El34 world logo

Back to Library page

Origin of the 6G15/6G12 Reverb/Vibrato unit

Note: I have since updated the Re-Vibe below to incorporate the Tore T mod.
This page has build info on the stand alone Re-Vibe
This page has info on my rack ReVibe

image
This is a Fender schematic for the 6G15 stand alone reverb unit.
The area outlined in Blue is the area we are interested in.
Click on the image above to see the full sized image.

 
image
This is a Fender schematic for the 6G12 Concert amp.
The area outlined in Red is the Vibrato circuit area we are interested in.
Click on the image above to see the full sized image.
 
image
Here we see how both Fender circuits were joined together to form a Reverb/Vibrato unit
The Blue 6G15 Reverb unit circuit is on the left.
The Red 6G12 Vibrato circuit is in the middle.
Click on the image above to see the full sized image
 
6G15 Notes:
The Fender 6G15 Reverb unit is actually a parallel effects loop. You will note that the input from the guitar comes in at the far left of the reverb circuit. The input then splits two ways.
(1) The upper path flows through the reverb circuit and comes out at the middle wiper of the tone control and then exits through a 250p capacitor. The upper path is the wet reverb signal.
(2) The input also goes down to a cathode follower stage. The cathode follower stage is the dry no effects signal.
 In the stock Fender reverb unit, the upper wet reverb signal and the lower dry cathode follower signal stage come back together at the mix pot and then exit the reverb unit via the output jack. This is how you get a dry no effects signal mixed with a wet reverb signal.
6G12 Notes:
The Fender Concert 6G12 Vibrato circuit receives input from the concert pre amp. The pre amp stage is above the vibrato circuit in the Original Fender schematic above.
The vibrato circuit will pass the pre amp signal right through with no vibrato added if the vibrato is turned off.
If the vibrato is turned on, the pre amp signal is subjected to the vibrato circuits vibrato effect.
The signal exits the vibrato circuit at the right end where the two 470K resistors join together.
 The 6G15/6G12 reverb/vibrato unit has a summing circuit to mix the signals from the Fender 6G15 reverb circuit and the Fender Concert 6G12 Vibrato circuit together.
 The summing circuit is a simple voltage divider but as mentioned above it also mixes two signal inputs and then the final mixed signal exits to the output jack. It's a simple circuit but it is doing several chores at one time.
-
There are few minor changes over the stock Fender circuits listed below.

6G15 Reverb unit changes:
R17, a 220k resistor was added to the reverb recovery circuit. This resistor is standard on most Fender reverb recovery circuits on the reverb combo amps.
R16 was added to present a load to the reverb output transformer secondary winding in case there was no reverb tank plugged in. I do not use this resistor on any of my reverb circuits. It's an optional item.
The stock plate load resistor on V2B is a 100K resistor. It has been replaced by R11/68K and R8/33K (total=101K) to form a plate load voltage divider. I imagine this was done to alter the gain of this particular stage before the signal is fed to the 6K6 reverb driver tube.

6G12 Vibrato circuit changes:
R39 is a 1 meg resistor in the Fender 6G12 vibrato circuit. It is a 470K resistor in the 6G15/6G12 reverb/vibrato unit.

-
Update: There was quite a bit of hum in the original Re-vibe. Tore T. has come with an excellent mod that eliminates the hum completely. See the original schematic and layout diagram on the library page and compare these to the updated Tore T mod layout and schematic to see what was changed. I updated my Re-Vibe with the Tore T mod and it is now dead quiet.



Enter My Tube Amp Parts Store Here

Mobile users Enter My Tube Amp Parts Store Here


The Tube amp Library of information
Click the link above for Tube amp info, Schematics, Board building information, Projects, Mods, Transformer diagrams, Photo's, Sound clips.
There are hundreds of pages of Tube amp information on my library page.

Please visit my Tube Amplifier Forum
Here's the place you can go to ask tube amplifier questions.
You will find a large community of friendly amp builders at the link above.

Check the huge library of Schematics here

Design your own custom Turret Board or Eyelet board

DIY Layout Creator file analyzer program

DIY Layout Creator file library

How to email me



MEMBER OF PROJECT HONEY POT
Spam Harvester Protection Network
provided by Unspam