Fender Reverb

Shawn Brown · Post by **Shawn Brown** » 11 Dec 2011 7:06 am

My Fender Vibrosonic amp has reverb that works however it is fairly weak. The amount of reverb I get at 8 is about the same as a friend's Deluxe Reverb with his reverb set on 2 or 3. Any tricks for improving the strentgh of the reverb on a Fender amp? My reverb strength was pretty good at one time but seems to have weakend lately.

Jason Hull · Post by **Jason Hull** » 11 Dec 2011 7:18 am

Tim Marcus · Post by **Tim Marcus** » 11 Dec 2011 9:31 am

could be the 12AT7 driver tube, but I find that most problems with reverb relate to the tank. They are not terribly expensive to replace - usually about $25

A good test is to put your amp back to back with another fender and swap in their tank using the RCA jacks on the rear of the amp. If your amp works with their tank, you know what to do - if not, its time to fiddle with the reverb circuit, starting by swapping tubes and ending with checking wiring and components inside of the amp (only if you know how to do this)

Fender reverb is usually peeled off of the signal via a 500pf cap (with a 1M to ground), then it hits the driver tube, then the spring, then there is a recovery stage, and then it mixes back in via a 3M3 resistor with a 10pf cap across it. If you know what to look for, check all of that stuff out. Verify that the values are correct and there are no broken leads.

Shawn Brown · Post by **Shawn Brown** » 11 Dec 2011 10:01 am

Thanks for the advice guys.

J Fletcher · Post by **J Fletcher** » 12 Dec 2011 5:53 am

The reverb signal is mixed with the dry signal through a 470k resistor. The dry signal resistor is the 3.3 meg with the 10pf bypass cap. FWIW...Jerry

Post by **Dave Mudgett** » 12 Dec 2011 6:36 am

Most instances of weak reverb I've experienced were indeed related to the pan. All the new pans are, to my knowledge, now made in Korea, but the inexpensive MOD pans from Antique Electronics that I've tried recently sounded OK to me. Sub a known-good pan (as Tim suggests, from another amp if available) and see if that fixes it.

If you're going to check reverb circuit values, I suggest you go to http://www.thevintagesound.com/ffg/ and look up the circuit for your specific amp. There are some small variations in how the reverb signal is mixed back in. On my favorite Fender amp reverb, the 6G16 brown Vibroverb, there is no 10pf/3.3M section going into the 3rd preamp stage, and it also uses a 12AX7 reverb driver tube and somewhat different cathode resistors and bypass caps. There are even some tiny variations between some blackface/silverface amps, I doubt they matter much. In fact, I think it's reasonable to play around with some of these parameters a bit if someone knows what they're doing. If the pan sub doesn't work and you don't know what you're doing inside a tube amp, get a good tech to go over it. My opinion.