Those of you with a predilection for copious amounts of glass and iron in
your amplifiers go scrute this site thoroughly:

http://www.sacthailand.com/


See the fabulous range of choice - 300Bs and 2A3s in particular and tell me
there's no demand for these seriously *broken* amps....???


Then see the 'Swing 32' and 'Swing 40' speakers and tell me they *ain't*
Jerichos:

http://www.apah69.dsl.pipex.com/fostexfe206e/fostex.htm

http://www.apah69.dsl.pipex.com/show/L1070577.JPG

http://www.apah69.dsl.pipex.com/show/L1070580.JPG

:-)

(Serious valve freaks note the Ulyanov GM-70s, btw....)

And finally, just for a laff, make your way to the Kiwame resistor page and
clock the nice Fluke Multimeter and tell me it ain't *identical* (apart from
the yellow case) from my trusty old Maplins Pro4 meter:

http://www.apah69.dsl.pipex.com/show/Meter.JPG

:-)

"Keith G" wrote in message
...

Those of you with a predilection for copious amounts of glass and iron in
your amplifiers go scrute this site thoroughly:

http://www.sacthailand.com/


See the fabulous range of choice - 300Bs and 2A3s in particular and tell
me there's no demand for these seriously *broken* amps....???


Then see the 'Swing 32' and 'Swing 40' speakers and tell me they *ain't*
Jerichos:

http://www.apah69.dsl.pipex.com/fostexfe206e/fostex.htm

http://www.apah69.dsl.pipex.com/show/L1070577.JPG

http://www.apah69.dsl.pipex.com/show/L1070580.JPG

:-)

(Serious valve freaks note the Ulyanov GM-70s, btw....)

And finally, just for a laff, make your way to the Kiwame resistor page
and clock the nice Fluke Multimeter and tell me it ain't *identical*
(apart from the yellow case) from my trusty old Maplins Pro4 meter:

http://www.apah69.dsl.pipex.com/show/Meter.JPG

:-)


Keith, congratulations:- An audio-relevant post on this ng.......

I don't think anyone has suggested there isn't a demand for these types of
amps, but then these things go in fashions. It certains avoids the
manufacturer having to worry that their products will meet tight
specs........

One oddity I've noticed. On the SILK attenuator pages, they say of
conventional resistor attenuators "That's why at high attenuation level (low
signal out, low listening level) the bandwidth of such volume control is
very poor and the bandwidth is not constant over any switch position."

This is only relevant if using very long high-capacitance cables. If using
cables of normal capacitance, and of normal domestic lengths, it has no
relevance as the bandwidth is already well in excess of the audio bandwidth.
Although I think a multi-tapped transformer as an attenuator is a bit of
overkill, it is a theoretically sound solution as the output impedance will
reduce as the attenuation increases. Pity they couldn't have 23 separate
secondaries, and keep the whole thing balanced input to output. Now that
*would* have given them a winding challenge!


They are AudioNote distributors..... nuff said....

As to the Maplins meter, there is a whole raft of Chinese OEM product
available for badging. I can't see why Fluke shouldn't do it like Maplins.
Going back a few years, before China became the manufacturing centre of the
World, thre was a magazine called JEI, the journal of the Japanese
Electronics Industry. In there you could find almost anything you wanted to
badge, provided you bought enough of them. I was particularly amused to see
several of the pick-up arms and cartridges sold by turntable manufacturers
as their standard product in the JEI.

Anyway, the SAC stuff looks nice, and if you like that sort of thing, I'm
sure it will give pleasure.

S.

