On Tue, 15 Mar 2005 11:32:02 +1100, Patrick Turner
wrote:



Stewart Pinkerton wrote:

On Mon, 14 Mar 2005 23:50:26 +1100, Patrick Turner
wrote:

Iain M Churches wrote:

"Patrick Turner" wrote in message
...
I made some wrong assumptions when i looked at the schematic,
but not about electros.
The mF apparently are 10,000 uF.

The lab engineer was critical of what he called "mixed marking"
C5 is correctly marked with the "mu" sign, while C4 is marked in
milliFarads.

He has clearly been following UKRA, because over a cup of coffee,
he remarked "This is a schematic from the man who said that if we was
in recording or broadcasting he would be the digital console designer,
and yet he does not bother to mark up the simplest schematic with
accuracy. No cigar!"

This is a comment from a man who doesn't understand industry-standard
component designations. Not even a Woodbine!

Nevertheless, it will still be interesting to build it, and compare with
the 300B.

Interesting to some, but somehow not very exciting.

Oh, if you cheesepare on the heatsinks or the power resistors, it
could get quite exciting!

Pinky just needs to package it the right language,
and make a kit out of it.
Maybe he'd sell squillions of them.

Sorry, I'm *way* too honest for that. Not that I'm especially honest,
just too honest for the SET racket, unlike say Nelson Pass, whose
'single-ended' Alpha series certainly aren't......

What exactly?

Single-ended. Duhhhh...........

Ill gotten gains if ever...... :-]

Indeed. Remind me - what do you charge for toob amps? :-)

Less than a lot of ppl charge for SS amps.

Jeff Rowland, Mark Levinson, or Krell? :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Tue, 15 Mar 2005 09:11:10 +0200, "Iain M Churches"
wrote:

"Patrick Turner" wrote in message
...
I made some wrong assumptions when i looked at the schematic,
but not about electros.
The mF apparently are 10,000 uF.


Stewart,

I am going to the component shop tomorrow.
Please confirm the value of C4.

C4 is a 4m7, or 4700 microfarad if you prefer, electrolytic, should be
at least 25 volt rating, preferably 35 or 40 volt if you want it to
last more than ten years or so.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Tue, 15 Mar 2005 09:08:41 +0200, "Iain M Churches"
wrote:

"Stewart Pinkerton" wrote in message
.. .

Keep that digital klutz away from it, he's clearly at sea with
analogue circuitry.

He has designed an analogue location console used by three
major broadcasting companies within EBU.

And he doesn't understand component marking conventions? Yeah,
riiiight..................

He also knows enough about analogue circuitry to have recognised
"your" vinyl RIAA stage as coming from a book book (either
Swedish or German) or possibly an early issue of Elektor.

No, he doesn't, it's an entirely original design and uses unusual
components in a very unusual (but logical) way. Sounds like a jealous
desk jockey to me, I'm sure you two get on very well.

Did the KISASS amp come from the same source?

KISASS is fundamentally very simple (that being the whole point!), the
basic Tr2,3,4 topology can be found in any EE textbook from the early
'60s onward, although the input emitter follower is unusual, as is the
lack of loop feedback and the divided power rails. I'd be surprised if
you could find the same overall topology in any book. I did use
something vaguely similar in the UUT driver stage of a piece of
automated military test gear about twenty five years ago (Marconi
GraduATE, to be precise), although with VFETs rather than BJTs.

Keep trying with the snide comments, if they help your ego.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
...
C4 is a 4m7, or 4700 microfarad if you prefer, electrolytic, should be
at least 25 volt rating, preferably 35 or 40 volt if you want it to
last more than ten years or so.

Thanks.

Iain

"Stewart Pinkerton" wrote in message
...
On Tue, 15 Mar 2005 09:08:41 +0200, "Iain M Churches"
wrote:

"Stewart Pinkerton" wrote in message
. ..

He also knows enough about analogue circuitry to have recognised
"your" vinyl RIAA stage as coming from a book book (either
Swedish or German) or possibly an early issue of Elektor.

No, he doesn't, it's an entirely original design and uses unusual
components in a very unusual (but logical) way.

Let's hope you are right.
We wouldn't want any "old forgeries" from
the Old Forge, would we? :-))

I am off to Prague tomorrow, to record some Dvorak.
Do you enjoy Dvorak?

Keep up the good work:-))

Iain

Stewart Pinkerton wrote:

On Tue, 15 Mar 2005 11:29:32 +1100, Patrick Turner
wrote:

I come from Astraya, and you ppl are always leading us astray.

