Ask Amp Man: Modifying an Early Fender Super-Sonic 60

Hi Mike,

The Fender Super-Sonic is a very versatile amp with two distinct channels. For those unfamiliar with this model, let’s review. Labeled “Vintage,” the first channel emulates two iconic Fender amps: the Bassman and the Vibrolux. And this is no virtual emulation! Fender designers accomplish this by actually switching between different component values and circuit paths. While this feature mimics the sound and response of these two amps, perfect replications would certainly require more than just a handful of component changes. That said, this is a cool feature. And it’s done with relays, I might add. I’m not a fan of solid-state LDR (light dependant resistor) switching, as it does not have a true “on” and “off” state. Relays are absolute. This channel also positions the tone stack after the first gain stage—a standard Fender design trait.

Channel 2 is labeled “Burn.” This channel offers an additional gain stage and less in the way of passive tone shaping. It also has the tone stack positioned after the fourth gain stage, which allows a more full-range signal to pass through all the gain stages before it’s tweaked by the tone controls. All in all, two different channel designs.

Okay, you want your older Super-Sonic to sound like the new model, so let’s get to it. The first model was designed in October 2005, and the updated model was designed in October 2009. According to your needs, the later model has some tonal improvements, which I’ll detail here so you can have your amp modified. Now, in full disclosure, this info is available online, but I’ve done my own research and will share the results of my findings. But beyond that, I’ll give you my opinion as to what each change does, should you desire to pick and choose.

1. The first change in the schematic occurs at C2. The original version uses a .0022 µF cap here. The later model ups this value to a .0033 µF in the combo version. This change causes a bit more of a full-range signal to be sent to the Burn channel.

2. The next change is at C7. Originally this was a 120 pF cap; the later model drops this value to a 47 pF. This causes less brightness at lower volume settings in the Vintage channel’s Vibrolux mode.

3. Next we find a change at C11 and R22. Original values were 3.3M and 10 pF respectively. In the newer model, these are changed to 1.5M and 330 pF. This change increases both the level and frequency range of the signal being fed to the subsequent gain stages of the amp. In my opinion, this change probably has the largest impact on the amp’s sound. If you’re simply looking for more out of the Vintage channel, this would be the change to make.

4. The next change consists of two additional components: C99 and R160. It’s a series network consisting of a 0.015 µF capacitor and a 47k resistor attached between the R22/R23 junction and ground. This is a simple low-pass filter that reduces some high frequencies in the Vintage channel. Since these components will need to be discretely added, as they have no circuit board locations in the earlier amps, you could always hold off installing them until your ears decided if they’re actually necessary.

5. Next we move on to C25. This capacitor is at the end of the Burn channel, electrically across the volume pot. Initially a 680 pF cap, it was increased to a 0.001 µF cap in the combo amps. This will shave just a bit more top end off the signal, probably in the hopes to make the combo amp sound a bit fuller and less shrill.

6. The next couple of changes happen in the reverb circuit, starting with R150 and R151. R150, originally a 220k resistor, has been changed to a jumper, and R151, originally 470k, has been changed to 1M. This change substantially increases the signal level to the reverb drive circuit. The result would be a fuller-sounding reverb.

7. The last change consists of changing R167 from a 470k resistor to 1M. This is the reverb return signal that gets mixed with the dry signal in the amp. The new 1M resistor serves to reduce the return signal a bit, likely to compensate for the increased drive signal.

There you have it: All the changes needed to bring your older Super-Sonic up to the latest specs, plus the result of each modification, so you can pick and choose how to enhance your amp.