This page picks up from the first page on AC10 Twins, late 1961 to mid 1964, which can be found here.

As has been mentioned, in mid 1964 JMI decided to assign to the Twin a new serial number sequence, much as it had for the AC30 Super Twin, the AC30 Expanded Frequency, and the AC15 Twin. The old AC10 Twin sequence ranged from around 3500 to 4500; the new one began at 1000. Single speaker AC10s continued through to around serial number 4900, at which point the model was deleted from the catalogue. AC10 Twins were still offered by sale for JMI in 1967.

Above, details from the Vox Amplifiers manual printed in October 1966 (10.66).

Detail from the JMI retail pricelist of April 1967.

From late 1964, the main drive was exports, particular to Thomas Organ in the USA following the "Million Dollar Deal" announced in late August 1964. Further multi-million dollar deals followed through to mid 1966.

During the course of 1964 and 1965, the majority of AC10 chassis were produced under contract for JMI by Westrex (North London) and Burndept Electronics (Erith). Triumph, which had produced large numbers of chassis from late 1961 through to early 1963, assembled small batches only - probably on special demand.

The relevant circuit diagram is OS/008, first drawn in September 1960, and updated twice in 1964 (once on the 7th September, again on the 16th). Note that these sheets are not assembly "blueprints". They were prepared for repairmen after the fact, and sometimes contains errors and small changes introduced during the course of production.

The highest chassis number for a Burndept-made AC10, appears at present to be 2426 (written report). Chassis number 2200 on another amp is attested in photos. At any rate, somewhere around 1425-1500 in total were assembled by the company. Most of the rest - around 500 or so - were made by Westrex, though a small batch or two was produced in this period (as mentioned) by Triumph.

At first, Burndept stamped its chassis numbers on top of the plinth, as it did also on the AC30 (the first 1000 or so it produced, autumn 1962 - mid 1963). Later, the number was stamped on the aluminium preamp upright underneath the voltage selector (as also on AC30s).

AC10 SER. No. 01280.

Initially stamped as AC10 SER. No. 2166 (?), re-done as 2200.

Below, a detail from a picture taken at 115 Dartford Road on the occasion of a visit by the Baron Knights in early August 1964. At left, a newly-assembled AC10 Twin with silver Elac speakers.

Detail of a photo taken at 115 Dartford Road, early August 1964.

Transformers

Transformers were sourced from both Parmeko and Albion. Units from the two makers were rarely mixed in a single amp. In terms of part numbers, Parmeko recorded two on its tranformers, one the JMI number, the second its own: mains = "66479" (JMI), "4E6142" (Parmeko); output = "66480", "4E6143"; choke = "66481", "4E6144".

Albion generally applied typed paper labels to its tranformers. These recorded the general characteristic of the units: - mains = "MT/300/120" (mains transformer, 300v secondary, and 120mA; output = "8/K/15" (8 ohms, common, and 15 ohms); choke = "10/120" (10 Henries rather than the 8H of the circuit diagram, 120mA choke).

A typed Albion sticker (upside down) on an AC10 mains transformer. The legend reads "ALBION" "MT/300/120".

Speakers

Speakers initially were a pair of ten-inch Elacs, model 10N/81, 15 ohms apiece, frames sprayed Jennings blue - wired in parallel for a total impedance of 8 ohms. Blue Elacs were also used in early Vox Line Source 40 speaker columns - the 10N/81 at first (four wired in series/parallel), then the 10N/82 (3-4 ohms apiece, four wired in series). The full trading name of Elac it should be said was "Electro Acoustic Industries Limited", factory in Tottenham, North London.

In the autumn of 1964, with the introduction of the new grey panels, Elac supplied JMI with speakers sprayed hammertone silver/grey. Early examples are stamped 10N/85 and have the same "tin-can" form of magnet cover as the earlier blue Elacs. Later ones have slightly smaller magnets and covers ("bells") with rounded ends. The new silver frames, both early and late, were often stamped "8431" (not "6431 as previously stated). Cones were made by Pulsonic (an example further below stamped "24/434/001").

One of the speakers in AC10 Twin serial number 1379. The cone code is partly obscured in the photos, the legible part being "...34/001".

It may be that the five-digit number stamped on the cork gaskets of most Elacs contains the date code. This is highly provisional for the time being, but so far the system holds. The first two digits are the month, the third the year. So in the case of a blue 10N/81: "10359" is 10th month of 1963; and in the case of a silver: "01656" = 1st month of 1966. Quite what the final two digits stand for is unknown.

Cabinets

The move to the new serial number sequence corresponds, so far as can be judged, with the move to a sturdier style of cabinet with thick edges. Quite whether there was any period of transition is not clear at present. AC10 Twin serial number 4505 has a thin-edged cabinet; all the amps illustrated on the page below - the earliest being 1076 - have thick-edged cabinets.

