# Conn 12au7 tubes?



## Frenchy99 (Oct 15, 2016)

I bought 43 Made in USA Conn preamp tubes yesterday , they came from an old Conn organ. The seller told me they were from the late 50s or 60's. Anybody know who made them? RCA, Philips? ???


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## gtrguy (Jul 6, 2006)

Pics might help identify them- especially if there are any etched codes on the glass.


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## Frenchy99 (Oct 15, 2016)

OK. ..I'll post pics once home...


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## Frenchy99 (Oct 15, 2016)

Here are some quick pics...


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## gtrguy (Jul 6, 2006)

RCA


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## Frenchy99 (Oct 15, 2016)

Cool ! Thanks...

Mind if I ask how you were able to determine that ? Im trying to learn...


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## gtrguy (Jul 6, 2006)

Frenchy99 said:


> Cool ! Thanks...
> 
> Mind if I ask how you were able to determine that ? Im trying to learn...


The EIA number, just like on pots identifies the manufacturer. In this case the '274'. Above it is the date code if I'm not mistaken, "59-17" being the seventeenth week of 1959 (April or May). The octagon around the 12AU7 label is often seen on RCAs.

I only looked at the markings on one tube but the others looked to be the same, maybe some different date codes or maybe they were all from one batch?

EIA isn't always there, then you have to look at the structure of the tubes or markings on the glass to try to figure it out.


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## Frenchy99 (Oct 15, 2016)

gtrguy said:


> The EIA number, just like on pots identifies the manufacturer. In this case the '274'. Above it is the date code if I'm not mistaken, "59-17" being the seventeenth week of 1959 (April or May). The octagon around the 12AU7 label is often seen on RCAs.
> 
> I only looked at the markings on one tube but the others looked to be the same, maybe some different date codes or maybe they were all from one batch?
> 
> EIA isn't always there, then you have to look at the structure of the tubes or markings on the glass to try to figure it out.


 Big thanks for the explanation! I ll do a search for the EIA numbers for tube manufacturers... should be a list somewhere...

They should the same date, its was a batch for one organ.


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## gtrguy (Jul 6, 2006)

https://www.tubemuseum.org/SearchResults.asp?Cat=30


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## Frenchy99 (Oct 15, 2016)

gtrguy said:


> https://www.tubemuseum.org/SearchResults.asp?Cat=30



Thanks again !!! Added in my favorites !


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## Davestp1 (Apr 25, 2006)

The mica spacers on RCA's have a sort of rectangular shape rather than round. You can see the straight sides of the spacer on all the photos here. RCA's are the only manufacturer to do this. It's pretty much a guarantee a tube is an RCA.


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## copperhead (May 24, 2006)

Not sure what the Nostalgia is ,as the 12aU7 is about 1/4 volume of the 12ax7 & about the same when comparing gain .... try them you may feel silly . as IMO NOT a alternative tube like 12at7 or 12ay7/ 5751 .


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## nonreverb (Sep 19, 2006)

12AU7A is usually used as a current source. Not for gain.


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## Frenchy99 (Oct 15, 2016)

copperhead said:


> Not sure what the Nostalgia is ,as the 12aU7 is about 1/4 volume of the 12ax7 & about the same when comparing gain .... try them you may feel silly . as IMO NOT a alternative tube like 12at7 or 12ay7/ 5751 .


I understand your point of view...

I bought these sine they cost me $1.00 each and use them in the effect channels …( nothing to do with gain) Since I have numerous amps that uses 2 of these in them , nice to have replacements on hand at such a low cost... Having to replace just one new one with shipping would cost more then half what I dished out...

Spares...


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## nonreverb (Sep 19, 2006)

They'd be great as the power tube drivers in an Ampeg SVT Classic.


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