Our gain stage mod

RHB phono preamplifier modify amp mods

What’s a gain stage?  It’s the circuit in your amplifier that does the amplifying.

Our gain stage mod supercharges your tubed preamp or power amp.  It works like no other audio circuit in the world.

We call it “JB Gold”.

We are proud that JB Gold is the only circuit in the world with Active Management.  This revolutionary technology:  (1) optimizes the preamp to work best with each specific tube you insert, (2) continually monitors and adjusts to match the needs of your tubes, as they age and gradually require different operating parameters, and (3) stabilizes bias in real time by continually negating the “bias tugging” effects caused by playing music.

JB Gold is also the only circuit in the world with Active Output Correction.  This (1) monitors and continually corrects the preamp’s output to adjust it back to the immediate, pure signal output of the tubes, (2) negates the harmful effects of interconnect inductance and capacitance, and (3) stabilizes the preamp’s output in light of any variations in your power amplifier’s impedance.


  • Active Management means the circuit is automatically self-optimized when using different brand tubes (see our discussion on tube rolling here)
  • Active Management also automatically optimizes operating parameters as the installed tubes change over time
  • No local negative feedback
  • No global negative feedback
  • Designed to be incredibly “easy” on your tubes, prolonging tube life
  • Greatly reduced loading effects on gain stage triodes, allowing improved linear operation
  • Incredibly low output impedance is inherent to the circuit, eliminating the need for cathode followers, which impair linearity
  • Active Output Correction continually adjusts your preamp’s output to match the pure, uncolored signal produced directly at the output of your tubes, meaning that detrimental effects of cable loading and external component loading are eliminated