5 Classic Amp Circuits and Their Modern Boutique Counterparts

Barely a month goes past without one manufacturer or another introducing a "new and original" tube amp that will finally cure guitarists' universal quest for the ultimate tone.

Whether or not they live up to this marketing gambit is one thing, but behind the boast lies the fact that the vast majority of new tube amps designed and built today still rely, to some extent at least, on circuits that originated in guitar amps way back in the '50s and '60s.

Makers have strung all sorts of bells and whistles around these original templates—in the form of multiple foot-switchable channels, effects loops, added gain stages, and so on—but scratch the surface, and maybe nine out of 10 amps on the market today reveal the ghost of a circuit that was first laid out a good 50 or 60 years ago.

Let's dig into a handful of classics that have made their presence felt throughout the ages.

Mid- to Late-'50s Fender 5E3 Tweed Deluxe

The ubiquitous "tweed Deluxe" has never gone out of fashion. Plenty of players rediscovered the glories of its easily achieved grind and raw, textured overdrive tones after most other tweed amps had gone out of fashion, and it has been a studio and small-club favorite ever since.

The 5E3 remains popular in its own right exactly as it was first conceived, both via reissues from Fender itself, and in myriad clones from makers like Victoria, Clark, Tungsten, Tyler Ampworks, Speed Shop, Magic Amps, Greer, and several others. In addition, it's been a very popular "first kit" for many players going the DIY road, via suppliers such as Weber, Mojotone, Mission, and others.

Beyond the efforts that outwardly represent themselves as accurate emulations of the original article, though, many other great guitar amps offered over the years—and today—reveal an enormous proportion of the tweed Deluxe template once you dig beneath the surface, even if they ultimately take the design elsewhere.

Amps from highly regarded boutique makers such as Matchless and Divided by 13 have adapted the 5E3 circuit to their Spitfire (with a different phase inverter and EL84 output tubes) and CJ11 (with a modified preamp), respectively, while Carr's impressive new Telstar combo also uses this classic as a jumping-off point, before adding several original features and design twists. Lazy J's highly acclaimed, British-made J20 is also essentially just a beefed-up and well-put-together tweed Deluxe.

Matchless Spitfire 15W Combo
Divided by 13 CJ11

In essence, almost any smaller-mid-sized combo that generates 15 to 20 watts from a pair of cathode-biased 6V6 output tubes, partnered by two preamp tubes and a simple control panel with just volume and tone knobs is likely to have been derived from the 5E3 blueprint. If the amp also uses the tweed-era split-load (aka cathodyne) phase inverter, you know you're really in tweed Deluxe territory. Some makers substitute different or more powerful output tubes and add a variety of modifications without entirely fully disguising the DNA of the original.

Modern Picks
Late-'50s Fender 5F6A Tweed Bassman

This classic 4x10" combo from the late '50s became one of Fender's most popular amps for guitar, rather than for the bass for which it was designed. And it has remained that way ever since—both as a straight repro or reissue, or as the foundation for near countless amps that have been derived from its circuit. As is the way with many classic amps that are found in modern circuits, though, the much-lauded 5F6A tweed Bassman didn't just pop up years later as the inspiration for something new, but evolved within many of the greatest tube amps ever made throughout the history of rock.

This late-'50s model was already beloved on both sides of the pond when Fender changed up the Bassman formula for the blonde piggyback amps of the early '60s. Many players, however, still thought the old "tweed suitcase" sounded better for guitar.

Such was the impression of former jazz drummer and London music-store owner Jim Marshall and his cohorts Ken Bran and Dudley Kraven, who used the 5F6A Bassman circuit as the foundation of their own JTM45 amplifier in 1962. Marshall and co. virtually lifted the entire tweed Bassman circuit part for part, value for value, although they had to use more readily available British- and European-made components, which changed up the formula just a little.

With the Plexi models of the late '60s and others that followed, Marshall changed a few details in the preamp to make the amp brighter, as well as making a few other alterations (eventually dropping the tube rectifier too), but a good 85 percent or so of the circuit remained easily traceable to the original Fender 5F6A schematic, including essential elements such as the cathode-follower tone stage, long-tailed-pair phase inverter, and fixed-bias output stage with negative feedback.

Even as Marshalls evolved through the "hot-rodded" amps of the late '70s and '80s—the 2203 and 2204 Master Model amps—which carried master volume controls and, often, cascading-gain preamp stages, the foundation remained solidly 5F6A-based, as do many of the company's most popular models today.

Friedman Small Box
Friedman Dirty Shirley DS-40

What that also means, of course, is that any of today's very popular breed of Marshall-inspired amp heads you might encounter also carries a major chunk of tweed Fender Bassman DNA. Friedman Small Box head or combo, Friedman's Dirty Shirley, or whathaveyou? Yep.

Several amps by Germino, Bogner's Helios 50- and 100-watt and others, TopHat's Emplexador, several Reinhardts, 3rd Powers, and way too many to count also trace direct roots via the Marshall thing to the tweed Bassman.

