Safe Operating Area calculation for audio power amps

[Pooh Bear]

Phil Allison wrote:

"Pooh Bear"
Phil Allison wrote:

To repeat though. Have you taken the lid off a real MOSPEC MJ to compare
die size. ? Would be interested to know the result and any general
comments
you might have about MOSPEC parts.


** Try reading what I posted already:

" They seem however to be using older die designs than the current MJ
ones
and doing the mounting in the package a bit less well. "

Now - how do you reckon I know that ??


I did get that bit.

** But like most things - it did not sink in ??

I was hoping you might elaborate. And you did - cheers.

I'm surprised that the die design has significantly changed
on a mature device like that though.


** Yawn - shows how far out of touch you are.

Can I assume you're happy with die size then ?

** Same size and design as all MJ15003/4s sold up till the late 1990s.

If anything, it seems that semi makers are keen to reduce die size.

** Die size is not a reliable guide to power rating or overall quality.

It certainly plays a part ( in power rating ) though. Simple thermal resistance
assures that. In the same way that a copper slug in a TO-3 can helps power
rating too.

I have a collection of 2N3055s where the variation in area spans a range of
5:1. The smallest is the Motorola one - known to be a good example of the
beast.

Interesting. Do you have the dims ?

I've heard apochryphally that the die in a
2SC5200 is smaller than the 2SC3281 for example despite the outwardly
similar
spec.

** Quite possible - IME.

There was a big change in the MJ15024/25 chips a few years back -
Motorola initially used the new number, MJ21193/4 for the revised design.
Then, as they often do, reverted back to the familiar number. You can buy
both numbers now - exactly the same insides however. MJ21193/4s will cost
you more though.

The MJ21193/4 chip are identical to the ones inside the plastic
JL21193/4s - plastic packs cannot normally use chips designed for TO3
packs - that is how the new design came about. Now, one size fits all

Yes - that issue caught my eye. More interestingly On's 'indicative pricing' for
the higher dissipation rated TO-3 is significantly less than the TO-3P. At least
it was when I last looked.

Kinda blows a colleauge's theory that " *everyone* want plastic 'cos it's
cheaper " out of the water !

Over the last 20 years, Motorola has sold the MJ15003 device badged as a
2N3773, MJ 802 and others. Similarly the MJ15003 has be badged as an MJ4502
and several others - with a price hike attached !!

Seems Motorola figure that any device that equals or exceeds the basic
specs of another can be sold as that other !! Plays havoc with trying to
match up new and old devices in parallel sets - "your problem" says
Motorola.

Had similar issues with RCA devices in 1980.

Genuine MJ802/4502 pairs will give lower THD figures in amps than the later
MJ15003/4s - or if the rebadged ones are fitted. Lots of traps for the
innocent.

All interesting stuff. Thanks for that Phil.

BTW

If you follow EW magazine, you will be aware of Doug Self's " blameless "
amplifier design that nobody who has tried can duplicate the same
vanishingly low THD figures.

How vanishing btw ? I admit I haven't seen it.

I've a ( mosfet ) design ( from 1990 ) that measures 0.0008% THD+N @ 1 kHz @
600W / 4 ohms ( AP residual is 0.0007% ! ). And yes the decimal point's in the
right place - i.e. -102dB SINAD - better if you discount the test set residual.

In the fine print of the article, Doug says he used devices from his
private stash of old (and therefore genuine) MJ802/4502s in the prototypes.

QED.

I've heard that Doug has a high opinion of himself too.... Most of the stuff
I've seen of his is basically 'old hat' dressed up so he can look important.

Incidentally we both interviewed ( amongst others ) for a position as Graham
Blyth's 'sidekick' at Soundcraft many years ago ( I didn't know the other guy
was Doug until someone told me yrs later ). He got the position by blagging that
he *knew* microprocessors so I've been told. I took my time a little more before
adopting them for practical designs.


