"Jim Lesurf"

Just to let people know that I've now put up some webpages on Jim Sugden's
original Class A solid state power amps. You can find these via a new link
on the AudioMisc page (URL in my sig below). :-)

I will add more pages on JES as and when I get a chance. Next to be added
will be pages on the Hi Fi News 'home constructor' version of the
amplifiers, and pages on the A41/A51 and their control (pre) amps.

Hope people find the pages of interest.


** Only if they actually ENJOY reading tedious, pseudo technical drivel.

Your page on the A21 is particularly loaded with fallacies and nonsense.

Gullible readers are being expected to believe that 1968 was some kind of
"dark ages" in SS amplifier history, that the available silicon transistors
were of highly inferior quality and designers were all still struggling with
the evil bogey of crossover distortion.

And that class A operation was the answer.


WHAT ******** !!



Eg:

Quad released their famous 303 model way back in 1967 !!

In 1969 it won a Design Council Award.

The 303 delivered 45 watts per channel into 8 ohms loads.

It was short circuit safe.

It used all silicon transistors and exhibited no sign of crossover
distortion.

The power devices used were rugged planar types, RCA 38494s and 40411s.

THD measured at the 1 watt level was circa 0.003% and less than 0.03 % at
rated power - ten times less at both levels than Sugden's woeful A21.

The 303 used regulated PSU and drove the "difficult" ESL57 with ease.

It ran cool with very low idle current in the output devices.

Compared to the Quad 303, Sugden's A21 was a pile of junk.

It is * NO * surprise that a credible magazine like Wireless World failed
to mention its appearance at some 1968 audio fair.

Since it was clearly an embarrassment !!
---------------------------------------------


BTW:

This French page has some good pics of the insides of a Quad 303.

http://cf.geocities.com/quadfranco/a...33/amp303.html

Here is a schematic of the 1970 version.

http://www.geocities.com/quad_esl63/...c/power303.jpg





......... Phil

Quad released their famous 303 model way back in 1967 !!

In 1969 it won a Design Council Award.

The 303 delivered 45 watts per channel into 8 ohms loads.

It was short circuit safe.

It used all silicon transistors and exhibited no sign of crossover
distortion.

The power devices used were rugged planar types, RCA 38494s and 40411s.

THD measured at the 1 watt level was circa 0.003% and less than 0.03 % at
rated power - ten times less at both levels than Sugden's woeful A21.

The 303 used regulated PSU and drove the "difficult" ESL57 with ease.

It ran cool with very low idle current in the output devices.

Compared to the Quad 303, Sugden's A21 was a pile of junk.

It is * NO * surprise that a credible magazine like Wireless World failed
to mention its appearance at some 1968 audio fair.

Since it was clearly an embarrassment !!
---------------------------------------------


BTW:

This French page has some good pics of the insides of a Quad 303.

http://cf.geocities.com/quadfranco/a...33/amp303.html

Here is a schematic of the 1970 version.

http://www.geocities.com/quad_esl63/...c/power303.jpg


Yes thats the better one with the diode-less biasing arrangement. We
used to copy that diagram and made no end of them for mates and other
applications

I'm sure PW wouldn't have really minded after all it was spreading the
good word

I re-furbed a pair for my wife's study room a couple of years ago, new
uprated power, output, and PCB caps. New cermet pots, beefed up a bit
of the output wiring and its as good, possibly a bit better, than new
and will last many, many years yet:-)........

--
Tony Sayer

"tony sayer" wrote in message
...
Quad released their famous 303 model way back in 1967 !!

In 1969 it won a Design Council Award.

The 303 delivered 45 watts per channel into 8 ohms loads.

Performance into 4 ohm loads?

It was short circuit safe.

There are no classic SOA or current limiters. How was the output stage
protected?

It used all silicon transistors and exhibited no sign of crossover
distortion.

Par for the course.

The power devices used were rugged planar types, RCA 38494s and 40411s.

40411s were rugged, indeed.

THD measured at the 1 watt level was circa 0.003% and less than 0.03 % at
rated power - ten times less at both levels than Sugden's woeful A21.

OK, that's at 1 KHz. How about 20 KHz?

The 303 used regulated PSU and drove the "difficult" ESL57 with ease.

It ran cool with very low idle current in the output devices.

Compared to the Quad 303, Sugden's A21 was a pile of junk.

The interest in the Sugden amps mystifies me because they seem to be so
backward.


This French page has some good pics of the insides of a Quad 303.

http://cf.geocities.com/quadfranco/a...33/amp303.html

Here is a schematic of the 1970 version.

http://www.geocities.com/quad_esl63/...c/power303.jpg

It looks to me like there is no loop feedback from the output back to
anyplace near the input. Am I missing something?

Yes thats the better one with the diode-less biasing arrangement. We
used to copy that diagram and made no end of them for mates and other
applications

I'm sure PW wouldn't have really minded after all it was spreading the
good word

I re-furbed a pair for my wife's study room a couple of years ago, new
uprated power, output, and PCB caps. New cermet pots, beefed up a bit
of the output wiring and its as good, possibly a bit better, than new
and will last many, many years yet:-)........

The contemporaneous similar US amp might have been the Dyna ST-120 which had
a far more checkered reputation.

