[Patrick Turner]

I see New Sensor is putting out Tungsol KT120 tubes whch bias like
KT88 but have Pda = 60W.
I read a few forums comments and I guys are happy with the new tubes.
BUT, they will cost a bomb. About twice the price of a 6550.

And when I saw the anode curves for the KT120 it was all horrible to
look at.

But then these curves had quite irregular shapes to part of them and
look like they were drawn up by someome who does not know what they
are doing. Plus the voltage range over which the tubes were tested to
get the curves did not extend to the max Ea and max Eg2 which are both
+650Vdc. So I whoever made the tests and drew the pictures does not
have a very good test set or the experience of those genuine people of
the 1960s who spent their lives testing tubes.

The new tube seems aimed at guitar people who like rugged tubes and
where the distortion does not matter; in fact the more THD the better
as long as nothing clips.

The KT120 looks like the the insides simply have a 35% taller plate
structure and taller bottle than a KT88.

So with a taller plate there is more area to get rid of heat hence the
improved Pda. But what about the rigidity of the longer cathode tube
and the alignment of grid to cathode spacing? With extra length there
must be more tendency for the hot structure to bend or sway with
disatrous results.

The Electro Harmonix KT90 had Pda of 55W and looks just like a
KT88/6550 but with taller plate but straight sided glass, like an EL34
which has been fed steroids for a year. Initially, the KT90 were a
reasonable buy because the price wanted was only a bit more than a
6550. But that seemed to change.
Seems to me New Sensor is again "stretching" the KT 88 upwards even
more than they did with KT90.

But if a 6550/KT88 is $30, then when stretched upwards, it should only
cost for the extension in height of 35% so $40.50, not $70 being
talked about.

Two KT88,6550 will cost less than one KT120 and the Pda of the two
KT88/6550 = 84W,
and so a quad of KT88/6550 are going to beat the pants of a pair of
KT120.

But for those that must have the latest gizmo, you know where to go to
spend up.
But don't expect any more power or fidelity than you are getting now
with KT88/6550.
The curves I could see do not indicate any more anode voltage swing is
available if you just switch to KT120. Are the curves as good as for
the NOS KT88? I don't think so.

Many makers are already pushing their luck by running 6550 with Ea too
high and RL too low.

There seems to be an absurd trend where there is never enough power,
even with so called hi-fi amps they are set up in nearly all class B
working with low load and high Ea to get the sales figures and to hell
with the idea that for hi-fi about 50W max is all that should be ever
asked from a pair of KT88/6550.

I found the Sovtek small bottle 6550 and KT88 were excellent value for
the price. The guts of these didn't change when the bottle size
increased for the Electro Harmonix name range. OK, It was all a
marketting ploy eh, to get away from the old association of Sovtek and
the evil empire of the Soviets and USSR. I wonder how Mike mathews is
getting on with the Russian Mafia boyos who tried to put the squeeze
on him for a rouble or three. Maybe Mike needs the money, but then we
could all say that.

Patrick Turner.

[Ian Iveson]

Patrick Turner wrote:

I see New Sensor is putting out Tungsol KT120 tubes whch
bias like
KT88 but have Pda = 60W.
I read a few forums comments and I guys are happy with the
new tubes.
BUT, they will cost a bomb. About twice the price of a
6550.

And when I saw the anode curves for the KT120 it was all
horrible to
look at.

But then these curves had quite irregular shapes to part
of them and
look like they were drawn up by someome who does not know
what they
are doing. Plus the voltage range over which the tubes
were tested to
get the curves did not extend to the max Ea and max Eg2
which are both
+650Vdc. So I whoever made the tests and drew the pictures
does not
have a very good test set or the experience of those
genuine people of
the 1960s who spent their lives testing tubes.

Or has a better test set and/or greater knowledge. Or knows
how to test but falls short of the standards set in the 60s
for genuinely fiddling the results.

The new tube seems aimed at guitar people who like rugged
tubes and
where the distortion does not matter; in fact the more THD
the better
as long as nothing clips.

Er, not quite. If distortion were the only objective they
would use transistors.

