Uploaded May 2020 | Updated September 2026, 1 week ago

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Original Voc AC15TB from about 1963/64.
With factory fitted Top Boost circuit.
Also factory mod from EF86 to ECC83 at the same time.
Copper panel version with Celestion Blue speaker.

Analysis of the circuit design.
The Vibrato effect explained.
Modifications made with reasons.

Sound tests.