Serial number 15665 T, amp model and number machine stamped, voicing (T = Treble) hand-stamped.

Continued from the page on AC30s with serial numbers in the 14000s. So far no Super Twins with stray numbers in the 14000s have come to light.

Throughout the 15000s, as in the case of amps with numbers in the 14000s, one finds three models: the "Treble", designated with a "T" on its serial number plate; "Normal" voicing designated by an "N", and Bass designated "B". All three had their own schematics, in order: OS/056, OS/065 and OS/057. Some notes on the treble circuit, which was new in 1964, can be found on this page.

"TB" - also stamped on the plate - indicates that the amp was fitted with the Top Boost circuit (Treble/Bass Boost).

A growing collection of documents relating to the AC30 in 1964 can be found here.

Significant component date codes in amps on this page are mostly of mid 1964: June for a main filter capacitor made by TCC (serial number 15041); second quarter of '64 ("B/64") for Mullard "mustard" caps.

Transformers are Albions and Parmekos. At this point, Woden (hitherto used more or less exclusively by Burndept) was designing a simplified and cheaper set of transformers for JMI - see this page. Existing stocks had presumably been used up.

Celestion silver alnicos - the T1088 - designed for JMI in the Spring of 1964 did not wholly supercede the Celestion blue - the T530 - at first. Amps with serial numbers in the 15000s occasionally still have blues. The earliest date codes known for Celestion silvers are from the middle of May.

New grey control panels, which are also to be found sporadically on amps with numbers in 12000s-13000s, occur with increasing frequency in amps with numbers in the high 14000s and 15000s. Towards the end of the 15000s, new-style dome voltage selectors come in.

Most Twins have Burndept-made chassis; those produced by Westrex were generally alloted to Super Twins .Burndept chassis are always distinguishable by the flashes of paint (and red stamps) to indicate voicing; the presence of chassis numbers and the cut-outs in the aluminium preamp upright behind all three cage nuts. A page on the voicing colour codes can be found here. Notes on chassis numbers have been assembled here.

Detail of serial number 15084 (chassis produced by Burndept). The "T" and flash of red paint indicates at Treble model. Note the cut-out behind the cage nut. The chassis number is 05648.

As mentioned at the head of this page, serial number plates are normally machine stamped. The voicing - "N", "T" or "B" - is still hand stamped, however.

If anyone knows of further amps that should be incorporated on this page, do let me know.

Serial number 15023 T - currently in the Netherlands

Heavy black dimpled vinyl; copper panel; blue speakers. On the front grille a "BASS" logo, but the serial number plate says the amp is a TREBLE.

NEW

Serial number 15029 TB - currently in the UK

Assembled by Burndept, chassis number 07657. Grey panel with integrated top boost controls. The mains transformer has been replaced with a Lemark from an early 1970s AC30, possibly solid state rectified, as there is no GZ34 in the amp. Choke and output tranformer are original (Albions). In the preamp, WIMA and Mullard capacitors, the latter with "B4N" date codes = second quarter of 1964. The green TCC filter cap has "VC" = March 1964. Grille clothe replaced.

Serial number 15041 T - currently in the UK

Copper control panel. Basketweave vinyl. Black vents. A mixture of Mullard mustard and WIMA coupling capacitors in the preamp. The main preamp filter cap has the date code "VF" = June 1964. Speakers are Celestion silvers - T1088.

Serial number 15043 T - currently in the UK

Treble model. Black basketweave vinyl; copper control panel; silver Celestion T1088 speakers. The handles have blank panesl (no VOX logo).

Serial number 15050 T - currently in the UK

Much as serial number 15041. Copper control panel. Basketweave vinyl. Black vents. Wima and Mullard mustard capacitors in the preamp. Celestion silvers.

A second set of pictures shows: Burndept chassis number 07050; Mullard mustard capacitors in the premap generally with B4N date codes (second quarter of 1964); Albion transformers; and what looks to be the original GZ34 rectifier valve with the date code B4C2 = 2nd week of March, 1964.

