[Sean]

G'day Rats

Thought you might find this interesting:

A friend of mine recently set up a device to test the distortion figures
on some of the most popular and hideously priced octal dual triodes.

Unfortunately I wasn't there to witness this but a whole afternoon was
spent testing some of the most popular and hideously priced octals on
the market..These included ecc34, 5691, sylvania chrome tops, mullards,
brimars etc etc.

Of around 60 tubes tested, 10 were Tungsol 6SU7GT bought used for $2 US
each a few years ago.

Guess which tube,(not only one..but every single one) beat all others by
a big margin and posted the lowest distortion figures by a long long way?


Cheers

[Ernst]

On Feb 22, 10:02 pm, Sean wrote:

Guess which tube,(not only one..but every single one) beat all others by
a big margin and posted the lowest distortion figures by a long long way?

I'll take a stab...The Tung-Sols. How did your friend set up (the
device) for analyizing distortion?

Regards,

Ernst

[robert casey]

Guess which tube,(not only one..but every single one) beat all others by
a big margin and posted the lowest distortion figures by a long long way?



Must be the 6SU7's... The tube named after my alma matar college
Syracuse University (SU).. :-)

I have a spice 3f4 model for the 6SU7:

**********************************

* 6SU7 aka 6188 twin triode octal
..SUBCKT X6SU7 P G K
Bp P K
I=((0.001215378772/1.0e3)+(2.168783663e-005/1.0e3)*V(G,K))*uramp((68.72981286)*V(G,K)+V(P,K)+( 45.86279849))^
1.5 * V(P,K)/(V(P,K)+(3.649094098))
Cgp G P 1.5p
Ci G K 1.5p
Co P K 2.0p
..ends X6SU7

More at
http://home.netcom.com/~wb2jia/tubes/spice4.txt
http://home.netcom.com/~wb2jia/tubes/spice3.txt
http://home.netcom.com/~wb2jia/tubes/spice2.txt
http://home.netcom.com/~wb2jia/tubes/spice.txt

[Andre Jute]

The post below is a good example of how gee-whiz ignorance of tube
history and
basics, like looking up the bloody spec sheet, leads to a tube
rolling
street myth, whereas in fact the result has nothing to do with the
brand name of the tubes that "won" contest but lots to do with the
contest being rigged from the beginning by the ignorance of the
participants.

The 6SU7, which no doubt won the contest described below hands down,
is
a specially designed and selected version of the 6SL7 (itself already
a
superior tube), the parameter of selection being to minimize
differences between the two halves, which of course in itself implies
that each half must be particularly well made. The 6SU7 was
particularly aimed at differential amps of various kinds, which are
vastly important in all kinds of test, measurement and control amps,
and in which it is important to minimize the out-of-balance index
(mu1 - mu2)/(mu1 x mu2) where the numerals refer to the sections of
the
double tube.

Since the quantity (mu1 - mu2)/(mu1 x mu2) in 6SL7 rarely exceed 0.1
per
cent, the superior 6SU7 is a truly amazingly linear tube, but that
has
everything to do with its specification and manufacturing tolerances
and nothing to do with the Tungsol label on the bottle.

HTH clear up the burgeoning misunderstanding in this thread.

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

Sean wrote:

G'day Rats

Thought you might find this interesting:

A friend of mine recently set up a device to test the distortion figures
on some of the most popular and hideously priced octal dual triodes.

Unfortunately I wasn't there to witness this but a whole afternoon was
spent testing some of the most popular and hideously priced octals on
the market..These included ecc34, 5691, sylvania chrome tops, mullards,
brimars etc etc.

Of around 60 tubes tested, 10 were Tungsol 6SU7GT bought used for $2 US
each a few years ago.

Guess which tube,(not only one..but every single one) beat all others by
a big margin and posted the lowest distortion figures by a long long way?


Cheers

[Sean]

Andre Jute wrote:
The post below is a good example of how gee-whiz ignorance of tube
history and
basics, like looking up the bloody spec sheet, leads to a tube
rolling
street myth, whereas in fact the result has nothing to do with the
brand name of the tubes that "won" contest but lots to do with the
contest being rigged from the beginning by the ignorance of the
participants.

