Experiences of Class A solid-state ?
 

On Tue, 17 Oct 2006 07:27:51 +0100, Eeyore
wrote:



Don Pearce wrote:

"Bret Ludwig" wrote:
Trevor Wilson wrote:
"Dave Plowman (News)" wrote in message
Eeyore wrote:
Have you ever spent any time listening to a true Class A solid state
amplifiers ?

Yes. A mate drove his ESLs with a Sugden. One of the cleanest sounding
systems I've ever heard. Wouldn't shake the windows, though. ;-)

**Sugdens have never built pure Class A amps (whatever that means). They
have only ever built high bias Class A/B designs. And, of course, Class A is
only Class A when specified into a particular load impedance. Usually 8
Ohms. Given the fact that ESLs vary all over the map, impedance-wise,
suggesting that the amp is Class A is even less likely.

This is actually true.

High bias AB amps operate in class A through most of the power range
they spend all their time in, giving the advantage of Calss A operation
where it is needed, and rather than running out of power when this is
exceeded they simply transition into Class B.

So-called experts, and their toadies and asskissers (such as
Jeboo-selling Randy Slone) have pounded on the idea that Class AB is a
poor design methodology because of "transconductance doubling".
Obviously this is nonexistant in the region of Class A operation.

Do you mean nonexistent in the region of class B operation? It is
class A that provides the transconductance doubling because there are
two active devices operating in parallel.

I'm concerned about the transconductance 'modulation' with signal level since this
introduces non-linearity.

Graham

That would be greatest in the transition region between class A and
class B.

d

--
Pearce Consulting
http://www.pearce.uk.com

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Experiences of Class A solid-state ?
 

Don Pearce wrote:

Eeyore wrote:
Don Pearce wrote:
"Bret Ludwig" wrote:
Trevor Wilson wrote:
"Dave Plowman (News)" wrote in message
Eeyore wrote:
Have you ever spent any time listening to a true Class A solid state
amplifiers ?

Yes. A mate drove his ESLs with a Sugden. One of the cleanest sounding
systems I've ever heard. Wouldn't shake the windows, though. ;-)

**Sugdens have never built pure Class A amps (whatever that means). They
have only ever built high bias Class A/B designs. And, of course, Class A is
only Class A when specified into a particular load impedance. Usually 8
Ohms. Given the fact that ESLs vary all over the map, impedance-wise,
suggesting that the amp is Class A is even less likely.

This is actually true.

High bias AB amps operate in class A through most of the power range
they spend all their time in, giving the advantage of Calss A operation
where it is needed, and rather than running out of power when this is
exceeded they simply transition into Class B.

So-called experts, and their toadies and asskissers (such as
Jeboo-selling Randy Slone) have pounded on the idea that Class AB is a
poor design methodology because of "transconductance doubling".
Obviously this is nonexistant in the region of Class A operation.

Do you mean nonexistent in the region of class B operation? It is
class A that provides the transconductance doubling because there are
two active devices operating in parallel.

I'm concerned about the transconductance 'modulation' with signal level since this
introduces non-linearity.

Graham

That would be greatest in the transition region between class A and
class B.

Exactly spot-on Don and readily visible when looking at a distortion analyser's output.
This is why Trevor's ideas baffle me.

My intention is to entirely eliminate this with a kind of 'hybrid' output stage.


Graham

Experiences of Class A solid-state ?
 

Eeyore wrote:
Geoff wrote:

Eeyore wrote:
Have you ever spent any time listening to a true Class A solid state
amplifiers ?

Any comments on how it sounded compared to any other types ?

Hotter ?

I can't remember the models - it was a while ago. Only audible
difference to me was that the AB one sounded harsher when louder.

Not too surprising.

But the Class A
ampcouldn't actually get that loud anyway, so not fair comparison I
guess.

Did you notice any differences at lower levels ?

Subtle, and not that couldn't be explained by pyschological factors. Not
blind, let alone 'double'.

geoff

Experiences of Class A solid-state ?
 

"Eeyore"


** Transistor car radios made in the 1960s were class A.

They had a 2N301 or similar TO3 pack Germanium PNP power transistor for
output, fed with 12 volts via an iron cored choke.

The speaker connected directly across the choke - it made a small click
when you did.


It *could* have been capacitively coupled had it been a problem of course.

