This month, I felt like taking a little dive into circuits for you solder-breathers out there.
There are two main ways that diode clippers work, and there are subtle but important differences in the two ways. In the electronic sense, diodes are used as one-way valves for current. The arrow in the diode’s schematic symbol is the anode, or positive terminal, and the bar is the cathode, or negative terminal. A voltage that is more positive on the anode side than the cathode side lets current through in the direction of the arrow. When the diode is reverse biased (the cathode is more positive than the anode), then the diode blocks current from flowing, as shown in Figure 1.
In real diodes, you don’t get that one-way valve stuff for free. The price is that there must be some voltage lost across the diode, even in the forward direction, before the diode will begin to conduct. This forward voltage is different for different kinds of diodes. For silicon diodes, it’s about 0.5- 0.7V, for germanium about 0.2-0.3V, and for LEDs, it can be 1.5V–3V or more.
If I force a signal through a resistor, then place a pair of diodes from the end of the resistor to ground (as shown in Figure 2), the diodes will do nothing to the signal until it is more positive than D2’s forward “penalty” voltage, and again nothing until it is more negative than D1’s conduction voltage. At voltages bigger than the diode voltage, one or the other of the diodes will conduct heavily, and any greater signal level will be clipped off the top and bottom. This kind of clipping is fairly abrupt, and gives a ‘60s kind of fuzz all by itself. The MXR Distortion Plus and the Armstrong Blue Clipper, among others, used this kind of clipping.
A slightly more sophisticated way to use diode clippers is in the feedback loop of an opamp, as shown in Figure 3. This works differently from Figure 2. The opamp forces a current equal to the current through input resistor R2 to flow from its output to its negative input through R3. The diodes have the output voltage across them, but only start conducting when the output voltage of the op-amp gets more positive or more negative than the diode voltages. After that output voltage size, the diodes conduct all the output current back to the input. This is a more “delicate” way to run the diodes in clipping, and this results in a softer-sound.
You can modify the resistor-diode clipping from Figure 1 as shown in Figure 4 by putting another resistor (R5) between the original resistor (R4) and clipping diodes. This resistor causes some of the original signal to be mixed with the clipped diode signal and adds some soft-sounding roundness to the output. Representative values for R4 and R5 are 10K fixed and 10K variable. It’s a fun mod for the Distortion Plus.
The final circuit in Figure 5 shows the feedback clipper of Figure 3 but with the signal applied to the non-inverting (+) input of the opamp. This forces the op-amp to add the input signal to the feedback-multiplied signal. So the output consists of a 50/50 mix of the input and the multiplied-and-diode clipped signal, and the clipping harmonics are effectively cut in half. You may already have recognized it – this is the circuit for the clipping stage of the Ibanez Tube Screamer.
The diode clipping circuit in either the resistor-diode or feedback-diode forms is highly flexible and modifiable. If you experiment with these circuits, play with both identical diodes and non-identical diodes. Changing from, say, 1N4148 to 1N4007, or even one of each may not make much difference. Using one silicon 1N4148 and one or two germanium 1N34s will provide a subtle change in the tone of the distortion. Using one silicon diode and one LED makes a much more obvious change in tone.
Like making stew, making a good diode clipper requires some thought, some good ingredients, and some tasting as you go along. If you like cooking your own clippers, be sure to try some of these recipes.
R.G. Keen
Cheif Engineer
Visual Sound
www.visualsound.net
Gibson originally launched the EB-6 model with the intention of serving consumers looking for a “tic-tac” bass sound.
The Gibson EB-6 was announced in 1959 and came into the world in 1960, not with a dual-horn body but with that of an elegant ES-335. They looked stately, with a thin, semi-hollow body, f-holes, and a sunburst finish. Our pick for this Vintage Vault column is one such first-year model, in about as original condition as you’re able to find today. “Why?” you may be asking. Well, read on....
When the EB-6 was introduced, the Bass VI was still a glimmer in Leo Fender’s eye. The real competition were the Danelectro 6-string basses that seemed to have popped up out of nowhere and were suddenly being used on lots of hit records by the likes of Elvis, Patsy Cline, and other household names. Danos like the UB-2 (introduced in ’56), the Longhorn 4623 (’58), and the Shorthorn 3612 (’58) were the earliest attempts any company made at a 6-string bass in this style: not quite a standard electric bass, not quite a guitar, nor, for that matter, quite like a baritone guitar.
