[John Jensen]

I've got a pair of 6550 amplifiers that are due for a replacement set (a
couple of the tubes are falling off in emission and messing up my balance
adjustments). My current set are the =C= 6550s by way of Ned Carlson. What
is the current thinking of the 'best' in terms of AQ, robustness, etc? I'm
sure I will get a lot of differing opinions.

Thanks,

John

P.S. These are in a pair of amplifiers lovingly hand-built over the
1959-1960 winter. The Herbert Keroes Acrosound 60W Ultra-Linear Williamson
(but with the Dyna 431 transformers).

[John Jensen]

Sorry for any duplicate messages on this. Having some connection problems.

"John Jensen" wrote in message
. net...
I've got a pair of 6550 amplifiers that are due for a replacement set (a
couple of the tubes are falling off in emission and messing up my balance
adjustments). My current set are the =C= 6550s by way of Ned Carlson.
What is the current thinking of the 'best' in terms of AQ, robustness,
etc? I'm sure I will get a lot of differing opinions.

Thanks,

John

P.S. These are in a pair of amplifiers lovingly hand-built over the
1959-1960 winter. The Herbert Keroes Acrosound 60W Ultra-Linear
Williamson (but with the Dyna 431 transformers).

[[email protected]]

Hi RATs!

Tubes are not encyclopedias. They are simple machines which may wear
out. Buying a "fresh team" seems quite glamorous, but, all you need to
replace is the weak ones.

Not all tubes will fail in our lifetimes. We will definately die. We
will also throw away many good tubes in our ignorance of the
technology.

If you want better sound, add a choke to the PS

Or, buy some new speakers 8^0

Happy Ears!
Al

[Sander deWaal]

"John Jensen" said:

I've got a pair of 6550 amplifiers that are due for a replacement set (a
couple of the tubes are falling off in emission and messing up my balance
adjustments). My current set are the =C= 6550s by way of Ned Carlson. What
is the current thinking of the 'best' in terms of AQ, robustness, etc? I'm
sure I will get a lot of differing opinions.


The best replacement is a quad of JJ KT88s ;-)

BTW if your bias current is going up and down the place, check the
coupling capacitors and the bias circuit (expecially if there's a
selenium rectifier in there).

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[John Jensen]

Thanks for the comments. I always keep the best of the batch for future
spares.

The power supplies (also independent) already have chokes, 8 Henry (if I
recall right).

JJ

wrote in message
oups.com...
Hi RATs!

Tubes are not encyclopedias. They are simple machines which may wear
out. Buying a "fresh team" seems quite glamorous, but, all you need to
replace is the weak ones.

Not all tubes will fail in our lifetimes. We will definately die. We
will also throw away many good tubes in our ignorance of the
technology.

If you want better sound, add a choke to the PS

Or, buy some new speakers 8^0

Happy Ears!
Al

[John Jensen]

Thanks for the suggestion of JJ KT-88s. Variously through the years it has
used GEC KT-88s.

I'll check the coupling caps and the bias circuit (but it uses a silicon
rectifier).

JJ

"Sander deWaal" wrote in message
...
"John Jensen" said:

I've got a pair of 6550 amplifiers that are due for a replacement set (a
couple of the tubes are falling off in emission and messing up my balance
adjustments). My current set are the =C= 6550s by way of Ned Carlson.
What
is the current thinking of the 'best' in terms of AQ, robustness, etc?
I'm
sure I will get a lot of differing opinions.


The best replacement is a quad of JJ KT88s ;-)

BTW if your bias current is going up and down the place, check the
coupling capacitors and the bias circuit (expecially if there's a
selenium rectifier in there).

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[John Jensen]

Thanks for your comments. I'll also consider the JJ KT-88s. Didn't they
have lots of arcing problems when they first came out (which I assume has
been fixed)?

JJ

"François Yves Le Gal" wrote in message
...
On Sun, 15 Oct 2006 01:59:16 GMT, "John Jensen"

wrote:

My current set are the =C= 6550s by way of Ned Carlson

The SED Svetlana =C= SV6550C are excellent tubes, IMO some of the best
currently manufactured. You may also consider the JJ/Tesla KT88's, which
come really close to the original GEC's.

[Mike Gilmour]

"François Yves Le Gal" wrote in message
...
On Sun, 15 Oct 2006 01:59:16 GMT, "John Jensen"

wrote:

My current set are the =C= 6550s by way of Ned Carlson

The SED Svetlana =C= SV6550C are excellent tubes, IMO some of the best
currently manufactured. You may also consider the JJ/Tesla KT88's, which
come really close to the original GEC's.



I'll second that. The Svetlana SV6550C are indeed excellent tubes in my
experience. All have measured well out of the box, good sonics with long
life. Able to take (IME) occasional abuse and survive. I preferred these to
the original GEC's.

[Sander deWaal]

"John Jensen" said:

Thanks for your comments. I'll also consider the JJ KT-88s. Didn't they
have lots of arcing problems when they first came out (which I assume has
been fixed)?


I never had them arcing, but there seemed to be a problem with grid
current in the first batches.
The grid leak in my case was 100k (in cathodebias), but that still was
too high, apparently.
Positive grid voltages of 1...5 V were measured, most likely due to
cathode material that contaminated the grid and acted as a cathode all
by itself, probably because of the heat from the nearby cathode.
I got them replaced free of charge from the distributor (twice!).

That was years ago, though.
I have 2 quads running for over 2 years now (in 2 different amps)
without problems.

