12AO7?

[airwarrior]

My grandfather recently gave me an old hi-fi. I'm not sure if it is reparable ( I haven't opened it up yet, but I imagine the electrolytics need replacing, and I know it needs new tubes), and it is missing several tubes, but there is a single Sylvania preamp tube labeled on the side as a 12AO7. Are these usable in guitar amps?

[Billm]

I'm guessing that's a 12AD7, not 12AO7 (no such animal). The 12AD7 is a low noise/low hum preamp tube, typically found in phono stages. I don't recall how much gain it had relative to a 12AX7, but it would work.

They're still available NOS. Pricey.

[Trout]

Originally Posted by Billm

I'm guessing that's a 12AD7, not 12AO7 (no such animal). The 12AD7 is a low noise/low hum preamp tube, typically found in phono stages. I don't recall how much gain it had relative to a 12AX7, but it would work.

They're still available NOS. Pricey.

Yep, and its a High MU twin Triode.
The specs sheet looks very interesting, I wonder how common they are.

http://tubedata.milbert.com/sheets/137/1/12AD7.pdf

[airwarrior]

Possibly, the label is a very old piece of tape.

I'm using a JTM-45 style amplifier, do you know in which socket is the best place to stick this?

[riffmeister]

Originally Posted by airwarrior

1. Possibly, the label is a very old piece of tape.

2. I'm using a JTM-45 style amplifier, do you know in which socket is the best place to stick this?

1.

2. Shouldn't matter, try sticking it in each of the three sockets and listen for what sounds best. My prediction is that it will not improve the sound of the amp.

[airwarrior]

Originally Posted by riffmeister

1.

2. Shouldn't matter, try sticking it in each of the three sockets and listen for what sounds best. My prediction is that it will not improve the sound of the amp.

Yep. It's an old piece of masking tape with 12AD7 penned onto it.

I tried it in the first socket, and it did seem to improve the sound. It sounded less noisy, and the amp seemed to have a more open sound. Maybe it was the placebo effect; I'll record it later and figure out what I like better. Regardless, I'll be saving this tube for a time when I can really use it.

[riffmeister]

Originally Posted by airwarrior

I tried it in the first socket, and it did seem to improve the sound. It sounded less noisy, and the amp seemed to have a more open sound. Maybe it was the placebo effect; I'll record it later and figure out what I like better.

Hey, I like that......an honest recognition of the possibility of psychoacoustic effects. Most folks around here just listen to the voices in their heads....