Re: NFB windings, was there a US style and UK style?

[mike s]

On Monday, May 30, 2011 12:42:51 AM UTC+1, Bret Ludwig wrote:
> On May 21, 4:53*am, Patrick Turner > wrote:
> > I happened to mention......
> >
> > >> *The Williamson is *FAR BETTER amp design than
> > > > anything with two pentode input tubes. But in 1950, many designers had
> > > > a real bad case of pentoditis, the affliction where blokes chose a
> > > > pentode instead of two low µ triodes which give much less THD and
> > > > IMD.
> >
> > > I'll post the whole Baxandall article soon. *The design was a direct response to Williamson, *attempting to show how equivalent performance could be achieved with fewer components and greater efficiency. *This is probably why broadcasters favoured pentodes and tetrodes over triodes, *because if you've got a lot of amplifiers in a small space all triode amps would be very hot.
> >
> > The original Williamson was a 16W class AB1 amp with lots of class A
> > from two hot running KT66. It didn't need to run hot if biased for for

Don't forget "triode strapped"! Everything done to improve linearity, nothing done to reduce power consumption.

> > less Ia, because the OPT was very wide BW ( for 1947 ) and the
> > crossover THD was mostly 3H and reduced by NFB OK.
> > The Williamson could easily be made to run with input and driver being
> > two 9 pin mini twin triodes, 12AT7 for input and concertina phase
> > inverter and 12AU7 for balanced amp. If the OP stage was configured in
> > UL, then you have a truly superlative tube amp for 30W class AB with
> > KT66, and the tubes need not take up any more space than a Quad-II,

I was meaning "at the time, i.e. 1947". Yes there were a few new "miniature" valves launched in that year, e.g. the EF40 was launched around then. However I expect most designers of high quality audio weren't too keen to experiment with such things. The ultra-linear circuit possibly crossed the Atlantic about that time too. In reality the starting point for Williamson's amplifier was the 1930s Wireless World Quality amplifier, not the Mullard 5-20 as that would have required a Tardis.

http://mike.wepoco.com/Home/retro-geekery/valve-amplifiers/wireless-world-quality-amplifiers


> > many of which were parked under benches out of sight, out of mind
> > until their terrible biasing method made tubes run with unbalanced Ia
> > thus slowly ruining the sound. The main benefit of a genuine
> > Williamson was avoided like the plague by most makers because none
> > took Williamson's ideas seriously about OPTs, including Quad. Only a
> > few old Leaks ever had OPTs made to the Willy specs. After awhile,
> > makers just used crap in all things they foisted upon the public.
> > After Williamson, there was only lip service to quality.
> >
> > There were a few companies which evolved to have a "no compromise"
> > approach to tube amp engineering such as ARC and others, but you paid
> > through the nose to buy such things, and more recently even these
> > companies make things without many refinements such as "simplicity
> > with circuit integrity", ie, over engieneered stuff, and it all too
> > often ends up at my repair bench because of bad smoking habits.
>
> The original Willy OPT is WAY too complicated and the amplifier
> needlessly complicated. Commercial opt winders in the UK (Partridge),
> USA (several) and Japan (Hashimoto, Tango, Lux) all excelled the Willy
> design with much simpler interleaving.

It was actually "typically" complicated for its day. Many commercial British amplifiers of the time were still transformer coupled, I have Vortexion and Sound Sales amps from 1947 that use L63 driving a phase splitter transformer into a push-pull pair of 6L6, or 6V6, or similar. All of these amps were drawing on British designs from the 1930s but using American valves or British copies as WWII had pretty much put an end to classic British valves such as MH4, PX4, PX25 etc.

[Patrick Turner]

On May 31, 1:08*am, mike s > wrote:
> On Monday, May 30, 2011 12:42:51 AM UTC+1, Bret Ludwig wrote:
> > On May 21, 4:53*am, Patrick Turner > wrote:
> > > I happened to mention......
>
> > > >> *The Williamson is *FAR BETTER amp design than
> > > > > anything with two pentode input tubes. But in 1950, many designers had
> > > > > a real bad case of pentoditis, the affliction where blokes chose a
> > > > > pentode instead of two low µ triodes which give much less THD and
> > > > > IMD.
>
> > > > I'll post the whole Baxandall article soon. *The design was a direct response to Williamson, *attempting to show how equivalent performance could be achieved with fewer components and greater efficiency. *This is probably why broadcasters favoured pentodes and tetrodes over triodes, *because if you've got a lot of amplifiers in a small space all triode amps would be very hot.
>
> > > The original Williamson was a 16W class AB1 amp with lots of class A
> > > from two hot running KT66. It didn't need to run hot if biased for for
>
> Don't forget "triode strapped"! *Everything done to improve linearity, nothing done to reduce power consumption.

