Lincoln Walsh: Brooks Amps
Andre Jute
> Lincoln-Walsh made nice PP amps with CFB AND an IST driver tranny.
> Back in maybe 1955. Its been done before.
> But I only saw a LW schematic once, and have not seen an electronic
> copy,
> so LW might have gone broke or stopped production long ago
> after not making very much.
>
> Anyone have a copy of the Lincoln-Walsh amps?
I don't know about Lincoln Walsh amps, but those Brooks Amps people
are always raving about were designed by Lincoln Walsh. I can let you
have circuits and some specs for:
1. Brooks 12A 10W
2. Brooks 10C 30W
3. "HIGH QUALITY" class A1 30W design by Lincoln Walsh in Electronics,
July 1939 -- this is the advance guard of the famous Brooks Amps.
Let me know.
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
Patrick Turner
Andre Jute wrote:
>
> Patrick Turner wrote:
>
> > Lincoln-Walsh made nice PP amps with CFB AND an IST driver tranny.
> > Back in maybe 1955. Its been done before.
> > But I only saw a LW schematic once, and have not seen an electronic
> > copy,
> > so LW might have gone broke or stopped production long ago
> > after not making very much.
> >
> > Anyone have a copy of the Lincoln-Walsh amps?
>
> I don't know about Lincoln Walsh amps, but those Brooks Amps people
> are always raving about were designed by Lincoln Walsh. I can let you
> have circuits and some specs for:
>
> 1. Brooks 12A 10W
>
> 2. Brooks 10C 30W
>
> 3. "HIGH QUALITY" class A1 30W design by Lincoln Walsh in Electronics,
> July 1939 -- this is the advance guard of the famous Brooks Amps.
>
> Let me know.
Send me a schema for the Brooks 30 watter please.
But its 1939? Maybe they used CFB before Quad did, I dunno.
If they did, it'd be on the schema.
See if there is an IST as well.
AND global NFB.
Patrick Turner.
Andre Jute
This is the post-war Brook 30W amp; the 1939 30W
amp by Lincoln Walsh was different; I can look it
out and send you the schemo of that too if you
like. HTH. -- Andre Jute
> > Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/
Bret Ludwig
> Patrick Turner wrote:
> > Lincoln-Walsh made nice PP amps with CFB AND an IST driver tranny.
> > Back in maybe 1955. Its been done before.
> > But I only saw a LW schematic once, and have not seen an electronic
> > copy,
> > so LW might have gone broke or stopped production long ago
> > after not making very much.
>
> > Anyone have a copy of the Lincoln-Walsh amps?
>
> I don't know about Lincoln Walsh amps, but those Brooks Amps people
> are always raving about were designed by Lincoln Walsh. I can let you
> have circuits and some specs for:
>
> 1. Brooks 12A 10W
>
> 2. Brooks 10C 30W
>
> 3. "HIGH QUALITY" class A1 30W design by Lincoln Walsh in Electronics,
> July 1939 -- this is the advance guard of the famous Brooks Amps.
The schematics are on the Web and in various anthologies, magazine
articles and reference books. What is not readily available are the
specifications on the output transformer and the driver autoformer
(tapped choke). The sets themselves are rare and much in Oriental
demand, therefore they get sent over as soon as found by the gear
whores.
The amplifier is a good one with push pull triode outputs driven by a
low impedance driver section, and a reasonable level of NFB. The Altec
1570B was in essence a much scaled up version.
Anyone reverse engineering one and offering the iron (the opt and
driver choke) would probably do well with it. It uses the 2A3 tube
and gives ten or fifteen watts.
Walsh was also the inventor of the speaker manufactured by the Ohm
company as I recall.
Patrick Turner
Andre Jute wrote:
>
> Sent the 10C schemo to your mailbox:
>
> This is the post-war Brook 30W amp; the 1939 30W
> amp by Lincoln Walsh was different; I can look it
> out and send you the schemo of that too if you
> like. HTH. -- Andre Jute
That Brook amp is a class AB2 concoction.
It has a near standard Williamson front end
which drives a 1:1 IST to drive the pair of 6J5 cathode followers direct
coupled to 2A3 grids.