Regarding attenuators, I've been looking at alternatives for tube
equipment. As I see it:
- autoformer attenuators need such low impedence in that you're looking
at big caps before them to stop the DC. So anything you gain on the
autoformer you lose on the cap. I use russian teflon caps of 0.1uf
value, so I'm not keen on large multiples of them. I'm OK with up to
..3, maybe .5 in extremis.
- true transformer attenuators are interesting - eliminates the cap if
it allows DC.
- On the other hand you could, in balanced mode, just use a PP output
stage for the line out, and position the volume control after that - no
cap.
- Cap before stepped attenuator is what I use right now. It works, and
sounds good with teflon caps. My line stage is balanced, so I use a
shunt attenuator between legs, which in the present case is 47K shunt
with two series resistors of 22K before it, one in each leg. So the
resistance in the stepped attenuator isn't exactly constant.
- for convenience of input between SE and balanced, the next way I'm
going to build is integrated mono amps with stepped attenuator after
the first valve stage. this means I can use the same shunt attenuator,
but I can accept input as SE or balanced, depending on whether or not I
earth the second grid of the input pair.
Thoughts and ideas? Andy

"Serge Auckland" wrote


Keith, congratulations:- An audio-relevant post on this ng.......


Once in a while I manage to get one loosely on-topic....!! ;-)


I don't think anyone has suggested there isn't a demand for these types of
amps, but then these things go in fashions.


Possibly, but I think we're looking at decades for complete trend swings. My
guess is SE is back for a while now - especialli in the East.


It certains avoids the
manufacturer having to worry that their products will meet tight
specs........


Well, all I can say is that earlier this evening I was running the German PP
against one of the SETs and there's *no way* I'd pick the PP if it was an
'either or' situation....???



One oddity I've noticed. On the SILK attenuator pages, they say of
conventional resistor attenuators "That's why at high attenuation level
(low signal out, low listening level) the bandwidth of such volume control
is very poor and the bandwidth is not constant over any switch position."

This is only relevant if using very long high-capacitance cables. If using
cables of normal capacitance, and of normal domestic lengths, it has no
relevance as the bandwidth is already well in excess of the audio
bandwidth. Although I think a multi-tapped transformer as an attenuator is
a bit of overkill, it is a theoretically sound solution as the output
impedance will reduce as the attenuation increases. Pity they couldn't
have 23 separate secondaries, and keep the whole thing balanced input to
output. Now that *would* have given them a winding challenge!


I'm sure if there was enough of a potential market for them they would offer
them thus. I thought the Silk transformers at least *looked* the blx and the
website is very good with plenty of pictorial information - always a good
thing in my book!!



They are AudioNote distributors..... nuff said....


I have an 'efriend' who is a bit susceptible to AN stuff. I pointed out to
him the following, earlier this evening:

AN TT1 = Systemdek

AN Arm1/2/3 = Rega

AN IQ2 = Goldring

Then he was asking me about Linn, so I told him Linn Decks werre Ariston
ripoffs with Audio Technica arms and carts!

(I hope that wasn't too far from the truth!!)


As to the Maplins meter, there is a whole raft of Chinese OEM product
available for badging. I can't see why Fluke shouldn't do it like Maplins.

I bet my Maplins version was a lot cheaper than the Fluke!!


Going back a few years, before China became the manufacturing centre of
the World, thre was a magazine called JEI, the journal of the Japanese
Electronics Industry. In there you could find almost anything you wanted
to badge, provided you bought enough of them. I was particularly amused to
see several of the pick-up arms and cartridges sold by turntable
manufacturers as their standard product in the JEI.

:-)

See above re. 'Brand Name Bull****'...!!


Anyway, the SAC stuff looks nice, and if you like that sort of thing, I'm
sure it will give pleasure.


I thought the whole site was very appealing! - *Thailand* this one, don't
forget!!

(Scary innit?? :-)

In article , Serge Auckland
wrote:

[snip]

One oddity I've noticed. On the SILK attenuator pages, they say of
conventional resistor attenuators "That's why at high attenuation level
(low signal out, low listening level) the bandwidth of such volume
control is very poor and the bandwidth is not constant over any switch
position."

Can you give the URL for the page? I'm puzzled as I'd expect the maximum
output resistance of a conventional attenuator to occur at about the -6dB
setting, and fall as the output level is reduced below that. i.e. not have
a "poor bandwidth" at low settings, but at relatively high ones.

Is there some reason why the transformer referred to *doesn't* also have a
bandwidth that "is not constant" as the attenuation is altered? If nothing
else, I'd assume that the inductances, capacitances, and resistances, would
all tend to change, and affect the bandwidth...

