Which Pass amps scale?

[Fritz]

Im looking for an amp design that can be scaled to higher power output without changing gain and sensitivity characteristics. I need 6 channels in the 30-50 watt range and 2 in the 60-100 watt range. Does anybody know of Pass circuits that scale this way?
I have a ZenV4 underway so big brothers of this would be ideal.

Also any ideas on reducing the total heat output on something like this would be useful. Im not sure 1000+ watts of room heat will be much fun, may have to actively cool it and vent to the window.

Thanks,

Fritz

[nar]

Choose the alephs 3 for the 6 blocks,
and some Alephs 4 for the 2 left.

Gain and sensivity are mostly the
same,let's say 20 dB.Or 26 dB.
you can adjust gain by feedback
resistor.

1000 W are quite a lot for heat to be
rejected in a single listening room.

I suggest you have a separate room
for amplifiers and drill walls to achieve
speaker connections and other wiring.
And seriously think about a proper
ventilation for "the engine's room".
Don't forget to restrict acces to this
particular area

[Petter]

I would go with a Class AB (i.e not Aleph) type as these typically scale much more easily.

You need to have enough gain in input stage, and if you do, you can typically scale to whatever level you need (within reason) based on power supply, heatsinking etc.

Petter

[Fritz]

Apparently Nelson is considering posting an AB design. Does he have any AB designs already? Does anybody do boards based on the Adcom sponsored designs? I know some of the Alephs transition to AB but didnt think he had published any ABs.
A friend referred me to the elliot sound labs amps so I may start there if I go AB.
I do think the heat from the class A is too much at 1KW, not to mention a power draw like a floor sander.

Thanks

[moses]

Perhaps a leach amp would be more practical for that many channels, or one of the ESP projects.

Fritz: All of the X amps operate AB Class once they pass a certain point in power.

[GRollins]

I'm not sure whether the core question was ever answered clearly, so I'll take a whack at it.
All the Alephs (including the Volksamp versions) will scale quite nicely. The Aleph-X will also scale to any reasonable power.
What I'm not quite clear on is why you need to scale the circuit. There are already 30, 60, and 100W versions of the circuit readily available. Just build as many channels as you need.
People tend to get glassy-eyed when you talk about a few hundred watts of heat; as though the paint will melt off the walls or the carpet catch on fire. Ain't so. For perspective, go look at the wattage rating on a hair dryer--most of them are 1000 to 1500W. Ever tried to heat a room with one? Yes, it can be done, but it's hardly enough to turn a normal sized listening room into an oven. Class A amps do create more heat than AB or B amps, but they also sound better.
It's worth it.
Oh, and if you want to reduce the heat...drop back on the bias. Easy. Just make sure you've got enough to drive your intended load.

Grey

[Nelson Pass]

Originally posted by moses
Fritz: All of the X amps operate AB Class once they pass a certain point in power.

Not necessarily. XSOZ for example or versions operating
with constant current sources will not operate AB no matter
how you load them or drive them.

With a push pull follower output stage, as with X600's and
so on, this is the case.

With an Aleph current source, you can run the stages into
shutoff, but they become nonlinear enough that we don't
spec that as valid operation.

[mrfeedback]

"For perspective, go look at the wattage rating on a hair dryer--most of them are 1000 to 1500W. Ever tried to heat a room with one? Yes, it can be done, but it's hardly enough to turn a normal sized listening room into an oven. Class A amps do create more heat than AB or B amps, but they also sound better.
It's worth it."

Electricity here costs AUS13.94c per kWh - I do not leave 1000W (not even 40W) of lamps on if not needed.
These amounts add up, not to mention Greenhouse gases.

Eric.

[moses]

Nelson: Sorry, I wasn't including the non-commerical projects when I was thinking .

[Nelson Pass]

I think it's a matter of what you are willing to pay for
entertainment. I won't take any criticism for a 200 watt
Class A amp from anybody who takes his 70,00 watt
car for a spin.

Particularly if he leaves it idling for several weeks to get
the acceleration character just right.