Vox AC30: copper panels

Early to mid 1964: serial numbers in the 11000s

Serial number 11954 Treble.

In progress, April 2020

Continued from the page on AC30s with . Also encompassed below, some of the last Super Twins that were given numbers in the main AC30 sequence.

The new thing in the 11000s is the appearance of the new "Treble" model, for which a dedicated schematic was drawn out on 10th September 1964. One needs to be careful though. At least one amp on this page with a "T" on its serial number plate (to denote "Treble" voicing) is actually a "Normal" model.

The only way to determine voicing for certain at this point is to check the value of capacitors at key points in the circuit.

True "Treble" chassis regularly (though not infallibly always) have TREBLE stamped in red; BASS on bass-voiced amps.

Documents relating to the AC30 in 1964 are being assembled .

Vox contracted out the assembly of AC30 chassis to two companies: Burndept Electronics in Erith, and Westrex in Dollis Hill (north London). A sure sign of production by Burndept is the presence of a stamped serial number on the aluminium upright of the preamp chassis (normally on the right hand side a little way below the voltage selector):

Detail of serial number 9916. Chassis number 02607. The sequence began at 1000, but chassis awaiting assembly were not used in any particular order.

Also indicative of production by Burndept at this stage is the presence of Woden transformers with handsome green shrouds. Serial numbers in the 11000s (much as those in the 10000s) have date codes for late 1963 - "JU", "KU" and "MU" = September, October and December 1963; and early 1964 - "AV" and "BV", respectively January and February. JMI evidently ordered sizeable batches:

Serial number 11954 - date code is "AV" = January 1964.

The Woden part numbers were, in order: mains transformer 72318; output transformer no. 66310; and the choke no. 66311.

A good indication that a chassis was assembled by Westrex is the presence of Albion tranformers. Dark brown Dubilier resistors are found along with white Eries.

Cabinets are for the most part covered in black basketweave vinyl, though "pebble" ("dimpled") vinyl was evidently used from time to time, and likewise smooth black or charcoal vinyl. Back boards as a rule now have radiused corners rather than square.

Speakers in "standard" AC30s continue to be the Celestion blue (alnico magnet, Celestion part no. T530) - date codes in mid 1964, the final "H" in the code can indicate 1963 or 1964. The preceding letter is always the month (A-L).

Serial number plates are still hand stamped.

Just to note again, "N" indicates "Normal" voicing (schematic OA/026 and OS/065), "B" is bass voicing. No early schematic survives for the bass circuit, though in relevant respects most amps (from 1962 on) follow OS/065, drawn in September 1964. "T" denotes Treble voicing - schematic also drawn in September 1964: OS/056.

Notes on the "Treble" circuit will be provided shortly. The key capacitors to check are C5 and C7 (0.01uf, or 10000pf if they are Mullard mustards); C6 and C9 (0.047uf, or 47000pf mustards); and C10 (0.0022uf, generally a gold-coloured WIMA).

The page on AC30s with serial numbers in the 9000s, , and the page on serial numbers in the .

If anyone knows of further AC30s that should be incorporated on this page, .

Serial number 11137 T - currently in the UK

Cabinet recovered in beige. The plastic serial number plate has blackened as in the case of the amp below.

Serial number 11167 B - currently in the UK

Plastic serial number plate blackened as in the case of 11556 below.

Serial number 11350 - currently in the USA

Existence recorded by Jim Elyea.

Serial number 11452 T - currently in the UK

Pictures to follow

Serial number 11542 T - currently in the UK

Serial number 11556 T - currently in the UK

Currently (April 2020) on . Red paint over the original black covering. The "T" on the serial number plate denotes "Treble", but the circuit is actually "Normal". One of the Celestion blues has the date code 17MH which may be 17th December 1963.

Serial number 11571 T - currently in Europe

Note the blackened plate, much as serial number 11556, above.

Serial number 11613 T - currently in the UK

Complete with its original green cover. The Woden transformers have the date code "AV" = January 1964. The choke has "BV" = February 1964. In the preamp, the Hunts bypass capacitors have "IDI" = 38th week of 1963; and the filter cap underchassis "TSI" = 45th week of '63. Note that the cathode resistor is 47ohms.

NEW

Serial number 11718 T - currently in the UK

The cabinet still has its "Super Twin" runner. The chassis is unusual in having a Woden output transformer and choke, date codes respectively "JU" and "KU" = September and October 1963, and an Albion mains transformer.

Serial number 11727 T - currently in the UK

Old pictures. The Woden mains and output transformers have the date code "AV" = January 1964.

Serial number 11739 N - currently in the USA

In great condition, a Super Twin, chassis assembled by Westrex. Transformers look to be Albion. The original Celestion blues are in place in the speaker cabinet.

Serial number 11769 T - currently in Europe

The Woden transformers have date codes "JU" and "MU" = September and December 1963. The choke has "HU" = August 1963.

Serial number 11800 - currently in the USA

Existence recorded by Jim Elyea.

Serial number 11874 T - currently in the USA

Pictures coming soon.

Serial number 11912 N - currently in the UK

Sold on ebay in the USA some time ago. The serial number was said to be 11912N, but the chassis stamped "Westrex Treble". Top boost added later "a replica".

Serial number 11954 T - currently in the UK

Formerly owned by Max Boyce. Thanks to Phil for the pictures.

Serial number 11973 T - currently in the UK

Sold on ebay.uk some time ago.

Serial number 11974 T - currently in the USA

Serial number 11997 T - currently in the USA

.

.