6av6 preamp tube substitution.

[wrathfuldeity]

Bogen record player conversion, has a 6av6 preamp, 5y3gt rectifier, and a 6l6. Its a happy little guitar amp that sounds wonderful but wondering if there are substitute tubes or brands for a lower gain for the current 6av6 telefunken preamp tube. Anyway I'm a noob haven't found info...Thanks

[loudthud]

6AV6 has a gain (mu) of 100. 6AT6 has a gain of 70. 6BF6 has a gain of 16. You might consider changes to the circuit. Have you found a schematic anywhere?

[wrathfuldeity]

Loudthud, it is exactly what I needed. Don't have a schematic though have looked; the tech said it was an easy circuit, he did some minor mods to voiced as an old tweed and did the cap and filters. I've wondered about if it was possible to mod it to take 12ax7 tubes and even put to use the other preamp (phono) but figure it more of a problem due to it being a ptp rats nest and the thing sounds great anyway...so just thinking about lower gain preamp tube so it doesn't break up so early at 1/4 to 1/3. Thanks.

[loudthud]

The only problem with a 12AX7 is you'ld have to change the socket from 7 to 9 pins. There are probably other tubes that could be substituted, those are just the ones I found.

[loudthud]

Do you have a model number or can you post a picture?

[wrathfuldeity]

Its a Bogen VP12 record player with a mic circuit...for square dancing in PE, generally run into a homemade detuned cab with a weber 12A150

[Enzo]

If you look up 12AX7 in the RCA book, it will tell you that a 6AV6 is just a half of a 12AX7. SO other than the socket and rewiring, you could make the 6AV6 into one side of a 12AX7 with no circuit changes at all. And then you could change to 5751, 12AY7, or your favorite lower gain tube that way.

[stingray_65]

I had remebered those tube numbes (6AV6,6AT6) because I did a detailed inventory of the tubes in my work shop.

I remembered thinking they might be fun to experiment with, but IIRC they also have twin diodes.

I'm curious if the bogen doesn't use those diodes.

just for curiosities sake i'm wondering why you want to lower your gain in the preamp?

Ray

[wrathfuldeity]

Ray, Figured that changing preamp tube would be a cheap and easy way to experiment. As for lowering the gain, wondering if it would give a bit more clean headroom volume before breaking up since rarely use the upper 1/3rd of the range. btw, don't know what diodes are or do.
Tim

ps just got up a youtube vid

[ame="http://www.youtube.com/watch?v=YEnXEr8_X6Q"]YouTube - Bogen Guitar Amp[/ame]