Need more headroom or gain? Spin the bottles.
[Originally published: 9/2/2019]
You might guess from the title of this column that I love Fender amps. And you’d be right. From a musical and engineering perspective, I think vintage Fender blackface amps are the best ever made. With bright, American-style speakers, they deliver pure and natural tone. Their channels, with volume and EQ, are intuitive for any guitar, bass, or keyboard player. It’s impossible to not find a decent tone in less than 10 seconds. From a technical perspective, their handmade tube-based circuits are simple, and they were built with high-quality components. And today, there are easily available parts and schematics, and an abundance of other online technical information, which makes it possible for many techs and players—including you—to service these amps.
Classic Fender blackface amps have been an inspiration for an entire industry. They’ve appeared on countless stages and an incredible amount of great albums by legendary performers. Why? Mostly tone and clean headroom. So, for this debut column, let’s discuss what we can do to make those two factors work best for you via tubes.
Reverb and tremolo were the main functional innovations in Fender’s blackface line. The king of blackface amps, the Twin Reverb, produced 85 watts from four 6L6 tubes and had enormous power and output transformers, a non-sagging diode rectifier, and two powerful 12" speakers. The 4x10 dual-6L6 40-watt Super Reverb has half that power, a softer tube rectifier, and smaller transformers. Still, the massive array of four 10" speakers is screamingly loud and sometimes difficult to handle for its weight (65 pounds), size, and volume. A 4x10 is more directional and scooped in the low mids than a 2x12. So a guitar plugged into a Super Reverb can end up competing with the bass. Experience is required to tame these amps. Once you know how to handle them, you will be rewarded with an overwhelming and physical sonic experience.
In the blackface world, the 1x12, double-6V6 22-watt Deluxe Reverb’s advantage is that it’s small and light, at 42 pounds. It breaks up earlier than its bigger relatives due to the less powerful 6V6s, small transformers, and a small speaker cabinet. Additionally, the original Oxford 12K6-5 speaker farts out early and is very weak, although it also delivers a true signature vintage Fender sound. And who doesn’t want their amp to break up easily these days? I have kept the Oxfords in my Deluxe amps. Before the internet, few people knew they could replace the 6V6s with 6L6s and replace the Oxford to double the Deluxe’s volume.
The V6 12AT7 phase inverter tube can be replaced with a 12AX7 to reduce headroom in large 6L6 amps.
Via my website, fenderguru.com, I often get questions about how to achieve different tones in blackface amps run at lower volumes. The answer often lies in the tubes. So let me share some simple tube tricks that will help you develop an understanding of how tubes function—and how they can be used to affect changes—in the typical two-channel AB763 circuit in the Twin, Super Reverb, Vibroverb, Pro, Vibrolux, and Deluxe amps of the original blackface era.
The tubes in these circuits are typically identified as V1 through V10, looking at the back of the amp from right to left. Here are some tricks:
- The V1 12AX7 tube in an amp’s normal channel can be removed for more preamp gain and reduced headroom in the vibrato channel. It can also be replaced by weaker tubes, like 12AY7s or 5751s, for less volume/gain. I always pull out this V1 since I use the vibrato channel and want solid preamp gain, which the single V2 delivers.
- The V3 12AT7 reverb driver for the vibrato channel can be replaced with a 12AU7 for less reverb and improved reverb knob control.
- If you’re only using the normal channel, think about removing the V2 through V5 tubes for the vibrato channel. That will give you more gain and headroom in the normal channel. (FYI, the 12AX7 in the V5 position is the tremolo tube.)
- The V6 12AT7 phase inverter tube can be replaced with a 12AX7 to reduce headroom in large 6L6 amps.
- Several alternatives to 6L6 power tubes exist. I mostly use 6L6GCs. In a Twin Reverb, you can pull either the V7 and V10 or V8 and V9 tubes for half power and earlier breakup. Ideally, but not totally necessary, you should disengage one speaker to match the impedance change.
- In a blackface Deluxe, the GZ34 in the V9 slot is the rectifier tube. If I want reduced headroom and more sag, I use a 5U4GB.
And there you have it: You’re on your way to becoming a Fender guru, too!
An unsung sleeper from the black- and silver-panel years sees its DNA scrambled to intriguing ends.
Classic cleans and excellent pedal-platform versatility. Nice onboard reverb and tremolo. Light weight for an amp of this size.
No output-reduction feature.
$1,299
Fender '68 Custom Pro Reverb
fender.com
Fender's '68 Custom series won plenty of fans by resurrecting the stylish silver-panel amps of the late '60s and '70s and making some of those models into more modern gigging machines. One of the newest additions to the lineup is the '68 Custom Pro Reverb—an evolution of an amp that debuted as a black-panel model in 1965.