The 6SU7, which no doubt won the contest described below hands down,
is
a specially designed and selected version of the 6SL7 (itself already
a
superior tube), the parameter of selection being to minimize
differences between the two halves, which of course in itself implies
that each half must be particularly well made. The 6SU7 was
particularly aimed at differential amps of various kinds, which are
vastly important in all kinds of test, measurement and control amps,
and in which it is important to minimize the out-of-balance index
(mu1 - mu2)/(mu1 x mu2) where the numerals refer to the sections of
the
double tube.

Since the quantity (mu1 - mu2)/(mu1 x mu2) in 6SL7 rarely exceed 0.1
per
cent, the superior 6SU7 is a truly amazingly linear tube, but that
has
everything to do with its specification and manufacturing tolerances
and nothing to do with the Tungsol label on the bottle.

HTH clear up the burgeoning misunderstanding in this thread.


Andre, I very much doubt the participants were ignorant on the specs or
abilities of the 6SU7, It was more of an experiment to actually confirm
the specs.

Like I said, I didn't witness these tests myself, and as yet, do not
know what equipment was used. I do know that the guy doing the tests is
a very experienced electronics engineer.

Btw, a nos pair of Philips ecg 6188, which is the same tube as 6SU7 were
among those tested and the distortion figures were good, but nowhere
near as good as the Tungsol Brand.

I plan to be present next time and I will take along a few more 6188
,some rare B65's and definitely want to check how some 12sx7's compare.

My point is...Why pay ridiculous prices for nos 6sn7 6sl7 when there's a
far cheaper, better spec, better sounding? (debatable) direct plugin
equivalent.

Sean



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

Sean wrote:

G'day Rats

Thought you might find this interesting:

A friend of mine recently set up a device to test the distortion figures
on some of the most popular and hideously priced octal dual triodes.

Unfortunately I wasn't there to witness this but a whole afternoon was
spent testing some of the most popular and hideously priced octals on
the market..These included ecc34, 5691, sylvania chrome tops, mullards,
brimars etc etc.

Of around 60 tubes tested, 10 were Tungsol 6SU7GT bought used for $2 US
each a few years ago.

Guess which tube,(not only one..but every single one) beat all others by
a big margin and posted the lowest distortion figures by a long long way?


Cheers

[John Byrns]

In article ,
Sean wrote:

My point is...Why pay ridiculous prices for nos 6sn7 6sl7 when there's a
far cheaper, better spec, better sounding? (debatable) direct plugin
equivalent.

The 6SU7 is hardly a "direct plugin equivalent" for the 6SN7, they are
completely different animals. There are some 6SN7 circuits where a 6SU7
would yield horrendous distortion.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Sean]

John Byrns wrote:
In article ,
Sean wrote:

My point is...Why pay ridiculous prices for nos 6sn7 6sl7 when there's a
far cheaper, better spec, better sounding? (debatable) direct plugin
equivalent.

The 6SU7 is hardly a "direct plugin equivalent" for the 6SN7, they are
completely different animals. There are some 6SN7 circuits where a 6SU7
would yield horrendous distortion.


Regards,

John Byrns


sorry, my mistake , that should read "mostly direct plugin equivalent"

( :

[Andre Jute]

Sean wrote:
Andre Jute wrote:
The post below is a good example of how gee-whiz ignorance of tube
history and
basics, like looking up the bloody spec sheet, leads to a tube
rolling
street myth, whereas in fact the result has nothing to do with the
brand name of the tubes that "won" contest but lots to do with the
contest being rigged from the beginning by the ignorance of the
participants.

The 6SU7, which no doubt won the contest described below hands down,
is
a specially designed and selected version of the 6SL7 (itself already
a
superior tube), the parameter of selection being to minimize
differences between the two halves, which of course in itself implies
that each half must be particularly well made. The 6SU7 was
particularly aimed at differential amps of various kinds, which are
vastly important in all kinds of test, measurement and control amps,
and in which it is important to minimize the out-of-balance index
(mu1 - mu2)/(mu1 x mu2) where the numerals refer to the sections of
the
double tube.

