Hello everyone, This thread covers mods of the WM-D3, for better sound and accurate dB metering. 1. Capacitors upgrade. I referenced the kit from Marian Mihokm, which can be found at: https://fixyouraudio.com/product/sony-wm-dd3-capacitor-upgrade-kit/. The kit includes 47uF capacitors for the pre-amp feedback loop and 560uF phone output coupling capacitors. You can also purchase the components from DigiKey in larger quantities and select a pair with closely matching values. Here are some measurements regarding the capacitor upgrade. The sub-bass performance has significantly improved: 2. Op-amps upgrade. Replace the stock NJM4558M with NJM5532M. There were no noticeable changes in the measurements, but the response above 15kHz seemed better on some type II tapes: 3. VU meter upgrade. The stock VU meter LEDs are all red. For better visual effect, we can change the LED color. The most common color palette is Green-Yellow-Red. In WM-D3 the LEDs are axial through-hole type. Note that the forward voltage should be 2.0V or less, as two Ni-MH batteries may not be able to light up high-voltage LEDs. The LED current-limiting resistors should be changed to match the luminance of different colors. Moreover, the stock VU meter cannot respond well to sub-bass, because there are C141 and C241 at the CX10043 input. Since the Sony WM-D6C doesn't have that, I tried to bypass the caps. Now it works fine without any issues, and the meter responds well to sub-bass. Now my Sony WM-D3 sounds and looks great! Welcome to leave comments and share your opinions.
I also want to bypass the MPX filter because I don't usually record FM radio and modern FM receivers don't output a strong 19kHz signal. Firstly I soldered the wire to the Dolby amp at pin 3 instead of pin 6 of the filter, but the frequency response was worse. Then I tried other pins, and they all resulted in poor performance. I couldn't get rid of the deep notch; I could only move it.