IIRC, we spent most of our short sojourn over there trying to ensure
that you did *not* stray.................. :-)

We are glad to have gotten rid of you all mostly,
although evidence of british presence manifests itself
in the prodgeny of Astrayan sheilas....
I could say I am " tree quarters Irish, but since me dad
was a pom, I muss be two turds english ..."

But we have been giving you guys some embarrassing
football and cricket lessons, so it evens the score eh.







And analysis reveals that for best operation very high
current gain bjts are required for the outputs.

Yes - that's why I used the MJL4281/4302 pair.

But anyway a class A emitter follower driver buffer would be a good idea
to lower the impedance of the output stage driver to
a few ohms at most, or less than 1 ohm, 1/ Gm, in fact.

That would be another transistor, and another stage, which is hardly
adhering to KISS principles.

No, becaue you do away with the input buffer.

OK, but I still prefer my original approach, I believe that it's
simpler in spirit.

Oh, you got soul, eh.



Then he'd get Rout to have been well below the 1 ohm he has,
and the 70 dB of local emitter follower series voltage NFB would be
far more effective.
The input stage could be a single gain bjt with
current FB and low gain and therefore give a high enough Rin for any preamp.

It's *supposed* to have highish output impedance, to simulate the
load-dependent FR variations of a SET amp.

Why simulate anything else?

Just let it be what it will be.

Well no, because if it's not a SS equivalent of a tube SET, it has no
merit as an amplifier. Use the Linsley Hood design, for superior
results and an even simpler topology.

Not necessarily so....



Or else just allow the emitter resistors of the output stage to determine
the Rout; its a purer way of doing it.
And you'd have more class A bias stability.

That's pretty much what I *did* do. You can certainly increase the
output emitter resistors to 1 ohm if you want the amp to be
rock-stable - and you're going to avoid low impedance speakers.

Two transistors together in class A each with Re = 1 ohm have 0.5 ohms effectively

Your 1 ohm of Rout comes mostly from the EF config
with a rather too high drive R.

I am saying it would be purer to make the most of the EF config.
use a lower R driver, and let Re be larger, and the 0.5 ohms isolates the
load better from the workings of the output transistors.



It's also supposed to be
d.c. stable and easy to build, which is why the raw gains of the BJTs
haven't been pushed to eliminate the input buffer.

I think the input emitter follower buffer is wrongly placed, and should be
between the gain stage and EF output stage.

Your opinion is noted, but I don't agree..................

You'd be stubborn then.

Oh yeah, more dig-in-ness than a Missouri mule! I think your
suggestion would spoil the basic ethos, that of a central 'character
determining' gain stage, with impedence transformers on either side.

The gain stage shouldn't need a buffer.
I don't place a cathode follower at the input to my tube amps.
And in any case, for high Rin, I'd be using a darlington pair for the input stage.
The current NFB of the gain stage will raise Rin in sufficiently.


Then he could make the emitter resistors of the output stage up to
1 ohm each, and Rout would still be about only 0.5 ohms.

If you read old Wireless world articles, a few samples of
class A bjt designs with no global FB were published,
and they relied on the bags of emitter follower NFB available.

In higher powered amps where one wants say 100watts into 8 ohms, we
need about 29vrms into the emitter follower output stage.
Ideas about cost and economy dictate class aB, with only milliwatss of class
A.
Therfore the main pirpose of the necessary applied global NFB is to
linearize
the not so wonderful VAS powering the output.

I *have* built a true class A amp with 80 watts/channel into 8 ohms,
but it was kinda big. It also drew about 450 watts from the wall at
idle, which was handy for the Scottish climate! :-)

Probably as big as a 350 watt class AB amp would be.

It was 18" wide, two feet deep, nine inches high, and weighed about
forty kilos! Sure intimidated visitors, who assumed it must put out
skull-splitting power levels! :-)

Overkill.

But for 80 watts of **pure** class A you need to dissipate
at least 200 watts in the output devices.

I build a 300W/ch AB amp which hase a few watts of class A,
and about 40 watts diss per channel at idle, see
http://www.turneraudio.com.au/webpic...et400w302h.jpg

The heatsinks are 150 mm high, 40 mm deep, 300 mm long with 30 fins
Its very difficult to raise the temp to 75C even with a sine wave at clipping
into 4 ohms.

I figured for 50 watts of class A these heatsinks would be OK,
since 100 watts is dissipated,
and a monoblock 50 would weigh about 15 Kgs, and i built a pair,
but I made the heatsinks from scrap aluminium I had laying around,
http://www.turneraudio.com.au/webpic...no400w288h.jpg

It has an OPT to couple to the load, and transformer bw is 10 Hz to 300 kHz,
and low thd.
The tranny allows a simple circuit, and all output devices are the same polarity,
so no problems with P and N differences.

