New mosfet amp from ESP

[Christer]

Originally posted by millwood



Rod is in the business of making money by marketing to the diy community. Do you think he would sell any boards if he had designed a 'sophisticated' amp with 2 million transistors?

I doubt that.

Well, Randy Slone is also in the business of selling PCBs and
kits, and his amps often adress all or most of the issues PMA
brought up. Of course, he also makes money from writing
books, which might be his main income.

[millwood]

Originally posted by PMA
OK. I am not argueing. Just expressed my point of view.

I understood that and was just trying to bring some different perspective to the discussion.

[millwood]

Originally posted by Christer


Well, Randy Slone is also in the business of selling PCBs and
kits, and his amps often adress all or most of the issues PMA
brought up.

maybe they are targetting different segments of the market? Sloan more on the high-end / experienced and Rod on the low-end / entry-level?

To be fair, Sloan does have some fairly "elementory" designs in his book as well.

[Christer]

Originally posted by Nelson Pass
Other things aside, I don't agree with using a resistor for
the bias voltage when it is not fed by a constant current
source. With the bootstrapped loading, the quiescent current
becomes a function of the supply rails, so anyone building this
should use a well regulated supply.

Do you mean it is only in combination with bootstrapping you
don't like the method, or do you want a CCS anyway? I am
asking since most or all designs I have seen that use lateral
MOSFETs use only a bias resistor without a CCS, but none of
them has been bootstrapped, I think.

[millwood]

Originally posted by Christer
I am asking since most or all designs I have seen that use lateral MOSFETs use only a bias resistor without a CCS, but none of them has been bootstrapped, I think.

probably becuase bootstrps went out of fashion in the 1970s, .

I have simulated quite a few circuits with bootstraps and they actually work very well in terms of performance, stability and distortion figures. I will re-run my version of citation 12 tonight which uses a bootstrap and the current variations though the bootstrap is like 0.01ma on ~40ma bias, if I recall correctly.

[Christer]

Originally posted by millwood
To be fair, Sloan does have some fairly "elementory" designs in his book as well.

That's true, but to some extent for pedagogical reasons, I think,
and to make it possible to start by building a very simple amp.
I am not sure if he sells/used to sell PCBs for all of the designs
in the book, though. It is also true, that some of the points
PMA listed are not considered a problem by Slone except in
certain cases. It is mostly his more powerful amps that seem
to address all of those points.

I am also not sure how much he cares about selling PCBs and
kits nowadays. I think somebody mentioned his Optimos design
has gone into commercial production.

[Christer]

Originally posted by millwood

probably becuase bootstrps went out of fashion in the 1970s, .

Yes, few designs use it nowadays, which is why I wondered if
it was the bootstrapping that worried Nelson, or the general
idea of a bias resistor.

[richwalters]

Hi there.....and I'm the fella who spends most of my time doing the mosamp repairs....the circuit configuration on all these amps hasn't really changed from the very day they came on the market......... I'm a severe critic of all the faults that time hasn't ironed out with busted mosfets/trannies, overheating with short frilly heatsinks and sloppy biassing techniques..the very stuff tubes grin over...

I've replaced so many complementary output pairs with other types that no-one even prof'ies could tell a difference in the sound...

Viva.... tubes anyday.

rich

[millwood]

about bootstrap going out of fashion. I suspect it may have a lot to do with cheap transistors and our inability to integrate capcitors into silicon.

If transistors were still $1k a piece, I am sure we would all be priasing bootstraps as the greatest invention since sliced bread,

[Christer]

Originally posted by richwalters
Hi there.....and I'm the fella who spends most of my time doing the mosamp repairs....the circuit configuration on all these amps hasn't really changed from the very day they came on the market......... I'm a severe critic of all the faults that time hasn't ironed out with busted mosfets/trannies, overheating with short frilly heatsinks and sloppy biassing techniques..the very stuff tubes grin over...

Have you had a high failure rate also for amps with lateral
MOSFETs? Due to their negative temp. coefficient above some
low Id, they are basically supposed to protect themselves
which I guess is why usually only a resistor is used for biasing.
Since you seem to have seen a lot of blown amps, your
"statistics"on this would be interesting to hear.