how to wire +/- power supply to PCB? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: May 28, 2024, 03:30:31 am
content: I think I am going to ditch the island regulator principle and instead make a regulator PCB that connects to my amplifier with wiring, because its getting big with the tracking circuit.What is the best way to wire a low noise +- power supply to a amplifier?Should I do1) 2x twisted pair, + and ground then - and ground (4-wire)a) Should these two twisted pairs be twisted together or laid as twin lead?2) twist +/- and then route with ground (3 wire)a) should I twist this up?Its for a differential signal. They will be close together so IDK if bothering with a shield makes sense for a few inches.

author: moffy
author_rank: Super Contributor
timestamp: May 28, 2024, 04:09:40 am
content: Quote from: coppercone2 on May 28, 2024, 03:30:31 amTwisting works to reduce the enclosed area of the wires i.e. inductance, as well as cancelling the magnetic field if the currents in the two wires are equal and opposite and in close proximity to one another. In your case it would have to be a triple twist as you can't guarantee that the current in the ground return twisted with say the +ve is the same as that delivered by the positive, it definitely won't be. So a tight triple twist should help. Shielding will help with the electrostatic part if that is an issue, just connect it at one end preferably the board end.

author: jonpaul
author_rank: Super Contributor
timestamp: May 28, 2024, 06:26:41 am
content: photos, schematics?

author: coppercone2
author_rank: Super Contributor
timestamp: May 28, 2024, 06:35:04 am
content: not decided yet I need to make sure its OK. Probobly LT3080 and LTsomething to do +- 15ish volts

author: coppercone2
author_rank: Super Contributor
timestamp: May 28, 2024, 07:55:52 am
content: Quote from: moffy on May 28, 2024, 04:09:40 amso having three wires twisted together is better then having 4 wires twisted together because there is no interruption between the twist of the - and + wires (with 4 wires they would be close sometimes but sometimes be interrupted by a ground)? Like, maybe confusing, but 3 wires means the + - are always touching along the entire length of the cable. But with 4 wires, + and - are always touching ground, but + and - are not always touching. I get the feeling that for differential you want + and - to be closely coupled, since the current might be between them, with little current going to the zero.Lol what if you just added more wire? +- +g and -G. three twisted pairs. Then you seemingly have the optimal conductor for both rail to ground and rail to rail currents? But I also guess you have more rail to ground capacitance that way, whatever that does. ..

author: moffy
author_rank: Super Contributor
timestamp: May 28, 2024, 08:01:25 am
content: Quote from: coppercone2 on May 28, 2024, 07:55:52 am4 wires twisted together, has 2 gnd wires, same potential, all it does is make the bundle larger with greater spacing making it slightly less effective for no benefit.

author: coppercone2
author_rank: Super Contributor
timestamp: May 28, 2024, 08:02:58 am
content: I mean two individually twisted pairs, not just 4 wires twisted up. Or now three individual twisted pairs.What happens at high frequencies?With three twisted pairs, you rail to rail load, and rail to ground loads, all have the optimum conductor. It seems like the return current will then always have a best path to follow under the source current. I imagine its not happy with two individual twisted pairs, but what if it has a favorable third path?like if you have a combination of fully +- and ground referenced loads at the end of the power supply? I.e. 1 resistor between V+ and ground, then another resistor between V- and ground, and another resistor between + and -.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: May 28, 2024, 12:57:36 pm
content: Come on let's twist again like we did last summerYeah, let's twist again like we did last yearDo you remember when things were really hummin'?Yeah, let's twist again, twistin' time is here

author: themadhippy
author_rank: Super Contributor
timestamp: May 28, 2024, 01:43:22 pm
content: go starquad,pair for + pair for- and the overall braid for ground

author: hneve
author_rank: Regular Contributor
timestamp: May 28, 2024, 01:45:46 pm
content: I'd go with the 2x twisted pair approach (4-wire) and twist the pairs together to reduce interference. As for shielding, since the wires are close together for just a few inches, it might not be necessary, but adding a shield wouldn't hurt either. It's really up to you and how much you want to prioritize minimizing any potential interference.