With the 50 watters the 4 mosfets are on a 12 mm thick angle onto the sink
in the centre bottom and the T rise is ok, even on days like today
when we had 30C indoors.

It is far better to spread the devices right along the sink as I did in the 300
watters,
than have them in the centre, but it still works OK.

Both these SS amps are very smooth sounding.

Patrick Turner.






--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Tue, 15 Mar 2005 09:48:06 +0200, "Iain M Churches"
wrote:


"Stewart Pinkerton" wrote in message
.. .

OK, so he knows feck all about precision analogue engineering.
I have replied to that in another mail.
Interesting that you call your amp
"precision analogue engineering" :-))))

I don't call it that at all - I simply observe that it's not an area
with which your colleague seems familiar.

It was *designed* with precision, to have lots of tolerance in
building, enabling most amateur builders to achieve sound rather than
smoke! :-)

I once
worked with a guy who gained his PhD in digital signal processing
while working with Rupert Neve, and he would have been *intrigued* by
KISASS,
and would have been fascinated to know exactly *why* it did so
many things 'wrong'.

I have yet to see a post where such a statement is made.

Well, granted I only picked up an MSc in digital techniques from
Heriot-Watt University, because Marconi thought I should broaden my
horizons from 'only analogue', and were happy to pay for it, but such
is life. Digital dorks deal in ones and zeroes, analogue engineers
handle *everything* from zero to infinity - and beyond! :-)

Surprising then that a man of your extraordinary capability

Not very extraordinary in the world of industrial electronics, but
certainly above most of the 'boutique' end of the audio indusrtry.

has an
audio system comprised entirely of other peoples engineering (with
the possible exception of the vinyl pre-amp) Nothing of your own.

The phono preamp, the main controller, and the cabling, are of my own
devising. I have in the past built fifteen or so power amps, but
there's no point nowadays, as I can buy a 'blameless' power amp for
pretty much the same as the parts cost of one of my homebrews.

Surprising too that a man of your extraordinary capability is
working in a post room, and at only 57 years of age is
"sliding into retirement" (your words)

I wouldn't describe a printing and distribution plant putting out 6
million packets a week, and being Royal Mail's biggest customer after
the Government, as a 'postroom', but whatever! The nice thing about
'retirement' is that you have much more time to do things that are
interesting but unprofitable - like audio.

But never mind, when you retire they might pass the hat round
at the bank for a down payment on a Conrad Johnson or even,
if you have been a very good boy, a Radford.

Why the heck would I want obsolete stuff like that?

You can then sell the boring old Audi, to your local cab firm,
and get youself a vintage motorcyle, or an early Aston and
start living:-))

As it happens, an Aston is in the pipeline, but not an old one.......

The cabbies here mostly drive Skoda Superbs, which at a stretch you
could think of as Audis. It's all about good reliable engineering -
you won't find any tube amps in taxicabs! :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Tue, 15 Mar 2005 11:35:13 +0200, "Iain M Churches"
wrote:

"Stewart Pinkerton" wrote in message
.. .
On Tue, 15 Mar 2005 09:08:41 +0200, "Iain M Churches"
wrote:

"Stewart Pinkerton" wrote in message
...

He also knows enough about analogue circuitry to have recognised
"your" vinyl RIAA stage as coming from a book book (either
Swedish or German) or possibly an early issue of Elektor.

No, he doesn't, it's an entirely original design and uses unusual
components in a very unusual (but logical) way.

Let's hope you are right.

It's not a hope, it's a fact.

We wouldn't want any "old forgeries" from
the Old Forge, would we? :-))

Nope, it's all authentic.

I am off to Prague tomorrow, to record some Dvorak.
Do you enjoy Dvorak?

Mostly, and I love Hovis........ :-)

Have fun, and don't drink too much of that good Czech beer!

Keep up the good work:-))

Like all true engineers, I dedicate my life to minimising work! :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Wed, 16 Mar 2005 01:11:13 +1100, Patrick Turner
wrote:



Stewart Pinkerton wrote:

On Tue, 15 Mar 2005 11:29:32 +1100, Patrick Turner
wrote:

I come from Astraya, and you ppl are always leading us astray.

IIRC, we spent most of our short sojourn over there trying to ensure
that you did *not* stray.................. :-)

We are glad to have gotten rid of you all mostly,
although evidence of british presence manifests itself
in the prodgeny of Astrayan sheilas....
I could say I am " tree quarters Irish, but since me dad
was a pom, I muss be two turds english ..."

