# wrong tube mistake **FYI**



## Gene Machine (Sep 22, 2007)

Hi everyone. Well, i went to put new tubes in my Champion 600 after changing the grill cloth, and 'thought' i was putting a JJ tesla 12AX7 in it.

WELL, after turning it on, it seems it was very quiet. I wasn't getting as much break up as i was at 50% volume. AFter closer inspection, the tube is a ECC832, not ECC 83. 

So what!?

So, it is actually a 12DW7, which is similar to a 12AX7 except that one half is a 20 gain stage, while the other is 100. So it's like 1/2 12AX7, 1/2 12AU7. The way the amp circuit is, the overall preamp gain is 20 * 100 instead of 100*100.

Turns out I got this from Songbird as a 12AX7. Oh well can't take it back.

I popped another 12AX7 (E-H) in and good as gold.

Anyway, anyone need a lower gain tube? anyone?


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## mrmatt1972 (Apr 3, 2008)

OK. Free?


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## Gene Machine (Sep 22, 2007)

*sorry*

someone already got to it before you, sorry it's already spoken for. 

people are quick.

Anyway, it would probably do fine in an amp where both sides of the tube are used in one channel, cascaded and you want to cut down some of the gain. I sounded fine inthe champion 600, but wouldn't overdrive at all for me and the volume was too low.

Anyway if anyone ever runs across one, that's what it is and what it does.

cheers.


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## Wild Bill (May 3, 2006)

Gene Machine said:


> someone already got to it before you, sorry it's already spoken for.
> 
> people are quick.
> 
> ...


The 12DW7 is used in Ampeg V4's and V4B's. It was out of production for some years and the prices went crazy until JJ started making them again. I still get V4's brought in for repair where somebody jammed in a 12AX7 as a sub, which sounds like ass!

Just FYI.

:food-smiley-004:


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