Revox A77 and B77 Board Numbers Compared

If you work on both an A77 and a B77, the numbers are close enough to confuse and far enough apart to matter. This page puts them side by side.

The pattern is simple once seen. The A77 family prefix is 1.077 and the B77 is 1.177. Everything after that is the position within the machine, and the positions correspond only loosely, because Studer redesigned the transport control between the two.

Where the two machines genuinely differ

The B77 is not an A77 with a new front. The transport control moved from relays and mechanical switching to a logic board, which is why several A77 cards have no single B77 equivalent and are marked as such above. Anything to do with record switching or transport logic should be read from the manual for the machine in front of you, not inferred across.

What does carry across is the audio chain in principle, the head terminology, the tape path vocabulary, and the habit of ordering by number and name together.

Reading a number you find somewhere else

A number quoted on a forum or in a listing will usually be given without saying which machine it belongs to. Check the second group first.

• 1.077.xxx Revox A77
• 1.177.xxx Revox B77
• 1.011, 1.021, 1.116, 1.736 shared across both, and often across other Studer machines too
• two-digit prefixes such as 21, 23, 24 are hardware and are shared throughout

The full lists are in the A77 parts reference and the B77 and A77 parts reference.

If you can correct this

This table is built from the two factory manuals and is the part of the archive most likely to contain a mistake, because it asserts a correspondence that no factory document states. If you know one of these pairings to be wrong, say so and it will be fixed and credited.