The Gibson RD Guitar Series
In 1977 Norlin owned several companies including Moog which manufactured synthesizers designed by Robert Moog. Due to the popularity of personal synthesizers during this era, Gibson partnered with Moog to design the RD Guitar (research and developement) which brought electronic circuitry to Gibson instruments for the first time.
Many of these guitars were fitted with a Bob Moog designed compression and expansion preamplifier. Gibson soon discovered that many players did not like the advanced electronics.
The guitars shape could be described as a weird looking reversed firebird with a Les Paul headstock.
The Gibson RD standard had a double cut solid body, 2 humbuckers, stop tailpiece, rosewood fingerboard, dot inlays, chrome parts, large back plate, and were made in natural, walnut or sunburst finishes.
(Note the top 2 guitar have an extra toggle switch on the bottom that engages the active circuitry.)
The Gibson RD Custom had basically the same specs like the rd standard but with active electronics and was made with maple fingerboards.
The Gibson RD Artist also featured active electronics, 2 humbuckers, a tp-6 tailpiece, tune-o-matic bridge, large back plate, ebony fingerboards with block inlays, 3 piece mahogany necks, gold plated parts, pearl logo and was made with various finishes. The line was discontinued in 1982.
The Gibson L-6S Series
The Gibson L-6S was really a nice instrument. It was a cheaper descendant of the L5S jazz solid body electric guitar. It was the same shape - very much like a wide Gibson Les Paul. It was the first Gibson to sport a 24 fret two-octave neck.
The L-6S was designed by a young Bill Lawrence in 1972, who had been given the task of designing a "multi-sound system" under a very tight budget. The final production guitar was somewhat different from the Guitar he had in mind but as he stated, "even with these changes, the early production L6-S was still an excellent performer.”
The guitar had a small following and at the time was favored by Al DiMeola, Keith Richards and Carlos Santana among others.
The L-6S came in three variants; all were maple-bodied with twin super-humbucking Lawrence designed pickups.
The L-6S Custom was the best known version with total production of over 12000 instruments. It featured a Maple body, and set neck with a choice of maple or ebony fingerboard. Controls include a six position pickup selector, master volume, mid-range and treble roll-off controls. The first production models were simply called the L-6S. Later Gibson renamed the guitar the L-6S Custom and added a badge on the truss rod cover.
The L-6S Custom is noted for its six way rotary selector switch, complete with "chicken head" pointer knob. Starting with switch position #1, in the most clockwise position, the available pickup switching options are as follows:
1 Both pickups, in series
2 Neck pickup, alone
3 Both pickups, in parallel
4 Both pickups, parallel out of phase, with the neck pickup's bass response restricted thought a series capacitor*.
5 Bridge pickup, alone
6 Both pickups, series out of phase.
• The capacitor in the #4 position gives a fuller tone than the otherwise very nasal out of phase tone. The capacitor serves to limit the low end response of the neck pickup, and also phase delays the signal from that pickup, resulting in a fuller tone, not too unlike the #2 and #4 switch positions on a Fender Stratocaster guitar.
The mid-range control on the L-6S Custom uses a 1.8Hy inductor, which is split wound for hum-cancellation, along with a capacitor. This is a variation of the notch filter concept introduced by Gibson with the VariTone circuit. In the VariTone, however, the resistance is fixed, and different capacitors are chosen.
In the L-6S's mid-range control, the resistance is variable, while the capacitance is a fixed value. The result is one which allows decreasing of the middle tones, while retaining a large degree of "sparkle" or "brilliance" to the tone of the instrument. The volume and treble roll-off controls work as they do in most other electric guitars.
There were two versions of the L-6S produced without the sophisticated tone swithing control. One version was The L-6S called The Midnight Special with total production of around 2000 instruments Maple body, and bolt-on maple neck with a maple fingerboard. Controls include a pickup selector, master volume, and tone control. This guitar was strung through the body.
The L-6S Deluxe was less popular than the Custom with total production around 3500 instruments The Deluxe had a set maple neck, with a rosewood fingerboard. Controls include a pickup selector, master volume, and tone control. Strung through the body. The guitars production was ended in 1979.
The Gibson Mark Series aka MK Series
Perhaps due to the popularity of Ovation guitars, designed with the parabolic sound bowl that was said to increase and improve the guitars sound, Gibson Norlin jumped on the bandwagon in an attempt to design the ultimate acoustic guitar based on the principles of physics.
This effort was initiated by collaboration between Dr. Michael Kasha, a physics professor at Florida State University and Richard Schneider, who at the time was an apprentice of Mexican Luther Juan Pimentel. The collaborative result was the Gibson Mark series.
Dr. Michael Kasha had been working on improving the classical guitar circa 1965. Encouraged by the classical guitar establishment he began to measure the sound response of great classical guitars. He had already been aided in his effort by Richard Schneider.
By 1971, Kasha was publishing many of his conclusions. Kasha loaded weight in or near the headstock to increase the transmission of string vibration down through the neck. (Many of us as young guitarist had discovered that placing the headstock of your guitar against a wall or the headboard of your bed resulted in transferred vibrations and increased sound. There is a company that builds a flat piece of metal called the Fathead that is designed to fit on the rear of a Stratocaster headstock for this purpose.) Kasha counterbalanced this by adding a weight in the tail block.
The soundboard received a radical revision to the bracing system.
Systems varied for classical and steel-stringed models, but basically it involved two transverse bars under the bridge and above the sound hole, then a sort of hybrid X and fan system. X bracing was used on the upper bout and fanned bracing on the lower, with braces get graduating from thick to thinner as they moved from bass to treble sides. FYI, steel string guitars normally use X bracing and classical/flamenco guitars use fan bracing. So this design was very unusual.
Kasha also came up with an impedance-matching bridge that was basically wide on the bass side and tapered on the treble.
Ironically in 1972 Kasha and Schneider signed an agreement to sell classical and steel string instruments through the Baldwin Piano and Organ Company, owners and builders of Gretsch and Baldwin/Burns guitars. That arrangement lasted only about a year, perhaps due to the financial problems Baldwin was experiencing at the time due to their purchase of Burns.
Kasha and Schneider then signed with Gibson in 1973 to develop a line of scientifically designed acoustic guitars, with Norlin picking up the development tab.
All sported 25 1/2" scales and had a plastic ring around the sound hole. The top of the line was the Mark 99 in spruce and rosewood with an ebony fretboard, gold hardware, and bow-tie inlays ($2,199). These were basically custom-made by Schneider.
The Mark 81 was the top production model, differing only in large pearl block inlays ($999).
The Mark 72, a plainer rosewood model with less binding, chrome hardware, rosewood fingerboard, and dots ($749).
The Mark 53 was maple-bodied with rosewood 'board and dots ($649).
The Mark 35 had a mahogany body with rosewood 'board and dots ($569). Cases were an extra $109. Two 12-strings were briefly offered, the Mark 45-12, probably made of maple (two made in '79), and the Mark 35-12 (12 made in '77).
The Mark guitars were only offered for four years, until 1979. Only one custom Mark 99 was ever produced and sold. Of the Mark 81s, 431 were produced. The second most popular was the Mark 72 clocking in at 1,229 units. The maple Mark 53 saw 1,424 produced. The most popular was the mahogany Mark 35, with 5,226 made
I have played a Gibson Mark 53. While it is a fine American-made, solid wood, extremely well constructed instrument, I am of the opinion that despite all the scientific research that went into producing and designing the Mark Series guitars, when it is compared with a Gibson Hummingbird or a Martin D28 the Martin and Hummingbird produce a better tone.