Jennings Electronic Industries AC40
1970 - 1973
Detail from the second version of the "Jennings News" brochure, 1970.
Introduced in time for the "Associated Musical Instrument Industries" fair in August 1970, the AC40 was the first valve amp in the "Jennings Electronic Industries" range. Everything up to that point had been solid state. To some extent, the appearance of the amp represents a capitulation on the part of Tom Jennings (who had hitched his wagon firmly to transistors) to the demands of the market.
The amp was initially also referred to as the "JV40" - presumably "Jennings Valve" - a designation reflected on the serial number plates of early production units.
Rough-print picture of the new "JV40" (with drawbar tone controls) in the music trade press, September 1970.
Short review of the Jennings stand accompanying the picture above.
The drawbars were effectively horizontal sliders - a reworking of the "harmonic drawbars" used on organs produced by the "Jennings Organ Company" from late 1957 - patent granted in 1960. See this page on the Vox AC30 website. A great idea but perhaps not entirely practical on an amplifier.
Notice from "Beat Instrumental" magazine, October 1970. Price of the AC40: £85.
Preview of the Associated Musical Instrument Industries fair published in "Beat Instrumental" magazine, August 1971. Price of the AC40 is now £150. Draw-bar controls are still in place.
A detail from the JEI pricelist of December 1972. The AC40 costs £150.00 (its price also in August '71).
Whether the AC40, which is cathode biased like the AC30, actually made 40 watts is doubtful. The EL84s in serial number 1275 each have their own 200R cathode resistor network (two 100R in series), equivalent to the single 50R resistor shared by the EL84s in the Vox AC30 (from late 1963). It is likely that the HT voltages of the AC40 are similar at all points to those of the AC30 too. "40" was a good sales pitch - better of course in marketing terms than "30" - and typical of Tom, but unlikely as an accurate expression of wattage.
Above, an early JEI AC40 photographed with an AC30. Controls for the Vib-Trem were standard.
To date no circuit diagram for the AC40 has come to light - but its circuit is not far removed from that of an AC30 (valve rectified).
Speakers are either Celestion alnico T1096s, 15ohms, wired in parallel for a total impedance of 8ohms, or ceramic Celestion T1217s, wired in the same way.
Some surviving amps
The serial number sequence is likely to have started at 1000, the run probably extending to around sn. 1300 - so around 300 produced before the model was phased out in 1973.
NEW
Serial number 1157
Currently in Belgium. "JV40" given as the model on the serial number plate. The plate also notes (as do the others) that the design is "Protected by Pat. App. 16598 and 50889 and Others". A search through the Patent Applied For records unfortunately leads nowhere (not for the first time). Thanks to Geert for the pictures.
Serial number 1172
On the serial number plate the model is designated as a "JV40" - see also the amp below. The date code on the Celestion alnico T1096 driver is "DD23" = 23rd of April 1971. Thanks to Nick for the pictures.
Serial number 1189
A rare surviving example of an AC40 with drawbars. The amplifier is described on its serial number plate as a "JV40". Thanks to Steve for the pictures.
NEW
Serial number 1197
AC40 serial number 1197 with JV40 serial number 1188.
Good condition all round. The speakers, Celestion T1096s, have date codes in November 1971. Thanks to Phil for the pictures.
Serial number unknown
Early grille cloth. No further details at present.
New style grille cloth.
"Beat Instrumental" magazine, January 1972.
Serial number 1230
Featured on all recordings by "The Manatees" from 2016. Thanks to Tyler Bloor for the pictures.
Serial number 1235
Note that the speakers are alnico Celestion T1096s - the 15ohm counterpart of the T1088. The frames of T1096s, as here, are normally sandy in colour, and the bells silver.
Serial number 1254
A gorgeous Jennings AC40 and matching 2x12" extension cab. Condition is immaculate. Grey-back Celestion G12H drivers in the AC40, and greenbacks in the extension cab. The date codes of the latter are LE28 = 28th November 1972. Mustard caps in the amp have 1970 codes. Thanks to Andreas for the pictures.
Serial number 1268
Excellent condition. Complete with its original cover.
Serial number 1275 - currently in the USA
Regrilled with new production Vox grille cloth. The speakers are Celestion T1534 greenbacks, date codes "JC29" and "CD24" = 29th September 1970 and 24th March 1971. Visible date codes on the Mullard mustard capacitors in the preamp are "B0" = second quarter of 1970.
Serial number 1278
Date code of the remaining original Celestion T1096 is DF6 = 6th April 1973. The other speaker is a replacement.
NEW
Serial number 1282 - currently in Europe
Unknown serial numbers
Currently in Europe
Equipped with Goodmans Power Range green label (15ohm) ceramic speakers.
An unused panel marked in the far right hand corner "AC30", but probably for the amp generally known as the AC40, sold on ebay in 2012.
Click here for the Jennings J40, the solid state precursor of the AC40.