The KT120 looks like the the insides simply have a 35%
taller plate
structure and taller bottle than a KT88.

So with a taller plate there is more area to get rid of
heat hence the
improved Pda. But what about the rigidity of the longer
cathode tube
and the alignment of grid to cathode spacing? With extra
length there
must be more tendency for the hot structure to bend or
sway with
disatrous results.

Just what I thought. There are quite a few modes of
vibration...side to side, up and down, and rotation about
three axis, each for lots of bits relative to lots of other
bits, etc. etc. All in all, however, we have the impression
that long thin things, including "pin ended" beams like
bridges or joists, are weak or floppy. If they compensate by
making the grid support rods thicker, they risk changing the
characteristics of the valve perhaps. Maybe they use modern
material to make stiffer thin structures despite the change
in aspect ratio. Or maybe they just make everything longer
and hope they recoup the investment before anyone notices
they sound bad and fall apart in no time.


The Electro Harmonix KT90 had Pda of 55W and looks just
like a
KT88/6550 but with taller plate but straight sided glass,
like an EL34
which has been fed steroids for a year. Initially, the
KT90 were a
reasonable buy because the price wanted was only a bit
more than a
6550. But that seemed to change.
Seems to me New Sensor is again "stretching" the KT 88
upwards even
more than they did with KT90.

But if a 6550/KT88 is $30, then when stretched upwards, it
should only
cost for the extension in height of 35% so $40.50, not $70
being
talked about.

Ah, but not if they've actually solved the problem of
retaining stiffness. Maybe they've used an exotic
titanium/carbon nano-tube composite for the grid support
rods, so they're twice as stiff and half the weight. Or they
just put the price up because there are fewer rich people
now, but each of them has more money.

Two KT88,6550 will cost less than one KT120 and the Pda of
the two
KT88/6550 = 84W,
and so a quad of KT88/6550 are going to beat the pants of
a pair of
KT120.

As would a hundred EF96. But you need to include the cost of
extra bases, wiring, bias provision, heater current, chassis
work, and the general perception that fewer, bigger valves
are better.

But for those that must have the latest gizmo, you know
where to go to
spend up.
But don't expect any more power or fidelity than you are
getting now
with KT88/6550.
The curves I could see do not indicate any more anode
voltage swing is
available if you just switch to KT120. Are the curves as
good as for
the NOS KT88? I don't think so.

Many makers are already pushing their luck by running 6550
with Ea too
high and RL too low.

There seems to be an absurd trend where there is never
enough power,
even with so called hi-fi amps they are set up in nearly
all class B
working with low load and high Ea to get the sales figures
and to hell
with the idea that for hi-fi about 50W max is all that
should be ever
asked from a pair of KT88/6550.

Something to do with modern speakers in big rooms maybe. The
room size of the average audiophool is much bigger now.

I found the Sovtek small bottle 6550 and KT88 were
excellent value for
the price. The guts of these didn't change when the bottle
size
increased for the Electro Harmonix name range. OK, It was
all a
marketting ploy eh, to get away from the old association
of Sovtek and
the evil empire of the Soviets and USSR. I wonder how Mike
mathews is
getting on with the Russian Mafia boyos who tried to put
the squeeze
on him for a rouble or three. Maybe Mike needs the money,
but then we
could all say that.

Erm, logic has never been you're strong point. Why wait for
the collapse of the "evil empire" before changing the name?
The Soviet Union, and several of its dominions, had a
reputation for the mass production of primitive but famously
tough and serviceable engineered goods, such as tanks,
rockets, planes, cameras, machine tools, and valves.

"Soviet" was a very successful fashionware label here. It
had a kind of heroic ring to it. They did, after all, win
the war against Fascism.

Incidentally, the UK's new Conservative government is
pushing the idea of soviets to replace parts of local
councils, but they don't use the word, obviously. For
example, they reckon they can get parents' commitees to set
up schools. It would be cheaper if it worked, but naturally
it won't, and in some of the more sordid suburbs, the
results wouldn't be what we might hope for anyway. I guess
the idea is just one of many imaginative ways they are
finding to blame the poor for the **** we're in. It's a lot
easier to take £1 from 60 million people than it is to take
£60m off one rich *******.

