Why do the Princeton Reverb and Deluxe Reverb amps sound so different?

Did you ever think to yourself, “why do the Princeton Reverb and Deluxe Reverb seem to sound so different?” They are technically both “Blackface Fender” amps, they both have reverb in the circuit…but why is the Deluxe always a bit brighter, cleaner and louder?

The obvious differences between the Princeton and Deluxe reverb amps are wattage, transformers, cabinet size, 10” speaker vs 12” speaker, 1 channel vs 2 channels etc…This article is a bit more granular and nuanced than that.

I will try to keep this on guitar player level tech talk, that is, I will use terms that guitar players use rather than a bunch of terms that amp techs and electronic guys tend to use. I feel that is a strength that I developed early on in my 20 year building career. Not alienating guitar players with a bunch of technical talk…Sometimes guys with a more electronic based background, who lack knowledge of the tone terms (as well as dealing with an eccentric group of people) we like to use a players, can get a little defensive and throw a bunch of big words at you…I prefer to use the vernacular that the players use and bridge the gap between the two sides of the fence so to speak.

I started as a player who knew NOTHING about why tube amps sounded so good other than, every time I played one, I knew that was the tone! Communicating with amp techs (if you could find one) could be dicey and uncomfortable at best. Leaving us wrought with anxiety over how our amp was going to sound when they finished the “work”. Not wanting to offend anyone, was NOT my forte in those days…and I remember a few times the “old guy in the back” gave me that look! How could “I” be wrong I thought, that guy is Full of it I thought to myself!..Yeah man, it was all him!

Fortunately times have changed and there are of course many great options now, but in the 90’s, no internet, no forums etc, you were shooting in the dark with techs.

Now, back to the topic at hand

To me the Princeton reverb still has a foot in the Tweed and Brown era tone. I feel this is due in large part to the Phase inverter section of the amp. In the old days, Fender used what is referred to as a “split load Phase Inverter” meaning that the phase inversion is accomplished by using only half of the 12AX7. The 12AX7 is known as a dual triode…two sides, 3 pins on each side (plate, grid, cathode). Make sense? By only using half of the tube to do the job, like using 3 of the 6 cylinders in your car, it is inherently less efficient than the Long Tail pair type found in other blackface amps, such as the Deluxe reverb and all other BF amps above it. The Tweed Deluxe, had the split load as well. Basically this means the signal is less powerful heading to the power tubes so the sag and break up happens much earlier. Also, to my ear, it is a bit darker and lacks a little of the scooped mid sound of the rest of the Blackface Fender amps above it. The other difference in the Princeton Reverb from other Blackface amps is in the tremolo…The PR has the Bias Vary/Wiggle circuit. This uses the power tubes to modulate the bias to create what I think is one of the most swampy, bluesy tremolo sounds they ever did. This type of tremolo is also found in the Brown Vibroverb, Princeton and Deluxe. (NOTE: It is not to be confused with the only true “Vibrato” Fender did in the Brown Concert, Super, Pro and Bandmaster…That is a completely different beast and I will go over that in a future article. FYI, I will be building that Brown Super this year!) In closing, the Princeton Reverb, to me is still a Brown Princeton, but with the Blackface reverb circuit added. Fender kept the Princeton Reverb virtually the same until the early 70’s barring a few adjustments and general butchering.

The Deluxe Reverb is VERY different from a Brown Deluxe, thus different from a Princeton reverb as well. This is where I feel the real blackface tone people are referencing comes from. Cleaner, brighter, scooped mids etc. The tremolo circuit is also different, Fender moved to the Opto-coupler based tremolo that basically modulates the volume to create the tremolo effect, and to my ears is a little less organic sounding. Still a cool sound, and obviously, used by many legends over the years. They stuck with that circuit on all the other Blackface amps from that era as well. The other difference is the “Long Tail Pair” phase Inverter (both sides of a 12AT7 powered this) making it more efficient, brighter, slightly higher voltages across the amp. The first stage filter caps were also higher than a Princeton so it is a bit tighter. The voltages on the power tubes are significantly higher in Deluxe Reverb amps as well. Some are as high as 470V (JD Simo’s DR is that high at 120v!!!) You often see, “will handle the high plate voltages of a Deluxe Reverb” in some 6V6 power tube descriptions. This is what they mean!

For reference, The Royal Reverb, the Headstrong Deluxe Reverb replica comes in at about 425-435 VDC (Volts DC) @120 volts (AC from the wall). By contrast the Princeton Reverb came in at 400-415 VDC…The Lil King is usually 400-410 VDC range.

Pre-amp gain stage (V1 and V2) voltages are a bit higher in the Deluxe Reverb amps. 170-180 VDC on the plates of the 12AX7 tubes (vs. the Princeton reverb pre-amp plates at 150-160vdc). I think this is may be an under discussed topic…The higher the plate voltage on those pre-amp tubes, the cleaner and brighter the sound. The lower voltages, like in a Tweed amp, you get a darker tone…less spike in the notes. Finding a balance between the two is what I try and do when someone wants to tweak the amp a little to their liking. Rather than make these big changes to the circuit, sometimes a small resistor change will get you what you need without drastically changing the tonal character of the amp that you loved. Thus avoiding a case of diminishing returns.

So in closing, the main differences electronically between these two amps is why you may have noticed a big difference in these two amps. Some people may feel, the Princeton Reverb is just a lower watt Deluxe Reverb and that is just not the case. The Princeton will always be darker, softer on the bottom end, less spiky on the top end as well as much easier to carry around to the gig!

I could keep rambling on this topic for days, but I also have to actually build these things! As always, thanks for reading and thank you ALL for the 20 years of support! I still can’t believe this is what I get to do all day!!

Talk soon,

Wayne