Re: A Challenge for Stewart Pinkerton


Iain Churches wrote:
"John Byrns" <jbyrns@xxxxxxx> wrote in message
news:jbyrns-2602061554290001@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Hi Stewart,

In response to Andre's KISS amp you gave us your solid state KISASS
amplifier design, although you never built it. Considering this is
actually a tube group, and you are a very clever engineer, I challenge you
to design a tube amp for the group that will meet your exacting standards,
show some originality, and be relatively simple in concept and design. In
this challenge, since you are a solid state guy, negative feedback can be
used freely, and there is no need to actually build the amplifier, as long
as it is a reasonably simple and practical design capable of an output of
a few Watts of high quality audio. The question is do you have the
necessary engineering skills to actually meet the challenge?


Regards,

John Byrns


Morning John. Parallel thoughts:-) I wrote a post to Stewart on
exactly the same topic last night, and put in in the drafts folder to be
sent this morning. My post was not a "challenge" but a request for
an interesting project.

Stewart is, as far as I know, the only "precision analogue engineer"
on RAT. With a couple of notable exceptions, most of us are
hobbyists. So he seems to be the perfect person to lead a good
project.

I had in mind something a bit more high.end. Maybe 80-100W
UL PP. Many people like the sound of the EL34 so maybe four pairs
per channel :-) and a differential cascode front end would be nice:-)
he can choose the LTP.

We are all familiar which the schematics from the GEC handbook,
Jones, O'Connor and Glass Audio, so I sure Stewart will not need
to cut and paste anything from those, but will want to present us
something high in performance and innovation.

A project is incomplete while only on paper, and any
self respecting designer would surely take the treouble to build and
test his design. I would like to see this as a more "in depth" project
than the one you describe above, John. For many amp builders,
the most difficult part is achiveing unconditional stability
.
Stewart could take us through the procedures of dominant
poles, and step networks etc, and setting the bandwidth
open and closed loop.

I will be happy to host Stewart's schematics, design
notes, metalwork drawings, pics, transformer specs etc
on my website for as long as necessary.

Let's look forward to an interesting project.
Please start the ball rolling Stewart.

Iain

An EL34 amp will be good. Many people have EL34 amps they will be able
to alter to Pinkerton's design to listen to and measure against his
design. For instance, I have commercial and own-design EL34 all the way
from 2W in SE through a double handful of trioded PP Class A watts to
100W Class A/B. Everyone knows what EL34 sound like. A major leap
forward, as we should expect from a man of Pinkerton's expertise in
precision analogue engineering, will be most welcome. He needn't be
alone in this endeavour, Graham Stevenson, who posts here as Pooh Bear,
is a trained analogue engineer who works in audio. Pinkerton is known
to correspond with Henry Pasternack, who has an EE master's degree from
Stanford. I'm sure they would be delighted to help him, in subsidiary
positions of course, because every project must have a definite leader.

An EL34 design has another advantage, that we can decide later whether
we can eyeball it and declare it desirable on all parameters, or
whether it needs to be built to ascertain beyond doubt that it performs
as intended.

But, if the amp needs to be built, I'd be delighted to send Pinkerton a
set of good quality transformers (outputs and power) on loan for the
project if he will undertake to pay carriage both ways. In fact, if he
wants to send the completed amp to me for testing, I will throw in very
flexible casework as well, with high quality socketry already sitting
on it and the transformers bolted in.

Can't say fairer than that.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

.

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