There is no local CFB from OPT to output tubes, but there is a small
amount
of global NFB.
Maybe you could get 30W AB2 from a pair of 2A3.
I know trioded 6L6 or 6CM5 will work similarly.
There is no info on B+ or 2A3 a-a loading.
This circuit is different from the LW I remember seeing.
Regards with many thanks,
Patrick Turner.
roo...@gmail.com
> Patrick Turner wrote:
> > Lincoln-Walsh made nice PP amps with CFB AND an IST driver tranny.
> > Back in maybe 1955. Its been done before.
> > But I only saw a LW schematic once, and have not seen an electronic
> > copy,
> > so LW might have gone broke or stopped production long ago
> > after not making very much.
>
> > Anyone have a copy of the Lincoln-Walsh amps?
>
> I don't know about Lincoln Walsh amps, but those Brooks Amps people
> are always raving about were designed by Lincoln Walsh. I can let you
> have circuits and some specs for:
>
> 1. Brooks 12A 10W
>
> 2. Brooks 10C 30W
>
> 3. "HIGH QUALITY" class A1 30W design by Lincoln Walsh in Electronics,
> July 1939 -- this is the advance guard of the famous Brooks Amps.
>
> Let me know.
>
> Andre Jute
> "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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fiul...@yahoo.com
Precision" Jute
On Mar 22, 2:22 am, Andre Jute <fiul...@yahoo.com> wrote:
> Patrick Turner wrote:
> > Lincoln-Walsh made nice PP amps with CFB AND an IST driver tranny.
> > Back in maybe 1955. Its been done before.
> > But I only saw a LW schematic once, and have not seen an electronic
> > copy,
> > so LW might have gone broke or stopped production long ago
> > after not making very much.
>
> > Anyone have a copy of the Lincoln-Walsh amps?
>
> I don't know about Lincoln Walsh amps, but those Brooks Amps people
> are always raving about were designed by Lincoln Walsh. I can let you
> have circuits and some specs for:
>
> 1. Brooks 12A 10W
>
> 2. Brooks 10C 30W
>
> 3. "HIGH QUALITY" class A1 30W design by Lincoln Walsh in Electronics,
> July 1939 -- this is the advance guard of the famous Brooks Amps.
>
> Let me know.
>
> Andre Jute
> Visit Jute on Amps athttp://members.lycos.co.uk/fiultra/
fiul...@yahoo.com
> Of course they're Brook amplifiers, not Brooks. -- Andre "Mr
> Precision" Jute
Cause I wouldn't want to be thought of as a calloused cyclist (like
Patrick) sitting on a leather Brooks saddle for real men who know how
to manage pain. -- Andre "The Hedonist" Jute
Andre Jute
> On Mar 27, 5:38 pm, fiult...@yahoo.com wrote:
>
> > Of course they're Brook amplifiers, not Brooks. -- Andre "Mr
> > Precision" Jute
>
> Cause I wouldn't want to be thought of as a calloused cyclist (like
> Patrick) sitting on a leather Brooks saddle for real men who know how
> to manage pain. -- Andre "The Hedonist" Jute
Besides, as has been mentioned elsewhere, when I ride my bike in a
cocktail dress, a pointed Brooks saddle would make a rude impression
on the air.
These remarks, considering who's making them, are probably more on-
topic than three-quarters of what on RAT daily passes for electronic
conversation...
Andre "No Prejudice Here" Jute
Pics of my noseless saddle on my Trek L700 "Smover" are here:
http://members.lycos.co.uk/fiultra/BICYCLE%20%26%20CYCLING.html
Patrick Turner
fiul...@yahoo.com wrote:
>
> On Mar 27, 5:38 pm, fiult...@yahoo.com wrote:
> > Of course they're Brook amplifiers, not Brooks. -- Andre "Mr
> > Precision" Jute
>
> Cause I wouldn't want to be thought of as a calloused cyclist (like
> Patrick) sitting on a leather Brooks saddle for real men who know how
> to manage pain. -- Andre "The Hedonist" Jute
The Brooks saddle is a very decent British invention and a google search
will reveal some details.
