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Hello, こんにちは,
In this part I will continue with the VU-meter driver for needle instruments. The circuit is very simple just a half-wave rectifier with adjustable gain and a comparator for clip indicator.
POT3 should be chosen to match your meter’s sensitivity but i think 100k will do for most. Components are not critical so it should be fairly easy to build.
Whats important to note is that the voltage at the inverting input of the LM339 comparator will set the clipping threshold, so you can use a voltage divider there to set it to what you want.
You will need to adjust POT3 to your preferred 0dB point, I usually use the dBV scale.
Slowly but steady the whole unit is coming along. In next part i will do the source selection and front end.
Parts List:
| Quantity: | References | Value | |||
| 3 | R1, R3, R5 | 10k | |||
| 1 | R2 | 1k | |||
| 1 | R4 | 680-1k | |||
| 1 | C1 | 10u | |||
| 1 | C2 | 3.3u | |||
| 1 | U1 | TL072 | |||
| 1 | U2 | LMV339MT | |||
| 1 | D1 | 1N4148 | |||
| 1 | D2 | LED | |||
| 1 | J1 | CONN-SIL3 | |||
| 1 | POT1 | 10k | |||
| 1 | POT2 | 4.7k | |||
| 1 | POT3 | 100k-470k | |||
Thank you for visiting