Meanwhile, since I'm digressing, that's my pension washing
up on Florida beaches.

Perhaps we should all call it a day and make digital stuff
instead. You argue that energy profligacy is OK because
there aren't many valve amps in the world, but that's a
typical capitalist fat cat argument if ever there was one.
By the same token, they'll be able to keep their useless
powerboats and private jets when the proletariat are forced
to ride bicycles to save the planet.

Except we can't make digital stuff, because the active bits
are so small we can hardly see them and certainly can't
solder them. Shame coz, being so short, I guess they're
pretty stiff.

All in all, if you're wondering where valve technology is
going, the answer is clear. Nowhere.

Ian

[Patrick Turner]

On Jun 13, 12:29*pm, "Ian Iveson"
wrote:
Patrick Turner wrote:
I see New Sensor is putting out Tungsol KT120 tubes whch
bias like
KT88 but have Pda = 60W.
I read a few forums comments and I guys are happy with the
new tubes.
BUT, they will cost a bomb. About twice the price of a
6550.

And when I saw the anode curves for the KT120 it was all
horrible to
look at.

But then these curves had quite irregular shapes to part
of them and
look like they were drawn up by someome who does not know
what they
are doing. Plus the voltage range over which the tubes
were tested to
get the curves did not extend to the max Ea and max Eg2
which are both
+650Vdc. So I whoever made the tests and drew the pictures
does not
have a very good test set or the experience of those
genuine people of
the 1960s who spent their lives testing tubes.

Or has a better test set and/or greater knowledge. Or knows
how to test but falls short of the standards set in the 60s
for genuinely fiddling the results.

Nobody in the tube making industry invests enough money on quality
control and data preparation.
There are reasons of course; probably because there isn't the volume
there once was, and all the old testing labs were junked when
transistors came in.

The new tube seems aimed at guitar people who like rugged
tubes and
where the distortion does not matter; in fact the more THD
the better
as long as nothing clips.

Er, not quite. If distortion were the only objective they
would use transistors.

The musos regularly drive their amps well into class C. This happens
when the coupling caps stay charged up with grid current effects. The
amp makes a basic square wave. The speaker does the rest to give you
that driving sound so liked by the rockers and rollers. But well
before the point and up to clipping on sine waves the distortion of
tubes is cherished because it is so much better sounding than bjts.

So distortion that occurs in beam tetrodes can be quite high level or
low level and it all sounds better than bjts.

So if the new ball tearing KT120 make a bit more THD than a pair of
KT88s at 10 watts it won't matter.



The KT120 looks like the the insides simply have a 35%
taller plate
structure and taller bottle than a KT88.

So with a taller plate there is more area to get rid of
heat hence the
improved Pda. But what about the rigidity of the longer
cathode tube
and the alignment of grid to cathode spacing? With extra
length there
must be more tendency for the hot structure to bend or
sway with
disatrous results.

Just what I thought. There are quite a few modes of
vibration...side to side, up and down, and rotation about
three axis, each for lots of bits relative to lots of other
bits, etc. etc. All in all, however, we have the impression
that long thin things, including "pin ended" beams like
bridges or joists, are weak or floppy. If they compensate by
making the grid support rods thicker, they risk changing the
characteristics of the valve perhaps. Maybe they use modern
material to make stiffer thin structures despite the change
in aspect ratio. Or maybe they just make everything longer
and hope they recoup the investment before anyone notices
they sound bad and fall apart in no time.

In the old days they tested things arduously for months on end or
years to see how things failed. This was done BEFORE launching a
product on the market.

I doubt we will ever see honest reports about tests Mike Mathews has
conducted on KT120.



The Electro Harmonix KT90 had Pda of 55W and looks just
like a
KT88/6550 but with taller plate but straight sided glass,
like an EL34
which has been fed steroids for a year. Initially, the
KT90 were a
reasonable buy because the price wanted was only a bit
more than a
6550. But that seemed to change.
Seems to me New Sensor is again "stretching" the KT 88
upwards even
more than they did with KT90.

