On one of my trips to Goodwill’s Computer Store, I picked up the subwoofer part of a Harman/Kardon H/K-395, 2.1 computer speaker set. The satellites were missing, and since the sats hook up through a customized mini-DIN connector, and the volume control is on one of the sats, it couldn’t be used as-is. So it sat on the as-is speaker shelf for $5.

Here’s what you need to do to make it useful again.

Remove the screws holding the back on. Flip the back over so you can get at the works. If you want, unplug the wires to the woofer and the front panel. We’ll need to make the wiring to the DIN connector more accessible. I chose to add four terminal posts at the top of the back panel to connect satellite speakers of my choice, and add a stereo volume control located on the back panel. IF I were doing it again, I’d leave off the volume control and just jumper the amp at full volume. The volume at full gain is just about right to match an iPod’s earphones or a computer. If you want to use it with a source which doesn’t have a volume control, then of course install one, but the volume pot is the most difficult part of the mod.

Tracing out the wiring to the jack PCB:

12 wires, black wire is #12

according to H/K marking.

1- Input jack L ch (tip)

2- Input jack Gnd (sleeve)

3- Input jack R ch (ring)

4- Volume pot R top of element

5- Vol L top

6- Vol R wiper

7- Vol L wiper

8- Gnd

9- On/Off (pull up for On with 3K to +16V)

10- Spkr + R

11- Spkr + L

12- +16V (black wire)

I chose to leave the existing input jack, so leads 1-3 were not cut. Knowing what I know now, I’d just jumper wires 4 to 6 and 5 to 7, leaving out a volume control. If you want an on/off switch, connect it with a a 2K or 3K series resistor between pins 12 and 9, otherwise just connect them with a resistor. Pins 10 and 11 are the hot leads to the satellite speakers and the common leads go to ground at pin 8. Since I had the PCB off to trace wiring, I soldered a separate lead to ground under the board.

Making a hole for a small stereo 10K audio volume control involved removing the power transformer and the amplifier board, drilling the hole, and cutting away some of the plastic ribs so the pot sits flush. I find I always leave the volume full on.

This makes a nice small stereo with an iPod and a couple of the Iced Tea speakers.