Replies to This Discussion

Permalink Reply by Tommy Tomcat Arnold on March 6, 2010 at 12:45pm

FWIW, here is my to do list for this project:
Michael S's Custom Vibrolux Reverb

Things to do

Bright Channel, make AB763 tone stack:
x1. Bright channel, reduce V2A bypass cap C6 to 10uF. From 22uF
x2.. Bright channel, reduce treble cap C7 to 250pF. From 390pF
x3. Bright channel, remove C10 treble shunt cap and replace with a jumper to ground.
From .0068uF

V1B/V2B plate load.. lower gain, help with hiss.
x1. Increase R23 to 82K, from 47K.

Improve reverb:
x1. Replace recovery coupling cap C16 with .0022uF, from 500pF.

Add NFB:
x1. Add 10K resistor to R41, which is empty now.
2. Run jumper from speaker jack positive to hole to connection point 2, which shold be empty.
x3. Add 470ohm resistor to R42.
x4. Replace R37 with 6.8K, from 39K.
x5. Put 100pF cap in C20.

Upgrade components:
x1. V1B/V2B .022 coupling cap.. Change to STK film/foil .022uF.
x2. Upgrade reverb feed C13 with PIO 500pF.
x3. Upgrade PI coupling cap C18 to Mojo Dijon .001uF, from 500pF

Ground reference resistors:
1. Change to 47ohm R62 & R63.
x2. Remove diodes from power tube sockets.

Permalink Reply by Michael Schaefer on March 6, 2010 at 1:10pm

Yeah, I'd love to comment. Basically, I was mildly happy with the Vibrolux. It had decent Fender tube amp tone. But overall, it was kind of bland. I began to think that I might need to sell the amp to buy something else when I started playing more jazz. I bought a hollowbody guitar with humbuckers. And I started to notice that I didn't have much headroom when things got kind of bassy. It started to break up way earlier than I wanted.

I started talking to Tommy about it because I had heard the amps he put together for Jimmy Mac, which I considered to be one of the best sounding amps in town. I guess Tommy had heard of this modification, and he asked me if he could give it a try, to see if the end result resolved some of my issues.

What can I say? I cannot believe how great it sounds now. There is so much more sparkle and clarity. My guitars just sound different now. There's so much more clarity. When I play a chord, I heard each string very clearly. Before, it would kind of mush together.

I couldn't be happier with the way it sounds now. I'm pretty sure that now after Tom's changes, I have one of the best sounding amps in town. I can't thank him enough. Fantastic.

Permalink Reply by Michael Schaefer on March 9, 2010 at 9:25am

Tommy, do you have a link to the site that talks about the mod you did to the amp? I forget what the mod is called. You told me the other day, but I forget.

Permalink Reply by Tommy Tomcat Arnold on March 9, 2010 at 9:43am

Mike Moyer mods..
Mods:
http://archive.ampage.org/articles/1/open/003260/Custom_Vibrolux_Re...
http://www.tdpri.com/forum/amp-central-station/99305-vibroverb-v-vi...http://gretschpages.com/forum/other-amps/fender-custom-vibrolux-rev...

Schematic:
http://www.schematicx.com/schematic/fender-custom-vibrolux-reverb-g...


Michael Schaefer said:

Tommy, do you have a link to the site that talks about the mod you did to the amp? I forget what the mod is called. You told me the other day, but I forget.

Permalink Reply by Michael Schaefer on March 9, 2010 at 10:40am

Thanks Tom. Now those links are available here for all to peruse. Appreciate 'cha.

Permalink Reply by David Smith on April 1, 2010 at 8:29am

Tommy,
Does the NFB loop affect both channels, or just the bright/blackface channel?

Permalink Reply by Tommy Tomcat Arnold on April 1, 2010 at 8:47am

The negative feedback is 'fed back' into the the phase inverter (the tube that drives the power tubes).. which is part of the power section. The two channels are combined before the reverb circuit, which both proceed the phase inverter. So, to answer your question.. since it's in the power section, it effects both channels.

David Smith said:

Tommy,
Does the NFB loop affect both channels, or just the bright/blackface channel?

Permalink Reply by Rockin' Robert T. on October 7, 2011 at 10:09pm

Haven't had any experience with the Vibrolux solid state- I have the Fender 40 watt tube Fender Delux Hotrod as its sometimes refered and I love it. The roll off on the volumn with just the right amount of drive setting and with my PRS Santana Sig. makes a sound just like butter- Love -rrt