In article , Mike Gilmour
writes

"Iain M Churches" wrote in message
...

"Stewart Pinkerton" wrote in message
...

It's probably better if we try not to mention your personality again.

Can we still discuss your prospects as a digital console designer
with Neve International Ltd? :-)

Iain


That would be NIL? (Neve Intnl. Ltd) :-)



Aren't they called AMS international now 'opp North somewhere near
Burnley?....
--
Tony Sayer

"tony sayer" wrote in message
...
In article , Mike Gilmour
writes

"Iain M Churches" wrote in message
...

"Stewart Pinkerton" wrote in message
...

It's probably better if we try not to mention your personality again.

Can we still discuss your prospects as a digital console designer
with Neve International Ltd? :-)

Iain


That would be NIL? (Neve Intnl. Ltd) :-)



Aren't they called AMS international now 'opp North somewhere near
Burnley?....

Burnley? That doesn't sound salubrious enough for a man in a
Leicester suit:-(( Maybe SP had better turn his attention to SSL
(at Begbroke near Oxford, IIRC)

"tony sayer" wrote in message
...
In article , Mike Gilmour
writes

"Iain M Churches" wrote in message
...

"Stewart Pinkerton" wrote in message
...

It's probably better if we try not to mention your personality again.

Can we still discuss your prospects as a digital console designer
with Neve International Ltd? :-)

Iain


That would be NIL? (Neve Intnl. Ltd) :-)



Aren't they called AMS international now 'opp North somewhere near
Burnley?....
--
Tony Sayer


....and some fell on stony ground ;-)
See www.ams-neve.com

Mike

"Patrick Turner" wrote in message

Iain M Churches wrote:

"Arny Krueger" wrote in message
...
"Patrick Turner" wrote in message



I think it will be quite some time before anyone comes up with an
8 watt two transistor single ended amp which has no global NFB
and which sounds as well as a 300B amp when correctly set up.

Given the incredibly convoluted criteria used to establish that the
300B amp sounds good...

I find it surprising that many of those who speak out so vehemently
against the SET have never actually heard one:-)

Iain

And they have probably never owned any.

For a number of pretty good reasons, I'd say.

First and foremost is the desire to avoid self-abuse.

"Jim Lesurf" wrote in message


Well, I don't know the design of SET amp you refer to, so can't
comment on it specifically. However when I had a student build a
transistor SET amp some years ago the expensive and difficult part
was the o/p transformer. This is a bit easier in some ways than for
valve as it didn't have to isolate very large voltages, and didn't
have a large turns ratio. But you still end up requiring a
significant (expensive) transformer if you want it to work OK even
down to LF.

I don't know if I still have a copy of his project report. When I get
a chance I'll have a look for it. My (perhaps unreliable)
recollection is that the performance was limited by the transformer
not by the choice of gain devices. Hence such theoretical
'simplicity' can become quite complex and costly to attain. Looks
simple on a circuit schematic, though. :-)

Yes, that is a big concern of mine as well.

One of the nice things about push-pull amps is the flux cancellation in the
output transformer. Of course no output transformer is usually even better.

"Jim Lesurf" wrote in message
...
In article , Iain M Churches
wrote:



Andre's SET thread on RAT was of considerable interest to a great number
of people. There are many who would like to build Andre's amp.

Afraid I don't know anything about "Andre's" amp (or, indeed, Andre). Can
you give me a URL for a webpage that shows the circuit diagram and specs,
etc?

Slainte,

Jim


This amplifier is the subject of a design/building project on RAT.
You can find many relevant threads, under KISS.

Iain

Arny Krueger wrote:

"Jim Lesurf" wrote in message


Well, I don't know the design of SET amp you refer to, so can't
comment on it specifically. However when I had a student build a
transistor SET amp some years ago the expensive and difficult part
was the o/p transformer. This is a bit easier in some ways than for
valve as it didn't have to isolate very large voltages, and didn't
have a large turns ratio. But you still end up requiring a
significant (expensive) transformer if you want it to work OK even
down to LF.

I don't know if I still have a copy of his project report. When I get
a chance I'll have a look for it. My (perhaps unreliable)
recollection is that the performance was limited by the transformer
not by the choice of gain devices. Hence such theoretical
'simplicity' can become quite complex and costly to attain. Looks
simple on a circuit schematic, though. :-)

Yes, that is a big concern of mine as well.

One of the nice things about push-pull amps is the flux cancellation in the
output transformer. Of course no output transformer is usually even better.

