An early Vox AC80/100 with no control panel legends

Preamp

An early AC80/100 with no legends on its control panel, continued from the previous page.

There are only three changes in the preamp - two filter capacitors and one resistor. The date code of the remaining Dubilier filter cap is "UH" = August 1963. The date code of the volume pot (made by Egen) is "LK" = December 1963.

Interesting to note that the amp came with three yellow-print Mullard preamp valves with date codes for June and November 1963. But instead of two ECC82s (V1 and V3 on the schematic) and one ECC83 (V2), there are one ECC82 (V1) and two ECC83s (V2 and V3). An ECC83, if balanced and of low noise, works perfectly well from an electronic standpoint in position V3, i.e. as the driver valve. The result: more gain.

For related amps, see the main . The pictures below were taken in 2020. Click on the thumbnails for larger versions.

Dubilier filter capacitor, date code "UH" = August 1963. The other two caps were replaced with grey 1970s Radiospares caps.

1970s Radiospares replacement for the original Dubilier filter capacitor.

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1970s Radiospares replacement for the original Dubilier filter capacitor.

A detail of the date code on the Egen volume pot - "LK" = December 1963 - photographed in a small mirror and the image reversed.

The original yellow-print preamp valves - one ECC82 and two ECC83s. The date codes for the final finishing of the valve - the application of the yellow print paint - are found either side of the BVA logo: "KF" = June 1963 and "KK" = November 1963. The date codes for the making of the valve itself are "B3H2" (ECC82) = 2nd week of August 1963; and "B3J2" (one of the ECC83s) = 2nd week of October 1963. The date code of the second ECC83 - the one on the far right in the picture above - is very feint, but the first three elements look like "B3F" = June 1963, which is borne out by the date code for the application of the yellow print.

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