Amplifier unstable when bridged
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=70581
Printed Date: April 27, 2024 at 12:48 PM
Topic: Amplifier unstable when bridged
Posted By: xentrix
Subject: Amplifier unstable when bridged
Date Posted: January 11, 2006 at 11:29 PM
Hi readers.
I have a Clarion HU driving a Fusion FR4-1000X amp and a little Sony XM-150 amp. The Sony runs fine, no issues.
The FR4 is a 4 channel amp running in 3 channel mode. Ch 1 & 2 drive the fronts in stereo, 3 & 4 are bridged to run the sub which has 4 8's, 2 in series, 2 in parallel.4 ohms. The Sony runs rears.
After installing and running up, the speakers on the FR4 all produced an oopa oopa oopa type sound and the FR4 went into protect mode.
To isolate things down, I ran a discman off its own batteries into the FR4 and it ran fine.
The head unit running the Sony amp works fine.
The head unit running ch 1 & 2 of FR4 works fine
The head unit running ch 3 or 4 went unstable (even with no music playing)
The head unit running ch 3 or 4 sperately driving the sub is fine. Its just when its bridged it goes gaga.
I know it sounds like the subs load is to low for the amp in bridge mode, but its fine with the discman, and was fine in the previous car.
The car is a 1983 Australian Ford Falcon, factory electronic ignition, no other mods apart from a 40A noise suppressor on the battery.
Replies:
Posted By: memphis11223344
Date Posted: January 12, 2006 at 9:52 AM
trtyed the LPF filter on the amp and is the amp bridgeable and what are your ohm wired at?
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6 memphis PR 15's sealed enclosure. indash mobile video system. alphasonik HC800PMA 3000 rms
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Posted By: DYohn
Date Posted: January 12, 2006 at 12:09 PM
Your gain is too high. ------------- Support the12volt.com
Posted By: xentrix
Date Posted: January 12, 2006 at 9:14 PM
Yeep the amp is bridgeable. 4/3/2 channel. 2 ohm stable in stereo. The sub has 4 4ohm drivers. 2 in series and 2 in parallel, which presents 4 ohms.
I'l give it a try with the gain turned down, but it went unstable without any music playing, and its fine with the discman. Have tried it on LPF and Flat and got the same result.
I'l post a reply a bit later. Cheers.
Posted By: xentrix
Date Posted: January 14, 2006 at 4:23 PM
Damn! I was listening to Bass Mekanik on the discman and it put the amp into protect and it hasn't reset, neither fuse has blown. I think i'll (run off and finance a new system), pull it apart again and run it up out of the car.
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Clarion HU Fusion FR4 Sony XM150 Boschman 6X4's Melton all weather 3ways 4 8" Audiophile subs in sealed box...and i'm havin a few problems.
Posted By: forbidden
Date Posted: January 14, 2006 at 7:32 PM
Turn the gain down and rewire the subs. (according to your limited info they are wired incorrect). Current takes the path of least resistance, if you have a pair of 4 ohm subs wired in parallel to 2 ohm and a pair wired in series to 8 ohm, you are asking for problems. You need to wire each pair in series to 8 ohms and then wire each combined pair in parallel to see a net 4 ohm load. Confirm that this is how you wired the subs.
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