A minor detail. In 1947, and until compact fluorescent lamps became
compulsory, a typical suburban house might have 20 incandescent light
globes, with 40W each, and 6 might be turned on for 6 hours a night,
and then there were the electric heaters and fridges and stoves and
hot water systems. Nobody gave a **** about the 10% of the total power
they used for lighting and amplifiiers and radio. Williamsons draw
about 160W from the mains at idle, 4 light bulbs's worth. 4 hours is
0.64 KWH, at 16c per KWH, its 10c to listen to 4 hour's music. Heating
160Litres of water for 3 people's baths takes 9,000 watts for an hour,
so that's 9KWH, and so baths cost $1.44, and 365 days a year its a
total of $525. A water bed which is turned on permanently with a
thermostat set for 23C and in a cool climate and without central
heating might average 250 Watts 24/7, maybe $350 pa. Mine used to cost
that much to run and when it began to leak I dumped it. Teenage
daughters might easily drain a whole 160 hot water tank on their own
during their long showers and hair washing expeditions.

>
> > > less Ia, because the OPT was very wide BW ( for 1947 ) and the
> > > crossover THD was mostly 3H and reduced by NFB OK.
> > > The Williamson could easily be made to run with input and driver being
> > > two 9 pin mini twin triodes, 12AT7 for input and concertina phase
> > > inverter and 12AU7 for balanced amp. If the OP stage was configured in
> > > UL, then you have a truly superlative tube amp for 30W class AB with
> > > KT66, and the tubes need not take up any more space than a Quad-II,
>
> I was meaning "at the time, i.e. 1947". *Yes there were a few new "miniature" valves launched in that year, e.g. the EF40 was launched around then.. *

But there were plenty of miniatures instead of EF86.

However I expect most designers of high quality audio weren't too keen
to experiment with such things.

There were not too many who wanted high quality amps. Hi-fi in homes
was a tiny concern amoung a few nutters who might afford it. But BBC
and institutions afforded anything they wanted when the Chief Bean
Counter wasn't looking.

The ultra-linear circuit possibly crossed the Atlantic about that time
too. * In reality the starting point for Williamson's amplifier was
the 1930s Wireless World Quality amplifier, *not the Mullard 5-20 as
that would have required a Tardis.

I doubt I suggested Mullar 520 preceeded junk like the WWQ amp of the
1930s. What a lemon! even had output triodes which could be biased at
Eg = 0V. NO NFB, Pitiful electro C values. JUNK. Anyway, the
Williamson is much better, and the Mullard which followed was better
than WWQ amp but worse than Willy's amp. Mice had got into Mullard
designers's brains after being released there by the accountants
worse task it was to measure the costs and keep them low, so EF86 and
a 12AX7 were cheaper to implement than two far better performing 6SN7.

> http://mike.wepoco.com/Home/retro-geekery/valve-amplifiers/wireless-w...

