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