Section1: Introduction; Circuit Description - Audio Note Interstage Mono Block 300D Instruction Manual

Section1: Introduction

Thank you for choosing to purchase the new version Interstage Mono Blocks from AudioNoteKits Ltd.

Circuit Description

The model is the 300B Parallel version which provides approx 20W of single ended power with zero feedback – The
design is unique in that is uses a 1:1 interstage transformer between the driver stage and the output stage – see below for
a brief circuit description:
These amps are fronted by a 6SH7, connected as a triode, which may seem a little unusual, but apart from the 6SH7 and
the similar, but in a smaller package 6AU6 both being good sounding valves, and the fact that they are available at
reasonable prices there are good technical reasons for using it. The idea with these amps is to use an interstage
transformer, and only ONE amplifying stage before the output valves. This makes for an incredibly direct route, and the
amps sound better for it. Really, listening to such an amp is a revelation, there is only one gain stage, and there are no
coupling capacitors. The underlying coloration which coupling caps of all sorts produce is absent, and there is a far
greater sense of immediacy and dynamics. If you can imagine, the effect of the bifilar interstage is to knit together the
anode circuit of the driver valve and the grid circuit of output valve, what happens in one happens in the other.
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