The Vox AC30/4: black panels, split-front cabinets

autumn 1960 - early winter 1961

A split-front AC30/4 TWIN from mid 1961. The Shadows had fawn TV Front AC30/4s in December 1960 and it is now known split front AC30/6s (not AC30/4s) in March 1961.

In terms of what went out for sale, the first runs of the new split-front AC30/4 overlapped with the last of the AC30s in TV front cabinets. Serial number 4414 TV front; number 4401 (below) new split front.

From a practical standpoint the new cabinets were a marked improvement on the old - three carrying handles instead of one, and three vents in the top to allow air to circulate better around the chassis (at least that was the theory). Backboards were stouter. Cosmetics changed too: a new type of beige covering (sometimes called "fawn" or "tan"), and two lines of gold piping around the body of the cabinet.

The circuit and control panel of the AC30/4, however, remained much the same as for the TV front amps. The legend by the fuse continued to have the Greek alpha rather than an "A", and the two tone controls, "Brilliant" and "Bass", held their place.

From mid 1960 production of the AC30/4 went side by side with that of the AC30/6. All preamp chassis were drilled for six inputs, though two were naturally blanked off by the control panel of the AC30/4:

A detail of the chassis of AC30/4 serial number 4715.

"Melody Maker" magazine, 19th November, 1960. The AC30/6 is 89 guineas; the AC30/4 is 85 gns. There is also an AC30/4 Bass model at 89 gns.

On serial number plates "N" stands for "Normal voicing", and "B" for "Bass". Often in the lower compartment of the plate, there is a "4" in the upper panel (to indicate the AC30/4), and a "W" (an upside-down "M"), which may signify something along the lines of "wide frequency", distinguishing these amps from the more constrained tonal response of the early AC2/30 and AC/30.

Further images of AC30/4 sn. 4669 BASS below.

The explicit designation of the amp as a "4" on the plate (something not found on the TV front amps) was a means of making record keeping easier (the registers kept of sales and despatches). Since AC30/4s and AC30/6s had serial numbers in the same sequence (in the range low 4200s to low 4700s), one could not tell simply from the number alone whether the amp was of one type or the other. Black panel AC30/6s (Twins and Super Twins) continued on their own from the low 4700s to mid 4900s.

The speakers chosen for the split-front cabinet were new - and standardised (or at least regularised): the Celestion "blue" - G12 alnico T530, sprayed Jennings blue - as depicted in the page from the brochure below.

Note that the brochure illustrates a control panel for the new circuit of the AC30/6.

By October 1961, Jennings was signalling the phasing out of the AC30/4. See the . Orders for the AC30/4 were honoured though at the old price of 95 guineas (£99 5s). For a limited time, one could purchase the AC30/6 at the special price of 100 guineas (£105).

Components, assembly, etc.

Chassis were assembled at the Vox works at 115 Dartford Road. For pictures of the site and the factory, (on the Vox AC100 website). In Spring 1961, Westrex took over the assembly of AC30/6 chassis, but evidently not the AC30/4. Farming production of the former out will have simplified production considerably.

Notes on how to read component date codes, are .

The transformers for both the AC30/4 and AC30/6 were made by Haddon ("Haddon Transformers Ltd." of South Ruislip), the choke by Radiospares.

Haddon mains transformer of AC30/4 serial number 4401.

The schematic for the AC30/4 is JMI sheet OA/032 (drawn 29th April 1960, and registering a change dated 7th Feb. 1961).

Information panel of circuit diagram OA/032, the AC30/4, 29th April, 1960. Changes for "Bass" models are noted in the diagram with asterisks.

On the introduction of a new capacitor - marked C42 in the diagram - into the circuit in February 1961, .

The circuit of the AC30/4 Bass differed only in the values adopted for six coupling capacitors (C3, C6, C10, C7, C9, C11). Most are of a higher value to reduce the amount of treble admitted.

Detail from a JMI brochure of early 1961 prepared for "Musicland" in Bexleyheath - principally guitars, but the AC30/4 Bass is mentioned (even if the wattage is given incorrectly).