Thin-edged cabinet.

Thick-edged cabinet.

Dates

Effectively there are three points of departure to take into account: (1) the assembly of the chassis; (2) the completion of the AC10 as a whole - the point at which it was ready for sale; (3) the actual sale - whether to a shop, dealer, or an individual. It should be said in relation to (1) that the latest component date codes found so far in an AC10 are of early 1965. The picture, in provisional outline, is that assembly of chassis in 1964 and 1965 outstripped sales to a fairly large degree - ie. that in 1965 and 1966 JMI was selling AC10s containing chassis that had been assembled many months before.

An overview of surviving AC10 Twins (mid 1964 - 1967)

Serial numbers beginning at 1000 and stretching through to the 3100s. By the 1300s, and probably for some time before, grey panels are standard.

Note that all serial number plates are still hand stamped.

Serial number 1046

Thick-edged cabinet; basketweave vinyl. Chassis assembled by Westrex; copper control panel; link voltage selector. Albion transformers. In the preamp, the main filter cap has the date code "UG" = July 1963 for its manufacture. In the power section, the cathode bias resistor has the date code "UM" = December 1963. The original blue Elacs are present.

NEW

Serial number 1055

Thick-edged cabinet; basketweave vinyl. Chassis assembled by Westrex; copper control panel; link voltage selector. An additional (impedance matching?) transformer has been added under the chassis slider board. The original blue Elacs are present.

Serial number 1076

Copper panel, blue Elacs, link voltage selector. The cabinet covered in basketweave vinyl. The cover is a Thomas Organ cover, identifiable by the slits up its side (to allow for a swivel stand) - probably for an AC15 rather than an AC10.

Serial number 1089

Chassis assembled by Westrex. Copper control panel; Albion transformers; link voltage selector, blue Elac 10N/81 speakers.

Serial number 1111

Copper panel, link voltage selector, blue Elacs.

Serial number 1151 (or 1161)

Chassis assembled by Burndept; number 1004. Grey panel, link voltage selector, Albion transformers. The mains transformer has been replaced, so too the original speakers. In the preamp, visible Mullard mustards with date codes "B3N", "A4N" and "B4N", respectively second quarter of 1963, and first and second quarters of 1964.

Serial number 1155

Grey panel, link voltage selector, early silver Elacs with "can" magnet covers. The mains transformer is new. Almost all capacitors and resistors replaced.

Serial number unknown

Copper panel; dome voltage selector. Parmeko transformers. The speakers are a pair of Celestion T7442s (15 ohms apiece). The cabinet has black grille cloth and double pin corner protectors (either 1966 and later, or repro.).

Serial number unknown

As above, copper panel; dome voltage selector. Parmeko transformers. The presence of Mullard mustard capacitors in the preamp indicates the chassis was assembled by Burndept. Speakers replaced with modern Celestions.

Grey panels standard from this point

With the grey panels come silver Elac speakers

Serial number unknown

Chassis probably assembled by Burndept. Albion transformers. The serial number plate is a repro with an impossible number. Grey panel, link voltage selector. In the preamp, the Mullard mustard capacitors have the date codes: "B3N", "B4N" and "B/64", respectively the third quarter of 1963 and second quarter of 1964. The silver Elacs are of the early type, with "can" covers.

Serial number 1275

Grey panel, link voltage selector. Sold in the UK fairly recently. No shots of the electronics unfortunately. The speakers are silver Elacs.

Serial number 1277

A Twin, grey contol panel. Original silver Elacs and footswitch present.

Serial number 1281

A Twin. Only the serial number plate known at present.

Serial number 1325

Chassis assembled by Burndept; Parmeko transformers (with JMI part/stock numbers printed on the stickers). Slot voltage selector. Silver Elac speakers.

From this point Arrow black bat ON/OFF switches come in

Serial number 1329

Assembled by Burndept; chassis number 01473. Parmeko transformers; slot voltage selector. In the preamp, Mullard mustards with a spread of date codes: "C3W", "B4N", "B/64", and "C4N", respectively third quarter of 1963, and second and third quarters of 1964. The original silver Elacs and footswitch are present. One of the Elacs has cone code 26/43[4/001]. Pictures to follow.

Serial number 1350

An AC10 Super Reverb Twin reported by J. Elyea, p. 529.

Serial number 1354

An AC10 Super Reverb Twin, amplifier section only, no mention of the model on the plate though. In the preamp, a "Fender" sticker.

Serial number 1365

Chassis assembled by Burndept, number 01280. Albion transformers. Dome voltage selector. The speakers, probably replacements, are Celestion T7442s.

Serial number 1379

An AC10 Super Reverb Twin. Grey panel; link voltage selector, brown grille cloth; early silver Elac speakers. In the preamp, Mullard mustard capacitors with date code "B/64" = second quarter of 1964.

Serial number 1382

Nothing further known of this amp at present.

