Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: walteralter on October 23, 2024, 01:22:07 pm

Title: Champ build questions
Post by: walteralter on October 23, 2024, 01:22:07 pm

Hello everyone,

new to this forum. Thinking about building a second amp (built Robs Blackvibe 2 years ago).

Option 1) Basically a Champ circuit with reverb. To get higher voltages for the AT7 reverb driver I was thinking using a GZ34 and adding an additional filter stage (see attached schematic).

Option 2) Champ circuit but with 1 6BM8 Tube Reverb (see schematic). My question now is what to do with the 2nd half of the Preamp 3 12AX7, could a Princeton style cathodyne phase inverter work in this circuit and is it advisable?

Any input would be appreciatedd, thanks! 

Title: Re: Champ build questions
Post by: Willabe on October 23, 2024, 01:34:31 pm

I'd go with the 12AT7 for the verb. Run it in || (parallel) like a Fender.

Use a 40uF/500v for the 1st A node B+ filter stage.

You can't use a PI with a SE (single ended) power amp. Push/pull (PP) power amps use a PI.   

 

Title: Re: Champ build questions
Post by: kagliostro on October 23, 2024, 03:03:33 pm

https://el34world.com/Forum/index.php?topic=25922.0 (https://el34world.com/Forum/index.php?topic=25922.0)

https://en.uraltone.com/blog/ut-vibro-champ-with-reverb-build-guide/ (https://en.uraltone.com/blog/ut-vibro-champ-with-reverb-build-guide/)

Franco

Title: Re: Champ build questions
Post by: walteralter on October 23, 2024, 03:40:47 pm

thanks, found the uraltone site 2 days ago - option 1 is based off of their schematic

Title: Re: Champ build questions
Post by: kagliostro on October 23, 2024, 04:28:47 pm

I'll not use a vacuum tube rectifier, in an SE amp it didn't give advantages (the disadvantage is you have a higher B+ if you don't change the TA)


Franco

Title: Re: Champ build questions
Post by: labb on October 23, 2024, 06:55:22 pm

There are some really good reverb pedals.

Title: Re: Champ build questions
Post by: walteralter on October 24, 2024, 05:19:06 am

Quote from: labb on October 23, 2024, 06:55:22 pm

There are some really good reverb pedals.

nothing comes even remotely close to a real tube driven spring reverb.
Got a UA Golden Reverberator after all the hype and didnt like it.

Title: Re: Champ build questions
Post by: Lectroid on November 01, 2024, 10:27:42 am

@walteralter,

You can build a one-tube reverb with a 12DW7. It's a low-µ triode plus a high-µ triode.  I've done it and it produces pretty good reverb.  Not quite up to surf music like the old Fenders, but otherwise it's completely acceptable.  It's a more feathery, jazzy reverb rather than the sharper, "clattery" reverb sound like a Fender design.

If you haven't already, check the Archives sub-board for "one-tube reverb."

If you have a triode left over, maybe add in a switchable gain stage?