But if a 6550/KT88 is $30, then when stretched upwards, it
should only
cost for the extension in height of 35% so $40.50, not $70
being
talked about.

Ah, but not if they've actually solved the problem of
retaining stiffness. Maybe they've used an exotic
titanium/carbon nano-tube composite for the grid support
rods, so they're twice as stiff and half the weight. Or they
just put the price up because there are fewer rich people
now, but each of them has more money.

I agree that the longer something is made with respect to its width,
the more likely you will get unwanted bending especially if it is
metal and its at 300C of higher.

I would have though the GFC would have dampened down tube sales. Hell,
maybe the tube makers are having a hard time, so they need to think of
something new.....


Two KT88,6550 will cost less than one KT120 and the Pda of
the two
KT88/6550 = 84W,
and so a quad of KT88/6550 are going to beat the pants of
a pair of
KT120.

As would a hundred EF96. But you need to include the cost of
extra bases, wiring, bias provision, heater current, chassis
work, and the general perception that fewer, bigger valves
are better.

If I were to make a 100W amp I can put in a pair of EL34 with RLa-a
12k, Ea = 900Vdc, and Eg2 = 400V and flog the damn things to death.
Before they die they teeter on the edge of bias failure and arcing
sockets.

Same goes for using a pair of KT88/6550. Its a bit dodgy. And this
amount of power can only come with high THD with the near class B
working.

To get right away from such garbological thinking and doing, I never
build crap like everyone else.

I will use a cheap six pack of EL34 to make the 100W or a quad of
KT88/6550/KT90. The majority of the cost is NEVER in the extra 2 tube
sockets and output tubes but in the transformers and rugged chassis to
carry the weight needed for 100W. I hapen to think that a six pack of
EL34 with Ea at a relaxed 440V max is fine. Its easy to get the first
30W in pure class A with very little THD. If one want so get 100W even
with just a pair of KT120, and you plan to run them at Ea = 600V, then
Pda would not want to be more than 30W per tube if it was a hi-fi amp
and maybe only 20W if in a guitar amp. If you do your sums the amount
of class A into the load one needs to get 100W in class AB is tiny.

The musos don't mind the distortion. I most certainly do mind the
distortion. So if KT120 were any good, then I'd sure like to use them
because you coud probably run a pair at Ea 400V and 90mA safely for
36W Pda so that the class max available would be 30W from the total
Pda of 72W from the pair. In class A SE amps I have made the
efficiency is up to 45%. The SE35 I made with 4 x 6CA7/EL34 has each
output idling along with Pda = 21 W. I made amps last year with 6 x
6550 in SE mode for 60W. Pda was 24W per tube. The use of KT120 would
not mean I could have 3 tubes instead of 6 x 6550. And if I was able
to use 3 tubes instead of 6 for 60W of class A then I'd expect the
price to be the same: ie, the cost of the KT120 not more than twice
the price of a 6550. But if the KT120 has only 30% more bang for the
buck then I doubt I'll ever buy any. I do quite like the KT90EH. But
gees, its expensive, and not much more bang for buck, so I have only
ever bought any when a client asked me to because he'd read somewhere
that they gave better bass. I have no reson to believe he was right.
But I just do what people ask me to.

In hifi amps the extra power one might get by changing from KT88/6550
to KT120 may be tiny because of the loading.

The KT120 curves don't tell me there is some magical source of heaps
more power which justifies their purchase.

BTW, should anyone like to make a class Ab2 amp with Ea at 800V, they
could do worse than use TT21 which are KT88 internally but with anode
top caps to prevent arcing, 140W can be had this way.
I'm not interested though.

My next large project is a pair of monblocks with one pair of PP 13E1.
Although just one pair is capable of 250W, I will only want 85W max
with lots of class A. These tubes are unlikely to ever be made again
but they are far more rugged than any KT88, KT90, or KT120 could ever
be.

