How do you measure the output of a line driver?

Capital_M · Post by **Capital_M** » Thu Feb 28, 2008 6:22 am

Maybe I am doing this all wrong but I am puting one measuring thingy off a dmm in each out put channel. Im guessing this is wrong.

Are you suppose to measure each channel alone, if this is the case, is each channel suppose to give out 4 volts on a 4 volt preout or 2 volts per channel to make 4 volts total? This is for both a sub output and for my fronts

Post by **Eric D** » Thu Feb 28, 2008 6:29 am

What are you using as a signal?

You should be playing a tone, like 1kHz for most items, and 60Hz for sub signals.

Capital_M · Post by **Capital_M** » Thu Feb 28, 2008 6:30 am

Thats what Im using

Post by **Eric D** » Thu Feb 28, 2008 6:30 am

O, and you do measure each channel separate. Each one should do 4V.

In my experience though, none of these things ever seem to do what the manufacturer rates them at. A 4V deck for example which I tested was only 2V.

One deck rated at 2.2V, was 2.2V.

Capital_M · Post by **Capital_M** » Thu Feb 28, 2008 6:32 am

Eric D wrote:O, and you do measure each channel separate. Each one should do 4V.

In my experience though, none of these things ever seem to do what the manufacturer rates them at. A 4V deck for example which I tested was only 2V.

One deck rated at 2.2V, was 2.2V.

Right but im not measuring a deck, im measuring the output off a line driver.

So for measuring, one line inside the female part and one on the outside of it?

Post by **Eric D** » Thu Feb 28, 2008 6:33 am

Capital_M wrote:
Eric D wrote:O, and you do measure each channel separate. Each one should do 4V.

In my experience though, none of these things ever seem to do what the manufacturer rates them at. A 4V deck for example which I tested was only 2V.

One deck rated at 2.2V, was 2.2V.
Right but im not measuring a deck, im measuring the output off a line driver.

So for measuring, one line inside the female part and one on the outside of it?

Right, but a deck and a line driver are no different.

Yes, the inside of the RCA is the positive (+), and the outside is the negative (-).

Capital_M · Post by **Capital_M** » Thu Feb 28, 2008 6:35 am

ok, so this is a TLD 66, what is the maximum voltage i should push out of this thing on each channel

Post by **Francious70** » Thu Feb 28, 2008 6:36 am

Connect the line drive to an amp, and turn the amps gain to 0, then measure across on channel or bridged, and turn the line driver up until the voltage stops going up, then back it down a hair.

Post by **Eric D** » Thu Feb 28, 2008 6:38 am

Francious70 wrote:Connect the line drive to an amp, and turn the amps gain to 0, then measure across on channel or bridged, and turn the line driver up until the voltage stops going up, then back it down a hair.

If he does that, I think he will blow a speaker, or maybe damage the amp.

Once you hit clipping, if you keep turning the gain up, the voltage still goes up. The sine wave just becomes more and more of a square wave.

Post by **Eric D** » Thu Feb 28, 2008 6:41 am

Capital_M wrote:ok, so this is a TLD 66, what is the maximum voltage i should push out of this thing on each channel

What amp are you using and what deck are you using?

Post by **Francious70** » Thu Feb 28, 2008 7:11 am

Eric D wrote:
Francious70 wrote:Connect the line drive to an amp, and turn the amps gain to 0, then measure across on channel or bridged, and turn the line driver up until the voltage stops going up, then back it down a hair.
If he does that, I think he will blow a speaker, or maybe damage the amp.

Once you hit clipping, if you keep turning the gain up, the voltage still goes up. The sine wave just becomes more and more of a square wave.

Oh, for real? I figured that it would have a limit. Like having an 8V sine wave, if you push it into clipping, you're not going to be making the amplitude any greater. So I figured the voltage would cap.

Post by **Eric D** » Thu Feb 28, 2008 7:15 am

If you have an amp for example with a since wave at max unclipped and it is lets say 10V, you can get more out of it.

I always get the math wrong, but it involves the square root of 2 to convert from RMS.

I am guessing in the case of the 10V amp, it would go up to 14V.

Well, 10V is 25W into 4 ohms, whereas 14V is 49W. That is twice the power, but maximum clipping.

Post by **Francious70** » Thu Feb 28, 2008 8:50 am

So I just want to make sure I understand this,

as you increase the gain of an amp/line drive/ect... both the voltage AND current increase?

Post by **Eric D** » Thu Feb 28, 2008 8:56 am

The gain matches the output of the deck to the input of the amp, but turning it up effectively increases the output voltage of the amp.

As the output voltage goes up, the load (speaker) will draw more current from the amp.

I could explain this a whole lot better if I took some photos of an oscilloscope measuring these things.

Capital_M · Post by **Capital_M** » Thu Feb 28, 2008 9:27 am

well i have an x600.1 and an x100.2 and a Pioneer 6800MP (2 volt)

Post by **Francious70** » Thu Feb 28, 2008 9:37 am

Eric D wrote:The gain matches the output of the deck to the input of the amp, but turning it up effectively increases the output voltage of the amp.

As the output voltage goes up, the load (speaker) will draw more current from the amp.

I could explain this a whole lot better if I took some photos of an oscilloscope measuring these things.

This makes sense to me.

So basically, as you throw more voltage to a load (speaker) it will naturally want to draw more current as well.

Capital_M · Post by **Capital_M** » Mon Mar 03, 2008 1:52 pm

One more question, do you measure the voltage right out the linedriver output, or off the rca male connectors that would be going into the amp?

dedlyjedly · Post by **dedlyjedly** » Mon Mar 03, 2008 2:13 pm

Capital_M wrote:One more question, do you measure the voltage right out the linedriver output, or off the rca male connectors that would be going into the amp?

You can measure at either spot, but I prefer to do it at the male end of the RCA.

Capital_M · Post by **Capital_M** » Mon Mar 03, 2008 2:28 pm

thank you