1960 Gibson Explorer GA-18T

Gibson is one of the most famous companies in the world for manufacturing guitars, but few people know that Gibson also made great tube amplifiers for many years. In fact, Gibson started making guitar amps all the way back in the early 1930’s, well before Fender started producing the amps that would later come to dominate the market. Gibson started making small 5-10 watt tube combo amps to capitalize on the Hawaiian Guitar craze that was popular in the 1930’s. They went on to make many models ranging from 5 to 90 watts of power, until they decided to pull the plug on making amplifiers in 1967. Almost all the amps they made were small combo amps with 25 watts or less of power and often came with Reverb or Tremolo. Gibson was innovative with their designs, and were one of the very first to put Spring Reverb in a guitar amp. The Explorer GA-18T we have here is a 14 Watt combo with a single 10” Alnico speaker, and features the swampy Bias Modulating Tremolo. It has a two 12AX7 preamp tubes, a pair of 6V6GT’s for the power amp, and a 5Y3GT rectifier tube which gives the amp a lot of sag and compression when pushed. This amp has some similarities in circuitry and tonality to the Fender 5E9 Tremolux, to provide a comparison. People who know Gibson amps will often pay a lot of money for them because they are fantastic quality hand-wired tube amps, they are unique in their tone, and because they are rare in terms of how many were ever manufactured. This amp is quite collectible and special, it was a pleasure to restore it and help keep it going for another 60+ years. If you come across a vintage Gibson amp, be sure to play it.

This amp came in to my shop in completely original condition. The customer inherited this Gibson from his father and so it was important to keep it as original as possible while making it reliable for the future. Hopefully it will be passed down to another generation one day. This amp needed a full restoration including a cap job, new power/plate/misc. resistors, cleaning, 3 prong AC cord conversion, and a new speaker.

Amp was completely restored. All axial leaded filter/bypass caps were replaced with upgraded voltage and temperature rated MOD brand electrolytic’s. The chassis mounted multi-section “fire-cracker” cap was replaced with a new CE brand 10uf/10uf 450v unit. New 5 Watt Wire-wound/2 Watt Metal Film power dropping resistors were installed for better reliability and lower noise floor. All non-Tremolo circuit preamp plate resistors were replaced with 2 Watt Reduced Mass Metal Film type units for preventative maintenance and reliability. The lone paper/foil coupling capacitor in the Tremolo circuit was replaced with a polyester Vishay brand unit with the same ratings. All parts installed point-to-point were done with vintage style enameled fiberglass insulation put around the leads just like it was done originally - this is for safety from accidental shorts. A new 3 Prong AC cord was installed to replace old and worn-out 2 Prong unit present and the death cap was removed. A brand new correctly sized 3AG 250V fuse was installed as the one in place was the wrong value.

The customer wanted the speaker changed to a model that was the most historically accurate to the original Jensen brand 10” Alnico unit. A new Weber 10A125 10" Alnico Speaker (8 Ohm, 30 Watt, Light Dope, Standard Dust Cap) was installed. This is Weber's take on the early 1960's Jensen P10Q/Oxford 10K5 - an extremely close and high quality reproduction. All new speaker wiring was installed as well.

The original tubes all tested good and were kept in place. V1-V2 = RAYTHEON 12AX7S, V3-V4 = RAYTHEON 6V6GT Matched Pair, V5 = RAYTHEON 5Y3GT. The 6V6GT’s Cathode Bias was set to %94 Class AB Plate Dissipation with a B+ of 320VDC. The tube sockets were all treated with De-Oxit to remove/prevent corrosion. The pots were sprayed out and the amp was cleaned inside and out. Amp sounds and works great.