GDIY VU Meter Driver PCB (PRE-ORDER, ships Oct. 2023)

"ORDERING" INFO: I am planning on placing an order with my PCB fab around September 25th, 2023, so I will close this pre-order page at that point in time. Based on previous orders, I should have the boards in-hand by early to mid October and will ship them out to you shortly after that. Will ship cheapest possible option via USPS with tracking. I am not a Black Market seller and this will probably be a one-time-only situation, considering I am providing the gerber files for free for anyone to use.

NOTE REGARDING INTERNATIONAL SHIPPING: the shipping quote is for a small padded envelope 8oz or less. If your order is more than 8oz, I'll reach out and we can figure out the difference in shipping cost.

INFO / HOW-TO / BACKGROUND ON THE BOARD/CIRCUIT:

Okay, dug up my old VU driver layout and did some quick cleanup.

I have laid out two different versions of the board:

— v1.0a: VU Buffer / Driver with AC/DC Input Voltage Regulator scheme (hookups via 5.08mm LS terminal blocks). Board size: 48mm x 46mm


— v1.0b: VU Buffer / Driver w./ AC/DC Input Voltage Reg. scheme w./ pads to solder directly to meter tabs similar to JLM units. This isn’t really something I would usually use, but figured someone might like it and was easy enough to implement the pads. Board size: 48mm x 48mm

I originally laid out this board in 2018 and the circuit I used is originally from an Audio Technology article by Rob Squire (https://web.archive.org/web/20190819103415/https://www.audiotechnology.com/PDF/TUTORIALS/AT51_DIY_VU.pdf). Some part values were adjusted based on what components I typically stock. This is (I think) the same circuit as many other VU meter driver boards available from JLM and elsewhere -- you can change component values based on your application, as well.

Build is very similar to the info found in this JLM thread and there are some helpful notes in here on substitutions / omissions / jumpers based on your ideal application: https://www.jlmaudio.com/forum/viewtopic.php?f=2&t=109

You can use whatever Schottky type diodes you want for D1 through D6 (1N400X, 1N5819, etc), but D7 and D8 should be BAT85 because they have a low forward voltage like a germanium. Some VU meters have diodes built in, in which case follow the notes on the schematic on what to omit.

My layout uses one side of a TL072 or other dual opamp rather than a single on the original scheme just because I always stock duals.

REGULATOR NOTES:

The regulator is a standard LM317 adjustable scheme so you can use DC or AC voltage input up to 40v. You could also use a LM317HV, which handle 60v max input voltage. The footprint is on the edge of the board so you can attach a heatsink or bolt to your chassis (with an insulator) if you’re worried about dropping a lot of power (or LM338 if you need more current for whatever reason…)

If you know your exact meter voltage and don’t want to use the "V+ADJ" trimmer, use a handy calculator (https://circuitdigest.com/calculators/lm317-resistor-voltage-calculator) to come up with a fixed resistor value and solder that in place of the trimmer. 

If you don’t want to use the regulator at all, jump D5 and omit the following components:

- C7 and C8
- D6

- IC2
- R16
- V+ADJ trimmer


FUTURE NOTES:
When I have some time, I’ll do another without the regulator scheme.

Here is a link to the schematic with part values: https://drive.google.com/file/d/1WHfSMMSNJ5zRZPLyEeUI4-zhi375XI5M/view?usp=sharing

Bill of materials / partslist here: https://docs.google.com/spreadsheets/d/13xRC2moRkIAikeBnX3xfViB94S35QPKQK3rxiuA7M9U/edit?usp=sharing