Also, replacements in customer's amps seem to survive well, and their
sound quality is beyond question.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[John Jensen]

I did have a set of JJs or Teslas (KT88s) at the time (I forget which).
What I described as arcing might have been a grid to cathode short. The
fellow who sold them to me did an exchange of the two bad ones for some
Sovtek 6550s which lasted for a long time. He said that there was a known
problem that cropped up as the tubes aged (which he was not aware of
originally). For a while I was running one amp with 6550s.and one with
KT88s.

JJ

"Sander deWaal" wrote in message
...
"John Jensen" said:

Thanks for your comments. I'll also consider the JJ KT-88s. Didn't they
have lots of arcing problems when they first came out (which I assume has
been fixed)?


I never had them arcing, but there seemed to be a problem with grid
current in the first batches.
The grid leak in my case was 100k (in cathodebias), but that still was
too high, apparently.
Positive grid voltages of 1...5 V were measured, most likely due to
cathode material that contaminated the grid and acted as a cathode all
by itself, probably because of the heat from the nearby cathode.
I got them replaced free of charge from the distributor (twice!).

That was years ago, though.
I have 2 quads running for over 2 years now (in 2 different amps)
without problems.

Also, replacements in customer's amps seem to survive well, and their
sound quality is beyond question.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Mark S]

"Mike Gilmour" wrote in message
...

"François Yves Le Gal" wrote in message
...
On Sun, 15 Oct 2006 01:59:16 GMT, "John Jensen"

wrote:

My current set are the =C= 6550s by way of Ned Carlson

The SED Svetlana =C= SV6550C are excellent tubes, IMO some of the best
currently manufactured. You may also consider the JJ/Tesla KT88's, which
come really close to the original GEC's.



I'll second that. The Svetlana SV6550C are indeed excellent tubes in my
experience. All have measured well out of the box, good sonics with long
life. Able to take (IME) occasional abuse and survive. I preferred these
to the original GEC's.



Here's a third. Make sure you get the real SED's. I'm currently running a
recent set of SED KT88's from Upscale and they are nothing short of
fabulous; sonics, stability are among the best I've heard / seen.
Mark

[Superhet]

Upscale, is that a guy named Kevin who used to post here long ago?

Mark S wrote:
"Mike Gilmour" wrote in message
...
"François Yves Le Gal" wrote in message
...
On Sun, 15 Oct 2006 01:59:16 GMT, "John Jensen"

wrote:

My current set are the =C= 6550s by way of Ned Carlson
The SED Svetlana =C= SV6550C are excellent tubes, IMO some of the best
currently manufactured. You may also consider the JJ/Tesla KT88's, which
come really close to the original GEC's.


I'll second that. The Svetlana SV6550C are indeed excellent tubes in my
experience. All have measured well out of the box, good sonics with long
life. Able to take (IME) occasional abuse and survive. I preferred these
to the original GEC's.



Here's a third. Make sure you get the real SED's. I'm currently running a
recent set of SED KT88's from Upscale and they are nothing short of
fabulous; sonics, stability are among the best I've heard / seen.
Mark

[MarkS]

"Superhet" wrote in message
news
Upscale, is that a guy named Kevin who used to post here long ago?

Yep. Kevin Deal. Got a nice set of Sylvania 6550's there a few years ago as
well.
Mark




Mark S wrote:
"Mike Gilmour" wrote in message
...
"François Yves Le Gal" wrote in message
...
On Sun, 15 Oct 2006 01:59:16 GMT, "John Jensen"

wrote:

My current set are the =C= 6550s by way of Ned Carlson
The SED Svetlana =C= SV6550C are excellent tubes, IMO some of the
best
currently manufactured. You may also consider the JJ/Tesla KT88's,
which
come really close to the original GEC's.


I'll second that. The Svetlana SV6550C are indeed excellent tubes in my
experience. All have measured well out of the box, good sonics with
long
life. Able to take (IME) occasional abuse and survive. I preferred
these
to the original GEC's.



Here's a third. Make sure you get the real SED's. I'm currently running
a
recent set of SED KT88's from Upscale and they are nothing short of
fabulous; sonics, stability are among the best I've heard / seen.
Mark

[tubegarden]

Bret Ludwig wrote:


Bull****.

Tubes in a push-pull-parallel amp should be replaced as a set.
However, ones still usable should be not thrown out but repurposed.
They can be used in certain guitar amp applications, by experimenters,
as emergency spares, etc. Also, in amps with large sets, if one dies
early in the life cycle it may be replaced singly. If someone is
building a first amp (or, really any new build amp) using some good
used tubes that match up reasonably well is smart until the amp is
debugged.


Hi RATs!

Don't let rude posers should on you.

Happy Ears!
Al

[west]

"tubegarden" wrote in message
oups.com...

Bret Ludwig wrote:


Bull****.

Tubes in a push-pull-parallel amp should be replaced as a set.
However, ones still usable should be not thrown out but repurposed.
They can be used in certain guitar amp applications, by experimenters,
as emergency spares, etc. Also, in amps with large sets, if one dies
early in the life cycle it may be replaced singly. If someone is
building a first amp (or, really any new build amp) using some good
used tubes that match up reasonably well is smart until the amp is
debugged.


Hi RATs!

Don't let rude posers should on you.

You needn't worry about that. Most everyone knows that the Lude suffers from
chronic irregularity.

west

Happy Ears!
Al