In general outline, the preamp of the AC30/4 goes hand in hand with that of the AC15 (schematic OA/31) - an EF86 as V1, three ECC83s (V2, V7 and V9), and an ECC82 (V8). The output section is of course doubled up: four EL84s (V3-V6) instead of the AC15's two.

The EF86 which added so much to the sound of the AC30/4 was unfortunately also its weak point - EF86s can be extremely sensitive to vibration and prone to microphony. The AC30/6 with its complement of ECC83s was much less troublesome.

Jim Elyea's book, "Vox Amplifiers. The JMI Years" (California, 2009) is again a wonderful repository of info on these amps and other AC30s.

"A Service Engineer's Guide to the Vox AC30 Valve Amplifier" by Stephen Grosvenor (2006), gives excellent schemas of the circuit boards and electronic layout. His site .

If anyone knows of further early new-style black panel AC30s that should be incorporated on this page, .

AC30/4 new split-front cabinet: Winter 1960 - Sept./Oct. 1961

Serial number 4250

Fawn covering, split front. Belonged to Chas McDevitt. The amp arrived as the fulfilment of an order for AC15s placed in May 1960. But when the amplifiers (one for Shirley Douglas, number 4270 below), arrived some months later they were new AC30/4s. The amplifier was later recovered in black and a top boost module fitted. Existence noted by J. Elyea, p. 624.

Serial number 4270

Fawn covering, split front. Belonged to Shirley Douglas, p. 624. Existence noted by J. Elyea.

Serial number unknown - currently in the UK (?)

Old, old pictures, but a reasonably intact AC30/4 chassis and its rather battered cab. The drivers are Goodmans Audiom 60s, 15 ohms each. The cab is probably later - note the rounded corners to the back boards and the presence of new-style plastic handles. Are the speakers the originals from the original cab? TV front or split front?

Serial number unknown - currently in the UK (?)

Old pictures from ebay. One can just see the four inputs on the control panel. The serial number plate has distinctive wear. Speakers are hammertone/oyster T530/CT3757.

AC30/4s with Celestion blues - late 1960/early 1961 to late 1961

The amps below for the most part have Celestion T530 blue speakers. The earliest known to be original to speaker cabinet or serial number plate, are those that belonged to serial number 4606N, date code 16FF and 29FF = 16th and 29th June 1961.

Serial number 4290N - currently in the USA

Serial number 4290 also apparently belongs to a TV front amp (circuit said to be AC2/30) in light grey . "N" signifies normal (rather than bass) voicing.

Serial number 4304 N (?) - currently in the UK

The serial number plate, apparently deliberately scratched, is now on a refurbished beige cabinet containing a copper panel chassis from 1962 / 1963.

Serial number 4347 B - currently in the USA

Pictures from some time ago (the three smaller ones from 2005). The date code on the TCC capacitor by the choke is "RD" = April 1960. The detail of the plate has been blown up a little beyond its natural size to show the number better. A relatively rare early instance of a bass voicing.

Serial number 4400 - currently in the USA (?)

Existence noted by J. Elyea.

Serial number unknown - currently in the USA

The green TCC filter capacitor in the preamp has the date code "RC" = March 1960. The Hunts Tropydur capacitors have been replaced.

Serial number 4401 - currently in the USA

From the holes along the lip of the preamp it may be that this chassis was originally prepared for a TV front box but actually went out from the factory in a new split-front cabinet. No designation of voicing (normal or bass) on the serial number plate. Sold by in 2016/2017.


Serial number 4402N - currently in the UK

One Goodmans Audiom 60, one Celestion blue. The top edge of the back panel has three rather than two fixing points. Thanks to Richard for the pictures.

Serial number 4430 - currently in the USA (?)

Existence noted by J. Elyea.

Serial number 4495

Existence noted by J. Elyea.

Serial number 4530

Existence noted by J. Elyea.

Serial number 4570

Existence noted by J. Elyea.

Serial number 4586 N - currently in the UK

Sold in the UK in 2018. A nice example. Haddon transformers, the output transformer marked on its underside "0H083". Note the green Welwyn ceramic 80ohm cathode resistor in the second last picture. On the serial number plate the "N" for normal voicing.

