pass labs xa30 to valve amplifier.

It's a confusing amp to rate for some folks.

Pass rates it as 30wpc class A. It's pure class A for 30wpc.

Stereophile got about 40wpc class A from it in their review IIRC.

Past 40wpc, their amp moved into class A/B operation. It didn't clip until it reached about 130wpc/8 ohms IIRC. So some folks feel it should be rated as a 130wpc amp that does 30wpc class A.

So it is pure class A for its entire rated power of 30wpc.

Pass has an article on their site titled "Leaving Class A" that explains it in more detail:

https://passlabs.com/articles/leaving-class-a

We get a lot of questions about this. A typical email reads, “I can’t sleep at night – I keep worrying about where my amplifier stops being Class A. As I listen to my system, I think I can hear the Klunk as the special Class A part of the amplifier kicks in and out!”

For starters, there is no special Class A circuit that kicks in and out, and for that matter, there certainly is no Klunk. There is just a push-pull amplifier output stage which is operated at a constant idle current known as the bias. In this regard, our power amplifiers are like other amplifiers on the market. The vast majority of amplifiers are push-pull designs with a certain amount of bias current.

Push-pull amplifiers generally operate in Class A mode up to a point where the output current is twice the value of the bias current. In the Class A region, both halves of the circuit share the signal simultaneously. Beyond that the signal is handled solely by the push (+) half of the amplifier or the pull (-) half.

There amps that never leave Class A? For some reason, I think my CAT JL2 worked that way, but not sure if that is even possible. Techheads?

Thanks. Thats very interesting. The amount of sound it produces, it certainly sounds far more powerful than 30 watts.

I'm no tech-head by any means, but the published sensitivity should take into account the power eaten up by the crossover, BUT the x-over can produce those impedance dips and large phase angles that make a speaker "difficult to drive" as Magfan wrote. Applying this to the OP's question, does anyone have a link to an impedance and phase angle vs frequency curve for the Zingalis?

Hi everyone. From some of the responses here, it seems the pass xa30.5 has greater power output than 30 watts. i am still looking at valve amplifiers am aware now that a move to valve amplification may be, at best, a sideways move. Im hoping to hear a few products to judge. Am i right in thinking a 30 watt valve amplifier would not have the same volume output as the xa30.5, even though both are rated at 30 watts ( the pass very conservatativly, it seems). i am considering low powered tiode amps ( i understand they sound better) How are low powered valve amps with regard to slam and attack with clarity?
When a valve blows, can speakers be damaged? Sorry for all the questions, but i rather get some further background into valve amplification. i have picked up some very useful pointers here and thank everyone for their input.