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Hiss from Tweeters. Anyone else hear it?

Old 06-07-2019, 11:25 AM
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Join Date: Feb 2008
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Question Hiss from Tweeters. Anyone else hear it?

Non-Bose system. Upgraded Alpine Component speakers in the front only. 2018 Mazda 3, but most Mazda's have been using this TAU (Tuner Amplifier Unit) for over a decade now.

Even with the car off, in accessory mode, once the infotainment system boots up, a high frequency (10kHz) hiss appears. It is very faint, however after adding an external amp to the system the hiss is more pronounced and noticeable, even when driving and all sound muted. Using a phone spectrum analyzer, the hiss is a 20db spike above background noise at exactly 10kHz, and only 10kHz. Without the amp connected it is only a 6db spike, so it is clear the hiss is from the TAU and not the amp. Note that the hiss is there even when the audio is paused, volume at zero or muted. Unfortunately, you can't turn off the Mazda audio system.

I wanted confirmation if others have this condition (this way, the system is just poorly designed, I will just live with it).
Does anyone have an idea to solve it?

It is unlikely anyone will hear or notice this with the stock tweets, for they are near useless and do not even reproduce 10kHz frequency. The issue would be noticeable with upgraded speakers and/or secondary amp.
Old 06-07-2019, 01:11 PM
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Join Date: Jan 2018
Location: York PA
Posts: 373

The vast majority of new car buyers stick with the stock system so it may be difficult to find others who have experienced the problem if it is not noticeable with the stock speakers. If you have the equipment to detect and quantify the problem where average drivers might not, you may want to go to a dealership and see if the problem is on a few cars on the lot.

Is it true that you have been a member for 11 years and this is your first post? If so a belated welcome to the forum - it is good to hear from you.
Old 06-08-2019, 12:14 AM
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Location: Queensland Australia
Posts: 3,547

If your aftermarket amp isn't connected, how on earth are you getting anything thru the speakers? I would be checking your wiring.
Old 06-08-2019, 11:07 AM
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Originally Posted by grim_reaper View Post
If your aftermarket amp isn't connected, how on earth are you getting anything thru the speakers? I would be checking your wiring.
I added a male/female connector for the speaker wiring to the external amp under the dash just below the steering column. I use a return plug that sends the signal back to disable the external amp. This way, I can isolate a problem should the amp fail.

This audio connector location is excellent for a crossover connection for component speakers. This way, there is no breach of the factory wiring harness into the doors, as many attempt to mount the crossover to the door. Access to the area is a bit cramped though. Connector is C-35 where the output from the factory amp connects to the front door and dash speaker, both left and right are at the same connector. Unplug the car battery and use a test signal to determine if the wire comes from the amp or which speaker it goes to, for all 3 wires are the same color without specific identification. Don't remove the C-35 connector, for the yellow and violet wires are power leads to other circuits in the car.
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