New 91A amp

Re: New 91A amp



"John Byrns" <byrnsj@sbcglobal . net > wrote in message
news:byrnsj-0C914B.07542313052008@newsclstr02.news.prodigy . com ...
> In article
> <ed1d83aaf13e6a5da263087932961bf2@localhost.talkaboutaudio . com >,
> "BretLudwig" <bratzirules@gmx.us> wrote:
>
>> Shame to put all that work into something with a crappy circuit like the
>> WE 91.
>
> How could the circuit be improved, short of going push=pull?
>

My thoughts also. Perhaps Bret would take us through his
ideas of how this circuit could be upgraded.

regards to all
Iain

Re: New 91A amp

BretLudwig wrote:
> Shame to put all that work into something with a crappy circuit like the
> WE 91.
>
> --
> Message posted using * w w w .talkaboutaudio . com /group/rec.audio.tubes/
> More information at * w w w .talkaboutaudio . com /faq.html
>
>
I'm open to suggestions.

Raymond

Re: New 91A amp


"Raymond Koonce"

> I'm open to suggestions.


** Prove it !!!

By changing those puny, under-rated & unsafe AC switches switches.




.... Phil

Re: New 91A amp



Phil Allison wrote:
>
> "Raymond Koonce"
>
> > I'm open to suggestions.
>
> ** Prove it !!!
>
> By changing those puny, under-rated & unsafe AC switches switches.
>
> .... Phil

I have a 7070 VAC amp here for some repairs and "slight" upgrading.

Its got 4 x 300B in mainly class A PP for each channel, giving a max of
70W AB.
There are two mains inputs and two mains PT because its a genuine dual
monoblock
amp.

Its also a royal pain in the arse because the fuckin thing weighs maybe
60Kg.

The two mains switches are tiny toggle things and mains wiring isn't
thick like I would use. But, they have worked for over 10 years OK.
Its a complete miracle that the toggle levers have not been broken off.

Because I hate such switches, I will be using them to switch 12Vdc
from a low VA auxiliary PS and a rugged relay for the mains which also
is used to interupt the mains if excessive Ik flows in any output tube.
I am fitting active protection against bias failure and/or thermal
runaway.

The amp was bought cheap and failing tubes caused a fire to
scorch part of the circuit board.
The repair by someone else was bodgied, and a dry joint caused more
failings.....
Another saga of a high end bitta crap producing too much smoke...
VAC had the 300B running with 37 watts of idle dissipation
which was way too high, and not at all necessary to get
a huge amount of pure class A PO before the class AB threshold.

The power and output trannies seem to have wiring colour coding
that looks very like what Hammond have.

But PT is quiet, and the OPT has wide BW, and the loading is OK.

Many hi-end amps use thin wiring, teflon insulated, with silver plated
stranded copper wire.
Initially, before I changed the HT tap, the B+ went up
to +600V before the loading pulled it down a bit.

So just after turn on there is 600Vdc across a 0.2mm thickness of
teflon.

Not good, but it seems to work.

Patrick Turner.

Re: New 91A amp



Raymond Koonce wrote:
>
> Hi RATs,
>
> I put up a page for a new amp I built.
>
> * w w w .timebanditaudio . com /Harald%20van%20Haaren%20Amp/vanHaaren300B.html
>
> If the link doesn't work go to my main page at
> * w w w .timebanditaudio . com /timebandit.html and go to the bottom of
> the page.
>
> This one sounds really nice. Zero audible hum.
>
> Best regards,
>
> Raymond

Nice, and they tell me your favourite colour = red....

Patrick Turner.

Re: New 91A amp

Patrick Turner wrote:
>
> Raymond Koonce wrote:
>> Hi RATs,
>>
>> I put up a page for a new amp I built.
>>
>> * w w w .timebanditaudio . com /Harald%20van%20Haaren%20Amp/vanHaaren300B.html
>>
>> If the link doesn't work go to my main page at
>> * w w w .timebanditaudio . com /timebandit.html and go to the bottom of
>> the page.
>>
>> This one sounds really nice. Zero audible hum.
>>
>> Best regards,
>>
>> Raymond
>
> Nice, and they tell me your favourite colour = red....
>
> Patrick Turner.

Thanks Patrick. I like the red color (my personal amp is silver), but
it seems to be the color of choice for my customers. I offer them
whatever they want and they invariably choose red.

Raymond

Re: New 91A amp



Raymond Koonce wrote:
>
> Patrick Turner wrote:
> >
> > Raymond Koonce wrote:
> >> Hi RATs,
> >>
> >> I put up a page for a new amp I built.
> >>
> >> * w w w .timebanditaudio . com /Harald%20van%20Haaren%20Amp/vanHaaren300B.html
> >>
> >> If the link doesn't work go to my main page at
> >> * w w w .timebanditaudio . com /timebandit.html and go to the bottom of
> >> the page.
> >>
> >> This one sounds really nice. Zero audible hum.
> >>
> >> Best regards,
> >>
> >> Raymond
> >
> > Nice, and they tell me your favourite colour = red....
> >
> > Patrick Turner.
>
> Thanks Patrick. I like the red color (my personal amp is silver), but
> it seems to be the color of choice for my customers. I offer them
> whatever they want and they invariably choose red.
>
> Raymond

I only had one customer asking for red; and to match the colour of
Cabernet Sauvignon.

