A Nerd's Guide to the Fender Princeton Reverb

The Princeton Reverb houses a 10–inch speaker, a dual 6V6 fixed–bias amp, and 12–15 watts of mean, American Fender tone. This little guy has been the secret weapon of an entire range of artists, from Ryan Adams to Glen Campbell and Tommy Tedesco to Jim Campilongo.

The Princeton Reverb is characterized by the mid–range tummy tuck that some Fender amps are known for. It has those slightly reduced mids and fattens up with some low–end breakup when the player cranks the master volume. That breakup lets some extra low–mids ring.

That kind of meanness just isn’t heard from some of this amp’s bigger counterparts, like the Twin, when they're pushed in the same way.

A Note on the Reverb

The Princeton Reverb is identical to the regular Princeton circuit except for two key additions. One, of course, is the reverb unit. The other is an additional gain stage that follows the reverb — utilizing a 12AX7— that pushes the amp to heavier saturation when played at breakup volume.

The Princeton (without reverb) never quite enjoyed the mass appeal, go–to status as the Princeton Reverb. Even so, Mike Campbell has made heavy use of the Princeton in the studio and on tour with The Heartbreakers. Jason Isbell has been known to plug a custom Tele directly into a Princeton when touring with his wife, Amanda Shires.

But the Princeton Reverb is the stuff of legend. The opening riff to The Beach Boys’ “Surfin’ U.S.A" is rumored to be ghost player Tommy Tedesco on a Fender Telecaster running through a Blackface Princeton Reverb.

Two Faces, Many Circuits

The original Blackface circuits were produced from 1964 to 1967, going through three circuit changes along the way. The first of these changes was due to the CBS buyout of Fender and happened on January 5th, 1965. Leo’s office was emptied a day before.

The Princeton Reverb, therefore, marks the end of the pre–CBS era, and its changes can help trace the entirety of Fender’s CBS years.

The rectifier tube used in the original pre–CBS AA1164 circuit was a 5AR4. This tube is also found in the ‘65 reissues. Where things get interesting is with the AB1270 and AA764 Blackface circuits.

The AA764 configuration used a GZ34, which would eventually make its way into the Silverface AB1270. The AA1270 Blackface circuit, however, would use a 5U4. This made the CBS Blackface and early Silverface circuits very similar, lending the Silverfaces to Blackface modification.

The original speaker in the pre–CBS blackface is a Jensen C10R, providing responsiveness and tight bass control.

The Silverface era of the Princeton Reverb would start in 1968, with a pull–knob boost getting added in 1978 and lasting through 1981. A Princeton Reverb II would follow in 1982, but it was unremarkable and deserves little to no mention.

During the Silverface era, one change would alter the sound of the amp in a subtle way. The rectifier tube used in the AB1270 configuration was a 5U4, which had a sag effect that resulted in compression. The replacement was a GZ34 rectifier tube, which removed a significant amount of sag and gained a small amount of responsiveness.

A little known fact about the pull–boost Silverface Princeton Reverbs is that Fender actually had a surplus of the less powerful 5U4 rectifier tubes. The company printed configuration labels replacing the GZ34 with the 5U4 until the tubes were depleted.

These pull–boost Silverfaces have that sag mentioned earlier. Fender never made an official effort to put the 5U4 into those pull–boost amps, but there are ‘78 through ’81 Silverfaces with 5U4 on the printed schematic sticker and in the circuit nonetheless.

The ‘68 through ’77 Silverface Princeton Reverb is, for lack of a better explanation, the least Silverface–sounding Silverface circuit Fender ever put out, eventually becoming an affordable player’s amp on the used market.

The pull–boost may be those amps’ only glaring failure, one of the many manufacturing and design flubs that presaged the end of CBS’s ownership of Fender in 1985.

Even the inefficient phase inverter circuit — another example of a cut corner during the CBS era — delights players with breakup at bedroom volume.

Modding the Silverface Princeton Reverb

Due to portability, tone, and price points, the Silverface circuit sans pull–boost is a popular buy for players interested in modding these amps to Blackface specs. As mentioned earlier, the circuit is fairly similar, so this conversion is fairly straightforward.

First, you replace the rectifier tube with a 5AR4. Blackfacing then requires replacing the cap powering the tremolo circuit and replacing the highpass cap for the 12AX7 reverb recovery circuit for a darker reverb. That darker reverb and compressed sound are exactly what make the Blackface version prefered among many players.

Often, people modifying these amps will replace one of the V1 or V2 12AX7s with a 12AY7 or 12AT7 in attempt to get some extra headroom or “clean up" the amp. However, this is a mistake.

That change actually alters the gain stage, giving it a tonal difference at sub–breakup volumes. When the amp does breakup, you get a cleaner, slappy overdrive.

Replacing the existing 10" speaker with a 12" is a popular mod for those looking to juice some extra low–mid end from the 6V6 power amp. The overdrive dynamic changes to be slightly less responsive. But if you also swap out the output transformer for more power, these two mods in conjunction will create larger, louder sound for gigging musicians.

There seem to be an endless amount of ways to mod these little amps. I’ve seen tweeter speaker cutouts in the baffle board of a Princeton Reverb in local shops before. Other mods include increasing dynamics for the tremolo circuit, adding a middle pot, and the Stokes mod, which increases power sent to the phase inverter (often paired with swapping output transformer).

The Princeton Reverb Today

Starting in 2008, Fender put out a ‘65 reissue, followed by a ‘68 reissue in 2013, with a blue jewel and all. Both reissues have been well received and are often picked up by players who want to leave their vintage gear in the living room when they play shows.

The ‘65 reissue lacks a bit of the reverb nuances of the original, and most notably, the compression isn’t there, even with the 5AR4.

The ‘68, however, has a tremolo that may even surpass Jim Campilongo’s original 1968 Princeton Reverb — at least, according to the man himself. This trem really does the ‘68 justice.

The Fender guitar that’s more popularly paired with the Princeton Reverb has to be the Telecaster. This is Glen Campbell’s preferred rig, and Ryan Adams claims not to have used anything other than a Princeton Reverb on recordings since 2005.

Vintage Silverface Princeton Reverbs can be found at reasonable prices, and the reissues really do the originals justice as much as a reissue can. Those iconic tones from Nuggets Vol I can be channeled in on these little guys without blowing your neighbors out of the water.

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