But we have been giving you guys some embarrassing
football and cricket lessons, so it evens the score eh.

Not really - I'm not any turds English................. :-)

And analysis reveals that for best operation very high
current gain bjts are required for the outputs.

Yes - that's why I used the MJL4281/4302 pair.

But anyway a class A emitter follower driver buffer would be a good idea
to lower the impedance of the output stage driver to
a few ohms at most, or less than 1 ohm, 1/ Gm, in fact.

That would be another transistor, and another stage, which is hardly
adhering to KISS principles.

No, becaue you do away with the input buffer.

OK, but I still prefer my original approach, I believe that it's
simpler in spirit.

Oh, you got soul, eh.

Nah, I leave that to James and Thelma.

Then he'd get Rout to have been well below the 1 ohm he has,
and the 70 dB of local emitter follower series voltage NFB would be
far more effective.
The input stage could be a single gain bjt with
current FB and low gain and therefore give a high enough Rin for any preamp.

It's *supposed* to have highish output impedance, to simulate the
load-dependent FR variations of a SET amp.

Why simulate anything else?

Just let it be what it will be.

Well no, because if it's not a SS equivalent of a tube SET, it has no
merit as an amplifier. Use the Linsley Hood design, for superior
results and an even simpler topology.

Not necessarily so....

Whatever.



Or else just allow the emitter resistors of the output stage to determine
the Rout; its a purer way of doing it.
And you'd have more class A bias stability.

That's pretty much what I *did* do. You can certainly increase the
output emitter resistors to 1 ohm if you want the amp to be
rock-stable - and you're going to avoid low impedance speakers.

Two transistors together in class A each with Re = 1 ohm have 0.5 ohms effectively

Your 1 ohm of Rout comes mostly from the EF config
with a rather too high drive R.

I am saying it would be purer to make the most of the EF config.
use a lower R driver, and let Re be larger, and the 0.5 ohms isolates the
load better from the workings of the output transistors.

Nah, I like it my way, it's easier for the beginner to understand how
it's all glued together. Remember, it's not *supposed* to be a
high-performing device, despite what sad sack thinks about
'ultrafidelity'.

It's also supposed to be
d.c. stable and easy to build, which is why the raw gains of the BJTs
haven't been pushed to eliminate the input buffer.

I think the input emitter follower buffer is wrongly placed, and should be
between the gain stage and EF output stage.

Your opinion is noted, but I don't agree..................

You'd be stubborn then.

Oh yeah, more dig-in-ness than a Missouri mule! I think your
suggestion would spoil the basic ethos, that of a central 'character
determining' gain stage, with impedence transformers on either side.

The gain stage shouldn't need a buffer.

Depends how high an input impedance you want. If you have a
low-impedance source capable of outputting at least a couple of
milliamps, then you could remove Tr1 and rebias Tr2.

I don't place a cathode follower at the input to my tube amps.
And in any case, for high Rin, I'd be using a darlington pair for the input stage.
The current NFB of the gain stage will raise Rin in sufficiently.

What's the difference? Take out R4 and it *is* a Darlington pair, but
has less d.c. stability than my design.

Then he could make the emitter resistors of the output stage up to
1 ohm each, and Rout would still be about only 0.5 ohms.

If you read old Wireless world articles, a few samples of
class A bjt designs with no global FB were published,
and they relied on the bags of emitter follower NFB available.

In higher powered amps where one wants say 100watts into 8 ohms, we
need about 29vrms into the emitter follower output stage.
Ideas about cost and economy dictate class aB, with only milliwatss of class
A.
Therfore the main pirpose of the necessary applied global NFB is to
linearize
the not so wonderful VAS powering the output.

I *have* built a true class A amp with 80 watts/channel into 8 ohms,
but it was kinda big. It also drew about 450 watts from the wall at
idle, which was handy for the Scottish climate! :-)

Probably as big as a 350 watt class AB amp would be.

It was 18" wide, two feet deep, nine inches high, and weighed about
forty kilos! Sure intimidated visitors, who assumed it must put out
skull-splitting power levels! :-)

Overkill.

Not if you want a *reliable* amp that puts 80 watts of pure Class A
sound into an 8ohm load, without cooling fans. It was certainly big,
but no bigger than say a KSA80 Krell, which had a similar output
capacity.

But for 80 watts of **pure** class A you need to dissipate
at least 200 watts in the output devices.

Indeed so - note where I said it drew 450 watts from the wall at idle.

