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shiva
 
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Default 6eu7 or 12ax7? what to to use...

Hi all -
I'm still trying to figure out what to build for a RIAA section, and, while
some claim that 12ax7 is a non-starter, it seems like quite a starter to me.
Here's a (possibly) stupid question - I've got a pile of mullard 6eu7's, and
the specs look suspiciously like 12ax7, except for the pinout & a claim that
the pinout (and presumably the twisted fils) make EU a better choice (GE
data sheet).
I know that 12ax7Axxx's have twisted fils, but does anyone have any
experience with EU's? This is a really tight layout, and the pinout
certainly works better for me (heater pins at 1&2 right next to each other,
isolated by the empty pin 3, which could be used as a nice hanging point for
either HT or ground...
Any thoughts?
-dim


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Sander deWaal
 
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"shiva" said:

Hi all -
I'm still trying to figure out what to build for a RIAA section, and, while
some claim that 12ax7 is a non-starter, it seems like quite a starter to me.
Here's a (possibly) stupid question - I've got a pile of mullard 6eu7's, and
the specs look suspiciously like 12ax7, except for the pinout & a claim that
the pinout (and presumably the twisted fils) make EU a better choice (GE
data sheet).
I know that 12ax7Axxx's have twisted fils, but does anyone have any
experience with EU's? This is a really tight layout, and the pinout
certainly works better for me (heater pins at 1&2 right next to each other,
isolated by the empty pin 3, which could be used as a nice hanging point for
either HT or ground...
Any thoughts?


Dunno about 6EU7, but I subbed the CV4004 (a 12AX variety) for 6072
and ended up with substantially less noise, slightly lower gain but
far better sound overall.
The design is CC, passive RIAA and again CC.

BTW twisted filaments? Surely you do use DC on the heaters in this
app, so that won't matter at all?

--
Sander de Waal
" SOA of a KT88? Sufficient. "
  #3   Report Post  
Phil S
 
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"shiva" wrote in message
news:6lnYd.752$db6.365@trndny02...
Hi all -
I'm still trying to figure out what to build for a RIAA section, and,

while
some claim that 12ax7 is a non-starter, it seems like quite a starter to

me.
Here's a (possibly) stupid question - I've got a pile of mullard 6eu7's,

and
the specs look suspiciously like 12ax7, except for the pinout & a claim

that
the pinout (and presumably the twisted fils) make EU a better choice (GE
data sheet).
I know that 12ax7Axxx's have twisted fils, but does anyone have any
experience with EU's? This is a really tight layout, and the pinout
certainly works better for me (heater pins at 1&2 right next to each

other,
isolated by the empty pin 3, which could be used as a nice hanging point

for
either HT or ground...
Any thoughts?
-dim


Nearly the same (some say exactly) tube, so go ahead, and those Mullards can
stop loafing in the tube caddy. The only disadvantage I can think of is
that there is no sub for a 6EU7. If later you want to used something of the
12A?7 varitey, you'll need to rewire. The nice thing about the 12A?7 family
is that you can experiment with relative gain and adjust to your ears.
Sometimes going down a notch to a 12AT7 is just the right thing to do.
Otherwise, not much difference between 12AX7A and 6EU7. Convenience is as
good a reason as any to use the 6EU7. Having idle Mullards is another good
reason.


  #4   Report Post  
Ned Carlson
 
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On Fri, 11 Mar 2005 20:38:26 +0000, shiva wrote:

Hi all -
I'm still trying to figure out what to build for a RIAA section, and,
while some claim that 12ax7 is a non-starter, it seems like quite a
starter to me. Here's a (possibly) stupid question - I've got a pile of
mullard 6eu7's, and the specs look suspiciously like 12ax7, except for the
pinout & a claim that the pinout (and presumably the twisted fils) make EU
a better choice (GE data sheet).
I know that 12ax7Axxx's have twisted fils, but does anyone have any
experience with EU's?


Internally 6EU7 is the same as 12AX7 except for the filament
connections. Externally, 6EU7 was pinned differently so it wouldn't
pick up as much hum when it was run on AC filaments (that was
the sales talking point of the whole exercise). Assuming you are
running the tubes on DC filaments, you can use either one
(taking the different pinout into account, of course), in the
same circuit.