At the time when th 13E1 was developed ppl wanted something capable of
high Pda per tube and no high voltages. Industry had many uses for
such gut busting tubes. When you look at the 13E1, it is so much more
rugged than anything else in Octal land. It has two cathodes, massive
anode. They last very well even when spending many years running at
Pda = 75W. Another great beam tetrode of that era was the QE208A with
a pair of carbon anodes on rods each side of 3 cathodes. Tubes like
13E1 allowed high power at low voltages that would otherwise needed
things like 813........

Hopefully the KT120 actually does have much better TRIODE curves than
the ones I have so far seen seem to indicate.
If so then they should be good for hi-fi even if like most beam
tetrodes and pentodes they are not very linear in beam tet or pentode
mode.

Patrick Turner.












But for those that must have the latest gizmo, you know
where to go to
spend up.
But don't expect any more power or fidelity than you are
getting now
with KT88/6550.
The curves I could see do not indicate any more anode
voltage swing is
available if you just switch to KT120. Are the curves as
good as for
the NOS KT88? I don't think so.

Many makers are already pushing their luck by running 6550
with Ea too
high and RL too low.

There seems to be an absurd trend where there is never
enough power,
even with so called hi-fi amps they are set up in nearly
all class B
working with low load and high Ea to get the sales figures
and to hell
with the idea that for hi-fi about 50W max is all that
should be ever
asked from a pair of KT88/6550.

Something to do with modern speakers in big rooms maybe. The
room size of the average audiophool is much bigger now.

I found the Sovtek small bottle 6550 and KT88 were
excellent value for
the price. The guts of these didn't change when the bottle
size
increased for the Electro Harmonix name range. OK, It was
all a
marketting ploy eh, to get away from the old association
of Sovtek and
the evil empire of the Soviets and USSR. I wonder how Mike
mathews is
getting on with the Russian Mafia boyos who tried to put
the squeeze
on him for a rouble or three. Maybe Mike needs the money,
but then we
could all say that.

Erm, logic has never been you're strong point. Why wait for
the collapse of the "evil empire" before changing the name?
The Soviet Union, and several of its dominions, had a
reputation for the mass production of primitive but famously
tough and serviceable engineered goods, such as tanks,
rockets, planes, cameras, machine tools, and valves.

"Soviet" was a very successful fashionware label here. It
had a kind of heroic ring to it. They did, after all, win
the war against Fascism.

Incidentally, the UK's new Conservative government is
pushing the idea of soviets to replace parts of local
councils, but they don't use the word, obviously. For
example, they reckon they can get parents' commitees to set
up schools. It would be cheaper if it worked, but naturally
it won't, and in some of the more sordid suburbs, the
results wouldn't be what we might hope for anyway. I guess
the idea is just one of many imaginative ways they are
finding to blame the poor for the **** we're in. It's a lot
easier to take £1 from 60 million people than it is to take
£60m off one rich *******.

Meanwhile, since I'm digressing, that's my pension washing
up on Florida beaches.

Perhaps we should all call it a day and make digital stuff
instead. You argue that energy profligacy is OK because
there aren't many valve amps in the world, but that's a
typical capitalist fat cat argument if ever there was one.
By the same token, they'll be able to keep their useless
powerboats and private jets when the proletariat are forced
to ride bicycles to save the planet.

Except we can't make digital stuff, because the active bits
are so small we can hardly see them and certainly can't
solder them. Shame coz, being so short, I guess they're
pretty stiff.

All in all, if you're wondering where valve technology is
going, the answer is clear. Nowhere.

Ian- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

[Patrick Turner]

There seems to be an absurd trend where there is never
enough power,
even with so called hi-fi amps they are set up in nearly
all class B
working with low load and high Ea to get the sales figures
and to hell
with the idea that for hi-fi about 50W max is all that
should be ever
asked from a pair of KT88/6550.

Something to do with modern speakers in big rooms maybe. The
room size of the average audiophool is much bigger now.

I forgot to answer the rest of your post.

Yep, houses are getting bigger an dspeakers are getting less
sensitive.

