Problem statement: I have headphones and earbuds that are very high efficiency (due to low impedance maybe), and my WM-D6 is basically too loud and I have to keep the volume slide around 1/10 ~ 3/10 most of the time. Idea: I want to make volume slider less sensitive but still be able to produce same loudness at max position Research: I studied the service manual and found that the circuit is designed to produce loudness in a concave curve, making the volume slider sensitive at the lower end. I think it made sense when this product was designed when headphones were low efficiency or high impedance. After doing some math on spreadsheet, I found some resistors around headphone amplifier could be replaced to make the volume control more linear. Proposal: Replace R145+R245 from 27kΩ with 330kΩ Replace R146+R246 from 22kΩ with 120kΩ Result: Now my volume slider's sitting around 3~4/10 instead of 1~2 and don't have be very fiddly about the volume control. Still it's very loud when cranking up.
This I could use on most of the DDs! Especially the ones with 2 jacks could have 1 for new earphones, not studio over ears. With the efficient IEMs I never go above on 3 of 10. On a side note, I need mine to go to 11
Unfortunately the above suggestion modifies the volume control for both headphone jacks. To add impedance to just one headphone jack, we could simply replace resistor R148/R149 or R248/249 pairs. I recommend experimenting with commonly sold impedance adapters (70 ohm ~ 200 ohm) before actually replacing one of the resistor.
Certainly needs 11 on some later MD players that were designed for bud earphones. You can use a small USB rechargeable headphone amp to boost and lower the output Vol. Particularly useful when there is line out support connection available on the device to the headphone amp.
