Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: punkykatt on October 20, 2016, 09:46:31 pm

Title: One tube reverb in a Pro 6G5-A
Post by: punkykatt on October 20, 2016, 09:46:31 pm

Hey Guys,  I have a client that wants me to install a one tube reverb circuit in place of the normal channel in this amp http://el34world.com/charts/Schematics/files/fender/Fender_Pro_6g5A.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_Pro_6g5A.pdf)  .    Where would be the best place to insert the reverb circuit without messing up the  pitch shift vibrato?  Also which nodes should the reverb tube plates be tapped into? Thanks  in advance for any info and input.    Punky

Title: Re: One tube reverb in a Pro 6G5-A
Post by: VMS on October 20, 2016, 11:13:43 pm

Maybe this could work and I would probably tap the reverb driver to the phase inverter node or the node A.   :dontknow:

Title: Re: One tube reverb in a Pro 6G5-A
Post by: VMS on October 20, 2016, 11:19:55 pm

I just realized that my circuit is missing the reverb control pot but that could probably go between .05 cap and 220k resistor without it affecting too much the dry signal.

Title: Re: One tube reverb in a Pro 6G5-A
Post by: TIMBO on October 20, 2016, 11:35:19 pm

Hey Punky, Like this..........
http://el34world.com/Forum/index.php?action=dlattach;topic=7957.0;attach=44493;image (http://el34world.com/Forum/index.php?action=dlattach;topic=7957.0;attach=44493;image)

Title: Re: One tube reverb in a Pro 6G5-A
Post by: punkykatt on October 21, 2016, 09:36:58 am

Great, thanks VMS and TIMBO. 

Title: Re: One tube reverb in a Pro 6G5-A
Post by: hesamadman on October 21, 2016, 10:44:44 am

Please keep updated on results. I plan to try one tube reverb soon.

Title: Re: One tube reverb in a Pro 6G5-A
Post by: punkykatt on October 21, 2016, 10:35:07 pm

Yes, I will let you know how I make out.  May take a few days before  I dig into this.
Punky

Title: Re: One tube reverb in a Pro 6G5-A
Post by: punkykatt on October 27, 2016, 02:17:25 pm

The one tube reverb in place of the normal channel works well.  Not surfabilly level but plenty of reverb for rock and blues.  I used node B for  plate voltage sources cause it was real close by. Pin 1 ended up with 276v and pin 6 ended up with 173v.   I used a 500p input cap, the existing 1M volume pot for dwell and a 2M pot for level control.  I inserted the level control between the .05 cap and the 220k leading to the PI but was picking up DC voltage from the vibrato circuit(scratchy sound on level pot) . I added a .001 cap between the level control and the 220k all is fine.   Thanks to all for your input.  Punky

Title: Re: One tube reverb in a Pro 6G5-A
Post by: VMS on October 28, 2016, 11:49:29 am

I'm glad it worked.

Quote from: punkykatt on October 27, 2016, 02:17:25 pm

I inserted the level control between the .05 cap and the 220k leading to the PI but was picking up DC voltage from the vibrato circuit(scratchy sound on level pot) . I added a .001 cap between the level control and the 220k all is fine.

Yes, sorry about that. I totally overlooked the fact there are no caps after the vibrato channel.


Did you notice any difference on the vibrato channel before and after the mod?

Title: Re: One tube reverb in a Pro 6G5-A
Post by: punkykatt on October 28, 2016, 05:08:08 pm

Did you notice any difference on the vibrato channel before and after the mod?

No difference at all.   What a great sounding vibrato these amps have.    :guitar1