Thought I'd throught these two together.

Anyway. I'm adding an amp to the stock system to power a single 10" sub in my 1997 Camaro (non-Monsoon or Bose). I tapped into the wires for the rear speakers for the signal to run to the speaker-level inputs for the amp. The amp has an adjuster next to the input for 4V-0.2V. I wired everything up, and measured the voltage coming through the tapped speaker wires, and it reads 6volts. Is this OK, or will my amp have problems? Also, the multimeter measured 6volts when I tapped aither positive, or negative lines. The ground wire measured 0V Does it sound like I wired it corretly?

Now for the plexiglass. Is it OK to mount plexigalss so that it is resting ON the amplifier? If not, what could I use to put on the amp to cover. Space is very small, so it will be touching. TIA!

 

First of all you cannot accurately measure an audio signal using a multimeter.

Second, don't put anything on the amp. It needs air to cool and placing anything on the amp will impede it's ability to cool itself off.

 

Oh, OK.

Bummer, I guess I'll just have to make a mounting board out of MDF and put it in the spare tire well also.

 

I believe that you can measure the power output of an amplifier (even the one inside he head unit driving the speakers) by measureing the voltage on the wires. You just have to remember that it's AC current when it comes out of the amp and goes to the speaker, that's what makes the speaker move forward and back. The higher the voltage, the more the speaker moves...

As for the 6v versus 4v on the gain control. The gain control I believe is typically used primarily for the low level inputs into the amp. It allows you to set the amps sensitivity to match the output level of the deck's pre-amp outputs. It also acts as a sort-of "volume control", but it should not be used as such. The amps gain should be set to match the output of the head unit, and not turned up any louder. Most people do turn them up louder of course in an attempt to get more power or loudness out of the amp. All this usually does is introduce extra noise into the output of the amp and eventually damage speakers.

At any rate, the high level input should damage the amp in any way, since the amp has those inputs, it should be designed to handle it. I wouldn't worry about it.


As for the plexi, you could let plexi rest on top of the amp, but you'd have to run cooling fans (preferrably one drawing air toward it and another pushing the air away from it) to keep air moving across the surface of the amp. Most amps casings are made of metal to dissipate heat, in fact the casing is usually just one BIG HEATSINK just like on your CPU in your computer. So actively cooling that heatsink is only going to help you.

I run plext about 1/4-1/2 inch above the top of the top amp in my amp rack (see link in sig) and don't have any problems. I do run cooling fans to ensure that this won't be problem though.

 

Man, you have a nice system!

As for the speaker-level inputs, the gain control still adjusts the loudness of the system, which is why I'm concerned. I don't want to set that at the wrong position because I know it's importance. The 4ch amp came in, and I purchased 2 line converters for it since it was advertised that it only had line inputs (even though it has speaker-level inputs ). Even though I heard it's better just to use the speaker-level inputs, because you want to add as few components to the signal chain as possible, I've decided to use them because I already wired the whole car based on the premise that I would be using RCAs. Also, I found that the 4ch amp also has a stero line output off of the rear channels, so I can just daisy chain that over to my sub amp. This will really cut down on the wire clutter back there. So, when I go to set the gain on the amp, should a I use a voltmeter to check the voltage going through the RCAs, and then set the gain to match that?

 

You can't accurately measure output power with a DMM and voltage and current measurements. Without having a distortion analyzer it can't be done. You could have a 50W RMS amp that measures 250W or more. The thing you don't know is the amount of distortion. It could be 10-20% or even higher.

 

Oh, wait, I don't think I said that right. I meant, should I measure the voltage coming from the line converer to determine what I should set the gain on the amp at.
Also, the line converters have adjustable attenuation levels. They come with no instructions on these, and the adjusters have no markings. How do I know what to set them at?

 

I can understand what you mean now LS1 RULZ. I guess I have read wrong... It makes sense that without taking noise into account, any measurement will be WAY off.

snorkelface, thanks for the compliment. I worked hard on it.. I actually have a new enclosure that I am finishing up on. I'll be posting pics of it as soon as it's done...

Using the output converters will make things much easier on you as far as amps go, since if you decide at some point later that you want bigger amps, you don't have to buy anything but the amps..

Your line output converter instructions should tell you what the output level is, and you just set the amp(s) to that level. But if you don't know the output level of the converters, I'd start with the amp gains all the way down, turn the head unit up till it starts to clip, then back it down just a little. Now begin bringing gain on one of the amps up until it just starts to clip (distortion), then back it off just a hair. Do the same for the sub amp and you SHOULD be fine.

The only way to be 100% sure that you have the gains set 100% correctly is to use an o-scope from what I understand from reading Dave Navone's writings on the subject.

Good luck!

EDIT: You posted while I was typing my long winded response... In the case of no instructions, and adjustable output converters, I'd probably set them to 50% and adjust the amp the way I noted above. You could try using the multimeter to determine the output.. I've never tried that before.