--
Ned Carlson Triode Electronics Chicago,IL USA
www.triodeelectronics.com



  #5   Report Post  
shiva
 
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"Ned Carlson" wrote in message
news
On Fri, 11 Mar 2005 20:38:26 +0000, shiva wrote:

Hi all -
I'm still trying to figure out what to build for a RIAA section, and,
while some claim that 12ax7 is a non-starter, it seems like quite a
starter to me. Here's a (possibly) stupid question - I've got a pile of
mullard 6eu7's, and the specs look suspiciously like 12ax7, except for

the
pinout & a claim that the pinout (and presumably the twisted fils) make

EU
a better choice (GE data sheet).
I know that 12ax7Axxx's have twisted fils, but does anyone have any
experience with EU's?


Internally 6EU7 is the same as 12AX7 except for the filament
connections. Externally, 6EU7 was pinned differently so it wouldn't
pick up as much hum when it was run on AC filaments (that was
the sales talking point of the whole exercise). Assuming you are
running the tubes on DC filaments, you can use either one
(taking the different pinout into account, of course), in the
same circuit.


Thanks Ned. Haven't ordered from you in a while - do you have any
recommendations (or have in stock) any odd (russian?) output tubes (triodes,
pentodes, any plate dis. / any basing) which are cheap & fun to design
around? (I've given up on 807 / 6bg6 /8068's etc - the whole top-hat thing
is more of a pain at sub - 700V plate voltage). I don't care if it's not a
replenishable batch - this is strictly for one-off hobby projects. BTW,
ever heard of Oliver amps? I've got one for the tyranies & the GZ34, it's
made in Westbury, NY, and mine looks like some "wizard" was at it - this
thing's full of 6eu7's, too. I know you collect schematics - I've drawn out
the 2 PC boards & the tone /vol circuits, didn't bother with the PS 'cos it
looked like it was designed by an idiot, and added later. If you know where
i can download the schematics - i'd love to. If they don't exist, I can
send you my partials (everything but the PS, , I can even *draft* them out &
send a layout / PC drawings... Also, was the Stancor A-8053 the original OT?
Thanks.
-dim (with too many questions)




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Fabio Berutti
 
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BTW there's a cheaper substitute for 6EU7, which is the Russian 6N2P, but if
You have some Mullards ...

Ciao

Fabio


"shiva" ha scritto nel messaggio
news:4MEZd.5414$b_6.2248@trnddc01...

"Ned Carlson" wrote in message
news
On Fri, 11 Mar 2005 20:38:26 +0000, shiva wrote:

Hi all -
I'm still trying to figure out what to build for a RIAA section, and,
while some claim that 12ax7 is a non-starter, it seems like quite a
starter to me. Here's a (possibly) stupid question - I've got a pile of
mullard 6eu7's, and the specs look suspiciously like 12ax7, except for

the
pinout & a claim that the pinout (and presumably the twisted fils) make

EU
a better choice (GE data sheet).
I know that 12ax7Axxx's have twisted fils, but does anyone have any
experience with EU's?


Internally 6EU7 is the same as 12AX7 except for the filament
connections. Externally, 6EU7 was pinned differently so it wouldn't
pick up as much hum when it was run on AC filaments (that was
the sales talking point of the whole exercise). Assuming you are
running the tubes on DC filaments, you can use either one
(taking the different pinout into account, of course), in the
same circuit.


Thanks Ned. Haven't ordered from you in a while - do you have any
recommendations (or have in stock) any odd (russian?) output tubes
(triodes,
pentodes, any plate dis. / any basing) which are cheap & fun to design
around? (I've given up on 807 / 6bg6 /8068's etc - the whole top-hat thing
is more of a pain at sub - 700V plate voltage). I don't care if it's not
a
replenishable batch - this is strictly for one-off hobby projects. BTW,
ever heard of Oliver amps? I've got one for the tyranies & the GZ34,
it's
made in Westbury, NY, and mine looks like some "wizard" was at it - this
thing's full of 6eu7's, too. I know you collect schematics - I've drawn
out
the 2 PC boards & the tone /vol circuits, didn't bother with the PS 'cos
it
looked like it was designed by an idiot, and added later. If you know
where
i can download the schematics - i'd love to. If they don't exist, I can
send you my partials (everything but the PS, , I can even *draft* them out
&
send a layout / PC drawings... Also, was the Stancor A-8053 the original
OT?
Thanks.
-dim (with too many questions)




  #7   Report Post  
shiva
 
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"Fabio Berutti" wrote in message
...
BTW there's a cheaper substitute for 6EU7, which is the Russian 6N2P, but

if
You have some Mullards ...

Ciao

Fabio

I remember some company re-basing AX7's with a chunk of PC board & cut off
pins... I think I still have one, along with a ugo 12AX7 which tests well &
glows orange...
-dim


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