PM_P‑1 Practice
A long, narrow inline practice bar — patch it into your signal, drive everything from one clickable thumb‑roller, and read tempo and track names off an amber 14‑segment display.
What it is
A long, narrow practice bar you patch into your signal: instrument in one end, amp or headphones out the other, the click mixed in. One clickable thumb‑roller does everything (roll = tempo, press = start/stop, hold + roll = switch track), and an amber 14‑segment display shows tempo and track names.
The click is summed into your signal in the analog domain (plus a small monitor speaker). Powered over USB‑C — a wall adapter for a permanent practice‑space install, or a pocket power bank when you're mobile (no internal battery to wear out); ships with the editor's grooves built in.
Dimensions & layout — ≈ 6.3 × 1.4 × 1.0 in (160 × 36 × 26 mm), an extruded bar
(36 mm)
Spec & bill of materials
Rough parts list — a USB‑C‑powered RP2040 inline bar with analog click injection. Ballpark one‑off prices (USD); cheaper at volume.
| Part | Qty | ~$ |
|---|---|---|
| Brain & display | ||
| RP2040 board, USB‑C — e.g. Waveshare RP2040‑Zero | 1 | 4 |
| 4‑char 14‑segment alphanumeric LED + I²C driver — amber; HT16K33. Shows BPM & track names | 1 | 4 |
| Control | ||
| Clickable thumb‑roller — EC11 encoder + roller wheel · roll / press / hold‑roll | 1 | 2 |
| Audio — analog click injection | ||
| PCM5102A I²S DAC — line‑level click | 1 | 3 |
| Dual op‑amp, NE5532 / OPA2134 — hi‑Z instrument buffer + summing mixer | 1 | 1 |
| PAM8302A mono Class‑D + 8 Ω speaker — monitor | 1 | 4 |
| Connectors & power | ||
| 1/4″ jack — Inst In (TS) · Out (TRS) | 2 | 2 |
| USB‑C bus power (5 V) + PWR LED — wall adapter or power bank; also carries config | 1 | 1 |
| Build | ||
| Custom PCB (or perfboard) | 1 | 4 |
| Passives, headers, wire — R/C for the analog stage + decoupling | — | 2 |
| Extruded aluminium bar enclosure + end caps — bead‑blasted, matte‑black anodised | 1 | 8 |
| Total (one‑off) | ≈ $35 | |
Embed this widget elsewhere with one <div> + a script —
see the embed docs.