Serial number 15058 T - currently in the UK

Treble model; chassis assembled by Burndept. Textured black vinyl; copper control panel; silver Celestion T1088 speakers. In the preamp WIMA and Mullard mustard caps, the latter with "a4N" and "B4N" date codes = first and second quarters of 1964.

Serial number 15068 T

Treble model; chassis assembled by Burndept; chassis number 07087. Black basketweave vinyl.

Serial number 15084 T - currently in the UK

Chassis number 05648, assembled by Burndept. Copper panel, link voltage selector. Parmeko transformers. In the preamp, WIMA and Mullard capacitors, the latter with "B4N" date codes = second quarter of 1964. One of the blue Hunts cathode bypass caps has "WYT" = 10th week of 1964. Basketweave vinyl, Celestion silver T1088 speakers. The original brown cover with "VOX" in white cursive letters survives.

Serial number 15098 T - currently in Europe

Celestion blues in this one, perhaps replacements as the wiring looks new.

Serial number 15101 T - currently in Germany

A really superb amp. Chassis number 05744; assembled by Burndept. Transformers are Albions. In the preamp, a mixture of WIMAs and Mullard mustards, the latter with date codes "A4N" and "B/64", respectively the first and second quarters of 1964. The main preamp filter cap has the date code "VF" = June 1964. The Celestion blues have Pulsonic cone codes "40 H1777".

Serial number 15119 B - currently in the UK

Chassis assembled by Westrex. Albion transformers. WIMA signal caps in the preamp. TCC electrolytics with date codes "UM" = December 1963. Basketweave vinyl, the original Celestion blues still in place. On the front, lower right, the BASS flag.

Serial number 15206 T - currently in the UK

Simply the wooden case with its serial number plate (no slider board). Brown grille cloth, black basketweave vinyl, chipboard baffle.

Serial number 15235 T - currently in Europe

Chassis assembled by Burndept. Parmeko transformers. A mixture of WIMA and Mullard mustard capacitors in the preamp. Silver Celestion speakers. The cabinet is signed by "Alice".

Serial number 15241 T - currently in the USA

Serial number 15257 T - currently in the Czech Republic

Chassis assembled by Burndept. Copper panel, brown grille cloth. The original black cover survives. Albion transformers. In the preamp, mustard capacitors with date codes "A/64" and "B/64" = first and second quarters of 1964. Link voltage selector. Thanks to Martin for the pictures.

Serial number 15273 T

Strangely, an AC30 Super Twin - Super Twins had long had a numerical sequence of their own at this point. Copper panel; brass vents on the amplifier section (repro or a late instance of originals?); original cables present.

Serial number 15325 T - currently in the UK

A refurbished cabinet. Copper control panel. Celestion silvers.

Serial number 15344 B - currently in the UK

Copper panel, Celestion silver alnico speakers.

Serial number 15405 T - currently in the USA

Copper control panel. Basketweave vinyl. Black vents. Celestion silvers.

Serial number 15417 B - currently in the UK

Copper panel, Bass model. Chassis assembled by Westrex. Albion mains transformer, Parmeko output and choke (?). In the preamp WIMA signal capacitors. Speakers are currently later Celestion Greenbacks. The cabinet, perhaps recovered in black basketweave vinyl, now has brass vents.

Serial number 15419 B - currently in the UK

Grey panel, Bass model. Chassis assembled by Burndept. Parmeko transformers. In the preamp, WIMA and Mullard mustard capacitors, the latter with date codes "A4N" and "B4" = first and second quarters of 1964. One of the blue Hunts cathode bypass caps has "HNT" or "HWT" = 21st or 27th week of 1964. The cabinet is covered with textured vinyl. Speakers are modern Celestion blues.

