Cathode-biased AC80/100s - early grey panel amps

Spring and 1965

Serial nos 320 - 380

GREY PANELS, DOME VOLTAGE SELECTOR, SMALLER CHOKE

Continued from

In early 1965 Vox transferred production of the AC80/100 from Westrex, one of its principal contractors in 1964, to the Vox / Burndept works on West Street, Erith. Certain new elements were subsequently brought in: the smaller choke (rated at 19H 100mA), white Erie resistors, and a chassis number stamped on the left hand side of the aluminium preamp upright (normally just above the terminal block for the output connections) - all marking a break with standard Westrex practice. Gone too is the red dye on the solder joints.

A small run of amps with was produced initially. Thereafter they were grey.

Many of these amps were shipped to the US in 1965, probably in large batches.

As a result of problems encountered in 1965 with heat build-up, JMI redesigned the AC100, changing its circuit to fixed bias in autumn of that year - the "100W amplifier". For examples of these amps -

Serial number 320 - currently in the US?

  • 320
  • 320
  • 320
  • 320

Sold on ebay some time ago. Grey panel, dome voltage selector, and Woden transformers with unpainted shrouds. The code on the (small) choke is AW = January 1965, and the codes on the mains and output transformers BW = February 1965 - the same as for serial number 337, below. The amp seems later to have been changed to fixed bias - note the new 220K grid resistors in the last picture. Thanks to Paul Johnson for the images.

Serial number unknown - currently in the US

  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s

This amp actually inhabits the box with serial no. 880 - . The chassis number is 1040. The serial number of the original box will have been somewhere in the 300s. Transformers are Wodens with unpainted shrouds, the choke is of the later stand-up type (19H 100mA). There are a few new components in the preamp, but otherwise all intact. Condition is great. Thanks to Dave for the photos.

Pictures pre-restoration (ie. as above)

  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s

Pictures post-restoration (2015)

  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s
  • 300s

Expertly restored by BLC.

Serial number 323 - currently in the US

  • 323
  • 323
  • 323

A nice early grey panel AC80/100 with a handsome bass rig. Thanks to Christopher for the pictures. Below, the original box.

  • 323
  • 323
  • 323
  • 323
  • 323
  • 323
  • 323

Box of serial number 323, now in the UK. Made by GlaRev - the stencil just visible on the left hand inside. Single fixing point along the top edge. Arrangement of back panel as in no. 328, below. The Cannon connector was just popped in for the photo.

Serial number 328 - currently in St Louis

  • 328
  • 328
  • 328
  • 328
  • 328
  • 328

Chassis no. 1007. Grey panel; Woden transformers with unpainted shrouds, date code "BW" = Jan. 1965, as most AC80/100s on this page (evidently a job lot bought in by Vox). Carefully restored to full working order by the present owner. The wiring and various components in the power section had suffered from current-induced heat damage, the original bias resistors really only being correct for 110V, not the 120V delivered from wall sockets. Original connectors on the back panel. On the front, a cloth similar to that used by Jennings Electronic Industries. However, inspection showed that there were no signs of its having been replaced (no "old" staple holes in the white piping) - and there is reported to be one other amp in this rare custom cloth. This AC80/100 was acquired from the studio of Oliver Sain, friend of (and occasional musical collaborator with) Ike Turner, a Vox-endorsed artist. It is likely to have been part of a batch imported by the Thomas Organ Company in early to mid 1965 for sale in the US (note also the US provenance of serial numbers 331, 337, 406, 416 and 420 on this page).

Serial number 330 - currently in the US?

No pictures available, but reported as having a black panel by J. Elyea, Vox Amplifiers, p. 446. for a discussion of AC80/100s with black panels on a Plexi Palace thread.

Serial number unknown - though certainly 300s - currently in the US

Chassis number 1011. Grey control panel; Woden transformers. Reported by the amp's owner on a beatgearcavern.com thread.

