multimeter question
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=24511
Printed Date: July 30, 2025 at 2:47 AM
Topic: multimeter question
Posted By: italnpimp59
Subject: multimeter question
Date Posted: January 13, 2004 at 1:10 PM
ok i know how to measure the output voltage coming from thru rca's. when i install amps and subs for customers. i turn the gains down and bass boost down. turn the volume up so the mids and highs are as loud as they can go without distorting. and then start turning the amp up almost to the point of distorting..then back off a little bit. and ive never had problems as long as the customers dont get crazy with the volume knob. but i know there is a way to match the gain voltage on the amp with the RCA output voltage from the headunit. i measure the output on the rcas by setting my meter to AC voltage and putting one lead on the outside and the other lead on the inside post. so how do i measure the gain voltage on the amp? i think it is measured on the speaker outputs, but im not sure what to set my multimeter to for me to measure it. any help would be great, ive wanted to know the proper way to adjust an amp for a long time
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Replies:
Posted By: italnpimp59
Date Posted: January 13, 2004 at 9:29 PM
someone has to know how to do this
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Posted By: eargasm
Date Posted: January 14, 2004 at 5:44 AM
thats not the way i learnt an amp should be set up. on amp, turn gains all the way down. turn h/u all the way up. back it off if the sound isnt clear, but keep it as high as possible. now start turning amp gains up until you can just hear distortion, then back them off a fraction. all done. this way, the system can never be turned up too far. ------------- 2001 Ford Fairmont
Alpine DVD, screen,
5.1surround processor,
5ch Class-T amp, TV tuner
and centre channel.
Focal 3way Utopia splits.
VDO navigation. Stinger cap.
Soundstream Exact subs.
Posted By: bberman1
Date Posted: January 14, 2004 at 10:54 AM
I'm not 100% positive but I don’t believe you can measure the max input voltage (gain) of an amp with a voltage meter. And If you measure the speaker output you will be getting the wattage (watts squared divided by the independence = rms watts). However If you do find the answer please let me know
Posted By: forbidden
Date Posted: January 14, 2004 at 12:58 PM
I agree with bberman, the only way I know to accurately measure the voltage on an rca is with a Audio Control meter like the SA3055, there is probably another way,post it up if you find it.
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Top Secret, I can tell you but then my wife will kill me.
Posted By: italnpimp59
Date Posted: January 14, 2004 at 1:14 PM
hey eargasm...thats exactly how i said i set amps.
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Posted By: DYohn
Date Posted: January 14, 2004 at 2:41 PM
The short answer to your question is no, you can't measure input voltage requirements with a multimeter. Input voltage on an amplifier (or anything else) is not something that is externally measurable, it is a function of the amplifier input-stage components. There's no voltage to measure - this is an input sensitivity rating and not something the amplifier "generates." That being said, what you are really trying to do is match the input sensitivity of your amp to the max output voltage from your HU. Some high-quality amps (like JL or Planet or McIntosh) have calibrated input adjustment pots, so if you know (or measure) the max output voltage from your HU preamp, you can then guess-timate a match by setting the input poteniometer to the corresponding setting. Fine tuning from there can be done by ear or by measuring power output as described in this thread and elsewhere, but getting it perfect requires a tone generator and oscilloscope.
Posted By: eargasm
Date Posted: January 15, 2004 at 2:47 AM
sorry italnpimp59, i re-read it and yeah it says the same thing. i must've been very tired or something. in my head it was reversed. anyways - sorry bout that.
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2001 Ford Fairmont
Alpine DVD, screen,
5.1surround processor,
5ch Class-T amp, TV tuner
and centre channel.
Focal 3way Utopia splits.
VDO navigation. Stinger cap.
Soundstream Exact subs.
Posted By: italnpimp59
Date Posted: January 15, 2004 at 1:18 PM
no problem
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Posted By: sroth140
Date Posted: January 15, 2004 at 5:49 PM
the only ways to perfectly setup an amp is to either make tiny adjustments over a long time (usually with the EQ on a flat responce), or use an oscilliscope with a signal generator and watch your sine waves for squared clipping. then you know the amp is amplifying the signal too much. you can match it to the head unit that way too.
Posted By: RufNUSD
Date Posted: January 16, 2004 at 1:25 AM
This might help
https://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=2;t=003837
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Someone pass me that bottle.
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