Graham

 

[Phil Allison]

"Pooh Bear"

Phil Allison wrote:

I have a collection of 2N3055s where the variation in area spans a range
of
5:1. The smallest is the Motorola one - known to be a good example of
the
beast.

Interesting. Do you have the dims ?

** Yep - got a whole bag full of TO3s sans lids.


EGs

Motorola 2N3055, born circa 1978, area = 5.2 sq mm.

ITT brand 2N3055, born circa 1977, area = 19.4 sq mm

Motorola MJ15003, born circa 1980, area = 25 sq mm.


BTW

I also have a Hitachi 2SK176 mosfet with a neat, 2.5mm dia hole burnt
through the top of the lid !!

Wanna guess how that happened ?




............. Phil

 

[Pooh Bear]

Phil Allison wrote:

"Pooh Bear"
Phil Allison wrote:

I have a collection of 2N3055s where the variation in area spans a range
of
5:1. The smallest is the Motorola one - known to be a good example of
the
beast.

Interesting. Do you have the dims ?


** Yep - got a whole bag full of TO3s sans lids.

EGs

Motorola 2N3055, born circa 1978, area = 5.2 sq mm.

Maybe it wasn't just the fact they were epitaxial that made them go pop so
easily then ?

Sloppy JEDEC spec to blame on the process issue.

ITT brand 2N3055, born circa 1977, area = 19.4 sq mm

Motorola MJ15003, born circa 1980, area = 25 sq mm.

That sounds like the beast I know.

BTW

I also have a Hitachi 2SK176 mosfet with a neat, 2.5mm dia hole burnt
through the top of the lid !!

Wanna guess how that happened ?

I've heard of this happening but never seen one in person.

All the Hitachi TO-3s I've seen failed were simply open circuit with no visible
damage.

Hmmm.. I wonder if it's related to the device orientation ?

I'll guess something to do with the die bonding / bonding wire(s). Just a guess
though. Does the die unsolder itself from the header perchance or something
equally esoteric ?


Graham

 

[Phil Allison]

"Pooh Bear"

I have a collection of 2N3055s where the variation in area spans a
range
of 5:1. The smallest is the Motorola one - known to be a good
example of
the beast.

Interesting. Do you have the dims ?


** Yep - got a whole bag full of TO3s sans lids.

EGs

Motorola 2N3055, born circa 1978, area = 5.2 sq mm.

Maybe it wasn't just the fact they were epitaxial that made them go pop so
easily then ?

** The "them" is ambiguous.

Does it mean the Motorola 2N3055 of 1978 ?

Or all Motorola 2N3055s ?

Or all 2N3055s ??

Sloppy JEDEC spec to blame on the process issue.

** More Excreta Bear fucking egomaniac gobbledegook

I also have a Hitachi 2SK176 mosfet with a neat, 2.5mm dia hole burnt
through the top of the lid !!

Wanna guess how that happened ?

** Simple DC arcing from the head of the drain pin ( at + 115 volts ) to
the nearest part of the case - burns away until a hole is created. A
direct consequence of the drain bonding wire vaporising while the amp has a
near short on the output.




............. Phil

 

[Pooh Bear]

Phil Allison wrote:

"Pooh Bear"

I have a collection of 2N3055s where the variation in area spans a
range
of 5:1. The smallest is the Motorola one - known to be a good
example of
the beast.

Interesting. Do you have the dims ?


** Yep - got a whole bag full of TO3s sans lids.

EGs

Motorola 2N3055, born circa 1978, area = 5.2 sq mm.

Maybe it wasn't just the fact they were epitaxial that made them go pop so
easily then ?


** The "them" is ambiguous.

Does it mean the Motorola 2N3055 of 1978 ?

Or all Motorola 2N3055s ?

2N3055s made by an epitaxial process ( notably by Motorola ) had a smaller SOA
than competing devices made ( notably by RCA ) that were single diffused ( lower
fT but larger SOA ).

