15IPS mkII less distortion (30IPS mod)

The resistor R6 sets the amount that the following diode ladder will clip the signal. Increase R6 for more distortion or decrease it for less.

To dial in the exact amount of distortion by ear, replace R6 with a 1k trim pot.

One engineer who uses a pair of 15IPS for mastering sets his R6 to 180R and calls it the "30IPS" mod.

The resistor specifications are through-hole, metal film, 1% tolerance, 1/4 watt.