Tag Archives: PR99

Hi-End Hifi Upgrades for the Revox B77 / PR99 Reel to Reel Decks

The Los Angeles and Orange County Audio Society site hosts an interesting paper describing a step by step procedure for upgrading the B77 and PR99 Revox models for higher playback quality. The document is a work by Arian Jansen of Sonorus Audio. We talked about Sonorus Audio’s
ATR10 tube reel to reel deck here

The modified machine becomes a playback-only device, addressing hi-end hifi listening, however it is possible to preserve recording functionality by applying only part of the modifications.

The guide contains DIY instruction to perform:

  1. doubling operating speed up to 15 IPS, for lower speed models (US residents only, due to 60Hz power-supply requirement)
  2. conversion from NAB to IEC EQ
  3. upgrading the output capacitors to higher specs components
  4. removing from signal path the components (a couple of transistors) required for auto-muting, used to suppress audio output during ff/rew operations.

Visit the Los Angeles and Orange County Audio Society site here and the document in pdf format here.