Most want black, or black, and some also wanting black,
with the remainder wanting black as well....

Patrick Turner.

Re: New 91A amp



"Patrick Turner" <info@turneraudio . com .au> wrote in message
news:482A9A0B.16D3F7C0@turneraudio . com .au...

> I only had one customer asking for red; and to match the colour of
> Cabernet Sauvignon.
>
> Most want black, or black, and some also wanting black,
> with the remainder wanting black as well....
>

:-)))

I took a tube RIAA stage to show to a dealer who had
expressed an interest in it. We sat together in his listening
room, and played some LPs of his choice. He looked
pleased. He was silent for a long time, and then said,
"Sorry, I can't sell this. It's black"

* w w w .kolumbus.fi/iain.churches/Pics/ValveRIAA02.jpg

I thanked him for his time and the coffee, and put
my amp under my arm.

On the way out, I noticed that every single unit in the shop
was silver anodised. Most had blue-lit dials, and apart from
the maker's logo looked identical:-)

It's nice to be different:-)

Iain

Re: New 91A amp

Phil's a bit of a cunt isn't he?

Anyway, yes, SE is the big 91 flaw but it could be improved with NFB off
the secondary or via a tertiary. The 91 has NFB but the opt is not in the
loop.

--
Message posted using * w w w .talkaboutaudio . com /group/rec.audio.tubes/
More information at * w w w .talkaboutaudio . com /faq.html

Re: New 91A amp



Iain Churches wrote:
>
> "Patrick Turner" <info@turneraudio . com .au> wrote in message
> news:482A9A0B.16D3F7C0@turneraudio . com .au...
>
> > I only had one customer asking for red; and to match the colour of
> > Cabernet Sauvignon.
> >
> > Most want black, or black, and some also wanting black,
> > with the remainder wanting black as well....
> >
>
> :-)))
>
> I took a tube RIAA stage to show to a dealer who had
> expressed an interest in it. We sat together in his listening
> room, and played some LPs of his choice. He looked
> pleased. He was silent for a long time, and then said,
> "Sorry, I can't sell this. It's black"
>
> * w w w .kolumbus.fi/iain.churches/Pics/ValveRIAA02.jpg
>
> I thanked him for his time and the coffee, and put
> my amp under my arm.
>
> On the way out, I noticed that every single unit in the shop
> was silver anodised. Most had blue-lit dials, and apart from
> the maker's logo looked identical:-)
>
> It's nice to be different:-)
>
> Iain

There was a time in about 1975 when anodized bright and brushed
aluminium
was the peak of putting on the agony, and putting on the style.
Meters had green or yellow background lighting, and blue LEDs hadn't
been invented.

Then everything went black, and people complained they had to have a
torch
to find the "play" button, or the "on" switch.

Fashion has swung back to the silver look for much stuff.

But have you surveyed the colors of major hi-end gear?

Anyway, in Orstraya, which is at some large distance away from full
civilisation
and its fickle changing trendiness, ie, it is culturally "astray",
people wanting decent tube amps are very accepting of black.
They still like black speakers.
They even didn't mind my use of polished brass chassis which tended to
tarnish.

Real metal though.

Black was brought to hi-fi gear because it was cheaper to make,
and it covered a multitude of minor defects in a design.

But now the mass market colured junk is all moulded plastic.
Fake metalwork.
And once dropped, it splits and breaks, and you buy another....

Patrick Turner.

Re: New 91A amp



"Patrick Turner" <info@turneraudio . com .au> wrote in message
news:482AE7C7.71A21400@turneraudio . com .au...
>

> There was a time in about 1975 when anodized bright and brushed
> aluminium
> was the peak of putting on the agony, and putting on the style.
> Meters had green or yellow background lighting, and blue LEDs hadn't
> been invented.

Someome building a single amp, or very small batches
has the distinct advantage in that a standard chassis
can be used, but with a little ingenuity, each one
can look distinctly different. Colour is of course a
very personal thing. I generally use anodised panels,
so black is the obvious choice. Waiting times at anodising
firms for blue, gold or red is long, and to my conservative
eye the panels look garish.

But some people still like to work in copper or stainless steel.
One of the guys with whom I share a workshop has a stainless
steel chassis made for a tube amp. He spent four days polishing
it. When I complemented him on his patience, he said "This is
lightning quick compared with the time I spend sanding the
body of an acoustic guitar.
>
> Anyway, in Orstraya, which is at some large distance away from full
> civilisation
> and its fickle changing trendiness, ie, it is culturally "astray",
> people wanting decent tube amps are very accepting of black.
> They still like black speakers.

