Low wattage amps using 7 pin pentodes

[lastwinj]

i did it several years ago. great way to go on the cheap.

[David Root]

I did an all-7-pin 5F10 Harvard about four years ago. This circuit uses a 5Y3GT, a 6AT6, a 12AX7 and two 6V6GTs. AFAIK this is the only use of a 7-pin by Fender, so I thought, why not go all 7-pin?

I replaced the 5Y3GT with two 6X4s in parallel, kept the 6AT6 in V1 position, used two 6AV6 to replace the 12AX7 and two 6AQ5s replacing the 6V6GTs. Mercury Magnetics iron.

Awesome tone just like the real Harvard, even though I used el cheapo Xicon metal films at that time. I think the speaker made the tone (Tone Tubby 12" Alnico). Put it in a narrow panel deluxe cabinet stretched widthwise 2 inches to accomodate the Hammond 17x4x3 steel chassis I used. What a PITA that was, 20 ga. is too thin, it bends when you drill it.

I can retube it for $30 or so with all-NOS RCA!

I started playing around with different tubes and ended up with a 6BF6 in V1, followed by 6AT6 V2, and 6AV6 for the PI. Makes a great 15W harp amp, as the 6BF6 is 20 mu and mellows V1 right out. With the 6AT6, a Les Paul just turns it into a total screamer, with the Paul and the 6BF6, it's a great blues amp. I took it to one of Gerald Weber's Amp Camps and it got favorable reviews.

Recently I stole the Tone Tubby for another combo and replaced it with a Weber 12A125 which sounds great too, not quite as loud (11 oz vs 35 oz magnet, I guess).

[RJ Guitars]

David - that's awesome... The 6AQ5's are really nice sounding tubes. You mentioned a couple 7 pins that I haven't tried. I wasn't aware of any Fenders with 7 pins either. Gibson & Epiphone have a few and some of them also sound good.

I haven't heard much about Gerald Weber for a while, I assumed he was still around doing something in the amp business. It was his first book that I used as a reference to mod my first amps. I still refer to it often. He has some great stuff in it from Ken Fisher also.

Do you any pictures or sound clips?

rj

[klingo]

i found these links:
http://www.frontiernet.net/~jff/pipsque ... r_amp.html

http://lucidtone.com/misc/voltage_amp_data.pdf EDIT dead link!!!

seven pins & more!

[RJ Guitars]

Thanks Klingo - I've seen some of these and I think it's great that they share their schematics with us...

They've made some great little low budget tube tone amps. That's the main beauty of these 7 pin tubes is that you can get them cheap and they sound great.

I haven't built anything yet with a pentode front end, but these are inspiring efforts.

Thanks again for the links...

rj