20v DC from the amp speaker outputs?
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=86077
Printed Date: April 28, 2024 at 1:04 AM
Topic: 20v DC from the amp speaker outputs?
Posted By: sin0cide
Subject: 20v DC from the amp speaker outputs?
Date Posted: November 23, 2006 at 1:59 PM
It was my understanding that you should not see any DC voltage from the speaker outputs. I talk to this guy at my work who is a Electrical Engineer and he said that is common but I was told that if you see dc expectialy alot of it coming out of the speaker outputs its clipping or something even worse. The amp under question was not functioning but was hooked up and had the light on. It was an older amp so it had no status lights just the power light. Any idea's and has anyone ever tested for DC voltage on known good amp? This has been racking my brain
Replies:
Posted By: DYohn
Date Posted: November 23, 2006 at 2:10 PM
An amp should not have DC at the speaker outputs. In fact it should not have significant voltage on the speaker outputs at all if there is no input. Your amp is bad. ------------- Support the12volt.com
Posted By: i am an idiot
Date Posted: November 23, 2006 at 6:00 PM
It really depends on what kind of amp it is. There are some class D amps that have DC voltage on the speaker wires. Of course the amps have the same DC voltage on the positive and negative wire. If you check from positive to negative you get no voltage but if you check from ground to either speaker wire it will read 40 volts. I need to know where you are getting your voltage from speaker positive to ground or speaker positive to speaker negative.
Posted By: aznboi3644
Date Posted: November 23, 2006 at 6:02 PM
If an amp is clipping really really badly it'll put out a dc signal from the power supply...correct me if I'm wrong
Posted By: sparkie
Date Posted: November 23, 2006 at 7:03 PM
If you measure on a DC voltage scale, from a good ground to either one of the speaker output wires, you should get a reading of 1/2 the power input voltage. In most vehicles the operating voltage is 12 to 14 volts. Therefore you should expect to see roughly 6 volts DC when measuring one or the other speaker output wire. If you measure across the speaker outputs (negative to positive) your meter should be set to an AC voltage scale. It will vary depending on the volume setting and from other factors.
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sparky
Posted By: sin0cide
Date Posted: November 23, 2006 at 9:17 PM
I was reading the left channel + and - and did have a input signal.
Posted By: i am an idiot
Date Posted: November 23, 2006 at 9:21 PM
Your amp has shorted output transistors We are still trying to find out what kind of amp it is.
Posted By: sin0cide
Date Posted: November 23, 2006 at 9:32 PM
I think it was a crap emerson
Posted By: master5
Date Posted: November 24, 2006 at 5:06 PM
If your amp is operating properly it should only send out a low voltage AC signal that will increase with volume. If you are reading DC directly from a set of speaker outputs there is a major problem with the amp, or your meter is bad or being used wrong. Does the amp actually work? Because if it is sending 20volt dc to a speaker you will not have sound and the speaker cone will move in or out depending on the polarity and just stay there until it cooks, you will not get music. -------------
Posted By: master5
Date Posted: November 24, 2006 at 5:11 PM
Nevermind, you posted the amp does not operate. But yes, I have seen defective amplifiers "dc" before so it is absolutly possible, but it is NOT something that is supposed to happen per say. I couldn't imagine a speaker handling DC for any length of time.
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Posted By: sin0cide
Date Posted: November 25, 2006 at 1:19 AM
thats what I was thinking but this guy at my work like I said is a electrical engineer and he said it was normal. thats what I get for listening to a engineer. :-D thanks for all the replys
Posted By: master5
Date Posted: November 25, 2006 at 1:26 AM
I have a associates in electrical engineering and i have been installing for like 100 years. And i still make mistakes and still learn everyday. To our defense alot of things I learned from people with alot more education then me have been wrong so it happens. But it was a very legitimate question. -------------
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