This is only relevant if using very long high-capacitance cables. If
using cables of normal capacitance, and of normal domestic lengths, it
has no relevance as the bandwidth is already well in excess of the
audio bandwidth. Although I think a multi-tapped transformer as an
attenuator is a bit of overkill, it is a theoretically sound solution
as the output impedance will reduce as the attenuation increases.

Will the input impedance not also tend to change as the o/p tap is changed?

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

"Jim Lesurf" wrote in message

In article ,
Serge Auckland wrote:

[snip]

One oddity I've noticed. On the SILK attenuator pages,
they say of conventional resistor attenuators "That's
why at high attenuation level (low signal out, low
listening level) the bandwidth of such volume control is
very poor and the bandwidth is not constant over any
switch position."

Can you give the URL for the page?

http://www.sacthailand.com/transSilkVolume.html

"The benefit of replacing plastic type volume control to stepped attenuator
is obviously the accuracy of tracking and the quality of selector switch
plus low noise resistors can reduce the signal loss to some degrees. However
the regular stepped attenuator featuring resistor type fails to offer better
impedance matching over plastic volume control. That's why at high
attenuation level (low signal out, low listening level) the bandwidth of
such volume control is very poor and the bandwidth is not constant over any
switch position. "


I'm puzzled as I'd
expect the maximum output resistance of a conventional
attenuator to occur at about the -6dB setting, and fall
as the output level is reduced below that. i.e. not have
a "poor bandwidth" at low settings, but at relatively
high ones.

SAC Thailand seems to be challenged both technically and linguistically.

Is there some reason why the transformer referred to
*doesn't* also have a bandwidth that "is not constant" as
the attenuation is altered?

Magic!

If nothing else, I'd assume
that the inductances, capacitances, and resistances,
would all tend to change, and affect the bandwidth...

Of course. We both know the drill...

This is only relevant if using very long
high-capacitance cables. If using cables of normal
capacitance, and of normal domestic lengths, it has no
relevance as the bandwidth is already well in excess of
the audio bandwidth. Although I think a multi-tapped
transformer as an attenuator is a bit of overkill, it is
a theoretically sound solution as the output impedance
will reduce as the attenuation increases.

It's ironic that tapped transformer attenuators have achieved some
popularity in whole-house loudspeaker systems, but resistive attenuators are
making a come back based on wider bandwidth.

Will the input impedance not also tend to change as the
o/p tap is changed?

With transformers, lots of funny stuff happens. One reason why a pro audio
mic preamp with transformers is usually considered to be a kind of EFX box.

In article , Arny Krueger
wrote:
"Jim Lesurf" wrote in message

In article , Serge
Auckland wrote:

[snip]

One oddity I've noticed. On the SILK attenuator pages, they say of
conventional resistor attenuators "That's why at high attenuation
level (low signal out, low listening level) the bandwidth of such
volume control is very poor and the bandwidth is not constant over
any switch position."

Can you give the URL for the page?

http://www.sacthailand.com/transSilkVolume.html

Ok. thanks. :-)

"The benefit of replacing plastic type volume control to stepped
attenuator is obviously the accuracy of tracking and the quality of
selector switch plus low noise resistors can reduce the signal loss to
some degrees. However the regular stepped attenuator featuring resistor
type fails to offer better impedance matching over plastic volume
control. That's why at high attenuation level (low signal out, low
listening level) the bandwidth of such volume control is very poor and
the bandwidth is not constant over any switch position. "

I'll visit the page and see if I can discover how they ensure the source
and load are matched for all transformer settings. :-)

[snip]

Is there some reason why the transformer referred to *doesn't* also
have a bandwidth that "is not constant" as the attenuation is altered?

Magic!

I noticed a 'review' of an (expensive) transformer used as a variable
'volume control' attenuator in a UK mag a few years ago, but didn't follow
up my puzzlement about it at the time...

It is now reminding me of the undergrad we once had doing a 'project'. Part
of the system he had to build was to divide a voltage to half the value.

He used an ADC and a DAC, with the wires between them shifted by one bit.