I build a 300W/ch AB amp which hase a few watts of class A,
and about 40 watts diss per channel at idle, see
http://www.turneraudio.com.au/webpic...et400w302h.jpg

The heatsinks are 150 mm high, 40 mm deep, 300 mm long with 30 fins
Its very difficult to raise the temp to 75C even with a sine wave at clipping
into 4 ohms.

Sure, but it's not Class A.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

In message , Iain M Churches
writes

"Stewart Pinkerton" wrote in message
.. .

It's on alt.binaries.schematics.electronics. And it's only a paper
design, so no test results. It's a simple design though, so predicting
performance isn't too hard, given a decent physical layout.

I was interested to build your design for audible comparison
with Andre's 300B. So this morning I took your drawing to
the broadcast lab for their comments.

The chief engineer looked at the schematic and said
" It is normal practice to stipulate the devices used in
any circuit"

He then looked at the caps as marked and said "We have no
4.7milliFarad electrolytic capacitors, and tossed the drawing
into the bin.

Ho hum:-)

Iain



Really? I have quite a few of them, in voltage ratings from 25 to 100.

4.7millifarad is a very common value for a smoothing cap for example.
--
Chris Morriss

you won't find any tube amps in taxicabs! :-) Stewart Pinkerton | Music
is Art - Audio is Engineering

A tube amp has as much place in a taxicab as a Stewart Pinkerton has on
a tube newsgroup.
Music is Music - Tubes are Tubes

"Andy Evans" wrote in message
oups.com...
you won't find any tube amps in taxicabs! :-) Stewart Pinkerton | Music
is Art - Audio is Engineering

A tube amp has as much place in a taxicab as a Stewart Pinkerton has on
a tube newsgroup.
Music is Music - Tubes are Tubes


Hi Andy,

Good to see you he-)

Iain

On 15 Mar 2005 14:38:19 -0800, "Andy Evans"
wrote:

Music is Music - Tubes are Tubes

Glad you are starting to see the difference, Andy.

d

Pearce Consulting
http://www.pearce.uk.com

"Andy Evans" wrote in message
oups.com...

A tube amp has as much place in a taxicab as a Stewart Pinkerton has on
a tube newsgroup.

I'm just here on vacation, trying to show these poor benighted guys
how it *should* be done! :-)

Music is Music - Tubes are Tubes

Indeed, they are quite separate things............
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Hi Andy, Good to see you he-) Iain

I've been here for several years, but I participate very little due to
the presence of a number of certifiable mental cases who wreck threads.
As a psychologist I prefer "Asylums" where the practitioners are in
control! Andy

"Andy Evans" wrote in message
oups.com...
Hi Andy, Good to see you he-) Iain

I've been here for several years, but I participate very little due to
the presence of a number of certifiable mental cases who wreck threads.
As a psychologist I prefer "Asylums" where the practitioners are in
control! Andy

My wife is a sociologist. She looks at UKRA as a case study:-))

Iain

Andy Evans wrote:

you won't find any tube amps in taxicabs! :-) Stewart Pinkerton | Music
is Art - Audio is Engineering

A tube amp has as much place in a taxicab as a Stewart Pinkerton has on
a tube newsgroup.
Music is Music - Tubes are Tubes

In the face of stern opposition, we shall be resolute,
in the maelstrom of battle, we shall be brave,
When under fire from a foe, we shall return devastation,
and when battle is done, with victory secured, we shall raise the Tube Flag
high,
and with all difficulties, we shall overcome.

And then we'll call a taxi and bundle Pinky off home, if he has one to go
to.

Patrick Turner.

On Thu, 17 Mar 2005 01:01:51 +1100, Patrick Turner
wrote:

Andy Evans wrote:

Music is Music - Tubes are Tubes

See, at least Andy knows the difference!

In the face of stern opposition, we shall be resolute,
in the maelstrom of battle, we shall be brave,
When under fire from a foe, we shall return devastation,
and when battle is done, with victory secured, we shall raise the Tube Flag
high,
and with all difficulties, we shall overcome.

Trouble is, if you keep using tubes, defeat is certain......... :-)

--

Stewart Pinkerton | Music is Art - Audio is Engineering

In the face of stern opposition, we shall be resolute, in the maelstrom
of battle, we shall be brave, When under fire from a foe, we shall
return devastation, and when battle is done, with victory secured, we
shall raise the Tube Flag high, and with all difficulties, we shall
overcome.

Right on brother! If it ain't glowing it ain't going. I think a few
people ended up here from UKRA thinking it was a fisn and chip shop, if
you know the old drummer gag. Andy