Serial number 15491 B - currently in the UK

Sold on ebay uk recently (October 2023). Chassis assembled by Burndept; Bass voicing; Woden mains transformer has the date code "HV" = August 1964 for its manufacture. Some fancy colouring in on the grille cloth. In the preamp, a mixture of WIMA and Mullard mustard caps, the latter with "B4N" and "B/64" date codes = 2nd quarter of 1964 for their manufacture. The blue Hunts electrolytics have "HIT" = 23rd week of 1964.

Serial number 15513 B - currently in the UK

Chassis assembled by Burndept; chassis number 08264. Grey panel; Parmeko transformers. In the preamp, Mullard mustard caps with "B/64" and "B4N" date codes = second quarter of 1964; and main filter cap dated "VG" = July 1964. The cabinet is covered in black textured vinyl; metal vents; original speakers replaced.

Serial number 15541 B - currently in the UK

Thanks to William, pictures of AC30 serial number 15541, well used over the years. The amp is one of the earliest known at present to have a "slot" voltage selector - to some extent transitional (for a very short time) between the earlier link type and the later "dome" selector. Slot selectors are also found occasionally on AC10s and AC50s, not so far on AC15s or AC100s.

Serial number 15600 - currently in the USA

Existence recorded by J. Elyea.

Serial number 15626 TB - currently in Norway

Chassis number 07308? Grey panel with integral Top Boost. Celestion silvers. The amp was probably exported to Norway early on - the voltage selector was removed and further fuses added to bring it into conformity with local legislation. The cabinet has the name "Janet B" inside - it was probably Janet who made the box ready, applying the vinyl, grille cloth, logo, and so on, possibly fitting the speakers too. Thanks to Tor for the pictures.

Serial number 15631 TB - currently in the UK

The serial number plate alone, sold in the UK in August 2022.

Serial number 15640 - currently in the UK

Grey panel, integral top boost. One of the original Celestion blues remains (note the orientation of the label), the Celestion silver probably a replacement. Textured (non-basketweave) vinyl.

Serial number 15641 T - currently in the UK

Sold on ebay in 2010. Grey panel, Celestion silver alnicos.

Serial number 15653 TB - currently in the UK

Chassis assembled by Burndept, number 07477; Parmeko transformers. In the preamp, Mullard mustard capacitors with date codes "A4N" and "B4N" = first and second quarters of 1964. Long with the amp, the original users manual and what may be a slightly later cover.

Serial number 15687 T - currently in the UK

Grey panel. The chassis is probably later, however (i.e. replaces the original one). Note the dome voltage selector.

Serial number 15653 TB - currently in the UK

Chassis assembled by Burndept; chassis number 07477. Grey panel; link voltage selector. Parmeko (?) transformers. In the preamp, Mullard mustards with "B/64" and "B4N" date codes = second quarter of 1964. Cabinet covered in basketweave vinyl; silver Celestion T1088 speakers.

Serial number 15724 B - currently in the UK

Serial number 15725 B - currently in the UK

Serial number 15877 TB

Grey panel with integral Top Boost controls; brown grille cloth; original Celestion T1088s in place. Purchased second-hand in 1975 for £50. Thanks to Michael for the pictures.

Serial number 15888 TB - currently in Sweden

Grey panel with integral top boost, Celestion alnico speakers. In accordance with Scandinavian legislation, the voltage selector has been removed and the numnber of cycles excised from the serial number plate.

Serial number 15952 T - currently in the USA

Assembled by Burndept. Parmeko transformers. WIMA and Mullard capacitors in the preamp, the latter with date code "B4N" = second quarter of 1964. One of the yellow-print Mullard ECC83s has the date "LA" = January 1964.

Serial numbers unknown

Chassis number 05619, assembled by Burndept. A treble model. Grey panel; Albion transformers. In the preamp, a mixture of WIMA and Mullard mustard capacitors, the latter with "A4N" and "B4N" date codes = first and second quarter of 1964. The blue Hunts cathode bypass caps have "HYT" = 20th week of 1964. Silver Celestion speakers (T1088s).

On to serial numbers in the 16000s.

Back to serial numbers in the 14000s.