RJM Audio Gainbloc Preamplifier Mk. I

[rjm]

I move at a snails pace. No, worse than that!

I'd completely forgotten that I'd originally conceived of this as a preamplifier rather than a headphone amplifier.

This topic has been continued on a new thread

The circuit is endlessly configurable depending on the output load and power and desired balance of class A and class AB operation, and although I've been thinking of it mostly as a headphone amplifier lately it does make a rather neat little preamp at reduced bias currents.

[rjm]

And now it's a fully built prototype headphone amplifier, with "production ready" revision boards on order and a kit available momentarily. The relevant thread is
here.

I was asked in an email recently whether the Sapphire would make a good preamp. My response was an enthusiastic "yes!". The bias currents could be reduced somewhat, and the input section updated to include selectors switches, mono-stereo, mute, and balance controls, and could even add a phono stage like the VSPS300 or Phonoclone3. The output characteristics of the Sapphire are well-suited to be a line driver.