I found the Sovtek small bottle 6550 and KT88 were
excellent value for
the price. The guts of these didn't change when the bottle
size
increased for the Electro Harmonix name range. OK, It was
all a
marketting ploy eh, to get away from the old association
of Sovtek and
the evil empire of the Soviets and USSR. I wonder how Mike
mathews is
getting on with the Russian Mafia boyos who tried to put
the squeeze
on him for a rouble or three. Maybe Mike needs the money,
but then we
could all say that.

Erm, logic has never been you're strong point. Why wait for
the collapse of the "evil empire" before changing the name?
The Soviet Union, and several of its dominions, had a
reputation for the mass production of primitive but famously
tough and serviceable engineered goods, such as tanks,
rockets, planes, cameras, machine tools, and valves.

Yeah, remember the Paris Air Show in 1972? I recall the Russian copy
of Concorde fell out of the sky.

Then there was Chernoble in 1986.

The Soviet era was remarkable for huge amount of clunker junk it made
so very inefficiently and at huge cost to environments.

But the West wasn't much further ahead in refinements though. A book I
have was written in the USA about 1961 about reliability of
electronics in the US armed forces. If we had had a world war in 1961,
we could onlt have ever had 1/3 of a war because so much electronics
just didn't work well.

Think of the benefits.

We all would have been onlt 1/3 dead, wonderful, really.




"Soviet" was a very successful fashionware label here. It
had a kind of heroic ring to it. They did, after all, win
the war against Fascism.

Indeed. Some ******* had to do the real dirty work. Sure wasn't gonna
be us.

Incidentally, the UK's new Conservative government is
pushing the idea of soviets to replace parts of local
councils, but they don't use the word, obviously. For
example, they reckon they can get parents' commitees to set
up schools. It would be cheaper if it worked, but naturally
it won't, and in some of the more sordid suburbs, the
results wouldn't be what we might hope for anyway. I guess
the idea is just one of many imaginative ways they are
finding to blame the poor for the **** we're in. It's a lot
easier to take £1 from 60 million people than it is to take
£60m off one rich *******.

Yeah, but Europe's in a mess right. Debts all over and everyone
wanting to live like kings but nobody can pay for that.

Instead everyone in Europe has to be his or her own servant.

Meanwhile, since I'm digressing, that's my pension washing
up on Florida beaches.

Its OK, once they drain the water out of the Gulf there abd fill it
with oil they'll be plenty oil for all.



Perhaps we should all call it a day and make digital stuff
instead. You argue that energy profligacy is OK because
there aren't many valve amps in the world, but that's a
typical capitalist fat cat argument if ever there was one.
By the same token, they'll be able to keep their useless
powerboats and private jets when the proletariat are forced
to ride bicycles to save the planet.

Well, I figure tube amps should be allowed like having a few old
sailing ships and steam trains.

The % of tube amps is tiny compared to all other types that are much
more efficient.

Old people should be allowed to live until they get old.

We could instead just shoot everyone who didn't work, or who got old.
Maybe shoot everyone who isn't enviromentally correct, or politically
correct for that matter, or sick, or mentally retarded.

Let's just shoot each other more often.

It does the world a favour to get rid of people if they won't get rid
of their bad habits.

But Hitler tried a few things such as Drastic Change, and he didn't
get far.

So did Stalin and Mao.

Now we prefer to just consume the planet bare of anything worth
saving.


Except we can't make digital stuff, because the active bits
are so small we can hardly see them and certainly can't
solder them. Shame coz, being so short, I guess they're
pretty stiff.

All in all, if you're wondering where valve technology is
going, the answer is clear. Nowhere.

Its going in plenty of directions. I'm getting old and I don't have to
put on the agony and put on the style. Following, and aiding and
abetting the relentless arrow of Progress won't make me feel better or
get me a good ****.

There are huge changes slowly unfolding on our planet due technology.
Most are bypassing me. So I don't need to have a fixed bias against
change.

Patrick Turner.

Ian- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -- Hide quoted text -

- Show quoted text -

[NX211]

On Jun 12, 11:26*am, Patrick Turner wrote:
I see New Sensor is putting out Tungsol KT120 tubes whch bias like
KT88 but have Pda = 60W.
I read a few forums comments and I guys are happy with the new tubes.
BUT, they will cost a bomb. About twice the price of a 6550.

