Impedance load

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DYohn

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Joined: April 22, 2003

Location: Arizona, United States

Posted: May 14, 2004 at 8:21 AM / IP Logged

1. Are your front speakers running off the head or off an amp? If off your haed and you can only go to half and you get "mad distortion" it's bacause you have a crappy head unit. If off an amp, then ITS gain is set wrong too.

2. Does the sub amp work? You should be able to read the voltage output with speakers connected or not. (The amp will make voltas with no load, just no current.) Is the amp turning on? Is it getting a signal from your head?

3. Set your meter to AC volts and stick the leads into an outlet in your house. If it doesn't read 115 to 120 volts, then your meter is broken or you are not using it correctly.

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casedeez

Copper - Posts: 160

Joined: April 21, 2004

Location: United States

Posted: May 14, 2004 at 1:23 PM / IP Logged

1. My front speakers are hooked to another amp. That amp is not tuned correctly. However I turned the hi/low pass back on and I could reach 3/4 easily.

2. I will double check all of these but yesterday everything was working fine.

3. I checked the meter on my battery and got 12.5 constant.

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: May 14, 2004 at 1:36 PM / IP Logged

1. Start with this amp and set the gain correctly, or disconnect it until you do unless you want to blow your main speakers. What is the highpass setting you are using for your mains?

2. OK

3. Make sure you are not trying to read the voltage output from your amp in the DC volts scale (which is what is required to read the battery.) Audio is AC voltage.

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casedeez

Copper - Posts: 160

Joined: April 21, 2004

Location: United States

Posted: May 14, 2004 at 1:44 PM / IP Logged

1. The amp powering my mids highs is behind my 200 pound box, I was going to wait and tune this one after I got in the brown bread.

2. OK

3. Poo, I was trying to read off DCV. I thought since I was getting the power from the battery It would be direct current? Something inside the amp makes it switch?

casedeez

Copper - Posts: 160

Joined: April 21, 2004

Location: United States

Posted: May 14, 2004 at 1:45 PM / IP Logged

Jeez you even said to set it to AC, sorry I just woke up. Thanks DYohn.

casedeez

Copper - Posts: 160

Joined: April 21, 2004

Location: United States

Posted: May 14, 2004 at 2:06 PM / IP Logged

Hey Dyohn.

I went out and gave it a shot, and whatya know I can read the voltage. I set my meter to 200 on the acv, and my reading would go to about 5.0. Now 200 is my lowest setting. I am guessing that because I am showing single digits is b/c I am seeting the meter at 200. If I were to have and set it at 20 would it say 50.0 or what Im reaching for.. 37.94?

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: May 14, 2004 at 2:17 PM / IP Logged

If it had a 20 volt scale it would probably read 5.0. Set your HU to the proper output and turn up your gain until your meter reads 37 volts AC.

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haemphyst

Platinum - Posts: 5,054

Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: May 14, 2004 at 10:02 PM / IP Logged

OK, I got it! casedeez, (and I hope I have read all of these posts completely, and correctly) forget the RCA's for a minute... Plug 'em into the amplifier, with the system OFF, turn the gain control of the amp all the way to it's least sensitive point (down, be that either left or right, it will be the highest voltage indicated on the dial) hook the speakers back up to the terminals of the amplifier, turn the system on, with your test disc in the player (or any disc you know well, that is recorded fairly loud) turn the volume on your headunit up until you hear the distortion increase... you'll be able to hear it... back the volume off, until the distortion goes away, leave it there... go to your amplifier, and slowly turn the sensitivity knob (gain control) toward the more sensitive end of the gain range (opposite way you turned it in the beginning of this experiment), until you hear distortion again, OR your speakers start to complain, bottom, distort, etc; now back it off until that stops. You are now set correctly, and you should never have to mess with the gains again. All this talk of voltage, and meters, and 'scopes is simply confusing you, and you can probably vouch for that, can't you. Because music is a dynamic set of signals, you will NEVER be able to use a DVM to adjust your output voltage from your HU, or adjust the output from your amplifiers... yes, of course you are using the 50mv scale on your DVM, because you are indeed looking at the very low averave RMS output voltage from your deck, the peaks will be clipping, while the rest of it is not... oops, sss!Without a test CD that you know is recorded at 0dBfs, you will never be able to use a DVM to tell what your HU is putting out. Your ear is a FAR more sensitive instrument when setting gains.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst

Platinum - Posts: 5,054

Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: May 14, 2004 at 10:08 PM / IP Logged

oh, and I forgot to mention, the INPUT impedance of your amp will never change... it is fixed, and has nothing to do with the load on the amplifier, and even less with the output voltage.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

stevdart

Platinum - Posts: 5,816

This member consistently provides reliable information

Joined: January 24, 2004

Location: Pennsylvania, United States

Posted: May 14, 2004 at 10:40 PM / IP Logged

haemphyst, come on, let the man do his thing. This is the way we learn things. And he said he had the meter on DC. You didn't see that post.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

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