List of updates / new info. on Vox solid state amps (1967-1972)
Updates for September and October 2017
Just a quick note on early Supreme / Super Foundation Bass power sections. In the very earliest, the upright on which the transistor assemblies are mounted ends with a straight edge. The same is true for the first batches of Conqueror and Defiant power sections.
Below, a detail of power section no. 1029 (in an early Supreme). Note that the aluminium fins are level with the upright's top:
In later batches the upright has a lip, rolling over the bias resistors, as below. The aluminium cooling fins extend above it:
So far as one can tell, the change came in after the first 120 or so chassis had been made - ie. around 60 Supremes and 60 Super Foundation Basses.
Short entry for Supreme no. 1030 now added, along with one for serial no. 1047, which is on Reverb at present. Its original preamp may have been replaced.
Some quick pics of power amp and preamp of Supreme no. 1030. The preamp is 01390; the power amp 01164. The latest dateable element in the preamp is a yellow Lemco capacitor, "YC" = March 1967. In the power amp, a red CCL filter cap, "B7" = February 1967.
A few repairs were made to the amp in the 1980s/1990s - new black plastic input sockets and a few resistors and caps., but otherwise condition is not at all bad. The metal bath handles on the box will have to go though.
Supreme serial no. 1030 has just surfaced - well-used and needing some attention, but otherwise perfectly sound. Early Supremes were run hard. For others, see this page.
A page on the pre-production Traveller is now available here.
Some notes on pre-production solid state amps.
Examining an early Traveller, Steve Walsh recently found that "the tone stacks on both channels are identical to the Mk1 SS amps. The tremolo board seems to be almost identical to the USA version. The reverb board is identical to the UK SS ones. The distortion is unlike anything I've seen in either US or UK amps. That said, it sounds great! It's permanently on in this amp unless switched off via footswitch."
"It uses diodes for clipping, rather like the 7 series but there are only 3 transistors on the entire board."
The design process continued nonetheless, bringing in a new version of the distortion circuit, a new board (the mixer board), and other adjustments.
Above, the power socket on a pre-production Defiant currently in the UK. The socket is a 15A socket made by the Edison Company (USA), peculiar to find on a British amp. Perhaps these were imported along with RCA transistors and so on.
It is fantastically difficult to find a connector that fits - no luck yet. Above, a Hubbell Edison female plug from the 1980s, fractionally too big as all modern versions are, and perhaps those from the 1970s too. The Vox takes a connector of 1 1/4" diameter. The yellow one above is 1 3/8". Note also it has a square earth insert rather than circular.
13th September (2)
Above the latest known serial numbers so far (for which there are pictures) of amplifiers in the JMI range - Traveller to Super Foundation Bass. The Virtuoso is in the entry below. Late amps have "AMPLIFIER" at the head of the serial number plate rather than "VOX AMPLIFIER"
Traveller ser. no. 1297 "AMPLIFIER".
Virtuoso ser. no. 1238 "VOX AMPLIFIER".
Conqueror ser. no. 1565 "AMPLIFIER" (number 1581 is known but no shot of the plate).
Defiant ser. no. 1587 "AMPLIFIER".
Supreme ser. no. 1285 "VOX AMPLIFIER".
Dynamic Bass ser. no. 1241 "VOX AMPLIFIER" (but there is a later Dynamic with "AMPLIFIER" alone on the plate).
Foundation Bass ser. no. 1536 "AMPLIFIER"
Super Foundation Bass ser. no. 1229 "AMPLIFIER"
This list will be adjusted as further amps come to light. Very late JMI Virtuosos and Supremes - ie. later than the ones noted above - presumably also have "AMPLIFIER" alone at the head of their plates.
In terms of numbers, JMI (1967 to mid 1968) evidently produced around 600 Conquerors and Defiants, 550 Foundation Basses, and substantially fewer everything else.
The plate of Virtuoso serial number 1238 - further pictures here. If the sequence began at 1000 - amps made by VSEL certainly begin at 2000 (though there are no VSEL Virtuosos) - this was the 239th Virtuoso made, probably one of the last.
Some new Virtuosos without reverb added at the foot of the Virtuoso page.
10th September (2)
Below, the box for a Vox ("Jennings Musical Industries") piano mic. - not much seen these days. Perhaps earlier than 1967; here simply for interest.
An original copy of OS214 - the schematic for the Vox PAR100SS - has recently come to light. It apparently contains no notes of dates. "Equipment" in the legend "Vox Sound Equipment Ltd", however, has clearly been erased in two instances to leave "Vox Sound Ltd". Vox Sound Equipment Limited (VSEL) became Vox Sound Limited (VSL) in the summer of 1970.
The two details below have been flattened out from very oblique shots. Click as ever for larger images.
Above the printed circuit board from the preamp of a Vox PAR100SS, corresponding to the detail of OS214 immediately above. Note that the board is PCA5/2 B - "B" doubtless indicating a later revision. The presence of the "Birch Stolec" stamp - feintly visible just off centre - indicates that this PAR100SS was assembled after August 1971.
Above a prototype Traveller just come to light. Further details to follow. This represents a similar state of development to the Traveller already known - more pics on this page:
Defiant serial number 2086, "Vox Sound Equipment Limited", now registered here.
Pictures of Supreme no. 2210 now posted here.
Some details of a scrapped Vox PAR100SS posted here, mainly to show the arrangement of the chassis, and the preamp.