And when I saw the anode curves for the KT120 it was all horrible to
look at.

But then these curves had quite irregular shapes to part of them and
look like they were drawn up by someome who does not know what they
are doing. Plus the voltage range over which the tubes were tested to
get the curves did not extend to the max Ea and max Eg2 which are both
+650Vdc. So I whoever made the tests and drew the pictures does not
have a very good test set or the experience of those genuine people of
the 1960s who spent their lives testing tubes.

The new tube seems aimed at guitar people who like rugged tubes and
where the distortion does not matter; in fact the more THD the better
as long as nothing clips.

The KT120 looks like the the insides simply have a 35% taller plate
structure and taller bottle than a KT88.

So with a taller plate there is more area to get rid of heat hence the
improved Pda. But what about the rigidity of the longer cathode tube
and the alignment of grid to cathode spacing? With extra length there
must be more tendency for the hot structure to bend or sway with
disatrous results.

The Electro Harmonix KT90 had Pda of 55W and looks just like a
KT88/6550 but with taller plate but straight sided glass, like an EL34
which has been fed steroids for a year. Initially, the KT90 were a
reasonable buy because the price wanted was only a bit more than a
6550. But that seemed to change.
Seems to me New Sensor is again "stretching" the KT 88 upwards even
more than they did with KT90.

But if a 6550/KT88 is $30, then when stretched upwards, it should only
cost for the extension in height of 35% so $40.50, not $70 being
talked about.

Two KT88,6550 will cost less than one KT120 and the Pda of the two
KT88/6550 = 84W,
and so a quad of KT88/6550 are going to beat the pants of a pair of
KT120.

But for those that must have the latest gizmo, you know where to go to
spend up.
But don't expect any more power or fidelity than you are getting now
with KT88/6550.
The curves I could see do not indicate any more anode voltage swing is
available if you just switch to KT120. Are the curves as good as for
the NOS KT88? I don't think so.

Many makers are already pushing their luck by running 6550 with Ea too
high and RL too low.

There seems to be an absurd trend where there is never enough power,
even with so called hi-fi amps they are set up in nearly all class B
working with low load and high Ea to get the sales figures and to hell
with the idea that for hi-fi about 50W max is all that should be ever
asked from a pair of KT88/6550.

I found the Sovtek small bottle 6550 and KT88 were excellent value for
the price. The guts of these didn't change when the bottle size
increased for the Electro Harmonix name range. OK, It was all a
marketting ploy eh, to get away from the old association of Sovtek and
the evil empire of the Soviets and USSR. I wonder how Mike mathews is
getting on with the Russian Mafia boyos who tried to put the squeeze
on him for a rouble or three. Maybe Mike needs the money, but then we
could all say that.

Patrick Turner.


I bought a pair of KT120's from The TubeDepot a few weeks back just
for the heck of it. After about 24hrs operation one of the filaments
opened up (really). I pulled the tube and checked it with an Ohm
meter and noticed that when I move the tube the resistance changed. I
took a soldering iron to the filament pins for a few seconds and that
seemed to fix it. About 24hrs operation after that it happen again so
I heated the pins up a second time. So far them seem to be working
but quality control seems to be an issue. Aside from that, they do
really sound good with a lot of top end. I'm running 500Vdc on the
plates with 400Vdc on the screens in push-pull configuration at about
60 mA idle current.

[Ian Iveson]

"NX211" wrote:

I bought a pair of KT120's from The TubeDepot a few weeks
back just
for the heck of it. After about 24hrs operation one of the
filaments
opened up (really). I pulled the tube and checked it with
an Ohm
meter and noticed that when I move the tube the resistance
changed. I
took a soldering iron to the filament pins for a few seconds
and that
seemed to fix it. About 24hrs operation after that it
happen again so
I heated the pins up a second time. So far them seem to be
working
but quality control seems to be an issue. Aside from that,
they do
really sound good with a lot of top end...

*** Aha. I was wondering which end of the valve they'd
extended.

Ian