I have them on the two bikes of 3 that I ride most of the time.
Their principle is that you sit upon a peice of stretched leather,
and this has wonderful properties of damping vibrations from the road,
and providing a support to pelvis bones which contours under bones
immediately.
One can shift around a bit on a Brooks, and it always "fits".
I had a procession of plastic and foam crap saddles and found they
caused
lots of saddle sores and discomfort.
The Brooks changed all that, and I could ride 300km in a day
and not get off with a sore arse, or have one while on.
They do suffer from poor build quality.
Each of the two I have had for 22 years and probably done
100,000 km upon have eventually broken the 5/16 inch adjustable
leather tensioning bolt under saddle nose.
I have had to replace these with 10mm mild steel bolt and nut.
It's a mod that takes me 30 minutes as a skilled and well tooled up
tradesman.
Also the rivets pull loose in the tensioned leather, so I have replaced
these
with 1/4 inch gutter bolts with filed down screw slot ridges to avoid
gradual ripping of riding sorts.
So once you get decent leather fastening into service, and decent
tension bolting,
they are the best saddle by far.
So far this year I have averaged 200km+ per week.
I did a fast 51km in 1:34 two weeks ago to see if I could get near my
"age standard" for the 40km or 25 mile time trial.
Apparently I did, and it seems I am not ageing as fast as the rest of
the
riding population. I could never get near the age standard
when I was in my early 40s, probably because so many
very good riders are still strong and still riding at 40, and their
fastest times determine the "age standard".
But I can now get better than the age standard at age 61.
Most of the guys who were so good until about 45 must have dropped right
out.
The course I chose is a multilane highway running north of Canberra,
the Federal Highway, between Watson and Lake George. There is a fine
wide
"breakdown lane" away from the traffic, and no traffic lights or
roundabouts
and very few places where any traffic enters or leaves, so yone can go
like
greased lightning, and not worry about being run over.
I chose early sunday morning with little traffic and very light wind,
temp about 20C.
The course has approx 400metres of rise in uphills going out,
and 300metres of rise returning. Maximum gradients are
less than 6%, with an average in mid hill of 4.5%.
I dunno how much faster I'd have gone if it was flat
which favours good times.
But I was comfortable, and could keep pressure on myself to
pedal all around the circle, and down hill as well.
I was sore in the knees until a day after, but not in the arse.
And my ancient custom made steel framed bike with 753R tubing feels
sublime.
I do have new Mavic D profile rims and 32 spokes per wheel and
very ordinary 25mm Vitoria clincher tyres.
I used to have much lighter Mavic wheels and tubular tyres glued on
and flattened blade spokes to do time trials 20 years ago.
But it appears they must have done me little good if what I do now is
any guide.
I have standard race bars, with no "triathlon" bars for the time
trialing
to get arms and elbows within the smallest frontal area.
I'm using ordinary lycra shorts and a cotton top with junk in the rear
pockets.
I can't afford a special skin suit and special helmet; can't afford any
fuckin
special anything, except I do find time to ride, and ride fairly hard
whenever I go out.
I'm also using ancient shoes and pedal plates with leather foot straps
with toe clips.
I have installed 8 speed Shimano SORA index gearing, a change from the
old
down tube lever shifting I found I really liked.
The bike with its heavy Brooks saddle is maybe 11.5 Kg with a watter
bottle and pump,
and about 2Kg+ more than the carbon fibre bikes which are now
mainstream.
So, I'm pushing more weight than I need to but in fact it doesn't matter
much,
all the guys my age have real trouble keeping up with me.
A few of the guys in a "social" group I go out with sometimes
can get up hills slightly quicker than me, but they suffer on the down
hill and flats
where my weight assists or does not matter.
And I keep passing guys of 25 with all the latest crap they've spent
several thousand bucks upon.
But they got no Brooks saddle.
And BTW, having the inside of your lycra shorts lined with real fine
leather
also is a big plus; its the best; but now largely unobtainable cheaply,
and fortunately I have found a local shorts maker who
uses some synthetic junk which allows 130km at least without chafing.
Because I am giving this little OT talk about cycling,
I'd like to include a report important for anyone to read regarding
their likelyhood of heart problems.
