Re: Class A vs. Class A/B Tube Amps?

Ether <ether@xxxxxxxxxx> wrote:
RichL wrote:
Rick N. Backer <ken.wilson@xxxxxxxxxxxxx> wrote:
On Thu, 24 Jan 2008 04:12:08 -0600, "Elvis Kabong"
<ampscience@xxxxxxxxxxxx> did courageously avow:

"Rick N. Backer" <ken.wilson@xxxxxxxxxxxxx> wrote in message
On Wed, 23 Jan 2008 16:49:58 -0800 (PST), Premier Spigot
<bighorseshoebob@xxxxxxxxx> did courageously avow:

On Jan 21, 8:53 pm, Rick N. Backer <ken.wil...@xxxxxxxxxxxxx>
On Sun, 20 Jan 2008 21:07:37 -0500, "Phil S."
<psymonds_no_s...@xxxxxxxxxxx> did courageously avow:

"tmread" <tmr...@xxxxxxxxxxxxxxx> wrote in message
Can anyone explain what the difference between a Class A amp
and a Class
A/B? I looking online and getting confused.

The way i understand it is class A run hot, needs tubes
replaced more often and are not very powerful. but not really
sure how they sound.

Class A/B on the other hard are very dynamic sounding and have
lots of
punch. they are more powerful and are very stable.

Any one else want to comment?

This is the stuff of flame wars. You can Google this NG for
extensive discussion.

Here is my oversimplied and over opinionated summary. No guitar
amp (notice
I said "guitar amp") can operate in Class A 100% of the time.
It drops into
AB when driven to clipping (and that is the overdriven sound
you can hear.)

Not so. Mesa Lone Star Special runs Class A at 5W, 15W, or 30W
through 1, 2 or 4 tubes respectively.

Ken Wilson Hide quoted text -

- Show quoted text -

Learn a new chord. Until you get a handle on what is actually
occurring within the switching schemes and how the circuit is
changing the operation of the tubes, you are only aiding the
marketing hype. Don't like it? Sorry. It's a GREAT sounding amp,
but I hate to burst you & Randall's bubble, but it ~ain't~
running that hot in all modes. How do I know? I have *actually*
had to work on & measure things. Get some test equip. & measure.

And you are who? Randall has designed and sold many amps. Your
claim to fame is ...

Ken Wilson

And so has Jim Marshall and Leo Fender, but that doesn't mean
the Spigot cat doesn't know what he's talking about.
Did you try measuring as he suggested?

I'm a player. Not a tech. All I care about is that this is one of
the best amps I have heard in a while. My understanding of Class A
is the tube is never off but, rather, is idling using up about 1/2
the juice it can handle. Which explains the power reduction in a
single-ended Class A amp. The Lone Star Special uses 1 EL 84 for
5W, 2 for 15 and 4 for 30. That and given Randall's technical
explanation which ships with the amp, makes it, in my mind,
reasonable to accept what he's saying.

Is there ever any point at which these tubes are not juiced while
their counterpart in the corresponding pair isn't? Now, as far as
harmonics go, I will admit that a Class A running tubes in pairs is
not the same as Class A on a single-ended setup.

If the amp were running purely in Class A with one power tube (5 W)
*and* two power tubes (15 W), I'd expect the power in the latter to
be double that in the former. Since it isn't (according to their own
ratings), it makes me suspicious, at least.

No kidding. Funny that the 15 watts and 30 watts are exactly what the
Vox AC15 and AC30 produce with the same tube lineup--in Class AB1.

Gotta say it. That's the most sense you've made all either

Criticize the post, not the poster; the art, not the artist.
"War is over...if you want it." It starts with you.


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