"Arny Krueger"
Phil Allison


** Try answering the right person's post - Arny.

Sayer snipped the original context out of sight and now YOU are asking him
about MY post.

Then you sneakily introduce a NEW context of your own making.

What a posturing ASS you are.



The 303 delivered 45 watts per channel into 8 ohms loads.

Performance into 4 ohm loads?


** Not relevant - ask the same Q about the A21.

( The 303 spec was for 42 watts at 6 ohms. )



It was short circuit safe.

There are no classic SOA or current limiters. How was the output stage
protected?


** The output triples inherently limit at 4.5 amps.


It used all silicon transistors and exhibited no sign of crossover
distortion.

Par for the course.


** Absolutely not the case for domestic SS amps in 1967.

The 303 was non bias critical & output device temp did not affect the
setting.

Go look at the original context for MY post.

Stop being such a PITA smartarse Septic ASSHOLE !!!.



THD measured at the 1 watt level was circa 0.003% and less than 0.03 % at
rated power - ten times less at both levels than Sugden's woeful A21.

OK, that's at 1 KHz. How about 20 KHz?


** The 303 spec was for 0.1 % at any level up to 45 watts at 10kHz.



Compared to the Quad 303, Sugden's A21 was a pile of junk.

The interest in the Sugden amps mystifies me because they seem to be so
backward.


** A quirky, pommy amp only a quirky pommy could love.



Here is a schematic of the 1970 version.

http://www.geocities.com/quad_esl63/...c/power303.jpg


It looks to me like there is no loop feedback from the output back to any
place near the input. Am I missing something?


** You sure have missed it:

R113 (82k) and R 111 (2.2k) divide the output by 38.3 times, then R108 & R
101 ( both 22k) cause the whole amp to act as a unity gain inverter to that
divided down level.

So overall gain is - 38.3 and the input sensitivity = 500mV.


Hey Arny - still not corrected all those STUPID errors on your page about
the Crown amp ?

****ing compewter geek ******.




........ Phil

"Phil Allison"

http://www.geocities.com/quad_esl63/...c/power303.jpg

** The output triples inherently limit at 4.5 amps.


** Silicon diodes MR105 & MR106 (along with TR7, the 1.4 volt Vbe
multiplier used for bias setting ) are responsible for this - in
combination, they limit the drive voltage at the input to each triple to
about +/- 2.1 volts, relative to the output line.

MR106 affects the upper triple while MR 105 the lower triple.

The Vbes of TR103 and TR104 plus voltage drops across R120 and R121 &
R124 and R125 add to +/- 2.1 volts when the current flowing into a load is
+/- 4.5 amps, respectively. Current limiting is not sensitive to the phase
angle of the load impedance.

Under shorted or very low impedance load conditions, the power dissipation
in each output device limited to 70 watts, worst case.



........ Phil

In article , Phil Allison
scribeth thus

"Phil Allison"

http://www.geocities.com/quad_esl63/...c/power303.jpg

** The output triples inherently limit at 4.5 amps.


** Silicon diodes MR105 & MR106 (along with TR7, the 1.4 volt Vbe
multiplier used for bias setting ) are responsible for this - in
combination, they limit the drive voltage at the input to each triple to
about +/- 2.1 volts, relative to the output line.

MR106 affects the upper triple while MR 105 the lower triple.

The Vbes of TR103 and TR104 plus voltage drops across R120 and R121 &
R124 and R125 add to +/- 2.1 volts when the current flowing into a load is
+/- 4.5 amps, respectively. Current limiting is not sensitive to the phase
angle of the load impedance.

Under shorted or very low impedance load conditions, the power dissipation
in each output device limited to 70 watts, worst case.



....... Phil



Correct me if I'm wrong, and I'm sure you will;!, but the voltage
regulator is involved in the protection?....
--
Tony Sayer

"tony sayer"


Correct me if I'm wrong, and I'm sure you will;!, but the voltage
regulator is involved in the protection?....



** See what I mean about " insufferable pommies " ??





....... Phil

In article ,
Phil Allison wrote:
The interest in the Sugden amps mystifies me because they seem to be
so backward.


** A quirky, pommy amp only a quirky pommy could love.

I'd suggest you actually listen to one - especially into a pair of ELS 57s.
It sounds a deal cleaner than a 303 - although obviously slightly down on
power.

--
*Never put off until tomorrow what you can avoid altogether *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)"


** A quirky, pommy amp only a quirky pommy could love.

I'd suggest you actually listen to one ....


** Yaaawnnnnnnn - more audiophool DRIVEL !!

I suggest you go drop dead.




........ Phil

In article ,
Phil Allison wrote:
** A quirky, pommy amp only a quirky pommy could love.

I'd suggest you actually listen to one ....


** Yaaawnnnnnnn - more audiophool DRIVEL !!

I suggest you go drop dead.

So that's your response to a reasonable point?

As it happens I've done just this test which is why I brought it up. And
thought it might be of interest even to you - thinking you may have
changed your attitude to attempts at sensible discussion. So back in the
killfile you go.

--
*Experience is something you don't get until just after you need it *

Dave Plowman London SW
To e-mail, change noise into sound.