Our gain stage: JB Gold


The section of a preamplifier that does the amplifying is called the gain stage.  The Rhythm 1.1 preamplifier uses our tubed “JB Gold” gain stage.


When people hear JB Gold for the first time, they tend to focus immediately on the music.  It’s not about better treble, or better bass.  JB Gold is such a new approach, such a complete overhaul of the typical tubed amplification circuit, that audiophile phrases become less important, and what matters is the performance happening right now in front of you.

Life-like dynamics.  Spaciousness.  Real-life clarity.   No sweeteners, no thickeners, no “warmed up” midbass.  The JB Gold gain stage delivers music as it really sounds.

Tech Talk

The JB Gold gain stage has several technical features:

Constant Current:   Very few preamplifiers use a constant current circuit.  Backert Labs chose to keep the current on your tubes constant at all times.  This is easier on them, allowing your tubes to last longer.  Constant current also results in more linear amplification, or put simply, more accurate sound.

Automatic Bias Correction:  Unlike any other preamplifier, your Rhythm 1.1 will automatically adjust the bias of your tubes, continuously.

  • Just bought a new pair of NOS tubes?  Once you put them in, the bias is immediately adjusted specifically for them.  In fact every pair you insert will again receive a specific bias, customized just for them.  Automatically.
  • Using the same tubes for 10 years?  Bias will need adjustment to a small degree as they age, and to a larger degree toward the end of their life.  Bob Backert’s gain stage does that.
  • Playing music?  In other preamps, the bias will be changing constantly, in real time, due to the music signal itself.  The Rhythm 1.1 negates this effect, allowing your tubes to run at a constant, smooth and correct bias.

No Cathode Follower:  Many tubed preamps use an extra tubed circuit after the gain stage, called a cathode follower.  This circuit is intended to lower the preamp’s output impedance.  Because a cathode follower can impair the accuracy of a preamp’s dynamics, the Rhythm 1.1 does not use a cathode follower.  It doesn’t need to, because the JB Gold gain stage is naturally very low in output impedance.

For more about the JB Gold circuit, please see More Goodies.

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