Serial number 4606 N - currently in the USA

"AC30 4W" "4606 N" The "N" for "Normal voicing" was stamped over a "B" for "Bass". The cab is later - from 1964, with rounded corners to the backboards, basketweave vinyl, and black vents.

Date codes "16FF" and "29FF" = 16th and 29th June, 1961.

The amp does not survive, but its serial number plate and speakers, which travelled together, do. Given the date of the speakers, the amp will have been ready for sale in early June 1961. Thanks to Chris for the pictures.

Serial number 4627B - whereabouts unknown

Serial number 4633N - currently in Europe

Said to be in Italy, but it may be elsewhere by now. The pictures, supplied by a potential seller (caveat emptor, as always), actually come from an ebay auction.

Serial number 46x9 N - formerly in the UK

Noted as having original components with date code March 1961. The choke in this amp was made by Radiospares. Mains and output transformers are Haddons. The serial number plate was preserved with the chassis.

Serial number 4669B - currently in the USA

Serial numbers unknown

Serial number unknown - currently in the UK

Excellent condition. The chassis is not original to the cabinet however (note the screw holes along the preamp lip), and the serial number plate belongs to the cabinet, not the the chassis. Good shots of the Haddon transformer label, and the RIC cone code of the alnico blues - "RIC 1FY". The choke, which is probably a replacement, has a Drake Transformers code: 292-426. The chassis is also pictured in another box refurbished with modern beige vinyl.

Serial number unknown - currently in the UK

Serial number unknown - currently in the USA

Two sets of pictures, one from Plexi Palace days long ago, the others slightly more recent. The output transformer is a Radiospares unit. The shrouds of the choke and mains transformer have been painted blue in place (note the brackets on the mains transformer) shrouds. The speakers are likely to be Celestion CT3757s.

Serial number unknown - currently in the USA

Distinctive in having one large round black control knob (the first on the panel), and five smaller (normal sized) ones. At some point in or after the mid 1960s, the electronics were overhauled - visible mustard capacitors have 1964 date codes.

Serial number unknown - currently in Australia

Superbly restored, the Celestion B024s from a Hammond Organ.

Serial number unknown - currently in the UK (?)

Note the cigarette burns near the outer handles. Grille cloth possibly renewed.

Chassis - currently in the USA

An AC30/4 chassis with "cooker" style knobs in a later AC30 head cabinet. Sold by Cream Street Music. The serial number plate on the cab belongs to the cab not to the amp. Haddon transformers in place; no visible date codes on components.

Chassis - currently in the UK

The aluminium preamp has been drilled for six input jacks (see the last picture, top left corner), the centre pair blanked off by the control panel. The Lemark transformer is a replacement.

Chassis - currently in the USA

Voltage selector set to 115v. The box, with its black basketweave covering and plastic handles, is later.

Chassis - currently in the USA

Voltage selector set for 115v. The fuseholder is a replacement.

Chassis - currently in the UK

The pictures originally here were actually of the chassis of AC30/4 serial number 4586 - see above.

Chassis - currently in the UK

A knocked-down AC30/4 chassis - the "Brilliant" and "Bass" tone control legends just visible - sold on ebay some time ago along with a selection of parts. The panel is interesting. The control legends and outer decorative band look normal; but the inner bands marking off the pairs of control are gone, and instead there are what look like incised markers.


Chassis - currently in the UK

Thanks to Steve, pictures of a black panel AC30/4, for the time being exterior only. The cabinet may be the original, but reworked (and recovered) in the 1970s. The speakers are Goodmans Audiom power range, red label, 8 ohms apiece.


Chassis - currently in Germany

Out and about recently on (October 2023), an AC30/4 chassis in a new cabinet. The mains transformer has been replaced, and some of the original hardware is lacking (pots, fuse holder, voltage selector, knobs, and input jacks), but the Haddon output transformer is still present along with the Radiospares choke and - ununusually - a good spread of the original WIMA Tropydur capacitors. Normally these were the first things to be replaced by servicemen.

On to .

Copper panels appear in the high 4000s, see this page - .