<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by firebird1999us</i>
<br />...thing over at Harmonycentral.com:
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">This is what Orange told me about Orange amps being Class A.
A lot of people think of single-ended operation as being solely 'Class A' because this is a common configuration. However a push-pull configuration can run in Class A as well.
The AD30 is truly Class A circuitry. 'Class A' refers to the circuit design so that the grid-bias voltage is set to approximately one-half the cutoff voltage to obtain linear operation. The peak signal voltage at the control grid will not exceed the DC grid-bias voltage. The control grid is not permitted to go positive and plate current flows at all times. That is 'Class A' by definition. Class A amplifiers operate on about 20% efficiency and reproduce sound at a very high quality.
It is also operating in a Push-Pull configuration, to achieve maximum output voltage swing of each tube. It is also operating in a parallel configuration, whereas two pairs of tubes operating in push-pull configuration are running parallel to each other, allowing the power of four EL84 tubes to be twice that of using two.
<b>The way these amps are biased is what gives them their unique playing characteristics. You'll notice that the sound seems to compress as you play harder/ louder. This is because the bias is variable and changes as signal is applied to the tubes, giving you pseudo-compression like qualities, which is what gives these amps their "feel".</b><hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">Oh how I wish they'd try saying all that at The Gear Page Technical Amp Forum... [:p]
1/ It isn't purely the circuit <i>design</i> that defines the class of operation. It is also how it is operating!
2/ As I explained here:
http://forum.orangeamps.com/viewtopic.p ... hichpage=1
...(in 'Noddy terms' as requested), operation class does make a difference to how cathode biasing works!
<b>The last para quoted above, (in bold), is
1) Absolutely true!
2) Totally misleading!</b>
It is true of a cathode biasing circuit running in <u>class A/B</u>! It definitely wouldn't happen in class A running though because:
Constant overall current in the power valves ---> no bias adjustment response to varying input signal ---> <b>None</b> (= 0.0%) of that lovely compression.
<b>They are <i>implying</i> that means the amps are biased in Class A. That is a bit sneaky. It actually means they aren't!
<u>I really <i>do</i> wish they'd try saying that stuff on TGP</u>... </b>
Andy.
PS: Chris, sorry but I'm officially not interested in this subject any more. 'Class A' is such a minefield of mis conceptions and mis information that I have <i>much</i> better things to do then react each and every time someone mentions it. Especially when most people - quite sensibly - couldn't give a monkeys as to the real truth of it all.
When folk ask I'm probably just going to link to stuff. I've written <u>plenty</u> already!
Most people asking the questions lose interest when they get the answers. I've lost interest because I've given them too often. I'm not trying to put Orange or any other companies down, I just wish they'd stop being misleading. <b>That</b> is what really bugs me about this whole subject.
[/Rant] [/Interest]
[Over and out!]
Only dimly aware of existence, a dimly existing awareness...
You get a wonderful view from the point of no return.
:D:D:D:D