Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on May 25, 2011, 07:34:56 am

Title: 6SL7 and 6SN7
Post by: LooseChange on May 25, 2011, 07:34:56 am

Hi All,
If I were to take the Fender Blackface preamp values and apply them to some octals like the 6SL7, how would I change the Plate, Cathode and Grid components to build am equivalent circuit. I do understand that the 6SL7 is a bit lower in gain than a 12AX7 but I am not sure exactly how to deal with the differences.
Thanks!

Title: Re: 6SL7 and 6SN7
Post by: sluckey on May 25, 2011, 07:54:24 am

Here's what I did. Look at page 4 for my conversion. V1 is currently a 6SL7. I mostly just copied the original RockOla values.

http://home.comcast.net/~seluckey/amps/rocky/rocky.pdf (http://home.comcast.net/~seluckey/amps/rocky/rocky.pdf)

Title: Re: 6SL7 and 6SN7
Post by: HotBluePlates on May 25, 2011, 03:02:01 pm

You can treat a 6SN7 as a 12AU7, near enough.

For 6SL7, I would start with 12AX7 values. I would personally look at a 6SL7 as a 5751; the mu of both is 70. Plate resistance looks a little bit lower and Gm a little bit higher than a 12AX7.

I know at least one forum member who took a 5F6A board and simply changed the socket wiring, while dropping in 6SL7's. The end result was fine.

If you need to hit a specific target with either, or have a unique application, you'd need to go through using loadlines and/or the typical design process.