Jennings Musical Industries: 1967-1968

Foundation Bass: 50W solid state bass guitar amplifier, two channels - normal and bass. The normal channel has distortion (operated by a footswitch), and mid-range boost, operated by a switch on the control panel. The bass channel has Tone-X, a sweep tone control. Speaker cabinet was a 18" closed back unit, with a Celestion T1296 at first, later a Goodmans driver.

The analogue of the Foundation Bass in the solid state guitar amp range was the Defiant, which had the same 50W power section, but a different preamp.

In the price list of April 1967, the Foundation Bass is listed as £171 and 3 shillings - in today's money, around £2,850.

Both amp and cab were supplied with covers. Covers for the latter are exceedingly scarce these days; for the former, only slightly less so. for a fine survival.

The general characteristics of early amps are indeed much as early Defiants:

  • Serial numbers begin at 1001. Number 1165 has an original capacitor with a June 1967 date code so cannot have been ready for sale before July '67.
  • The very earliest numbers are probably in the form xxxx, as in the case of early Defiants. The standard thereafter became SB..xxxx
  • Back panels are cloth covered and have angled edges.
  • Control panels are generally deep black initially, then brown/bronze, then black again.
  • Fixings for the preamp - screws by the front corner protectors - are present on top of the wooden cases in the early amps.
  • Jack input sockets are metal and of open construction. Surrounds are white. After the first three hundred or so amps, black plastic jacks are used.
  • Logos simply state "VOX" at first in silver lettering. Later, one finds gold letters, then "Solid State".
  • The very earliest preamp sections were probably stamped: "50W. B PREAMP, SER. No. 0xxxx". Soon after the format changed to "PRE/AMP B. SER. No. 0xxxx". Later, when "Solid State" was brought into the logo, the format is:"B/S. No. 0xxxx". Power amp sections stampings are: "50W.PA SER. No. 0xxxx", then, when the preamp format changed: "P5A SER. No. 0xxxx."
  • JMI made amps always have two indicator lamps on the front panel.
  • The schematic for the preamp is OS/137, the power amp OS/134.

Below, a growing register of surviving amps. If anyone knows of any early Foundation Basses that have not yet been included, .


Serial number unknown - currently in Australia

No "Solid State" in the logo; control panel of the amp is black, so perhaps very early (ie. earlier than those amps with brown panels below), but unfortunately this is the only picture.

Serial number unknown - current whereabouts unknown

As in the case of the amp above, white-ringed metal jack sockets. Again, no "Solid State" in the logo of the amp, though it does appear on the cab's.


Serial number 1042 - currently in Belgium

Sold in Belgium some time ago. Thanks to Kris for details of the serial number. Brown control panel, white ceramic rings to input sockets, preamp fixing screws on top. A couple of new indicator lamps and control knobs, but no other external changes visible.

Serial number unknown - currently in the UK

Note that the logo of the cab is simply "VOX". The preamp has only one replaced capacitor. The power amp is original and untouched.

PREAMP component date codes: Yellow Lemco capacitors: "XL", "XM" and "YB" = Nov. and Dec. 1966, and Feb. 1967. Red CCL preamp caps: "L6" and "B7" = Dec. '66 and Feb. '67.

POWER AMP: RCA 2N4347 transistors are "6M" = December 1966. Red CCL filter caps: "B7" = Feb. '67. Welwyn cement resistor: "YB" = Feb. '67.

Serial number 1109 - currently in Germany

Foundation Bass serial no. 1109. Missing a couple of knobs but otherwise in good condition externally.

Serial number 1141 - currently in France

Note the white-ringed metal jack sockets and the preamp fixing screws on top of the box. The first set of pictures render the control black as black, the second (amp paired with a later cab) brown. A small switch has been added by the "NORMAL" legend.

Serial number 1150 - currently in the UK


Serial number 1161 - currently in the USA

Amplifier section.

Serial number 1165 - currently in the UK

Power amp chassis 1503, preamp 1180. The format of the preamp stamping (standard for mid run JMI bass preamps) is: PRE / AMP.B SER. No. 01180.

POWER AMP: CCL capacitors with date codes "B7" and "C7" = February and March 1967; yellow Lemco capacitor "YC" = March 1967; and wirewound resistors "YB" = Feb. '67.

