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Ask HN: Strange audio effect from my mixer, can anyone diagnose it?

2 points by ThinkBeat ↗ HN
A couple of weeks ago something strange started happening to my (audio) mixer.

An audio record of it can be listened to here:

https://d.pr/a/TklCXj

(DropLr if that is not cool I am happy to post it somewhere better)

After about 5 - 10 minutes it would start this odd phase warping.

I am sure that is the wrong term. I have not come across this before

I have changed out (all) audio cables, different speakers, various sources, different channels, different outputs. it keeps happening.

I hooked up a different mixer, same cables, sources, speakers, had it for two weeks now and it has no issues. (Its a loaner so I cant keep it)

I took it to the shop and they said they had no issues.

I take it back and I still have the issue.

I went to a PA place and harassed the guys to listen just to the recording and they had no idea either.

it is still under warranty but until I can get the shop to recreate it they wont take it.

Could it be an electrical wiring issue? It runs off an 240VAC adapter to 19V DC.

6 comments

[ 4.7 ms ] story [ 27.9 ms ] thread
metaloha
From that recording it's hard to tell what's being caused by the speakers and what's being caused by the phone recording and doing it's noise-reduction thing (it sounds like it's recorded with a phone). Can you record the main output of the mixer into a DAW instead and post the MP3 of that? What model of mixer is causing the problem?
ThinkBeat
Thank you. Yes I will do that later today
57FkMytWjyFu
19vdc? This video might help you if I'm right about the mixer brand. https://www.youtube.com/watch?v=ZilcEagVCdI - Modern Tech Fail: Behringer Eurorack UB1202 Repair
ThinkBeat
Thank you for the clip

I should have included all the specs for the mixers.

The wonky one is a Tascam MZ223 its (short) replacement is close to a Behring X2442USB but much older.

anigbrowl
Go on gearspace.com and ask in the pro audio forum, include details of make/model. Chances are someone else has experienced it. A lot of problems like this turn out to be capacitance quality issues in the power circuitry.

The shop will sometimes lie unless you can bring in a recording with two identical signal chains and only your mixer different. But it's also possible that you have a ground loop if your equipment is not all properly earthed. You didn't say if the different mixer which sounds OK is the same make and model as the problem unit. If it is then good, you have a simple demonstration of what's wrong. If it's two different kinds of mixer then it could be a design issue.

ThinkBeat
Thank you for your help.

You are right, I should have included the info about the mixers. They are completely different.

The one is a Behring I am borrowing that has to be 20 years old. My main one is Tascam MZ223 which is about one-year odl. It fits my use case brilliantly but its wonky