Norman Swan is a guy running a Health programme on ABC Radio National.
he interviews Dr Micheal Lauer from the US........
Norman Swan: Welcome to the program.
Today, Vitamin D from one of the world's leading researchers in the
field. In fact the person who found the active form of the vitamin, who
with others has gone on to discover that a vitamin people thought was
only important for bones might have a role in other parts of the body
too, like the prostate or breast.
And does sunblock affect your vitamin D status? You'll find out that
later, too.
Now I don't know about you but I'm always seeing joggers stopping to
take their pulses and I'm never sure why; they probably have some
esoteric knowledge about their fitness level which escapes me. But
research published last week in the United States may one day give them
a very good reason.
In a six-year follow-up study, researchers showed that in a group of men
and women aged around 57, the heart rate one minute after peak exercise
strongly predicted their likelihood of dying in the following few years.
It's a dramatic finding which could have an impact on the way people
with serious coronary risk are screened or indeed whether you need to go
on to have fancier tests like nuclear heart scans of angiography where
your coronary blood vessels are catheterised and X-rayed.
And if the findings are repeated outside the laboratory in real life,
for example in pulse-taking joggers, it could have wide public health
ramifications.
The person who led the research team was Dr Michael Lauer, a
cardiologist at the prestigious Cleveland Clinic in Cleveland, Ohio.
Michael Lauer: We looked at something very simple; we looked at the
heart rate at the end of exercise, in people undergoing exercise
testing, and then we looked at their heart rate one minute after they
finished exercise. We took the difference between the heart rate at peak
exercise and the heart rate one minute later, and we measured the heart
rate recovery. We followed 2,400 patients for about six years, during
which time 213 of them died. And what we found was that this change in
heart rate during the first minute after exercise was an extremely
powerful predictor of mortality, in fact it was the most powerful
predictor of mortality that we've looked at; it was a more powerful
predictor of mortality than nuclear tests, which look at blood flow
abnormality to the heart, and it was a much more powerful predictor of
mortality than the electrocardiogram we physically looked at during
exercise.
Norman Swan: Or during the stress test. So give me an idea of peak
exercise in the stress test; how far do you take people in the stress
test to get to this peak level?
Michael Lauer: Well typically we will exercise people for about 8-12
minutes, that's how long it usually takes to get somebody going very
quickly and getting them to the point of maximal exhaustion. Let's say
for a typical 50-year-old man, you'd expect the heart rate to rise from
about 70 at rest to about 170 at peak exercise. And then what we'd like
to see is the heart rate fall by at least 20 beats per minute during
that first minute after exercise. That would take us down to 150. People
with an abnormal heart rate recovery, the heart rate only falls by a
little bit during that first minute after exercise. They were the ones
who were at really high risk for subsequent death.
Norman Swan: I think in the paper you defined the heart beat reduction
as 12 beats per minute or less.
Michael Lauer: Twelve beats a minute, that's correct.
Norman Swan: As a reduction. Can you apply this knowledge, or is there
any other research which suggests if you go for your average jog,
measure your pulse at the end of it and your pulse a minute later,
that's got any measure worth considering here?
Michael Lauer: That's a very good question, because an average jog
typically is not maximal exercise. We are looking at people who
underwent some maximal exercise, and we're going to look at that as
well. My guess is that it will work, but that's something that will
require some further research.
Norman Swan: What is it about the heart, what is it about the
cardiovascular system that you're measuring here? Is it some sort of
holistic measure that you can't pin it down to one thing, in other words
you're getting a kind of global snapshot of the health of the
cardiovascular system, or is it something specific?
Michael Lauer: What we're actually measuring is something called the
autonomic nervous system, that part of the nervous system that regulates
heart rate and blood pressure and breathing. It's been known for a long
time that abnormalities of the autonomic nervous system are correlated
with death risk, but the problem is that the way in which these
abnormalities are measured are very difficult. They require
sophisticated equipment and they require the kind of tests which simply
have not entered the realm of normal clinical practice. What we find is
that these very, very simple measures that are obtained as part of
regular routine exercise testing deflect what happens to the autonomic
nervous system and provides us with just as powerful predictors of risk
of death.