The OPT for a single device class A mosfet or BJT
amp can be very easy to wind because instead of say 2,000 primary
turns of fine wire used for an SET amp, only about 200 turns of much thicker
and easier to
handle wire are needed.
The OPT will have to be the same weight as that for an SET, and the secondary
will have to be the same as for the tube amp since the turns per volt
will be the same.
A good diyer should be able to make a suitable OPT if he knows his theory,
but most have little idea.

But for 8 watts, a single pair of output devices in an complementary pair work
fine,
and if 2 mosfets are used in source follower then the thd at max po will be
about 1%
and acceptable at a watt, and all that's needed is a linear driver stage
capable of producing
about 9vrms at say 0.3% thd so it don't add much to the two output devices.

With a 6 ohm load, such a pair share the load between them and each device sees

12 ohms, so their open loop gain is about 10, and the amount of NFB applied via
the source follower
connection is about 20 dB with a 6 ohm load.

The driver device could be a high gain signal bjt with emitter current FB
and perhaps cap coupled to the fet follower.

But because you don't have triodes, don't expect the sound to be as acceptable.

The input device would perhaps better be a high Gm j-fet like 2SK369.
Load could be in the drain circuit, and global NFB used like it has to be in
pentode amps
to straighten out what is the open loop mess.
The beauty of the common source connection of mosfets is that
only about a volt rms of drive is needed to the gates, very doable
with a drive fet I have nominated, and the amount of
global NFB can be set up to the minimum amount to get
Ro = 1 ohm.
All devices are then included in the NFB loop.
The mosfet gate capacitance is high in common source mode, but low voltage
drive is needed.
In common drain, C is low, so the same drive can still swing the reqired
voltage either way
because the current in the driver device will be sufficient.

One can also connect the output mosfets as a totem pole connected pair of the
same
NPN or PNP polarity, and set them up as a mu-follower, or SRPP
so liked by tube orientated people for preamp stages.
This way there is a mix of SE and PP action, low drive, slightly
more 2H, and very easy to set up.

But BJTs?, nah, leave em for the boyos who
like to have 39 devices in an amp, and think all that junk is "elegant".

Patrick Turner.

In article , Iain M Churches
wrote:

"Jim Lesurf" wrote in message
...
In article , Iain M Churches


Afraid I don't know anything about "Andre's" amp (or, indeed, Andre).
Can you give me a URL for a webpage that shows the circuit diagram and
specs, etc?


This amplifier is the subject of a design/building project on RAT.

Afraid I'm not sure what 'RAT' may be. Is it rec.audio.tech?

You can find many relevant threads, under KISS.

But can you/anyone point me at a published circuit diagram and specs so I
can see what amp "Andre's" may be, and I can then see what they/you are
referring to?

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Andre started out with his interesting amp project.He was heckled by Stewart.
The thread looked as though it would turn into chaos.

Now where have I seen this before - jog my memory - uk.rec.audio?

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

On Mon, 10 Jan 2005 18:31:32 +1100, Tat Chan
wrote:

Stewart Pinkerton wrote:

On Sun, 09 Jan 2005 18:37:20 GMT, (Don Pearce)
wrote:

On Sun, 09 Jan 2005 17:30:06 +0000, Eiron wrote:

And the appalling sound of "103dB efficient speakers"

Hee hee.... I didn't actually want to go there.

But Eiron did place his bet where the smart money goes! Personally,
I've only heard *one* really good speaker with efficiency above
100dB/w/m, and that was the Avantgarde Duo.

sorry, why do highly efficient speakers usually sound bad? Is it because
you need really large cabinet sizes to obtain more bass for highly
efficient speakers?

Partly, since in those types it's *very* difficult to suppress panel
resonances, due to the large panel sizes. High efficiency direct
radiating drivers also tend to have ragged frequency responses and
sever breakup modes, as other engineering qualities are sacrificed in
the drive for high efficiency.

(changing subject)

And while we are on the subject of speaker efficiency, a local hi-fi
store has a pair of traded in Apogee Calipers (*). Would you know if I
need a Krell to drive them, or would an Audiolab 8000S do the job?

They're even less efficient than my Duattas, and are a 3-4 ohm load,
so an 8000S would be red-hot in ten minutes at normal listening
levels! You'll need something that can happily put out 300 watts into
4 ohms indefinitely. You could try a pro-audio unit, Yamaha make some
good ones, the only snag being noise from the fan cooling. Or there's
the big Rotels.
--

Stewart Pinkerton | Music is Art - Audio is Engineering