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Discussion Starter · #1 ·
Hi all,
I have an issue where one of my amps does not play music when the car is started. It works fine when the car is off, but stops playing when the car is started despite the power on light staying illuminated.

Car - 2018 Hilux with smart alternator
Headunit - Kenwood double din
DSP - Helix DSP.3
Amp for midbass and SUB - JL HD900/5
Amp for tweeters - Phass AP2.25i

Background:
I've been running 2 way active + sub for a while and want to go 3 way. The tweeters and midbass have both been powered by the JL amp, but to go 3 way I've swapped the tweeters to an old Phass amp to free up a pair of channels for the mids.
The Phass amp plays fine when the car is off, but as soon as it is powered on, there is a short buzz through the tweeters, and then no sound plays (although it has played briefly/intermittently whilst driving).
I thought this was a remote wire issue, but the power on light on the amp remains lit the whole time.
When I turn the ignition off, the tweeters will play music again.

I thought the output voltage may be too high from the DSP to the amp (input voltage on the amp is rated from 0.2-4V RMS) so I dropped the DSP output on the tweeters to -30db and slowly brought them up again but still no sound.

When I swap the RCA's and tweeters back to the JL amp, normal service is resumed!

Midbass and sub continue to play at all times.

The internals of the Phass amp look to my untrained eye to be ok, but I'm not sure what to look out for - it has been sat around for over 10 years without use.

Does anyone have any ideas on what the issue could be? I've played around with the ground switch, but this is not making any difference.

Thanks!
Paul
 

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Discussion Starter · #2 ·
As an update - swapped the amp out for a Phass AP 2.100i and it seems to keep playing when the engine is on.

Looks like I'll be feeding the mids with 100W of Phass, and use the JL for the midbasses and tweeters!
 

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The easiest problem to see if you take the lid off is if the electrolytic capacitors are bulging. I've noticed cases where the charging alternator voltage is within the car manufacturers design range, but above the audio equipments maximum voltage rating, so I'd double check that just to be sure.
 
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