When we asked why he hadn't used a pair of resistors he gave us a funny
look and it became clear that the idea hadn't occurred to him. :-)

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

"Keith G" wrote in message
...

Those of you with a predilection for copious amounts of glass and iron in
your amplifiers go scrute this site thoroughly:

http://www.sacthailand.com/


See the fabulous range of choice - 300Bs and 2A3s in particular and tell
me there's no demand for these seriously *broken* amps....???


Keith. This is something that has been puzzling me for a very long time.
My local dealer tells me that the interest in single-ended is unprecidented.
and that second hand quality valve PP amps, particularly Quad, Radford and
McIntosh are especially "hot" items.

What does that tell us????

Iain

"Iain Churches" wrote in message
...

"Keith G" wrote in message
...

Those of you with a predilection for copious amounts of glass and iron in
your amplifiers go scrute this site thoroughly:

http://www.sacthailand.com/


See the fabulous range of choice - 300Bs and 2A3s in particular and tell
me there's no demand for these seriously *broken* amps....???


Keith. This is something that has been puzzling me for a very long time.
My local dealer tells me that the interest in single-ended is
unprecidented.
and that second hand quality valve PP amps, particularly Quad, Radford and
McIntosh are especially "hot" items.

What does that tell us????



Well, add that info to the *many* sites like the SAC Thailand site I
referenced and I would say the future's looking very bright for valves in
audio!!

Valves or SS, the better legacy 'names' are commanding big money everywhere
(as your dealer is telling you and as the two Sugdens I was watching on eBay
told me) and I suspect you could easily sell empty cardboard boxes with the
names Tannoy or Lowther on them these days! But I hesitate to suggest why
there is great interest in SE - obviously it could be a 'sound quality'
thing (as it is for me) but there's no escaping the increased publicity and
much easier availability of SET amps will have some effect?

(One thing's for certain - they won't be buying them on the basis of spec
sheets, as so many here will tell you!! :-)

I think it's all very healthy - a number of the people I 'speak to' who are
getting (or have just got) valve amps are quite young, so it's not a
'nostalgia thing' for them and, if it is simply a question of free choice
falling in favour of valves, then all I can safely say is 'Well, it ain't
just me!'!!

:-)

"Keith G" wrote in message
...

"Iain Churches" wrote in message
...


Keith. This is something that has been puzzling me for a very long time.
My local dealer tells me that the interest in single-ended is
unprecidented.
and that second hand quality valve PP amps, particularly Quad, Radford
and
McIntosh are especially "hot" items.

What does that tell us????

Well, add that info to the *many* sites like the SAC Thailand site I
referenced and I would say the future's looking very bright for valves in
audio!!

Valves or SS, the better legacy 'names' are commanding big money
everywhere (as your dealer is telling you and as the two Sugdens I was
watching on eBay told me) and I suspect you could easily sell empty
cardboard boxes with the names Tannoy or Lowther on them these days!

:-) Indeed. I am happy to have a workshop full of worthless
old retro crap:-))

But I hesitate to suggest why there is great interest in SE - obviously it
could be a 'sound quality' thing (as it is for me) but there's no escaping
the increased publicity and much easier availability of SET amps will have
some effect?

It seems that people find SET pleasing in a musical way.
However, I am not sure if the Chinese presence is a good or a bad
thing. These amps do perhaps give people an "entry level" perspective
into thermionic audio, but at the same time the modest performance
may give the wrong impression of what a valve amp can do.

Few valve amps from Asia are sold through dealers, and so have
very questionable warranty rights. The component and build quality
is not too good at the moment (it will take them a while to get it right)
so failures within the first year are commom. This too creates a negative
impression.

I think it's all very healthy - a number of the people I 'speak to' who
are getting (or have just got) valve amps are quite young, so it's not a
'nostalgia thing' for them and, if it is simply a question of free choice
falling in favour of valves, then all I can safely say is 'Well, it ain't
just me!'!!

There was a whole generation that missed out on thermionic audio.

The members of the music appreciation group to which I belong
(now twenty two strong) have thirteen valve power amps between
them. These people are very serious listeners, so a thermionic
presence well in excess of 50% speaks for itself.


Iain