Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: newguitarsmell on February 24, 2019, 11:40:18 pm

Title: 5f2a mods
Post by: newguitarsmell on February 24, 2019, 11:40:18 pm

https://el34world.com/Hoffman/files/Hoffman_5F2A.pdf

What mods do I need to use:
El34 instead of 6V6
6SN7 instead of 12ax7

Is it possible?
Rectifier will be 5y3

Title: Re: 5f2a mods
Post by: PRR on February 25, 2019, 12:29:19 pm

EL34 is much higher heater demand.

6SN7 is much lower gain.

It's really a something-else.

Title: Re: 5f2a mods
Post by: sith on February 25, 2019, 01:16:55 pm

what do you plan to achieve, do you want to scratch build it or 'upgrade' exting amp?
To me, only viable differences (not upgrades, by any means) to tweed princetone circuits are using EL84 instead 6v6 for arguably different tone, rectifier - silcone vs tube, and bigger filter caps...Of all I stick to last only 

Title: Re: 5f2a mods
Post by: newguitarsmell on February 25, 2019, 01:34:51 pm

Interesting comments. How much bigger filter caps and what would they do?

Is there an amp that has both a 6SN7 and el34s and if so, what is it?

Thanks!

Title: Re: 5f2a mods
Post by: sith on February 26, 2019, 06:04:18 am

 you'll get more filtering and amp will (might) sound more tight,  some say modern

Title: Re: 5f2a mods
Post by: Papa Jim on February 26, 2019, 06:54:36 am

one tube reverb.

Title: Re: 5f2a mods
Post by: mresistor on February 26, 2019, 06:54:52 am

8wattjack is right on..   I have a 65 Champ that has vintage  10" 4 ohm Jensen black frame in it and it sounds great..  I think the speaker was reconed and changed to 4 ohm at some point. I put a huge Mercury Magnetics Champ OT in a 64 Vibro Champ that has a custom 12" speaker cabinet with an alnico 12" and it sounds like heaven.  Really chimey and clear.  Sweet..


But what is it you are trying to achieve? What sound are you looking for? I don't get the 6SN7 part, that's a low mu tube. I guess it indicates you might be wanting a clean sound. Like a 5F6A.


Are you going for single ended or open to push pull?   If SE then I would head over to Watkins SE forum and poke around.. sewatt.com