The only change this vintage EB-6 features is a replacement set of Kluson tuners.
Photo by Ken Lapworth
Gibson, Fender, and others during this era would in fact call these basses “baritone guitars,” to add to our confusion today. But these vintage “baritones” were all tuned one octave below a standard guitar, with scale lengths around 30", while most modern baritones are tuned B-to-B or A-to-A and have scale lengths between 26" and 30".)
At the time, those Danelectros were instrumental to what was called the “tic-tac” bass sound of Nashville records produced by Chet Atkins, or the “click-bass” tones made out west by producer Lee Hazlewood. Gibson wanted something for this market, and the EB-6 was born.
“When the EB-6 was introduced, the Bass VI was still a glimmer in Leo Fender’s eye.”
The 30.5" scale 1960 EB-6 has a single humbucking pickup, a volume knob, a tone knob, and a small, push-button “Tone Selector Switch” that engages a treble circuit for an instant tic-tac sound. (Without engaging that switch, you get a bass-heavy tone so deep that cowboy chords will sound like a muddy mess.)
The EB-6, for better or for worse, did not unseat the Danelectros, and a November 1959 price list from Gibson hints at why: The EB-6 retailed for $340, compared to Dano price tags that ranged from $85 to $150. Only a few dozen EB-6 basses were shipped in 1960, and only 67 total are known to have been built before Gibson changed the shape to the SG style in 1962.
Most players who come across an EB-6 today think it was a response to the Fender Bass VI, but the former actually beat the latter to the market by a full year.
Photo by Ken Lapworth
It’s sad that so few were built. Sure, it was a high-end model made to achieve the novelty tic-tac sound of cheaper instruments, but in its full-voiced glory, the EB-6 has a huge potential of tones. It would sound great in our contemporary guitar era where more players are exploring baritone ranges, and where so many people got back into the Bass VI after seeing the Beatles play one in the 2021 documentary, Get Back.
It’s sadder, still, how many original-era EB-6s have been parted out in the decades since. Remember earlier when I wrote that our Vintage Vaultpick was about as original as you could find? That’s because the model’s single humbucker is a PAF, its Kluson tuners are double-line, and its knobs are identical to those on Les Paul ’Bursts. So as people repaired broken ’Bursts, converted other LPs to ’Bursts, or otherwise sought to give other Gibsons a “Golden Era” sound and look ... they often stripped these forgotten EB-6 basses for parts.
This original EB-6 is up for sale now from Reverb seller Emerald City Guitars for a $16,950 asking price at the time of writing. The only thing that isn’t original about it is a replacement set of Kluson tuners, not because its originals were stolen but just to help preserve them. (They will be included in the case.)
With so few surviving 335-style EB-6 basses, Reverb doesn’t have a ton of sales data to compare prices to. Ten years ago, a lucky buyer found a nearly original 1960 EB-6 for about $7,000. But Emerald City’s $16,950 asking price is closer to more recent examples and asking prices.
Sources: Prices on Gibson Instruments, November 1, 1959, Tony Bacon’s “Danelectro’s UB-2 and the Early Days of 6-String Basses” Reverb News article, Gruhn’s Guide to Vintage Guitars, Tom Wheeler’s American Guitars: An Illustrated History, Reverb listings and Price Guide sales data.
Billy Gibbons is an undisputable guitar force whose feel, tone, and all-around vibe make him the highest level of hero. But that’s not to say he hasn’t made some odd choices in his career, like when ZZ Top re-recorded parts of their classic albums for CD release. And fans will argue which era of the band’s career is best. Some of us love drum machines and synths and others don’t, but we all love Billy.
This episode is sponsored by Magnatone
Originally released in the 1980s, the Victory has long been a cult favorite among guitarists for its distinctive double cutaway design and excellent upper-fret access. These new models feature flexible electronics, enhanced body contours, improved weight and balance, and an Explorer headstock shape.
A Cult Classic Made Modern
The new Victory features refined body contours, improved weight and balance, and an updated headstock shape based on the popular Gibson Explorer.
Effortless Playing
With a fast-playing SlimTaper neck profile and ebony fretboard with a compound radius, the Victory delivers low action without fret buzz everywhere on the fretboard.
Flexible Electronics
The two 80s Tribute humbucker pickups are wired to push/pull master volume and tone controls for coil splitting and inner/outer coil selection when the coils are split.
For more information, please visit gibson.com.
Gibson Victory Figured Top Electric Guitar - Iguana Burst