The original Pro Reverb is considered a great all-around stage amp, and remains a relative bargain among vintage Fenders. But the reconfigured '68 Custom Pro Reverb both adds and subtracts features to better suit the needs of contemporary players, and there are significant differences between the original Pro and this newest edition. Where the original was a 2-channel 2x12, the new incarnation is a lighter and more compact 1x12, has a single channel, and adds a midrange control. But it's still 40 watts and most of the features remain the same, making it a logical next-step-up from the popular Deluxe Reverb.
Silver Mine
Eliminating the underutilized normal channel from the original and adding the handy midrange control still equals a very streamlined control panel: volume, treble, middle, bass, reverb, and tremolo speed and intensity—a combination any Fender fan can love and relate to. The power and standby switches are on the back panel, where you'll also find two jacks for the onboard and extension speakers, and a TRS jack for the included two-button reverb and tremolo switch.
Much like its '60s predecessor, the '68 Custom Pro Reverb generates 40 watts from a pair of 6L6GC output tubes, with three 12AX7s and two 12AT7s in the front end. It lacks the original's tube rectifier—instead using solid-state diodes to convert AC to DC (as many other Fenders were doing in the '60s anyway). Players love tube rectifiers for their saggy, compressed attack, but Fender claims to have made up for the absence of a tube rectifier by using a transformer with higher-than-usual copper resistance, which helps replicate the higher forward impedance—and sag—a rectifier tube would provide.
Although it's compact and relatively light, the Pro Reverb can still be a loud amp.
A more obvious deviation from tradition is the inclusion of a single 12" Celestion Neo Creamback speaker. It's built around a lightweight neodymium magnet rather than a heavier ceramic one, like you'd see in the speakers from a vintage black-panel Pro Reverb. It's a critical part of a slimming effort that, along with a compact 22" x 17" x 9" meranti plywood cabinet, reduces the combo's overall weight to a manageable 35 pounds (originals weighed closer to 53 pounds).
The rugged printed circuit board includes a few thoughtful updates to the original circuit— most notably a reduction in the output stage's negative feedback, which adds a little more touch sensitivity. And the tremolo is tube-driven and grid-biased—borrowed from the vintage Princeton Reverb amp for a warmer throb. Elsewhere things stay close to vintage spec. The reverb is still a classic tube- driven Fender circuit that feeds a long spring pan mounted at the bottom of the cab. The transformers are custom made by Schumacher, which supplied these components to Fender in the '60s. For the most part, the Pro features the same preamp circuit that helped to make black- and silver-panel Fender amps so famously glassy, clear, bright, and slightly scooped sounding.
Given that the '68 Custom Pro doesn't attempt to be a period-correct reissue, it occasionally leaves us wanting for a few additional non-vintage conveniences. A master volume control is almost anathema to this circuit, but some form of output-reduction mode—a half-power switch, an onboard attenuator, or a voltage-reduction circuit—would be useful. Although it's compact and relatively light, the Pro Reverb can still be a loud amp and the inability to crank it up for natural bite and sting at lower decibel levels might limit its appeal to some players.
Pro-gnosis
Whether paired with a Fender Telecaster, a Gibson ES-335, a P-90-driven Novo Serus J, or a variety of overdrive pedals, the '68 Custom Pro Reverb delivers impressive variations of the vintage Fender amp sounds we know and love, and feels very familiar and dynamic in the process.
Players generally covet vintage Fender amps for their stellar cleans and creamy edge-of-breakup sounds. The '68 Custom Pro Reverb delivers on all counts. It's bright and clear without being harsh or brittle, and slightly mellow in the mids without sounding timid. It's a classic tone for anything from pop to country to jazz to blues, and it's an ideal foundation for pedals. Add the sumptuous reverb and tremolo to this palette—both of which impressively emulate their '60s predecessors—and there are many moods to conjure before you even add a stompbox.
Moving the amp from to clean to slightly dirty overdrive—at least with a Telecaster bridge pickup—is the difference of going from 4.5 to 5 on the volume control. Here, the '68 Custom Pro Reverb reveals the more aggressive side of its personality. Breakup is juicy and biting with just enough sag to compress hard pick attack without going mushy. The Pro can get a little raunchy and loose when pushed too far—especially when humbuckers or P-90s are involved. But it's still a delicious sound. (I also easily achieved all of these sounds at lower volume levels using the attenuator in a Mesa CabClone IR+. A similar attenuator might open up many such options).
The Verdict
Fender did a great job re-imagining one of their real unsung '60s combos as an amp that's probably more useful for most modern players than a detail-perfect reissue would have been. It does a great job of capturing those iconic black- and silver-panel tones at an accessible price, all in a lighter, more convenient package. Some form of output reduction would have been a plus, but even as is it represents a formula with a lot of practical appeal.
Fender '68 Custom Pro Reverb Demo - First Look