> > > many of which were parked under benches out of sight, out of mind
> > > until their terrible biasing method made tubes run with unbalanced Ia
> > > thus slowly ruining the sound. The main benefit of a genuine
> > > Williamson was avoided like the plague by most makers because none
> > > took Williamson's ideas seriously about OPTs, including Quad. Only a
> > > few old Leaks ever had OPTs made to the Willy specs. After awhile,
> > > makers just used crap in all things they foisted upon the public.
> > > After Williamson, there was only lip service to quality.
>
> > > There were a few companies which evolved to have a "no compromise"
> > > approach to tube amp engineering such as ARC and others, but you paid
> > > through the nose to buy such things, and more recently even these
> > > companies make things without many refinements such as "simplicity
> > > with circuit integrity", ie, over engieneered stuff, and it all too
> > > often ends up at my repair bench because of bad smoking habits.
>
> > *The original Willy OPT is WAY too complicated and the amplifier
> > needlessly complicated. Commercial opt winders in the UK (Partridge),
> > USA (several) and Japan (Hashimoto, Tango, Lux) all excelled the Willy
> > design with much simpler interleaving.
>
> It was actually "typically" complicated for its day. *Many commercial British amplifiers of the time were still transformer coupled, I
> have .Vortexion and Sound Sales amps from 1947 that use L63 driving a phase splitter transformer into a push-pull pair of 6L6, or 6V6, or
> similar. * All of these amps were drawing on British designs from the 1930s but using American valves or British copies as WWII had pretty > much put an end to classic British valves such as MH4, PX4, PX25 etc.

I guess the business models proposed after WW2 involved much
rationalisation, and as we know, mechancial marvels like Mustangs and
Spitfires were also phased right out of production. Progress. Nobody
can stop it. Steam Trains. GONE. Telegrams - GONE, now I have cheap
eamils. But its nice to see a few old things still running, like a few
Spitfires, even one or two Quality Amplifiers. Much technical
complexity and clever excellence for that time represents Angry
Technology, used for killing people. We must remember the worst we've
been through, lest it happen again, although some of the past imbodies
wonderment, the majesty of the large steam loco, the nimble flyer like
the Spitty, the triodes.
But the background to the life of peace and relaxation ppl enjoyed in
1947 wasn't all wonderment and roses. The workings of an average
abatoir in 1947 were very grim places to work where animals were
subject to serious torture during the killing process. Well, stun guns
and better ways to get the damn business over and done with quick were
introduced. Much of the horrible ****ed up past must be left behind
without remorse, nostalgia or bull**** emotions. But films were shown
on Four Corners, a TV doco in Oz, about Indonesian abatoirs, and their
methods remain locked in the past and severe cruelty at abatoirs by
callous workers prevails. The films blew the whisle on CRAP HAPPENING,
and a live meat export industry is theatened. See how MONEY is the
root of evil, and greed blinds us to suffering? See how religion
blinds us to suffering? Anyway, there's a big row going on about this
**** now. Reforms are to be forced if necessary, but difficult while
STOOPID Islamics insist on halal killings with beasts bled to death
after severe beatings and terrible injuries while trying to get the
beasts to pole where they are to be chained up and bled. The point is
that its not a bad thing to leave the past behind. Where examples of
the past are still present, it shocks us all the more. Factory workers
in developing countries are routinely being treated like animals like
the Satanic Mills of Deare Olde Englande in 1800. Nobody really can
justify manufacture of a Rolls Royce while the worlds poor suffer. Its
a huge waste of resources. Coal mining for power generation kills
3,000 blokes in China each year. Let's not weep when the mines are
closed.
Good old days? nope, just grime, dirt, and work and a short life for
most. That's what old artifacts remind me of; sure,a Spitty fly past
is grand, but it only needs to happen rarely for me.

But for those who just can't help themselves love the past, there are
things less boring than old british triodes.
http://www.aviationmuseum.com.au/

Patrick Turner.

[Big Bad Bob]

On 05/30/11 08:08, mike s so wittily quipped:
>>> The original Williamson was a 16W class AB1 amp with lots of class A
>>> from two hot running KT66. It didn't need to run hot if biased for for
>
> Don't forget "triode strapped"! Everything done to improve linearity, nothing done to reduce power consumption.
>
>>> less Ia, because the OPT was very wide BW ( for 1947 ) and the
>>> crossover THD was mostly 3H and reduced by NFB OK.

I thought the whole thing about using tubes in high end audio is 'damn
the efficiency' because Class 'A' output (PP or SE) has its own sound
and a lot of people prefer it...

'cause if you want efficiency, there are 'exotic class' amplifiers, plus
bi-amping and switching amps. Bi-amp works pretty well for most audio,
though it CAN give you some strange artifacts. I used to have a bi-amp
stereo system in my car, years ago. Anyway, that kind of efficiency
usually has 'other issues' that audiofiles would rather not mess with.
Back to tubes again. Cool-factor glass + metal that glow when they operate.