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Re: lateral mosfets vs. bjts in audio amplifier design

E

Eeyore

Jan said:
Care to tell me why graphic equalisers are crap?
I wrote one that seems to work just fine (actually copied some of that code
from xine).
Click to expand...

Do you want me to write a lecture ?


Graham
 
E

Eeyore

Jan said:
So far so good.


That remains to be seen, 'hearing' is for the largest part the processing in the brain.
Now that makes me wonder ....


Now it gets really bad, dinner was burned?


You decisively won the unpopularity contest again.


I wonder, if any of your customers put up with all that.
You are not involved in sales I guess.

Sales person: Our engineer says: "To me you're simply a deaf **** and competely irrelevant.'
That will do it.
Print it on the front of your amps.
Click to expand...

Well, I'm in high demand in the audio sector (amongst others).

There must be SOME reaon for that whether it it be my intellect, hearing or both.

Graham
 
E

Eeyore

You've been reduced to that level have you ?

Yes, a GREAT way to denigrate a superior designer. Let's see how many believe you since AFAIK
you never desisigned a commercial audio power amp that can regulsrly be found on ebay.

Graham
 
K

Kevin Aylward

Eeyore said:
Ditto. It's crazy to throw away that advantage.



Indeed so. Mind you, I actually *limited* my LF gain because it was
so huge already ! It didn't need any more. THD didn't start to climb
on the 1200B design until about 2-3 kHz. Knowing what I do now, I'm
sure I could do better than that. This was 20 years ago you know.
Click to expand...

Yeah, I was only a young pup at 21 in 1982. Obviously the err.. new bit in
the mosfet 1000 was err.. my idea to include the extra emitter follower
buffer from the hitachi design. It took me 3 weeks to realise this rather
obvious bit, for subtle reasons. Like:

Consider adding more and more output devices. Say the nchan is 600pf gate
souce, with 40pf gdrain. So, ignore the 40pf as an approximation. Now actual
capacitance is approx Cgs/(gmRL) and now inconvieniantly forget that the
approximation is now suspect with this new value. Now mentally keep adding
|| devices without actually doing the bloody sums...like oh.. gm goes up
with cap.. so er..net cap stays the same...me thinks, so drive current and
gain loading stays the say, ...f&**S*&^% forgot the approximation of Cgd now
fails and keeps adding on right on up there...


Kevin Aylward
www.kevinaylward.co.uk
www.blonddee.co.uk
www.anasoft.co.uk - SuperSpice
 
K

Kevin Aylward

John said:
With the qualifier "a bit of", sure. So there are now, and never have
been, any original circuits.


Like diff pairs, current mirrors, cascodes, are all the same

To get extreme performance, and to sell things for big multiples of
cost, you have to do something new and take some risks. The risks
should be concentrated only in the places where there is payoff. The
scut stuff, power supplies and firmware and cooling and simple
controls, should indeed be as low risk as possible.

YES.

Incremental fiddling of existing technology is a good way to get
bare-survival levels of margin, and even that takes luck.
YES


There are two variables in that relationship, not one. Moderate risk
could produce big profits. Everything fun is risky.
Click to expand...

Like shagging you best mates wife...indeed.
There are no

Yours, maybe. Not mine. I hate to copy circuits, even my own.
Click to expand...

I don't. I will use anything if it works,and can be shown to be reliable.


Kevin Aylward
www.kevinaylward.co.uk
www.blonddee.co.uk
www.anasoft.co.uk - SuperSpice
 
K

Kevin Aylward

Yes it is, but I truly don't have the time to through this all over again..
Have a read of
http://www.kevinaylward.co.uk/replicators/intelligence.html, especially at
the end of the page.
In the dim recesses of time, an idea flashed into being which was
unique and was fleshed out electromechanically into our being here,
now, so _that_ circuit wasn't stolen.

On a more mundane level, some of us work through the problems of
design without resorting to directly infringing the work of others,
whether that prior work exists or not.
Click to expand...

No. See link above.


Kevin Aylward
www.kevinaylward.co.uk
www.blonddee.co.uk
www.anasoft.co.uk - SuperSpice
 
K

Kevin Aylward

Eeyore said:
I thought he was wrong about that. I confess I didn't look it up
again at the time but my 1200B does exactly the same as your approach
Kevin.

Graham
Click to expand...

Indeed. ALWAYS use full push pull source and sink. Resisters and current
sources are just not as good. The exception is probably when you are doing
extremely fast comparators when its a good idea to never let currents cut of
to zero. The difference in these cases is that the amp is designed for non
clipping use, the comparators for clipping!

Kevin Aylward
www.kevinaylward.co.uk
www.blonddee.co.uk
www.anasoft.co.uk - SuperSpice
 
R

Rich Grise

On a sunny day (Thu, 23 Oct 2008 18:44:33 +0100) it happened Eeyore


Yes they are not hifi.
But I bought them for acoustic experiments, like chasing away rabbits.
Click to expand...

If you want to keep rabbits out of your garden, then have the family use
a chamber pot, and pour its contents (liquid only!) around the perimeter
of the garden - it sends an odor signal: "Large Carnivore Lives Here!"

Good Luck!
Rich
 
R

Rich Grise

Well, I'm in high demand in the audio sector (amongst others).

There must be SOME reaon for that whether it it be my intellect, hearing
or both.
Click to expand...

Audiophoolery?

Thanks,
Rich
 
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