Can't figure out why occasional severe distortion happening on power amp - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: April 13, 2019, 09:00:33 pm
content: Hello, I'm having a strange issue i'm having trouble tracking down. I have some passive speakers hooked up to a power amp which is also hooked up to a subwoofer. Most of the time the subwoofer is on standby mode to allow the audio to pass thru it.My problem is that every couple songs, the right channel will get very distorted and the Input/Output Comparator warning light will light up for that channel. So far I have tried everything from redoing all my cables to triple checking my levels. What i have found is that it's seemingly random and the only cure is....... to whack the side of my subwoofer.The wiring is as such:USB Audio Interface into Power Amp with XLR cablesPower amp into Subwoofer full range input with speaker wireSubwoofer speaker outputs to passive monitorsI was certain the problem was in the power amp or USB interface cables until i swapped them all out and the problem kept happening every once in a while, now i'm wondering if my subwoofer is the culprit, but could it even be a part of the problem if the problem ends up in the power amp?Does it sound like my power amp has issues if this same USB audio interface never has the same issues with any other setup i have used it on? Unfortunately i only have one power amp, so i can't swap them out to test that theory.

author: Mechatrommer
author_rank: Super Contributor
timestamp: April 13, 2019, 09:55:52 pm
content: Quote from: Mp3 on April 13, 2019, 09:00:33 pmmaybe broken solder joint in power amp stage circuit, that audio output cannot follow audio input hence comparator warning light.

author: David_AVD
author_rank: Super Contributor
timestamp: April 13, 2019, 10:52:13 pm
content: So the subwoofer has 8 speaker terminals - 4 for in and 4 for out ? All of the subs I've seen like this just have them in parallel.The subwoofer is just taking a sample off them. It doesn't act as a high pass filter for the speaker out binding posts.

author: Brumby
author_rank: Unknown
timestamp: April 14, 2019, 02:19:44 am
content: Quote from: Mp3 on April 13, 2019, 09:00:33 pmIf the whack reliably fixes (or interacts with) the problem, then I think the answer is likely to be a bad joint or connection inside your subwoofer.I'd be opening up the sub, reseat every connector and check for poor solder joints.Edit: I'd also include checking the connecting cables (give them a wiggle) and looking at the plugs and sockets for contaminated surfaces before diving inside.

author: Mp3
author_rank: Frequent Contributor
timestamp: April 14, 2019, 04:57:00 pm
content: Thank you everyone for your replies.It turned out the subwoofer was just fine.... the Crown power amp is disconnected and will be inspected for damage next. I ended up getting another power amp on Craigslist and have been using it for a few hours in the same configuration with absolutely no issues.So i'm pretty sure something will end up needing a little work inside the Crown D-45 amp I was using. It was not packed great when i bought it on ebay, so i should not be surprised it might have internal damage!