Left Binding Post | Right Binding Post |
Bias Meter
V1
V1 | V2 | V3 | V4 |
Potentiometers
12AX7 
Rotary Bias Switch
Bias Tool
6SN7 
Figure 1 Tube and Deck Layout
INSTALLING THE STEREO 90 INTO YOUR SYSTEM
Connecting the Stereo 90 to the Loudspeakers:
The Stereo 90 provides options for either 4 or 8 ohm speakers. The impedance selected will depend on the speakers used. Consult either the owner’s manual for your speaker or your local dealer to determine the correct choice. The amplifier is factory set to 8 ohm.
To switch impedance setting:
1)Using a ½” wrench remove the outermost nut from the positive (red) binding post.
2)Remove the 8 ohm tap (green wire marked 8) from the binding post. Be careful to leave the black wire with heat shrink on the post.
3)Remove the polyurethane tubing from the unused 4 ohm wire (yellow) and lug.
4)Place the 4 ohm wire onto the binding post and replace the outer nut.
5)Place the polyurethane tubing on the 8 ohm wire and lug.
3
