switches to B.

That is precisely what it means.

No, Mr. H9 is correct; the bias point for a class AB amplifier is intermediate between A and B bias -- and I was wrong way back when having implied (ahem, stated) otherwise.

Amplifier operating class & bias is way easier (for me, at any rate) to understand in the vacuum tube domain (particularly in the context of gee-tar amps) than the soiled state domain.

CLASS AB OPERATION

The Class AB amplifier is one in which the tube conducts for more than half, but less than the entire input cycle.

View B of figure 1-27 depicts an amplifier biased into Class AB operation. Notice that in this application, grid bias has been increased to -9 volts. We will assume that the tube reaches cutoff when the voltage on the grid is -10 volts. Under these conditions, when the input reaches -10 volts, the tube will cut off and stay cut off until the input goes above -10 volts. The tube conducts during the entire duration of the positive alternation and part of the negative alternation. If you remember back in the discussion of distortion, we pointed out that this represents distortion. In some amplifiers, faithful reproduction of the input is not an important requirement. Class AB amplifiers are used only where this distortion can be tolerated.

http://www.tpub.com/neets/book6/20j.htm

This is a pretty good discussion (utterly nontechnical) from a gee-tar amp perspective:
https://musicalilluminism.wordpress.com/2009/05/27/vacuum-tube-operation/

mhardy6647

oh, as usual, Elliott Sound Products (ESP) has a pretty good treatment -- that site is a good one-stop shop for basic info on the nuts and bolts of hifi, IMO (and FWIW).
http://sound.westhost.com/class-a.htm

Also note that Class A vs. AB or B amplifier bias is independent of single-ended vs. push-pull operation, in the sense that a push-pull amp can operate at any bias from A to B at the whim of its designer/builder :-) Single-ended amplifiers (AFAIK), though, operate Class A by definition (unless something goes wrong).

Bias points "colder" than Class A were developed (AFAIK) strictly as a way to increase the operating efficiency (i.e., watts of power from the wall needed for a watt of power delivered to the load) of an amplifier. Changing operating bias alters the spectrum of distortion products of the amplifier considerably -- some of us would probably opine for the worse ;-)

... and this probably goes without saying and/or has been said at his point -- but "class A" is and has always been pretty darned common (though, of course, not ubiquitous) in line-level circuitry (preamps).

FTGV

Mr hardy I regard you as one of the most technically astute folks on this forum and like reading your well mannered and informative posts.However I have to agree with your earlier position.A class A/B amplifier is defined as class A up to it's bias point then transitions to class B.
This guys is a bit of a hack but seems to define it as such. https://passlabs.com/articles/leaving-class-a

mhardy6647

I am a bit of a hack... Nelson Pass... not so much :-)

megasat16

mhardy6647 wrote: »

I am a bit of a hack... Nelson Pass... not so much :-)

What the hell? That looks dangerous! All I can say is stay the hell away from the guy with white hairs and lab power supplies!

FTGV

I am a bit of a hack... Nelson Pass... not so much :-)

Well at least he's a decent hack.
I'm in agreement about Rod Elliotts site.I discovered it about a decade ago and have refered to it many times since and even built a couple of circuits from his project page.

What the hell? That looks dangerous! All I can say is stay the hell away from the guy with white hairs and lab power supplies!

Yeah James he does sort of have that mad scientist look about him,

txcoastal1

FTGV wrote: »

I am a bit of a hack... Nelson Pass... not so much :-)

Well at least he's a decent hack.
I'm in agreement about Rod Elliotts site.I discovered it about a decade ago and have refered to it many times since and even built a couple of circuits from his project page.

What the hell? That looks dangerous! All I can say is stay the hell away from the guy with white hairs and lab power supplies!

Yeah James he does sort of have that mad scientist look about him,

Fred,
We miss you around here. You still have the (rekkid) store as Mr H would say

Your knowledge has always been golden

Cheers

Joey_V

I prefer A, ala Boulder.

But a good class AB amp is still a good class AB amp. A does not necessarily mean it's better than an AB amp... But it probably maxes out that circuit design.

mhardy6647

Class A at my house.

WagnerRC

I went with the AX30.5 and will ship next week. Thanks for all the input and great insight. Great member here for sure.

tonyb

Nice amp man, though you won't be pushing hard to drive speakers with it, it should sound fantastic though. Congrats, can't wait to hear your impressions.

F1nut

Yeah James he does sort of have that mad scientist look about him,

Sort of? He owns the look!

tonyb

F1nut wrote: »

Yeah James he does sort of have that mad scientist look about him,

Sort of? He owns the look!

Well....you haven't seen Russ before he got a haircut. Looked like he came out of one of those slasher movies from the 80's.

mhardy6647

tonyb wrote: »

F1nut wrote: »

Yeah James he does sort of have that mad scientist look about him,

Sort of? He owns the look!

Well....you haven't seen Russ before he got a haircut. Looked like he came out of one of those slasher movies from the 80's.

Do you mean, perhaps, a facecut?
I was thinking maybe he wore a combup instead of a combover, perhaps?

;-)

Typical egocentric aside: If I stopped trimming my beard now... I might manage something like Pete Townshend's 70s look in terms of facial hair after a year or two. ZZ Top-style beard? Never would happen.

lightman1

Dr. H comes out swinging with the jabs!
Top marks, sir!

