Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Effects => Topic started by: xan on May 02, 2021, 03:44:17 pm
-
Hi All,
I've been a long time lurker but finally registered today as I plan to soon build myself a ReVibe variant, and this forum seems to be the place to go for info on that! Where my plans for this deviate from the original ReVibe however are that I want to design this to be used in the effects loop of various Marshall flavored circuits (buffered loop between preamp and PI). Despite hours of trawling through the forum, I can't see that anyone has attempted this (there was one brief topic started but it didn't come to any kind of meaningful conclusion). I'm writing this in the hope that somebody has done it and is willing to share what they did, or give me some advice on how best to go about this.
As a side note, I remember seeing somebody's build pics with a "surf" switch on and can't remember where now - does any one know what this is changing in the circuit?
Thanks!
xan
-
I can't imagine the need for a "surf" switch. The revibe does surf very well simply by turning the reverb and/or dwell knobs.
Refer to these two schematics...
https://el34world.com/charts/Schematics/files/Fender/Fender_reverb_6g15.pdf
https://el34world.com/charts/Schematics/files/Fender/Fender_concert_6g12.pdf
The revibe is an instrument level device. The revibe is a combination of the 6G15 standalone reverb unit and the vibrato circuit from the 6G12 amp. The 6G15 is already an instrument level device but the vibrato circuit on the 6G12 is designed to operate on signal level found between the preamp and PI (perfect for Fx loop). So the challenge was to boost the instrument level to drive the vibrato circuit and then attenuate the vibrato output back to an instrument level. And then mix the vibrato signal with the reverb signal. The idea was straightforward on paper but in practice, required a lot of experimentation. Took a lot of time to get it right and work out the little kinks. Most of the experimenting took place at the output of the vibrato circuit.
Now your idea is just the opposite. The vibrato circuit is already optimized for loop level signals (input and output). Your challenge will mostly be concerned with the levels in the reverb circuit. The input would need less gain (probably just eliminate one gain stage). Or, you could leave the input as is and use a voltage divider to knock the signal down. The output stage should work as is. This will take a lot of experimenting to get it right. A sig gen and scope would be very handy for getting the levels right.
My suggestion would be to build the revibe as is, get it working with instrument level signals, and then start modifing to match the levels for line level. You would need to be able to read and understand the two schematics in the links above. Your project idea is totally doable if you have the necessary chops.
I'm not aware of any of the forum members doing a similar project so you will mostly be plowing new ground. Maybe your idea will appeal to someone that is willing to modify their revibe to work in an Fx loop. A lot of people would prefer to put their reverb in an Fx loop. I'm happy with my revibe as is.
If you decide to take on this project please post your progress. I'm interested and willing to participate. I know others will be interested too. Good luck.
-
xan,
Just "finished mine, I'm still tweaking little things, but I'm with Sluckey, I cannot imagine needing anything to get you more into surf territory. Switch or otherwise.
mike
* I'm nearly done tweaking I think. :icon_biggrin: :dontknow:
-
In the middle of a house move at the moment so things are going fairly slowly. The other obstacle I am likely to encounter is the 10M pot on the schematics. I'm in the UK and it's virtually impossible to find them here. I have seen mention of either substituting it for a 3M pot but also adapting the circuit to use different values. I'm wondering if anyone has such a schematic or knows what changes would need to be made? Thanks!
-
So... House move finally wrapped up and got a workbench ready for some soldering again now. Could anybody give me some pointers on how to adapt the trem circuit to use more easily obtainable pot values (IE not 3M and 10M!)? Haven't had much luck finding anything trawling through forums and I suspect my lack of familiarity with old Fender circuits is probably the issue here! Any advice would be greatly appreciated!