I agree. A good speaker in a piano lacquer cabinet looks very
good indeed, and gives the impression of being physically smaller
than it actually is. A young lady, an interior design consultant with
whom I recently discussed the subject of audio systems in rooms,
told me that actually mid-grey would be the best colour for speaker
cabinets, and would sit well in almost any interior. She also opined
that from interior designer's point of view speaker cabinets should
be narrow (across the front) but deep, front to back. Interesting
lass!


> They even didn't mind my use of polished brass chassis which tended to
> tarnish.
>
> Real metal though.
>
> Black was brought to hi-fi gear because it was cheaper to make,
> and it covered a multitude of minor defects in a design.
>
As I have mentioned before, it is fun to talk to people about their
consmetic preferences for amplifiers. Some have good ideas, and
others are clueless, unless you can show thewm something half-ready
as a starting point.

Iain

Re: New 91A amp

In article <0cGWj.950$_03.559@reader1.news.saunalahti.fi>,
"Iain Churches" <IainNG@kolumbus.fi> wrote:

> Someome building a single amp, or very small batches
> has the distinct advantage in that a standard chassis
> can be used, but with a little ingenuity, each one
> can look distinctly different. Colour is of course a
> very personal thing. I generally use anodised panels,
> so black is the obvious choice. Waiting times at anodising
> firms for blue, gold or red is long, and to my conservative
> eye the panels look garish.

I don't know about that, most of the pro audio equipment, mostly
broadcast, that I remember from the post WW2 tube era was painted in
shades of blue, green, umber, gray, silver, and the like, with very
little black. Black seems to have been the color of choice before WW2,
and of course is the standard in home audio equipment today.


Regards,

John Byrns

--
Surf my web pages at, * fmamradios . com /

Re: New 91A amp


"John Byrns" <byrnsj@sbcglobal . net > wrote in message
news:byrnsj-D1D666.13495214052008@newsclstr03.news.prodigy . net ...
> In article <0cGWj.950$_03.559@reader1.news.saunalahti.fi>,
> "Iain Churches" <IainNG@kolumbus.fi> wrote:
>
>> Someome building a single amp, or very small batches
>> has the distinct advantage in that a standard chassis
>> can be used, but with a little ingenuity, each one
>> can look distinctly different. Colour is of course a
>> very personal thing. I generally use anodised panels,
>> so black is the obvious choice. Waiting times at anodising
>> firms for blue, gold or red is long, and to my conservative
>> eye the panels look garish.
>
> I don't know about that, most of the pro audio equipment, mostly
> broadcast, that I remember from the post WW2 tube era was painted in
> shades of blue, green, umber, gray, silver, and the like, with very
> little black. Black seems to have been the color of choice before WW2,
> and of course is the standard in home audio equipment today.

Ah the old black crackle paint - good stuff covered up all the rough bits in
the tin bashing :)

Keith

Re: New 91A amp



"keithr" <keithr@nowhere . com .au> wrote in message
news:482bd343$1@dnews.tpgi . com .au...
>
> "John Byrns" <byrnsj@sbcglobal . net > wrote in message
> news:byrnsj-D1D666.13495214052008@newsclstr03.news.prodigy . net ...
>> In article <0cGWj.950$_03.559@reader1.news.saunalahti.fi>,
>> "Iain Churches" <IainNG@kolumbus.fi> wrote:
>>
>>> Someome building a single amp, or very small batches
>>> has the distinct advantage in that a standard chassis
>>> can be used, but with a little ingenuity, each one
>>> can look distinctly different. Colour is of course a
>>> very personal thing. I generally use anodised panels,
>>> so black is the obvious choice. Waiting times at anodising
>>> firms for blue, gold or red is long, and to my conservative
>>> eye the panels look garish.
>>
>> I don't know about that, most of the pro audio equipment, mostly
>> broadcast, that I remember from the post WW2 tube era was painted in
>> shades of blue, green, umber, gray, silver, and the like, with very
>> little black. Black seems to have been the color of choice before WW2,
>> and of course is the standard in home audio equipment today.
>
> Ah the old black crackle paint - good stuff covered up all the rough bits
> in the tin bashing :)
>

Crackle was good, and durable. Was it baked?

There was also what we used to call "hammer finish"
Most broadcast equipment was painted like this,
usually grey. The AVO MkIV tube tester is a good example.
* w w w .kolumbus.fi/iain.churches/Pics/AVO/MkIV/TopPanel03.jpg

One can now buy aerosol tins of "hammer lacquer"
Does anyone have experience of this?


Regards
Iain

Re: New 91A amp

Iain said:

> One can now buy aerosol tins of "hammer lacquer"
> Does anyone have experience of this?

Silicon, commonly. For bodging, IMO. Sticks to bare metal
pretty much regardless of corrosion, as long as it's dry and
not flaky. Crinkly or hammer finish disguises poor surface
preparation. Relies on being waterproof, so pinholes
eventually allow moisture to penetrate and corrosion spreads
underneath paint until eventually it falls off in sheets.
Otherwise it is hard to remove and nothing sticks on
top...not even more of the same paint...so it's a one-coat,
zero-maintenance eyesore waiting to happen, eventually.

It's about as good for painting as WD40 is for lubrication.

Ian