A customer sent me a Teac AN-180 for "upgrading". This activity allowed me to "update my understanding of" Dolby B decoders in general, this Teac, and an Advent 100A that I happened to have in my "to do" pile.
Most of these "stand alone" decoders were designed to "plug in" between your tape recorder and your system's preamplifier / control section and decode a pre-recorded tape that was encoded with Dolby B noise reduction.
The "upgrades" consisted of replacing 3 or 4 coupling capacitors in the input stages of the decoding section and adding regulation to the power supplies. The Teac had a "first generation op amp" in the output section which I bypassed. The output amplifier in the Advent was discrete so I left it in.
Listened to both finished units and slightly preferred the Advent. Sent both to the customer, and he did also. He may keep it - or it's "up for grabs".
Charles