PREAMP: Lemco date codes "XL" = November 1966. CCL capacitors "I6" = September 1966, and "F7" = June 1967. The amp was probably ready for despatch therefore in July/August 1967.

The main power transistors are RCA 2N4347. One can just see the "47" in the pic above. Unfortunately the surface of the metal is too pitted to make out the date code at present. For a brief overview of 2N3447s in Defiant power sections (which are identical to those of Foundation Basses), .

Serial number unknown - currently in the UK

Said in the ebay seller's description to be serial no. SB 2250; but this would place it in the Vox Sound Equipment period. As it is, the amp has a brown control panel, white surrounds to the metal jack plugs, top fixings for the preamp, and "VOX" in silver letters. If someone said SB 1050 or 1150, perhaps even 1250, that would be reasonable.

Serial number 1213 - currently in the USA

Excellent condition. Thanks to Kurt for the pictures. Sold on ebay in early 2018.

Serial number 1223 or 1225 - currently in the USA

Complete with speaker cabinet and chrome cradle for the amplifier section. Condition good.

Serial number 1237 - currently in the UK


Serial number 1267 - currently in the UK

Good order externally. Control panel brown, at some point there were two stickers left front.

Serial number 1277 - currently in Germany

Sold on ebay.de recently.

Serial number 1282 - currently in the USA

Vox Foundation Bass serial number 1282, Jennings Musical Industries, late 1967. Thanks to David for the pictures.

Updated (21/10/2020) - the amp was incorrectly given as number 1252 previously. Location is the USA, not UK

A preamp surviving from an early Foundation - currently in the UK

Preamp no. 1530. Panel brown in colour. A few new components inside, and the pilot lamps removed, but otherwise in reasonable condition electronically. The box, alas, has lost most of its fittings (apart from the "Foundation Bass" flag). Note the holes for the preamp fixing are visible in the first pic.

Date codes. Yellow Lemco capacitors "XL" and "YB" = November 1966 and Feb. 1967. Red CCL capacitors "L6" = December 1966.

Serial number unknown - currently in the UK

Serial number unknown - currently in France

An amp that has obviously seen some use. Indicator lamp lenses have gone (as regularly seems to have happened), but otherwise all there externally.

Serial number unknown - currently in the USA

Advertised by Guitar Center, USA, some time ago. Brown panel; condition reasonable.

Late 1967 / early 1968

"Solid State" now in the logo - input jacks black plastic.

Control panels are black again.

Serial number 1328 - currently in the UK

Power section no. 1589, and preamp 1782. Both sections are stamped in the new format. Note that Expertly restored. Accompanied by its cab and repro chrome support.

Serial number 1329 - currently in the USA

A replaced mains connector, but otherwise good condition. Thanks to Mark for the pictures.

Serial number 1339 - currently in Europe

Thanks to Paul for the pictures.

Serial number 1387 - currently in France

Presented for sale in France last year. Complete with its stand. Condition looks good. Footswitch socket changed.

Serial number 1420 - currently in Europe

Replaced front grille cloth, but otherwise in good order. Preamp chassis number 1820. The red CCL with cursive script has the date code "G7" = July 1967; one of the original RCA power transistors (a 2N4347) has the code "7F" = June 1967. On the driver transformer the letters "KMC" in white. The date codes on the solid state transformers have yet to be deciphered definitively, however.


Serial number 1439 - currently in the UK

Sold by Houlgate Gardiner in 2020. Formerly owned by the late great Bernie Marsden.

Serial number 1442 - currently in the UK

Plenty of character - this set obviously had a good working life.

Serial number 1444 - currently in the UK

Sold on ebay uk in August 2015. Footswitch socket changed and a jack input renewed, but otherwise all good.


"AMPLIFIER" rather than "VOX AMPLIFIER" on the plate

Serial number 1518 - currently in France


Serial number 15(36?) - currently in the UK

Sold on ebay in May 2014. Replaced indicator lamps, and lacking the grille for the back panel, but otherwise good.

Serial number unknown

Amp and cab sold on ebay recently.

Serial number unknown - currently in the UK

"AMPLIFIER" alone at the head of the serial number plate.

Serial number unknown - currently in Europe

No pics of the front. The vents on the box top, however, indicate that the amp is a Foundation Bass. "Amplifier" alone appears in the first line of the serial number plate. The footswitch socket has been replaced.

On to the next page of Foundation Basses -