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Post subject: Tubes Substitution and info!
Posted: Tue Jun 10, 2008 8:49 am
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Tubes!
Some quick/easy substitutions.
These subs are all taken from the Tube Substitution Handbook sold by Antique Electronics Supply or provided from the net.

*I didn't make anything up, i just put everything together*

A (short) catalog of tubes you are likely to see in a guitar

amp:
12AX7[A,WA] and subs: Preamp and driver tubes.
12AT7,12AU7 and subs: Preamp and driver tubes.
12AY7: Driver tubes.
6EU7: Dual triode used in some older amps for preamp tube.
6L6 types: Power output tubes, up to 50 watts/pair, a mainstay of Fender.
EL34: Euro power pentodes, up to 50 watts/pair, many Marshalls.
6V6: smaller, lower power cousin of the 6L6, 10-14 watts per pair; used in smaller Fenders.
EL84: fits a 9 pin socket like a 12AX7 but twice as tall; miniature power pentode, good for 12-18 watts per pair; used in smaller Vox amps, and a quad of these drives the Vox AC-30 for 30 watts.


Substitutions:
* means appropriate for parallel filament circuits
# means may not work in all circuits

Preamp and driver tube substitutions:

The 12AX7 family of dual-triod preamp tubes consists of the:
12AX7 (high gain dual triodes with pinout 9A)
5751 (SRV favorites, medium high gain 9A)
12AT7 (miniature medium gain dual triodes with pinout 9A)
12AY7 (low gain dual triodes with pinout 9A)
12AV7 (Medium low gain)
12AU7 (miniature moderately high gain dual triodes with pinout 9A)

These are all pin compatable with one another, the only differences being the gain factor of each tube. A common substitution is to replace a 12AX7 with a 5751 or a 12AT7 to tame a preamp that tends to overdrive too easily, allowing you to get a better 'clean' sound out of your amp.

Tube Gain Acceptable Substitutes
12AX7 100 5751*,12AT7,12AY7,
5751 70 12AX7,12AT7,12AY7
12AT7 60 5751,12AY7
12AY7 45 5751,12AT7,12AV7
12AV7 41 12AY7,12AU7
12AU7 19 12AV7

Others

12AX7:
12AD7*
12DT7
772912AU7#
B33912AU7A#
5751WA*
B75912AX7
6057
CV400412AX7A
6681
E83CC12AX7WA
6L13
ECC80312BZ7*
7025
ECC8312DF7
7025A
M813712DM7*
7494

12AU7:
12AU7[A,AW,]
6189
6670
ECC1865814[A,AW]*
6680
ECC8025963
7316
ECC826067
7489
M8136

12AT7:
12AT7[many suffixes]
7492
E81CC6201
7728
ECC8016679
A2900
M8162ECC81
B152
QA240612AZ7[A]*
B309
QB3096060
B7396671
CV4024

12AY7:
60722082


Power tube substitutions:
Here are some common power tubes:
6BQ5-US/EL84-euro (miniature pentode with pinout 9CV)
6L6 (beam power tube with pinout 7AC)
6CA7-US/EL34-euro (power pentode with pinout 8ET)
6550 (power pentode with pinout 7S)


6BQ5/EL84:
6267
7189
EF866BQ5
7189A
EL846BQ5WA
7320
N7096P15
E84L
Z729

6L6:
6L6(many suffixes)
7581(A)5881
WT65932
EL37

EL34/6CA7:
EL34
12E136CA7
KT777D11
KT88

6550:
6550[A]
7027A#7D11
KT8812E13

Cautionary Tubes - these are very hard to find
7591/7591A:
Legend has it that these otherwise excellent tubes were all bought up by a buyer who toured the USA paying cash for all of them he could find, then disappearing. You are likely to only find used ones or the odd pair in some out of the way place. Dealers will in general not have them.
These were used a lot in old Ampegs. They are very small and high gain for their physical size, so there may not be a lot of room in a chassis for a larger replacement. The 5881 will work in some circuits, but has significantly lower transconductance.
Luckly, you can now still get Russian made ones.


7199:
combination pentode/triode used as a one-tube voltage amp/phase inverter/driver for a pair of output tubes in some Ampeg amplifiers Note: These were once popular, but are now getting rarer and more expensive. There are a number of other pentode/triodes that can be substituted, but the pinouts are different and this will require require rewiring the socket for the tube. Examples are the 6AN8 and the 6U8. There is a also Russian tubes that are now labeled 7199 which may work.

7027/7027A:
this is a high power tube similar to a 6550. The supply of these is very poor.

7189/7189A:
a higher power/voltage version of the 6BQ5/EL84. Hard to find. A stock 6BQ5/EL84 may work if the power and voltage conditions in the amp are not right out at the limits of the tube design.


I Highly suggest These website!

The best tube store:
http://thetubestore.com/

Published by Canadian General Electric back in 1943!

*Information limited due by the fact that there were nowhere

near as many vacuum tubes in the post war years.* :
http://www.theoldradiofixerupperguy.com ... ubesub.pdf

Awesome tube database:
http://www.nostalgiaair.org/tubes/

Another chart:
http://www.playersboutique.com/pdf/TubeSubATF.pdf


Last edited by phuot on Tue Jun 10, 2008 9:51 am, edited 1 time in total.

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Post subject:
Posted: Tue Jun 10, 2008 9:10 am
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WOW! You sure have given this a whole lot of thought.

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Posted: Tue Jun 10, 2008 9:42 am
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I have spent many days reading over material such as that. It is all quite interesting.

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