Serial number 1412

An AC10 Super Reverb Twin. Good condition. Grey panel; link voltage selector, brown grille cloth.

Serial number 1427

Assembled by Burndept; chassis number 01374. Grey panel; voltage selector removed; grille cloth renewed.

Serial number 1461

A Twin. Assembled by Burndept; chassis number unknown. In the preamp, the visible Mullard mustard caps have "B4N" and "B/64" date codes = second quarter of 1964 for their manufacture. The original silver Elacs are in place. The footswitch is present too.

Serial number 1468

Chassis assembled by Burndept; number 01617. Slot voltage selector. Parmeko transformers. In the preamp, Mullard mustards with "B3W", "B/64" and "C4N" date codes = respectively third quarter of 1963, and second and third quarters of 1964. Further pictures can be found here.

Serial number 1485

Chassis assembled by Westrex; Parmeko transformers. Dome voltage selector. In the preamp, gold-coloured WIMA Tropyfol capacitors.

Serial number in the 1580s (?)

Serial number is indistinct, but could be 1583. An AC10 Super Reverb Twin. Grey panel, link voltage selector. Chassis assembled by Burndept. Apparently Parmeko mains and output transformers, and an Albion choke. Brown grille cloth.

Serial number 1614

Probably assembled by Burndept; Parmeko transformers. Grey panel; voltage selector since removed. In the preamp, Mullard mustard caps with visible date codes "C3W" and "B/64" = third quarter of 1963; second quarter of 1964. Silver Elacs with cone code "24/434/001".

Serial number in the 1600s

Assembled by Burndept; Parmeko transformers. Much as the amp above (serial number 1614). Grey panel, perhaps exported to Scandinavia early on (new internal fuses provided to comply with local legislation). In the preamp, Mullard mustard caps with visible date codes "C3W, "B/64" and "B4N" = third quarter of 1963; second quarter of 1964. One of the Hunts capacitors has the date code "HWT" = 21st week of 1964 for its manufacture. The Elacs have cone code 32/[434/001].

Serial number 1616

From this point, some chassis numbers have four digits only

There is no prefatory "0" for chassis with numbers higher than 1800.

Serial number 1623

Assembled by Burndept; chassis number 1867. A spread of Mullard mustard capacitors in the preamp, ranging from "C3W" = third quarter of 1963, to "C4N" = third quarter of 1964. One of the speakers (certainly) comes from a Vox Line Source 40 column.

Serial number 1635

Chassis number 2452. Parmeko transformers. The speakers are not original to the amp - a set of pictures of this amp exists with an entirely different pair in place. In the preamp, Mullard mustard capacitors with date codes "B/64", "B4W" and "D4N", respectively second and last quarters of 1964 for their manufacture. The original dark red cover survives.

Serial number 1689

Chassis produced by Westrex. Albion transformers. In the preamp, Mullard mustard caps with date codes "B3N" and "B4N", respectively third quarter of 1963 and second quarter of 1964 for their manufacture. The blue Hunts electrolytic has "WUx" - probably the 16th week of 1964 (rather than 1965).

Serial number 1722

Grey panel; dome voltage selector. One original silver Elac remains; the other is a Celestion.

Serial number 1808

Chassis assembled by Burndept; number 01521. Parmeko transformers; slot voltage selector. In the preamp, Mullard mustard capacitors with date codes "C3W", "A4N", and "B/64" = respectively third quarter of 1963, and first and second quarters of 1964. The main preamp electrolytic - a blue Hunts cap - has the date "HIT" = 23rd week of 1964.

Serial number 1818

The plate is one of those oddly stamped repros, so the serial number (and place here) is purely provisional. The amp's original cover survives.

Serial number 1825

Serial number 1890

Chassis assembled by Burndept; number 01910 (?). Parmeko transformers. Grey panel; dome voltage selector. In the preamp, Mullard mustard capacitors with date codes - "B/64" and "C4N" = second and third quarters of 1964. The Elac speakers are wired in parallel (not series as previously stated).

Serial number 1930

Chassis assembled by Westrex; Albion transformers. Dome voltage selector. Silver Elacs with "43/434/001" cones. In the preamp, gold-coloured WIMA Tropyfol signal caps. One of the gold-coloured TCC bypass caps has the date code "VF" = June 1964.

Serial number 1956

Not a thing changed in the preamp or on the upper chassis. Chassis number 1981; Parmeko transformers. In the preamp, Mullard mustard capacitors with date codes "B4W" and "C4N" = second and third quarters of 1964 respectively for their manufacture. The Mullard valves have the paint date code (final finishing of the valve) "LJ" = September 1964. The original Elac speakers are still in place. Thanks to Paul for the pictures.

Serial number 1997

On to AC10 Twins with in the range 2000-3200.

For earlier AC10 Twins see this page.

The main AC10 index page can be found here.