I just discovered in r.a.t that this has been done for SET outputs.

I had something more modern in mind though.



** No reason why SET cannot refer to Single Ended Transistor - is there
??

The choke protects the speaker from DC and you can still use oodles of NFB.





........ Phil

Experiences of Class A solid-state ?
 

Phil Allison wrote:

"Eeyore"

** Transistor car radios made in the 1960s were class A.

They had a 2N301 or similar TO3 pack Germanium PNP power transistor for
output, fed with 12 volts via an iron cored choke.

The speaker connected directly across the choke - it made a small click
when you did.


It *could* have been capacitively coupled had it been a problem of course.

I just discovered in r.a.t that this has been done for SET outputs.

I had something more modern in mind though.

** No reason why SET cannot refer to Single Ended Transistor - is there
??

LOL ! Since you mention it ! Well spotted Sir.


The choke protects the speaker from DC and you can still use oodles of NFB.

My current ruse is to avoid *any* global NFB. Not because it's important but for
pure marketing bull**** factor.

Graham

Experiences of Class A solid-state ?
 

In article ,
Trevor Wilson wrote:
Yes. A mate drove his ESLs with a Sugden. One of the cleanest sounding
systems I've ever heard. Wouldn't shake the windows, though. ;-)

**Sugdens have never built pure Class A amps (whatever that means).

Well there you go. If you don't know what it means, you can't define it.

They have only ever built high bias Class A/B designs. And, of course,
Class A is only Class A when specified into a particular load
impedance. Usually 8 Ohms. Given the fact that ESLs vary all over the
map, impedance-wise, suggesting that the amp is Class A is even less
likely.

In the terms of the question and accepted meaning it was a Class A amp.

--
*I took an IQ test and the results were negative.

Dave Plowman London SW
To e-mail, change noise into sound.

Experiences of Class A solid-state ?
 

In article m, Mike
Rivers writes

Eeyore wrote:
Have you ever spent any time listening to a true Class A solid state
amplifiers ?

Any comments on how it sounded compared to any other types ?

Amplifiers are amplifiers. Some sound better than others. There's
nothing magic about a Class A amplifier, but it sure sounds good on the
marketing literature. Most people have the good sense to not use a
Class C amplifier for high quality audio.

Anyone ever made a good commercially viable class D amp?...
--
Tony Sayer

Experiences of Class A solid-state ?
 

Eeyore wrote:

Have you ever spent any time listening to a true Class A solid state
amplifiers ?

Any comments on how it sounded compared to any other types ?

I designed one for driving a special load, where I already had awkward
phase shifts in an external feedback system and didn't want anything
unpredictable happening inside the amplifier at frequencies outside the
normal design range.

I can't really help you much with how it sounded, because it drove a
cutterhead for recording wax cylinders and there were quality issues in
the reproducing equipment that completely swamped any subtleties of the
recording chain!


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

Experiences of Class A solid-state ?
 

"tony sayer"

Anyone ever made a good commercially viable class D amp?...



** Crown did that is 1996.

Their K1 and K2 models are class D - both still current.





......... Phil

Experiences of Class A solid-state ?
 

"Dave Plowman (News)" wrote in message
...
In article ,
Trevor Wilson wrote:
Yes. A mate drove his ESLs with a Sugden. One of the cleanest sounding
systems I've ever heard. Wouldn't shake the windows, though. ;-)

**Sugdens have never built pure Class A amps (whatever that means).

Well there you go. If you don't know what it means, you can't define it.

**_I_ can define it, but manufacturers usually stretch theirs. Point is, it
depends on the load impedance.


They have only ever built high bias Class A/B designs. And, of course,
Class A is only Class A when specified into a particular load
impedance. Usually 8 Ohms. Given the fact that ESLs vary all over the
map, impedance-wise, suggesting that the amp is Class A is even less
likely.

In the terms of the question and accepted meaning it was a Class A amp.

**Nope. They only built high bias Class A/B amps. The first Sugden I ever
saw was about 40 Watts/channel. It ran bloody hot and people all said it was
Class A. I didn't believe it, so I tested one at 5 Watts Class A.
Substantial, but not Class A. About 100 times more Class A than most amps of
the time. It was still Class A/B though.


--
Trevor Wilson
www.rageaudio.com.au



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