Some notes on the preamp (upper) chassis of TV Front single-speaker AC30s, later 1959 to autumn 1960. The "Types" outlined below are fairly general in nature - within them, chassis could evidently be populated and fitted out differently. The main page on the TV Front AC30 can be found here.

Type 1

Re-purposed AC15 chassis (as Jim Elyea noted): choke and mains transformer removed, an upright output transformer added; EL34s close together; the Vibravox circuit housed in three cans potted with araldite.

Early, no serial number. Pic. from J. Elyea, p. 375.

Serial number 4041. Pic. from J. Elyea, p. 374.

Type 2

Based on the AC15 chassis, but specifically made for the AC30. A "lay-down" output transformer occupied the cut-out, still the provision for a capacitor to its left, no transformer or choke fixing points in the centre of the chassis though. EL34s spaced further apart; Vibravox cans three-in-a-row.

Serial number 4047.

Type 3

Chassis purpose-made for the AC30. No cut-out for a capacitor by the output transformer, EL34s spaced further apart; the three Vibravox cans here in staggered formation.

Serial number unknown.

Note that the can at left - Vibravox can no. 3 - was designed to be plugged and unplugged as required. As Glen Lambert has suggested, this was probably to allow a Vox piano pickup control unit to be used with the amplifier. See this page.

AC/30 serial number 4072, recently come to light, also has this functionality.

Additional note, 12th May, 2024: - one of the earliest (surviving) amps to have been built in such a way as to enable a control unit to be connected is an AC1/15 from early 1959.

Type 4

As above, chassis purpose-made for the AC30. No cut-out for a capacitor by the output transformer. The Vibravox circuit now concealed in a "doghouse", the idea probably copied from the Fender amps that Jennings had begun distributing in the UK.

Serial number 4060 (?) - white trafolyte control panel. Pic. from J. Elyea, p. 374. On p. 187 he indicates that serial number 4060 has a trafolyte panel.

Serial number 4158

Detail of the chassis above.

The reason for the move from cans to a single "doghouse"? Probably a "lift" from Fender. In early 1960, JMI became the main (though not exclusive) distributor of Fender amps in the UK. Below, the venerable chassis of a Fender Twin from 1958/1959, its "doghouse" containing the main filter capacitors.

Early Fender Twin.

As with other Jennings amplifiers, it clearly took a little while for production to reach a settled form - possibly as many as fifty or so amps. Thereafter things become more consistent - "more" necessarily being a relative term in this instance.

If serial numbers did indeed start at 4000, then around 160-200 single-speaker AC30s are likely to have been made ready for sale from later 1959 through to autumn / early winter 1960, the latest overlapping with the new TV Front twin speaker amps. Jim's note of a single speaker amp with serial number 4192 on p. 186 is likely to be a printer's error for 4102, which is recorded as being the latest he knew (on p. 378). That does not mean, however, that there never was a TV Front single speaker AC30 with that number.

The earliest genuine TV Front AC30 Twins known at present have numbers in the low 4200s. A starting point in the higher 4100s is likely though.

Back to the overview page on the single speaker AC30 - 1959-1960.

On to the TV front AC30/4 Twin, 1960