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 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

The Main Differences between the Brown and Black Fender Vibroverb Amps

In this blog post, I will discuss the main differences between the different Vibroverb amps that fender offered in the mid 60s as well as the options I offer as an alternative to the originals.

Side note: If you haven’t read my first blog about why you would buy a replica or clone of a Fender vs the original, please do as it will help you understand where my thought process stems from on these matters. Yes I want to sell amps, but I don’t want to sell you an amp you don’t need or won’t do what you need for the gig.

Let’s start first with the 6G16 brown Vibroverb that was built for one year in 1963.  This amp came in at about 35 watts. I call it a soft 35 Watts due to the fact that it is not overly bright, overly stiff or in any way harsh. First introduced in 1963 and made for just over a year by all reports, it was the first Fender amp to have onboard reverb, came with 2-10 inch oxford speakers at about 25 Watts apiece, the app came in at 35 watts with 5881/6L6WGB/6L6GC power tubes it had a GZ34 rectifier and all pre-amp tubes, including the phase inverter and reverb driver were 12AX7  

The component, layout in the pre-amp circuit, while laid out differently on the fiberboard is essentially the same pre-amp as a later blackface vibroverb. Like many Blonde and Brown era amps the treble control was Tapped at 70k which drastically changes the mid structure of the amp.


The reverb circuit was unique, which was considered a coupling circuit, and was never used in any other fender amp

And one final thing that really sets this amp apart from his blackface brother is the bias vary tremolo. This, of course is when the power tube bias is modulated to create the tremolo effect. This is the same tremolo essentially found in the Princeton Reverb and my personal favorite of all the Fender tremolo circuits.

Across-the-board, the brown Vibroverb had much lower plate voltages than later, blackface Vibroverbs, which I also think changes the tone of the amp to a little bit less high-end and clean headroom

The blackface Vibroverb (AA and AB763 changed, of course to blackface cosmetics in 1964 and also sported a larger cabinet with a single 8 ohm 15 inch speaker (Usually a JBL D-130) instead of the 2X10 layout in the 6G16

Power tube plate voltage was about 25 volts higher. They both basically share the same output transformer, but of course the brown vibroverb was 4 ohms and the black  AB763 was 8 ohms 

The tremolo in the later Vibroverb is like all other blackface tremolos where they simply ground out the signal right before the phase inverter to create the tremolo effect, also known as a opto-coupler circuit. 

There are very subtle differences between the AA and AB763 Vibroverb are in the inverter plates and the bypass resistor in the tremolo. These are very minor differences, so they are essentially the same amp.

The blackface Vibroverb is the amp that most people associate with the “SRV tone”, not saying that Stevie never played a brown Vibroverb, but generally speaking, he played blackface Super Reverb and blackface Vibroverb amps

I build and love both versions, and from all reports they are really close to the few good vintage examples left out there.

If I had to chose, I would take the Brown 6G16 as it is a nice bridge between Tweed and Blackface! I started offering the “Verbrovibe” aka 6G16 in early 2007 when prices were in the $4000 range. Those prices are now, of course higher. (just saw one yesterday on reverb for $20K!!) The other issue is they only built 500 and there are large number of those in private collections from what I hear. Some are used sparingly and others not at all…i.e they are sitting in a vault or display case due to the rare nature. So you can avoid all of that and a second mortgage on your home and get a replica or “clone”. There are a few options out there, but I am confident in the abilities I have accrued in the last 20 years, that the Headstrong Verbrovibe is about as close as you can get to an old one.

I've had a chance to play one years ago, and also hear a few goods ones in person, and it was glorious.

A fun story that is kind of about that amp (kind of) is when I was in my early 20’s, rent was cheap and I was supporting myself solely on blues gigs (a tough feat then and especially now) I wanted one of the re-issues and figured I would try and find someone to tweak the amp for me. This was of course before I had any real understanding of these things…and that the re-issue, while not a bad sounding amp (they actually came close on some features) was a ways off from the original…mainly the solid state rectifier…In any case, my band leader had a friend with 2 old brown amps, he said “I think they are Vibroverbs", one is pristine and the other is beat down with an unoriginal speaker. Turns out the pristine one was once owned by a blues legend who shall remain nameless (for a future story), and he wanted to sell that one. I did not have the $300(???!!!) to spare all at once…times were and always have been tight, fortunately my rent was cheap and my roommate (and band mate) had a regular job if I ever had a bad month (hey, we guitar players have our priorities) so I was gonna get that amp!…But fortunately the band leader knew I needed a stage amp…I had a small set up then that was kind of cool (another story soon), but not what I needed for this new 4 pc Harmonica band…so he offered to buy it and let me pay him back over a few months worth of gigs. I couldn’t believe my luck! I was going to get a Vibroverb, for $300, on PAYMENTS???

Well it turned out not to be a Vibroverb, but a 1962 Fender Vibrolux (with a 12” grey/blue powder coated Jensen Vibranto speaker)…I will tell that story in another post soon, we will call those blogs:

“Headstrong Origin Stories”

I had that amp for years and it is what I based the Sultan off of…

Now, on to the AB763 version

The blackface Vibroverb version that I build is called the King Reverb and it comes as a 1X15 but also as a 2x10 (Vibrolux Reverb) a 2x12 (Pro Reverb) and of course the classic 4x10 Super reverb set up. I will dig deeper in the differences between all of the king reverb versions in another blog, but the 1X15 version, I get asked about all the time so let me explain that here in a bit more detail. The 35-45 watt AB763 circuit are essentially all the same amps when it comes to the circuit itself other than some minor capacitance and resistance changes to compensate for bass response etc. In other words, a 4X10 won’t need the same bass signal as a 1X12 or 2X10. Then of course the output transformers came in different sizes and secondaries to match with the speaker loads. The 1X15 was an 8 ohm output and the transformer itself is the same size and the Pro and Vibrolux Reverb, while the Super Reverb OT was significantly larger than those models.

Generally you would find the famous JBL D130 ceramic speaker in the amp, but some had Jensen, Utah or CTS speakers in them as well. I have had a few of all of those speakers before, and I generally use the Weber California Ceramic for the JBL sound in the King Reverb 1X15 and it is so close it is startling.

Personally, I prefer the sound of a good P15N or Weber’s equivalent.

I had a client, who I trust has the ear as he owned 2 originals, he said “if I didn’t know that your amp was a clone with a clone speaker, I don’t think I could tell the difference form my old ones.” He called me last year, probably 10 years after that comment to tell me he still has the amp, and it is really the only thing he uses to this day. This is not to say I build something anyone else can’t, but to say that if you want to get those tones, and get as close as anyone else is, but couple it with a level of customer service or experience that I stand behind, The Headstrong King Reverb is worthy of consideration.

If you are familiar with Headstrong and my attention to detail across the board, you know what I am referencing, if not, please feel free to call me ANYTIME to discuss some of the options I offer. Or if there is something I cannot help with, I will point you in the right direction. And remember, I Love Fender Amps! I made a living as a player using them, and I make a great living as a builder, copying them! Even if they have missed the mark over the years, I am a loyal guy who will always speak highly of the legacy!

Thanks for reading and my goal is to put one of these more technical blogs up with some old stories about how I got here, or how I managed to deal with some of the people you’ve seen or heard play Headstrong Amps.

And as always, thanks for your support and interest for these last 20 years!

Wayne