2N3442s suffered similarly IIRC.

Or all 2N3055s ??

Sloppy JEDEC spec to blame on the process issue.

** More Excreta Bear fucking egomaniac gobbledegook

Not at all. There was talk of introducing a 2N3055H spec to cover the RCA style
part.

By that time my interest in such low voltage devices was limited so I'm not sure
how it was eventually resolved.

I also have a Hitachi 2SK176 mosfet with a neat, 2.5mm dia hole burnt
through the top of the lid !!

Wanna guess how that happened ?


** Simple DC arcing from the head of the drain pin ( at + 115 volts ) to
the nearest part of the case - burns away until a hole is created. A
direct consequence of the drain bonding wire vaporising while the amp has a
near short on the output.

Ok, so I got the bit about the bonding wire being involved.

With hindsight I realise I've seen this happen with an MJ in TO-3 too. Sure
looks bizarre.


Graham

 

[Phil Allison]

"Pooh Bear"


** Fuck off you stinking pommy psychopath.





................ Phil

 

[Mike Harding]

On Sun, 6 Feb 2005 17:45:57 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

"Pooh Bear"


** Fuck off you stinking pommy psychopath.

Pooh Bear!!!

I'll not have this!!!

I'm the only (according to the great Phyllis) _true_ "stinking
pommy psychopath" around here - please don't tread on
my toes

Mike Harding

 

[Phil Allison]

"Mike Harding"

I'm the only _true_ "stinking pommy psychopath" around here - please don't
tread on
my toes

** Useless lumps of human garbage are Pommyland's main export.

Don't go feeling special about it when you are one of millions.





............... Phil

 

[Johnny]

On Sun, 06 Feb 2005 01:37:57 +0000, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:

In the fine print of the article, Doug says he used devices from his
private stash of old (and therefore genuine) MJ802/4502s in the prototypes.

QED.

I've heard that Doug has a high opinion of himself too.... Most of the stuff
I've seen of his is basically 'old hat' dressed up so he can look important.

I think that making small improvements on traditional designs and
accurately documenting them, leads to much more advancement in the
science than others who claim to produce something new, which actually
is a sideways step with lots of hype attached.

Doug is very good at producing technically reasoned designs that are
based on traditional practices, he is also quite an effective writer
which I think helps his cause. If you want to produce a BOM with many
more components, I believe it is possible to get better performance
with error-correcting type output stages, and other compliciations in
many areas of audio design. But for commercially viable designs,
Doug's work is a typically a great place to start IMO.

regards,
Johnny.

 

[Mike Harding]

On Sun, 6 Feb 2005 18:29:51 +1100, "Phil Allison"
<philallison@tpg.com.au> wrote:

I'm the only _true_ "stinking pommy psychopath" around here - please don't
tread on my toes

** Useless lumps of human garbage are Pommyland's main export.

Don't go feeling special about it when you are one of millions.

Selective quoting if ever I saw it Phyllis!

And a bit racist too, if I may say. Actually, Phyllis, I'm
toying with the idea of hitting you with an action under one
or other of the racial vilification acts - I'm advised I'm in
with a fair chance and I thought it might be an interesting
test case if I can get "the powers that be" to take it up.
CLUTZ think there's a distinct possibility. And that might
put you in clink Phyllis

Mike Harding

 

[Phil Allison]

"Mike Harding"
"Phil Allison"

I'm the only _true_ "stinking pommy psychopath" around here - please
don't
tread on my toes

** Useless lumps of human garbage are Pommyland's main export.

Don't go feeling special about it when you are one of millions.


And a bit racist too, if I may say.

** Since when are pommies a race ???

What a crazy moron.



............. Phil

 

[Pooh Bear]

Johnny wrote:

On Sun, 06 Feb 2005 01:37:57 +0000, Pooh Bear
rabbitsfriendsandrelations@hotmail.com> wrote:

In the fine print of the article, Doug says he used devices from his
private stash of old (and therefore genuine) MJ802/4502s in the prototypes.

