On Sat, 31 Mar 2007 11:33:40 +0100, Eeyore
wrote:

Stunningly bizarre!

John

John Larkin wrote:

Eeyore wrote:

Stunningly bizarre!

Do elaborate. I know the circuit very well actually. I've improved it hugely in
a series of amplifiers I designed also using the 'grounded collector'
arrangement.

Graham

On Sat, 31 Mar 2007 18:07:26 +0100, Eeyore
wrote:



John Larkin wrote:

Eeyore wrote:

Stunningly bizarre!

Do elaborate. I know the circuit very well actually. I've improved it hugely in
a series of amplifiers I designed also using the 'grounded collector'
arrangement.

Graham

Where to begin?

Is this amp supposed to be based on the patent you posted? It isn't.

The output stage is magnificently twisted, just to implement a silly
and inefficient transistor protection scheme. The same algorithm could
be implemented much more quantitatively with a few opamps and diodes,
off the side of the main signal path instead of all tangled with it.

Beta-dependent design sucks.

Way too many parts. Must be hell to work on.

Before-feedback output impedance must be insane, leading to
interesting dynamics.


I've seen this phenom elsewhere. Somebody gets an idea, falls in love
with it, and bends the entire design around it, usually badly.

I like to protect transistors by digitizing their voltages and
currents, and the heatsink temperature, running a realtime thermal
simulation, and limiting *junction temperature*.

John

John Larkin wrote:

Eeyore wrote:
John Larkin wrote:
Eeyore wrote:

Stunningly bizarre!

Do elaborate. I know the circuit very well actually. I've improved it hugely in
a series of amplifiers I designed also using the 'grounded collector'
arrangement.

Where to begin?

Is this amp supposed to be based on the patent you posted? It isn't.

The patent relates to a protection method, not the amplifier design. This amplifier
does indeed use that protection method.


The output stage is magnificently twisted, just to implement a silly
and inefficient transistor protection scheme.

Actually it's done that way for a completely different reason AIUI.


The same algorithm could be implemented much more quantitatively with a few opamps
and diodes, off the side of the main signal path instead of all tangled with it.

Do go on.


Beta-dependent design sucks.

I agree. Those trimpots are loathesome.


Way too many parts. Must be hell to work on.

It actually has a far lower parts count than most amplifiers of that variety.


Before-feedback output impedance must be insane, leading to
interesting dynamics.

Uhuh. It's variable shall we say ?


I've seen this phenom elsewhere. Somebody gets an idea, falls in love
with it, and bends the entire design around it, usually badly.

It was Pat Quilter's trademark for ages. They've finally adopted emitter followers
now.


I like to protect transistors by digitizing their voltages and
currents, and the heatsink temperature, running a realtime thermal
simulation, and limiting *junction temperature*.

Digitising ? That's not going to be cheap.

Graham

On Sat, 31 Mar 2007 18:51:09 +0100, Eeyore
wrote:


I've seen this phenom elsewhere. Somebody gets an idea, falls in love
with it, and bends the entire design around it, usually badly.

It was Pat Quilter's trademark for ages. They've finally adopted emitter followers
now.


Horray! Give them another 20 years, and they may discover fets!


I like to protect transistors by digitizing their voltages and
currents, and the heatsink temperature, running a realtime thermal
simulation, and limiting *junction temperature*.

Digitising ? That's not going to be cheap.

Digitizing is cheap, especially when it lets you safely get, say,
twice the usable power from a given mass of transistors and heatsinks.

John