JMI Vox offered four UK made "plug in" boosters for guitar, bass and microphones in the mid to late 1960s. Each was powered by a nine volt battery and was housed in a steel case measuring ~4 ⅝ long, ~1¼" wide and ~¾" deep. A power switch and a ¼" input jack were mounted to one side of the booster case. A ¼" phone plug mounted to one end of the housing supplied the boosted audio output signal to the input jack of a guitar amplifier or PA head. #149 Treble Booster - The chrome plated #149 JMI Treble Booster was introduced in the September 1964 Jennings Vox price list and as the name suggests, accented treble frequencies. The #149 Treble Booster utilized a treble gain circuit powered by one silicon transistor and featured a three-way slide switch which offered true signal bypass. The UK retail price in 1965 was 4£ 4s. Thomas Organ purchased the right to design and manufacture Vox products for the North American marketplace from JMI in mid 1965. Some JMI Vox products, including the JMI #149 Treble Booster, were re-engineered by Thomas Organ. Thomas discovered that an excess of treble gain in the JMI unit was causing the preamp stage of some guitar amps to distort. To address this issue, the redesigned Thomas Vox V806 Treble Booster reduced treble gain by 7db. The V806 Treble Booster also eliminated the true signal bypass feature from the JMI unit.

#152 Bass Booster - The black painted #152 JMI Vox Bass Booster was introduced in the November 1965 JMI Vox price list. The #152 Vox Bass Booster utilized a low frequency gain circuit powered by one silicon transistor and featured a three-pole power switch offering true signal bypass. The UK retail price in 1965 was 4£ 4s. Thomas Organ produced the nearly identical but chrome plated V810 Vox Bass Booster for the North American marketplace. The US produced V810 Vox Bass Booster also eliminated the true signal bypass feature found in the JMI unit as a cost saving measure. #153 Distortion Booster - The #153 JMI Vox Distortion Booster "fuzz tone" was also introduced in the November 1965 JMI Vox price list. The steel case sported a dark red painted finish. The booster utilized a battery operated gain circuit driven by two silicon transistors and featured a three-pole power switch that offered true signal bypass. The UK retail price in 1965 was 4£ 4s. The #153 Distortion Booster provided a less costly alternative to the germanium transistor powered JMI Vox "Tone Bender" fuzz tone. Thomas Organ produced the nearly identical but chrome plated V816 Vox Distortion Booster for the North American marketplace. Like the V806 Treble Booster and V810 Bass Booster, the Thomas Organ eliminated the true signal bypass feature in the V816 Vox Distortion Booster as a cost saving measure. #157 Mic Booster - The #157 JMI Vox Mic Booster was painted blue and featured a battery operated microphone preamp. It accepted the ¼" phone plug from a high impedance microphone through a jack mounted on the side of the unit. A ¼" plug mounted to one end of the booster was inserted into the input jack of a PA or guitar amplifier. Although the #157 JMI Vox Mic Booster was pictured in the 1966 and 1967 Vox product catalogs it was not included in Vox price lists from this era. Thomas Organ did not offer the #157 Mic Booster in North America. How can I tell if my Vox Booster was made in the UK or in the USA? - Boosters made in the UK had a dash between the words in the name, such as "Treble - Booster." Boosters produced by Thomas Organ for US distribution eliminated this dash. Aside from the chrome plated JMI Vox "Treble - Booster," the other UK made boosters were painted either red, blue or black. All of the US produced boosters were chrome plated.

URL: http://www.voxshowroom.com/uk/misc/boosters.html