Will this circuit experience ground loop interference/noise?  - Page 1
Forum section: electronics / beginners

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: February 28, 2023, 11:47:36 pm
content: Basing this question on this GreatScott video:Circuit is the one attached.Will this circuit experience ground loop interference/noise? I assume it will because of the ~3.5v LDO (will actually use an adjustable LDO for this part, hence the odd voltage). If it will indeed experience the interference/noise, how can I get rid of it? Will the only way be to use an isolated DC-DC converter?

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: March 01, 2023, 02:39:33 am
content: Just realized that I don't even need that 12v LDO, so that can simply be ignored.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: March 02, 2023, 01:12:48 am
content: Bump?

author: coromonadalix
author_rank: Super Contributor
timestamp: March 02, 2023, 03:19:56 am
content: pls dont do the bumps many times, it will not be appreciated

author: tooki
author_rank: Super Contributor
timestamp: March 04, 2023, 02:01:41 pm
content: Quote from: LooseJunkHater on February 28, 2023, 11:47:36 pmYes. Or no. There’s really no way to know. It depends on the exact components used, and how they’re connected. (Like how you run wires, or how the PCB is laid out.) The GreatScott video doesn’t really go into the causes, just symptoms, so I wouldn’t extrapolate too much from it.What does concern me is the “Bluetooth earbuds” in the block diagram. How exactly do you intend to use earbuds as the audio source. How do you intend on connecting it?

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: March 04, 2023, 05:00:23 pm
content: Quote from: tooki on March 04, 2023, 02:01:41 pmBased on this videoThe image attached. The red/black wires of the attached image is ~4v (simulating the battery) and the white/black are the audio output wires. I'd connect to it via bluetooth

author: tooki
author_rank: Super Contributor
timestamp: March 05, 2023, 01:50:49 pm
content: The problem is that the amplifiers in the earbuds are likely class D, which means thatneither output pin is ground. They’re designed to go directly to a speaker driver. You cannot, for example, connect the two negatives together, nor to ground. (Or rather, without knowing precisely how the amp works, yo7 don’t know whether it’s OK or not.)If you use an amplifier with differential inputs, you should be fine. But bear in mind that most breakout boards convert these to single-ended inputs, so you likely can’t use an off-the-shelf board.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: March 05, 2023, 06:31:55 pm
content: Quote from: tooki on March 05, 2023, 01:50:49 pm(https://www.aliexpress.com/item/4001034367291.html) audio amplifier is based on the TPA3110 and looking at its datasheet (image attached), it appears that the audio signal is isolated from ground. So I assume then that this one (and similar ones) would not (or is less likely to) cause a ground loop issue?

author: tooki
author_rank: Super Contributor
timestamp: March 06, 2023, 09:42:26 am
content: That is a perfect example of what I meant when I said this:Quote from: tooki on March 05, 2023, 01:50:49 pmLook at the board: it has a three-pin (single-ended) audio input (L, GND, R). So that is NOT the differential input of the IC.Maybe an amp breakout board that preserves the differential inputs exists, but I haven’t seen one.This has nothing to do with the ground loop issue; it’s that without the differential inputs, you likely cannot connect the outputs of the earbuds to it.

author: LooseJunkHater
author_rank: Frequent Contributor
timestamp: March 15, 2023, 05:12:06 pm
content: Quote from: tooki on March 06, 2023, 09:42:26 amThis sentence made perfect sense to me, so I dug a bit deeper into the [TPA3110 schematic](https://www.ti.com/lit/ds/symlink/tpa3110d2.pdf?ts=1678839566824) and I'm pretty confident they are following the "typical application schematic" (attached image 1). If that's the case, I can tombstone the capacitors (lifting them off ground) on pins 4 (LINN) and 11 (RINN) and solder wires to them to easily make it a different input. I assume this will work??? I hope so as I ended up buying four of the modules.

author: tooki
author_rank: Super Contributor
timestamp: March 15, 2023, 06:19:12 pm
content: Yes, if you’re comfortable desoldering SMD parts and bodging a connection, then that should work. The TPA3000 series chips are great.