Serial number in the 300s? - currently in the UK

  • 300s

Left, Picture from D. Petersen and D. Denney, "The Vox Story", p. 54. Right, a still from the BBC documentary on Vox - the man pictured is Alan Harding, one of Vox's chief engineers. Note the chassis behind him - silver transformers, stand-up choke. The trailer is available on the . Note also the 760 amp, minus a few knobs.

Serial number 331 - currently in Florida (collection: Kent Pearson)

  • 331
  • 331
  • 331
  • 331
  • 331
  • 331

Chassis number 1032. Cathode biased. A nicely restored AC80/100, in the first picture sitting on top of a reproduction cabinet and trolley made by North Coast Music. The second picture shows the new reproduction copper panel, along with the original white warning plaque, serial plate and speaker XLR. In the other pictures one can see the new-style choke, and the white Erie resistors, which one also finds in AC100 Mk2 amps.

331

A great shot of the amp, cab and Telecaster.

Serial number 337 - currently in Sweden

  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337
  • 337

Sold in October 2010. Cathode biased. A nice clean AC80/100, probably made close to the end of the "formal" cathode biased production run. In the second quarter of 1965 JMI evidently assembled cathode biased amps side by side with the new fixed bias ones. Note in this instance the small choke, dome voltage selector, Cannon LNE-32 mains socket, and unpainted shrouds on the Woden transformers. This amp was for years pictured on the Vox website (in their archive) with the suggestion of possible use by the Beatles, a claim that unfortunately cannot be substantiated. Capacitor codes WA = January 1965; the Woden choke AW = January 1965; and the Woden mains and output transformers BW = February 1965. The last picture shows the amp in its new home in company with an original T60 cab and reproduction trolley.

Serial number 338 - formerly in the USA

  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338
  • 338

Sold in October 2012 (Heritage Auctions, first set of pics); and on ebay in January 2012. Chassis no. 1039. Good overall cosmetic condition. Converted from cathode bias to fixed bias (and the preamp also adapted to the fixed bias circuit). Main filter capacitors replaced. The output transformer has the code - "BW", as in the amps above and below; and the choke - "AW". The mains transformer is a replacement. Back panel arranged originally as serial no. 337 (above).

Serial number unknown - probably in the 300s

  • mid 300s
  • mid 300s
  • mid 300s

Sold on ebay some time ago. Box in good condition. Grey panel, dome voltage selector, Woden transformers with unpainted shrouds, cathode biased - further capacitance added later in the power section (image 3). The original cathode biasing resistors and capacitors are still in place.

Serial plate unstamped - probably in the 360s - currently in the USA

  • mid 300s
  • mid 300s
  • mid 300s
  • mid 300s
  • mid 300s
  • mid 300s
  • mid 300s
  • mid 300s
  • mid 300s
  • mid 300s

Chassis no. 1055, but no serial number on the back panel. Cathode biased (which one can tell from the preamp tagboard); small upright choke; white Erie resistors; dome voltage selector; transformer shrouds unpainted. The red warning plaque is a repro. The amp now has a new reproduction thin-edged box, matching the repro 2x15" cab. The original box survives, however, in good condition (photo 1). Thanks to Donald for the pictures.

Note that the un-numbered serial number plate is similar to one that sold on ebay in 2007 (below). At this point in production warning plaques were normally white.

  • mid 300s
  • mid 300s

LATER RUN CATHODE BIASED AMPS

(second quarter / mid 1965)

In 2002, a fascinating discussion took place on VoxTalks about these later amps. The archive of VoxTalks is now defunct, but the discussion is available in this PDF - download here. "TedB" is Ted Breaux, the guiding light behind Jade Liqueurs ).

Serial number 370 - currently in the USA

  • 370
  • 370

An amp sold on ebay in September 2012 with this serial number. The serial plate is unlikely to be original to the chassis however - a number in the low 500s being more probable. See for further information.

Serial number 380 - currently in the USA

  • 380
  • 380
  • 380

Chassis no. 1080. Cathode biased. Illustrated in J. Elyea, Vox Amplifiers, pp. 447, 449. Two further pictures added. Standard back panel arrangement - serial number plate in the centre, XLR and mains sockets centred vertically left and right, white warning plaque above the former.

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