Gibson GA8T

This Gibson amplifier from about 1963 was used by a working jazz musician and teacher as a second amp for a few years, then put in a closet for many many more years. The original tubes tested good, though the output tubes were a little weak, consistent with perhaps less than 1000 hours of use.

As designed by Gibson, this amp was capable of only about 8 watts output. It seems the designer's objective was to 1) keep down cost of building the amplifier by fitting an undersized output transformer and matching anemic speaker and 2) to keep this amplifier from competing for sound quality or volume with Gibson's larger, more expensive amps. It was therefore intended more as a "practice" amp. However, the amp has a cabinet sized for a 12" speaker, and the circuit design, with minor power supply modifications, is capable of the full 15-18 watts that the dual EL84 output stage can generate.  

Audio Atelier undertook a refurb and redesign to allow the amp to realize its full potential. On the electrical side, this included replacement of all capacitors (due to age, but also to improve tone through improved specifications), raising the high voltage to the output tubes sufficiently to obtain additional power out, and fitting a wide-bandwidth output transformer capable of about 20 watts RMS output, though not driven to that level in this circuit.  We also adjusted voltages to the gain stages to permit full range of gain/volume options including modest preamp-stage distortion at full gain with decent input levels. We fitted a matched pair of the best quality output tubes, and optimized their bias point. The resulting RMS output is about 15-18 watts, plenty to play acoustic or jazz sets anywhere, and blues and perhaps some rock in modest club venues.

This output would have been wasted on the original speaker, which had little low frequency response and very limited power handling capacity.   So we fitted a 12", neodymium magnet, hemp cone speaker of 99 db efficiency -- thus gaining even more volume from the amplifier, and more bandwidth. And saving a pound or two of weight, offsetting the increased weight of the output transformer.

As you will hear from the recordings, the amplifier is very full-bodied in sound, with excellent clean-tone reproduction; warmer than Fender amps like the Princeton reverb, and cleaner and fuller than a VOX AC-15. Its not quite as loud as a Mesa 20, but it's close. We hope you get to play the amp and enjoy its unique character which may compliment a variety of musical styles in the hands of an accomplished guitarist -- as you will hear in the recordings.

Finally, the amplifier was and remains extremely portable -- its dimensions of 22" wide, 18" tall and 10.5" deep -- are modest, and the weight of 26 pounds makes it decidedly one-handed, and a pleasure to tote.

Pricing is extremely fair at $1200. The new owner will receive a stable, classic, flexible, portable, capable combo amplifier which will underscore sonically, and visually, top flight musicianship.

For additional information contact:
Audio Atelier, 970-259-3746 - E-mail