Components
Below is a list of all the components you will need to put on the Drum Master PCB, along with their associated Digikey part numbers and approximate prices.
| Component | Quantity | Digikey Part # | Approx. Price |
|---|---|---|---|
| DG408 Multiplexer | 5 | DG408DJZ-ND | $12.00 |
| LM324 OpAmp | 9 | 296-1391-5-ND | $5.00 |
| 4 port RJ45 Jacks | 4 | 380-1034-ND | $14.00 |
| Schottky Diode BAT85 | 36 | 568-1617-1-ND | $9.00 |
| 1uF Ceramic Capacitor | 32 | BC1151CT-ND | $10.00 |
| Potentiometer 200k | 32 | D4AA25-ND | $10.00 |
| 6 pin Resistor Network (Bussed) 1k | 1 | 4606X-1-102LF-ND | $0.50 |
| 6 pin Resistor Network (Bussed) 5k | 8 | 770-61-R5.1KP-ND | $3.00 |
| 6 pin Resistor Network (Bussed) 20k | 8 | 4606X-1-203-ND | $3.00 |
| 6 pin Resistor Network (Bussed) 1M | 8 | 4606X-101-105LF | $3.00 |
| 10 pin Resistor Network (Bussed) 1k | 1 | 4610X-101-102LF | $0.50 |
| 24 Connector Male Header | 4 | WM4499-ND | $2.00 |
| 4x2 Pin Array | 8 | WM8122-ND | $7.00 |
| 4 Connector Female Header | 8 | S7002-ND | $5.00 |
| 8 Connector Female Header | 1 | S4008-ND | $1.00 |
| 24 Connector Female Header | 4 | S7022-ND | $5.00 |
| Total | $90.00 |
In addition to these, you will need a Drum Master PCB (either etched yourself, or purchased from me), plus an Arduino development board (approximately $35 from a number of sources, including Modern Device Company, where I purchased mine). Thus, you should be able to assemble the entire project for approximately $170, plus a bit more for shipping. If you are cheap, you can try to scrimp on the components (for instance, you can purchase more 24 connector headers, and manually cut them into the required sizes, instead of purchasing the higher priced 2 and 3 connector headers).
I assume that you have some short, small-guage wires available to create the jumper cables which will go between the pads and the input channels. Nothing special required here, although it would be nice to get some heat shrink to make the joints nice and clean looking.
An extra optional part you can use, which allows you to easily switch out resistors (for the 5.1k filter resistor, and the 20k op amp gain resistor), you can use a SIP socket like Digikey part #ED7150-ND. Since these resistors provide the majority of the control for the drop-off rate of the input signal, and the maximum gain factor for the op-amp, this lets you easily adjust the parameters. You can figure at most an extra $10 for this, plus the cost of various resistor values.