Alongside all of this, it's worth noting that the blonde Bassman head of the early '60s and blackface Bassman of the mid-'60s, although great guitar amps in their own right, had circuits that were different in many ways, and were far less an evolution of the tweed Bassman than were the British amps that carried the torch into the modern era.

Modern Picks
Early- to Mid-'60s Vox AC30 Top Boost

Never mind that the circuit Vox used to create its Top Boost modification to the original AC30 model contained DNA from a Gibson tone circuit of the late '50s, which was also kissing cousins with the treble-and-bass cathode-follower tone circuit in Fender's medium-sized tweed amps of the '50s. This JMI-made English classic put it all together with many other ingredients to create a sound all its own, and a guitar tone for the ages.

Alongside the tweed Bassman (and therefore Plexi-derived) circuits, the AC30 is one of the most-tapped of the boutique amp era, while still appearing in many mass-manufactured guitar amps as well. Basically, any time you find a guitar amp with three 12AX7-style preamp tubes (excluding any extras for reverb, tremolo, or effects loops), both Treble and Bass controls, and four cathode-biased EL84 output tubes with no negative feedback (often colloquially referred to as "Class A"), chances are it pays homage to the original AC30 Top Boost.

Among several such suspects are the Blackstar Artisan 30, Matchless DC30/SC30/HC30, TopHat King Royale, Bad Cat Black Cat, Divided by 13 RSA 31, Morgan AC20/AC40, Valvetech Heyseed, Dr. Z Z Wreck, 3rd Power Dream 40 AC, Bruno Underground 30, and several others. Modified elements of the AC30 are also found in footswitchable multi-channel amps like Mesa's TA-30 (and deleted Maverick model), and Orange's AD30HTC. Many makers add a midrange control to the Top Boost circuit, but this doesn't change the amps' lineage all that much.

Matchless DC-30
Dr. Z Z Wreck Combo

Smaller 15-watt amps today that might outwardly appear more AC15-like are actually more AC30s with only two EL84s instead of four (note that the original AC15 of the '60s never had the Top Boost circuit). On the other hand, amps that also include a channel with an EF86 pentode preamp tube are also tapping that part of the original AC15 magic, which was derived from that circuit. Dr. Z's Maz 18, TopHat's Club Royale and Supreme 16, Matchless's Lightning and many others are all very much AC30-derived—if in modified form—despite being 15- to 20-watt amps.

Of course, today's Korg-owned Vox also makes several outstanding variations on the AC30 and AC15, some of which are relatively true to the original (in so much as it is possible in 2018, and at a given price point), while others add modifications and variations to enhance versatility.

Modern Picks
Mid-'60s Fender Twin Reverb & Deluxe Reverb

Almost any amp that boasts a "blackface tone" will use elements from the Twin Reverb's preamp stage, especially if it includes a midrange control. Those with just treble and bass will lean more Deluxe Reverb, but they are largely similar otherwise—the Deluxe generating 22 watts from two 6V6s, the Twin 85 watts from four 6L6s. While newer makers have changed up the output formula in many ways, and added other bells and whistles, the similar preamp stages in these two classic mid-'60s Fenders have found their way into countless new designs.

The preamp circuit in these blackface amps, and the tone stage in particular—which also evolved into the silverface amps of the late '60s and '70s—was an original creation from Leo Fender and co., and very different from the cathode-follower stage of the tweed amps (as discussed above). Each of the two channels found in most original Fender models from this era had their tone controls sandwiched between the first and second gain stages of a single 12AX7 (or 7025) preamp tube, with the volume control following the treble control in the signal chain. Almost any time you find that topology in an amp today, you're looking at something derived from the Fender circuit.

When Howard Dumble started building his creamy-toned lead amps in the late '60s and early '70s to meet guitarists' needs for overdrive at controllable volumes, he used these Fender circuits as a starting point, adding on an overdrive stage after a modified rendition of the Twin Reverb preamp. He did plenty else besides, but that's at the root of the design.

As a result, any of the many Dumble-inspired amps on the market today from makers like Fuchs, Amplified Nation, Bludotone, RedPlate and others will reveal some blackface-Fender DNA. Other amps built without the high-gain overdrive stage are even more directly linked to the classic blackface tone. More in this vein are the RedPlate Blackverb, Fargen Blackbird, TopHat Ambassador, Allen Old Flame and Accomplice, and plenty of others.

Fender '65 Deluxe Reverb Reissue
Dr. Z Z-Lux

Of course, the most famous, and most successful, modified-blackface-style amps—and the one that makes for a real wolf in sheep's clothing as far as that's concerned—are the original Mesa/Boogie Mark Series amps, and many models that have followed those. Like the Fender circuit, the Boogie's takes the signal from the input to the first gain stage, then through the tone controls (using similar component values to Fender, in many places) before hitting its first volume control (labeled "Gain" in this case) and onward to the second gain stage... and many more, to create that famous cascading-gain overdrive tone when Lead mode is engaged.

Modern Picks

Even with the great breadth and variety of tube guitar amps available today, the vast majority of circuits within them will have discernible reference points to the classic designs discussed above. And if they don't, chances are they bear links to another classic that we can explore another time… unless they really are original.

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