SCompRacer

Fred, my wife said I needed some so I bought a Class A amp. She said that wasn't the class she was talking about. Any suggestions?

megasat16

FTGV wrote: »

I am a bit of a hack... Nelson Pass... not so much :-)

Well at least he's a decent hack.
I'm in agreement about Rod Elliotts site.I discovered it about a decade ago and have refered to it many times since and even built a couple of circuits from his project page.

What the hell? That looks dangerous! All I can say is stay the hell away from the guy with white hairs and lab power supplies!

Yeah James he does sort of have that mad scientist look about him,

Yep Fred! That photo of him reminds me of Doc from "Back to the Future". He just need to don the lab coat and I'd say he gets the roll.

F1nut wrote: »

Yeah James he does sort of have that mad scientist look about him,

Sort of? He owns the look!

He is au natural!

lightman1 wrote: »

Dr. H comes out swinging with the jabs!
Top marks, sir!

Now, who wants to see lightman shaving his facial hair naked? I recall police were searching door to door for lightman because someone called 911 and reported that they spotted the beast from the x-men!

WagnerRC

Thanks Tony. I am really expecting some great sound paired with the X1 pre. I believe the M6500i will be back on the market. But it won't go anywhere for awhile.

heiney9

If you decide the XA30.5 isn't for you, please give me a heads up before you list it. I would be interested in it.

Looking forward to your review

H9

FTGV

SCompRacer wrote: »

Fred, my wife said I needed some so I bought a Class A amp. She said that wasn't the class she was talking about. Any suggestions?

Merc C class.

halo

Saw this video when it popped up in my mail box and, if you listen closely, there seems to be a slight contradiction with Dan D’Agostino when he discusses taking his 100 wpc class A amp to a reviewer who has a 200 wpc class A amp there as well. Both Dan and the reviewer agree that the 200 wpc class A amp sounds wonderful only to discover it's not a class A amp because it isn't burning Dan's fingers when he touches it.

All of these guys wonder what it's going to take to get young people interested in becoming audio enthusiasts and engineers. Well, a few of them started out poor and hungry and now their gear is priced in the stratosphere where most young people cannot afford it. Wilson brags about making the world's most expensive loudspeaker and then cringes at the thought of looking at things from a "business' perspective. He later goes on to say that you have to give the customers what they want.

As a "young(er)" audio enthusiast I can tell you that some of the stories in this interview of esteemed panelists rubbed me the wrong way. Maybe it's just me but it seems like a lot ofthese guys areout of touch with what young people can afford, especially if you want to draw in new customers (Andrew Jones is on the right path there). That's my $.02. YMMV.

https://youtube.com/watch?v=CrncwM-Ezag

tonyb

There's a market for every price bracket in audio. Thing is, the higher in price you go the smaller the pie is to sell your products to. Diversifying your product line up to have a more vast appeal to various consumers is a way to ensure your company stays in business. That is the name of the game. Look at Polk for a perfect example.

The upper end of Audio, well.....the world has no shortage of rich folks either but that is a much smaller pie in comparison. To be an audio enthusiast one not need be rich or constantly in search of the latest and greatest.

Just like if you were a boating enthusiast. All this talk about 20 million dollar yachts that you will never see. Hard to relate to right ? Wouldn't stop you from trying out deck boats, party boats, ski boats, fishing boats, etc., from various brands that fit your wallet.

Everything is relative, but there is more than enough products in each price category to fit just about any preference and wallet. Listening to a bunch of rich guys wondering why more aren't on their level.....I'd pay little attention to.

megasat16

Technics said screw with Class A.

Here is CLASS AA!

FTGV

megasat16 wrote: »

Technics said screw with Class A.

Here is CLASS AA!

So that means it's twice as good then?
I always liked the look of those Technics amps with the big meters.I see they have re introduced one with them.
http://www.technics.com/us/products/r1/

mhardy6647

No - it (most) likely just means that, whatever bias scheme it uses, it isn't biased to class A operating points (i.e., devices biased to full on, conducting throughout the entire waveform cycle).

EDIT: As with any marketing hyperbole, if it doesn't say "Class A", it isn't. Wasn't Technics the purveyor of "New Class A" ca. 1980? :-)

Doesn't mean it's a good amp or a bad amp, just that it's not an amp operating at class A bias.


http://www.technics.com/us/about/history/

FTGV

I was being facetious.Actually the Class AA ( Sandman like cicuit) is a different beast than the earlier dynamic/sliding bias schemes ie"New Class A" marketed by Technics.And yes the marketing dept. may have been involved with those monikers.

mhardy6647

Thanks for the clarification -- I did, actually, give you the benefit of the doubt.
I just wanted to rag on Panasonic/Technics again, given the opportunity! :-)

Actually, based on brief blurb on the Technics history page, the "AA" amp was probably fairly sophisticated and fairly 'audiophile' for its time.

heiney9

Sophisticated = unusually complicated = degraded sound.








Just playing devil advocate based on owning and hearing the "New Class A" components back in the day.

H9

mhardy6647

Well -- not to be redundant -- but, over the decades, I've become pretty enamored of old Class A... very old Class A :-)

DSC_0124 by Mark Hardy, on Flickr

Circuitry so simple, even I can understand it!

megasat16

Ok' Mr. Hardy! I will raise the bar a little.

The amp is 845 SET but wait it's using SMPS for "experimental" filament heating. In fact, the amp is being upgraded right now and it's in my "LAB" room.

When I am done, it will be a 3 chassis with regulated dc (linear) filament heater with Coleman regulators. Of course, it can use AC heater with a simple flip of the switch.