White cathode follower speaker amps/preamps?

[Dusty Chalk]

From another thread:

or variant thereof then certainly covers it, as it is

still the white cathode follower design.

How about speaker amps, are there any speaker amps that follow this design? How about preamps? Is there a corresponding solid state design? Perhaps with MOSFETs?

[guzziguy]

google is your friend however

http://www.cavalliaudio.com/cj/docs/WCFOptimization.pdf

Tube CAD Journal: Tube regulators part 2, July 1999

and page 3 right after it. IMPORTANT read page 3

lots more about wcf at the tubecad site.

And should another manufacturer make such a headphone amplifier, then you

absolutely should listen to it. Why no one does may have to do with some

of the conclusions of john broksie at the tubecad site.

The capacitors thing is stupid to the extreme. If you were driving argon gas lasers

which is what those juice cans are really designed for, then great. But for a headphone

amplifier whose output power is 1 watt or less, those things are TEN THOUSAND

times overkill. Capable of 25 amperes peak each. You show me a headphone that

can take 25 amperes.

As far as speaker amps, this circuit just does not apply.

Now as to preamps, i do recall that someone did a preamp with a

WCF as the output stage.

I'll answer the other questions in the other thread in an hour or 2.

Added KG's post about this in the "Colorado" thread because its information is valuable here.

[kevin gilmore]

Can you use a mosfet as a WCF. The answer is clearly yes.

But why would you want to? The output impedance of a tube

is very high, and WCF is a trick to lower the output impedance.

The output impedance of a mosfet is very low, and no tricks

are necessary.

Now if you want to know what the closest thing is to a WCF

as solid state, the answer to that is simple. Nelson Pass.

Whose power amp designs really can be considered an upside

down WCF.

Both are single ended designs with an active current source.

A standard WCF has no voltage gain, an inverted WCF has

significant voltage gain.

[Dusty Chalk]

Can you use a mosfet as a WCF. The answer is clearly yes.

But why would you want to?

(shrugs) I don't know -- because asking stupid questions sometimes surprises me with good answers.

Now if you want to know what the closest thing is to a WCF

as solid state, the answer to that is simple. Nelson Pass.

Whose power amp designs really can be considered an upside

down WCF.

That makes perfect sense, I love what I've heard of Nelson Pass designed amps.

Thanks for the info. Will read that tubecad.com stuff offline.