QED.

I've heard that Doug has a high opinion of himself too.... Most of the stuff
I've seen of his is basically 'old hat' dressed up so he can look important.

I think that making small improvements on traditional designs and
accurately documenting them, leads to much more advancement in the
science than others who claim to produce something new, which actually
is a sideways step with lots of hype attached.

I can think of one design method I've used that isn't a radical redesign of a
topology but a new approach to stability compensation that markedly improves
in-band performance. Is that the kind of thing you meant ?

To be honest I doubt there's much new in power amp design any more.

I hate hype too.

Doug is very good at producing technically reasoned designs that are
based on traditional practices, he is also quite an effective writer
which I think helps his cause. If you want to produce a BOM with many
more components, I believe it is possible to get better performance
with error-correcting type output stages, and other compliciations in
many areas of audio design. But for commercially viable designs,
Doug's work is a typically a great place to start IMO.

A reasonable comment.

I've seen one notable example of one of Doug's commercial design ( Soundcraft
Spirit Powerstation - at least I'm told it was he who designed it ) and he happilly
throws the frilly bits out of the window.

Designers are rarely able to expound their art fully in the commercial audio arena
in which I operate.


Graham

 

[Pooh Bear]

Mike Harding wrote:

On Sun, 6 Feb 2005 17:45:57 +1100, "Phil Allison"
philallison@tpg.com.au> wrote:


"Pooh Bear"


** Fuck off you stinking pommy psychopath.

Pooh Bear!!!

I'll not have this!!!

I'm the only (according to the great Phyllis) _true_ "stinking
pommy psychopath" around here - please don't tread on
my toes

OK Mike - you're the boss ! ;-)

 

[Pooh Bear]

Phil Allison wrote:

"Pooh Bear"

** Fuck off you stinking pommy psychopath.

What an intruiging response to a fully detailed reply.

I think your post counts as *OFF TOPIC* btw !


Graham

 

[Phil Allison]

"Pooh Bear" = pommy bastard, puke puke.

Johnny wrote:

I can think of one design method I've used that isn't a radical redesign
of a
topology but a new approach to stability compensation that markedly
improves
in-band performance. Is that the kind of thing you meant ?

** How CAN he know when you did not explain what the hell you meant ???

WANKER !!!!

To be honest I doubt there's much new in power amp design any more.

** Pooh Face has not got a single honest bone in his Neanderthal head.

I hate hype too.

** POOH ADORES HYPE !!!!

His posts are full of nothing but public masturbation.

I've seen one notable example of one of Doug's commercial design (
Soundcraft
Spirit Powerstation - at least I'm told it was he who designed it ) and he
happilly
throws the frilly bits out of the window.

** Good design is completely invisible to a moron like Pooh Face.

Never forget - the fat pommy prick was a fucking DJ !!!!!!!!!!

Designers are rarely able to expound their art fully in the commercial
audio arena
in which I operate.

** ROTFLMAO

Pooh face is not a a designer's backside.

Graham

** Who ????????????????????????


An anonymous troll, a criminal liar, a friend to all and sundry scumbags
and sicko a usenet stalker is all we know.




................ Phil

 

[Alan Rutlidge]

"Mike Harding" <mike_harding@nixspam.fastmail.fm> wrote in message
news:trgb015mv868diad1aqu54dlspuh3kn9v1@4ax.com...

On Sun, 6 Feb 2005 17:45:57 +1100, "Phil Allison"
philallison@tpg.com.au> wrote:


"Pooh Bear"


** Fuck off you stinking pommy psychopath.

Pooh Bear!!!

I'll not have this!!!

I'm the only (according to the great Phyllis) _true_ "stinking
pommy psychopath" around here - please don't tread on
my toes

Mike Harding

Mike,

I see your "mate" Phil is having an attack of the Tourette's again.

Cheers,
Alan