Since the quantity (mu1 - mu2)/(mu1 x mu2) in 6SL7 rarely exceed 0.1
per
cent, the superior 6SU7 is a truly amazingly linear tube, but that
has
everything to do with its specification and manufacturing tolerances
and nothing to do with the Tungsol label on the bottle.

HTH clear up the burgeoning misunderstanding in this thread.


Andre, I very much doubt the participants were ignorant on the specs or
abilities of the 6SU7, It was more of an experiment to actually confirm
the specs.

Like I said, I didn't witness these tests myself, and as yet, do not
know what equipment was used. I do know that the guy doing the tests is
a very experienced electronics engineer.

Btw, a nos pair of Philips ecg 6188, which is the same tube as 6SU7 were
among those tested and the distortion figures were good, but nowhere
near as good as the Tungsol Brand.

I plan to be present next time and I will take along a few more 6188
,some rare B65's and definitely want to check how some 12sx7's compare.

My point is...Why pay ridiculous prices for nos 6sn7 6sl7 when there's a
far cheaper, better spec, better sounding? (debatable) direct plugin
equivalent.

Sean

This is precisely what I mean about ignorance. I'll now modify that to
*dangerous* ignorance. You plug a 6SU7 into a circuit designed for a
6SN7 and you're well on your way to meltdown and perhaps a housefire.
You should inform yourself
a) that the 6SN7 and the 6SL7 are not interchangeable tubes
b) that they have different current capabilites
c) that they have different transfer curves
d) that they have different maximum dissipations
and
e) understand that the 6SU7 is a substitute only for one of them, the
lower wattage 6SL7.

While you educate yourself, I agree with you: the price established by
Ebay for a tube on the whole has nothing whatsoever to do with its
electrical or sonic qualities. But you should learn to communicate
your point without the disturbing subtexts. It was your gee-whiz
assumption that the names of Mullard and Tungsol by themselves should
guarantee victory that set off warning bells with me in the first
instance. I used Mullard tubes for target practice; the vast majority
of Mullard tubes, like the vast majority of everyone else's tubes, are
fit only for table radios or the crusher; they have nothing to do with
high fidelity.

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


Sean wrote:

G'day Rats

Thought you might find this interesting:

A friend of mine recently set up a device to test the distortion figures
on some of the most popular and hideously priced octal dual triodes.

Unfortunately I wasn't there to witness this but a whole afternoon was
spent testing some of the most popular and hideously priced octals on
the market..These included ecc34, 5691, sylvania chrome tops, mullards,
brimars etc etc.

Of around 60 tubes tested, 10 were Tungsol 6SU7GT bought used for $2 US
each a few years ago.

Guess which tube,(not only one..but every single one) beat all others by
a big margin and posted the lowest distortion figures by a long long way?


Cheers

[Andy Evans]

Shame you didn't compare the 6SN7 with some of the 6J5G/GT types like
the CV1932, 6P5GT, 2C22. Those are truly wonderful sounding

[[email protected]]

On Feb 23, 7:39 pm, Sean wrote:
My point is...Why pay ridiculous prices for nos 6sn7 6sl7 when there's a
far cheaper, better spec, better sounding? (debatable) direct plugin
equivalent.

6SU7's are not incredibly rare but not highly-chased-after yet.

As Andre points out, direct-coupled differential amps and tube
selection were a highly developed area even before Mr. Philbrick. Look
for a publication called "The Lightning Empiricist".

You know, by saying anything about them you are making them harder for
YOU to get. Fads come and go and wouldn't you be sad if the fad you
started made it harder to get what you want?

I'm also a little critical of your vaguely specified test, there are a
number of circuit parameters you would want to vary to make 6SL7 vs
6SN7 be apples to apples rather than apples to oranges.

Tim.