Buffer Tweak on all Monicas

One of the highest recommend tweak for all versions of Monica is the JFET buffer tweak. This tweak has been described on this page using 2N3819 JFETs.

Since I finally got the 2SK170s, thought it’ll be beneficial to show how it’s done to your Monica. Note that the tweak on the main site uses 2N3819 and had the output caps soldered out. This tweak here does not remove the output caps but involves cutting PCB traces.

FIrst off, solder your 2SK170s like this.

You then need to cut the trace linking the I/V resistor to the output Black Gates caps. Shown here is for one channel. Confirm with a multimeter the trace is open before proceeding with the next steps.

Installed the pair of 2SK170s. VCC (24VDC) could be tapped from upper most end of the trim pot.

Another view with both channels installed.

This view shows the cut trace for both channels.

After everything’s soldered. Power her up. All LEDs should light up as before and confirm voltage across I/V resistor measures about half of your power supply. Then play music!

If there’s no sound, you have made a mistake somewhere. Don’t blame me.