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Mark Harriss
 
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Default What makes a good linear triode?


I've been drawing loadlines for my amp project input
triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7
and 12AX7. I notice that the minature B9A valve curves aren't
all that evenly spaced, is this somehow related to the geometry
needed to cram a dual triode into a small envelope?.

Is there such a thing as a nicely linear B9A triode with
medium to high gain suitable for an input stage?.


Mark Harriss
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Patrick Turner
 
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Mark Harriss wrote:

I've been drawing loadlines for my amp project input
triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7
and 12AX7. I notice that the minature B9A valve curves aren't
all that evenly spaced, is this somehow related to the geometry
needed to cram a dual triode into a small envelope?.


6CG7 were first developed using exactly the same internals
as a 6SN7, and the tube slightly derated for dissipation.
The 6CG7 then came out with various mainly smaller plate structures,
and just as linear as the octals.

6BQ5 strapped as a triode is also just as linear
as anything octal.

the 12AX7, 6SL7, 6SN7, 6CG7 are amoungst the most naturally linear
devices in the universe, especially when set up as U followers,
or loaded with a CCS.



Is there such a thing as a nicely linear B9A triode with
medium to high gain suitable for an input stage?


12AY7.
This is more linear but with similar gain to 12AT7.
Higher Ra though.
12AT7, 12AU7 are less linear than
the rest, but so what if there is 0.5% thd at 3 vrms output
from a typical set up? its only 2H.
My fav is NOS 6CG7 from Telefunken, or even Oz made
varieties.
Linearity is important, but then when you swap tubes in an amp,
sometimes you get a sound change.

12AU7 are generally more linear in practice than the curves indicate,
and I find its one of the nicest tubes for a line stage, or
as an LTP phase inverter in a power amp.

Patrick Turner


.

Mark Harriss


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John Harper
 
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Closer electrode spacing tends to reduce linearity. Unfortunately
it also increases Gm, which was the tube designers' holy grail.
Hence older, bigger designs do seem to be more linear. As
Patrick says, 6CG7 is a good bet in that regard.

John

"Mark Harriss" wrote in message
...

I've been drawing loadlines for my amp project input
triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7
and 12AX7. I notice that the minature B9A valve curves aren't
all that evenly spaced, is this somehow related to the geometry
needed to cram a dual triode into a small envelope?.

Is there such a thing as a nicely linear B9A triode with
medium to high gain suitable for an input stage?.


Mark Harriss



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Ronald
 
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You guys ever took a look at the ECC40 curves on a CCS ?? ;-)))

"John Harper" schreef in bericht
news:1075232292.917623@sj-nntpcache-3...
Closer electrode spacing tends to reduce linearity. Unfortunately
it also increases Gm, which was the tube designers' holy grail.
Hence older, bigger designs do seem to be more linear. As
Patrick says, 6CG7 is a good bet in that regard.

John

"Mark Harriss" wrote in message
...

I've been drawing loadlines for my amp project input
triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7
and 12AX7. I notice that the minature B9A valve curves aren't
all that evenly spaced, is this somehow related to the geometry
needed to cram a dual triode into a small envelope?.

Is there such a thing as a nicely linear B9A triode with
medium to high gain suitable for an input stage?.


Mark Harriss





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Tim Williams
 
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"Ronald" wrote in message
...
You guys ever took a look at the ECC40 curves on a CCS ?? ;-)))


*Looks at graph* Oooooooo...

If it had a vagina I'd be set. ;-)

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms




  #6   Report Post  
Andy Evans
 
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You guys ever took a look at the ECC40 curves on a CCS

Keep forgetting I have a handful of these I've never used. They do have a good
reputation.

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.
  #7   Report Post  
Ronald
 
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Hi Andy ,

Keep forgetting I have a handful of these I've never used. They do have a

good
reputation.


I dicovered this tube by ear and saw the curves after that because I liked
the sound .
The curves look good almost everywhere but I liked them best at some higher
voltage on the plate , 150V or so . A 6SN7 does great on 80V on the plate
but
you won't hear the best of the ECC40 at that voltage .....
The biggest problem might be the sockets ......

Best regards ,

Ronald .



=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.



  #8   Report Post  
Nothing40
 
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"Tim Williams" wrote in message ...
"Ronald" wrote in message
...
You guys ever took a look at the ECC40 curves on a CCS ?? ;-)))


*Looks at graph* Oooooooo...

If it had a vagina I'd be set. ;-)

Tim



Uhmm.. *blank stare* Whoa.. :-p
  #9   Report Post  
Tom Schlangen
 
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Hi Ronald,

regarding ECC40:

The biggest problem might be the sockets ......


At least for low quantities of either. If you intend
to use, say, 2 pcs of ECC40 in a circuit without
having both (tubes and sockets), this may be costly.

If you have a stash of either, the picture looks more
bright ;-)

Tom

--
If in doubt, mumble.
  #10   Report Post  
Andy Evans
 
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If you intend to use, say, 2 pcs of ECC40 in a circuit without having both
(tubes and sockets), this may be costly.

Not really - I buy in holland for these type of valves. No problem with tubes
or sockets, plenty of good dealers.


=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.


  #11   Report Post  
Mark Harriss
 
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Patrick Turner wrote:



Mark Harriss wrote:

I've been drawing loadlines for my amp project input
triode and have been considering the 12AT7, 6SL7, 6DJ8, 6SN7
and 12AX7. I notice that the minature B9A valve curves aren't
all that evenly spaced, is this somehow related to the geometry
needed to cram a dual triode into a small envelope?.


6CG7 were first developed using exactly the same internals
as a 6SN7, and the tube slightly derated for dissipation.
The 6CG7 then came out with various mainly smaller plate structures,
and just as linear as the octals.

6BQ5 strapped as a triode is also just as linear
as anything octal.

the 12AX7, 6SL7, 6SN7, 6CG7 are amoungst the most naturally linear
devices in the universe, especially when set up as U followers,
or loaded with a CCS.



Is there such a thing as a nicely linear B9A triode with
medium to high gain suitable for an input stage?


12AY7.
This is more linear but with similar gain to 12AT7.
Higher Ra though.
12AT7, 12AU7 are less linear than
the rest, but so what if there is 0.5% thd at 3 vrms output
from a typical set up? its only 2H.
My fav is NOS 6CG7 from Telefunken, or even Oz made
varieties.
Linearity is important, but then when you swap tubes in an amp,
sometimes you get a sound change.

12AU7 are generally more linear in practice than the curves indicate,
and I find its one of the nicest tubes for a line stage, or
as an LTP phase inverter in a power amp.

Patrick Turner


.

Mark Harriss



Hi Pat, I have some 6SL7 and 6CG7 on order now
but I'm also having some good results with a 12AX7 as gain
and concertina at the moment: I get a voltage slew of 18 V/uS
and it takes a square wave up to 80 KHz with a bit of leading
edge rounding off. The gain should be enough to have some
feedback as well.

About the only Phil in the ointment is the concertina
gets a bit out of balance at high frequencies and high levels
possibly due to losses in the cathode resistor bypass caps.

Regards
Mark
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