12AX7 Testing

[Gr8Scott]

I found an old tube in a defunct spot welder and I'd like to get it checked out to see if it is worth opening my amp and installing it. I've had it a while and I don't think it's seen much use, and it sure seems like it would be better than the Chinese 12AX7's that are in this amp. Thing is it could have seen heavy use and is totally microphonic and worn out by now. I won't know until I either plug it in or have it tested for microphonics. Is there a cheap way to do this or should I roll the dice and install it? RCA gray plate seems like it would own a chinese 12AX7. I'll have the back of this amp open in a couple of weeks when I work on some tone mods. This amp isn't easy to get into and there is a chance that I'll destroy a pot or two when I open it.

 

[More-Gear-Than-Skill]

Re: 12AX7 Testing

give it a whirl, and perhaps just order some nice new JJ's. 'cos you're worth it!

 

[HamerPlyr]

Re: 12AX7 Testing

If it's me, I just slap that thing in there and see how it sounds.

 

[Gr8Scott]

Re: 12AX7 Testing

I'll roll the dice then. As soon as my other parts get here, I'll install the RCA. I'll also buy a JJ to go with it. Best of both worlds hopefully. Which one should I throw into the cleans and which one goes to the dirty channel? I've always been told that mixing pre tubes is a good idea unless you want to emphasize one characteristic of a certain tube. Matched pre-tubes are less complex sounding than mixed ones is the theory. Kind of like making beer with only one variety of hops and not mixing things up... I'm gonna install better caps and re-voice the pre-tubes while I'm in there. I'll get to play with the pre-tube voicing quite a bit as it's something I can access right through the back plate. The other stuff requires much more work.

 

[Scott_F]

Re: 12AX7 Testing

A tube in a spot welder? Goodness. Next thing you know, you're going to find a tube in an old toaster...

 

[Quencho092]

Re: 12AX7 Testing

even toasters had good tone back then, scott! The idle buzzing sound of the coils was round and fat rather than the SS garbage they put out these days.

 

[shred-dog]

Re: 12AX7 Testing

even toasters had good tone back then, scott! The idle buzzing sound of the coils was round and fat rather than the SS garbage they put out these days.

that's good stuff now i am taking apart my blender looking for tubes since it has such a sweet sound !!:laugh2:

 

[Jeff Seal]

Re: 12AX7 Testing

A tube in a spot welder? Goodness. Next thing you know, you're going to find a tube in an old toaster...

:laugh2:...."thermionic toaster"

I have a SVT at the shop, I'll let you know which bias settings yield the best results for "dark" toast....(not burnt of course!)....:beerchug:

JS