Norman Swan: So what you're saying is you're not finding necessarily
blocked coronary arteries; in other words you couldn't replace the
stress test or some of these nuclear scans with this simple test,
because it's not picking up a blocked artery which then you can go on
and do an angioplasty on.
Michael Lauer: Well we may very well; we are looking at something
different than blocked coronary arteries. But what we can say is this:
people have a normal heart rate recovery are at extremely low risk, and
because they are at extremely low risk, it makes a lot more sense to
manage them conservatively, and not project them to essentially risky
procedures. If you know that somebody has a death risk of less than 1%
per year then it really doesn't make very much sense to refer them for a
procedure which carries with it a 1%-2% chance of death within 30 days.
Norman Swan: So in other words, it's almost a negative message that you
get from it from the positive result.
Michael Lauer: Well yes. I would say right now the immediate practical
use of this is that if a patient has a normal heart rate recovery, that
identifies them as a low risk, therefore we don't really need to send
them for further testing unless they're having for example refractory
symptoms. But if their symptoms are easily controlled by medicines, or
they're not having any symptoms at all, you know they're at very low
risk and so we know that we can comfortably manage them conservatively
without going on to any further testing.
Norman Swan: Now this paper is interesting in that you don't actually
commit yourselves to saying that these people died of heart attacks or
sudden coronary death. It's overall death. Now commonsense would say
that they karked it from their hearts, but you're not sure; why is that?
Michael Lauer: We're not sure why they died, that's something which is
going to have to require further research. What the exact mechanism is
between this and death is not known. The current most popular theory is
that if there's problems with the autonomic nervous system, people are
more vulnerable to developing fatal heart arrhythmias, like sudden
cardiac death and that's the most likely cause of death but that's going
to require more work.
Norman Swan: So just in summary: the next challenge with this is to see
whether without bringing somebody into the laboratory, there is a way of
predicting, with just regular exercise, whether or not your recovery is
adequate?
Michael Lauer: Right. And other things that we need to look at is how
well this is working in other populations. We also need to look at how
best to incorporate this with the rest of the exercise test result. And
then of course one big question is what do you do about people who have
an abnormal heart rate recovery beyond things that we already know
about, like smoking cessation, cholesterol reduction and blood pressure
reduction. Are there other things that we could specifically do to treat
this abnormality, and that's something which will have to await further
work.
Norman Swan: Let's say for a moment you had somebody who has an abnormal
heart rate recovery one minute after the stress test, but the stress
test doesn't show any ischaemic changes, there's no changes due to
shortage of blood supply, therefore nothing that otherwise would make
you suggest there's a blocked coronary artery. If it was you, would you
ask the doctor to send you off for an angiogram to see whether or not
you've got a blocked coronary artery?
Michael Lauer: I would be very worried. That would be an occasion I
would be worried about. What I would do next is an imaging test; I would
do like a nuclear test, or an echocardiogram to see if there's evidence
of a blockage there, then I would go from there. I would only get a
coronary angiogram if the imaging test showed that there is a problem.
Norman Swan: Michael Lauer, thanks for joining us on the Health Report.
Michael Lauer: Great, thank you so much for your interest in our work.
Norman Swan: Dr Michael Lauer is a cardiologist at the Cleveland Clinic
and that study was published in the current edition of The New England
Journal of Medicine.
Reference:
Cole et al. Heart-rate recovery immediately after exercise as a
predictor of mortality. New England Journal of Medicine
1999;341:1351-1357
Guests:
Dr. Michael Lauer
Department of Cardiology,
Cleveland Clinic Foundation,
Desk F25,
9500 Euclid Ave.,
Cleveland, Ohio 44195,
U.S.A.
email: lau...@ccf.org.
I hope this doesn't put too many people off getting from A to be with
only
200 watts or less to propel them.
The fact so many folks seem to need 22,000 watts at least is a
terrible folly of the human species.
Patrick Turner.
Andre Jute
Patrick Turner wrote:
> Patrick Turner.
The rest is about vintage Brook tube amps; I leave it for those
interested. -- AJ