Clamping without Clamp

[Jessica]

Just curious, If you put a volt meter on an amp without speakers hooked up, what do you assume the ohm load is?

I ask because I put my volt meter on my 4 channel today and was getting 25.1v with the clipping light just starting to flash slightly, soft clip with the 0db tone. I hooked a speaker up and it dropped to 24.8v The speakers read 3ohms. I am guessing that's between 150 and 203 watts.

[Wicks]

Just curious, If you put a volt meter on an amp without speakers hooked up, what do you assume the ohm load is?

I ask because I put my volt meter on my 4 channel today and was getting 25.1v with the clipping light just starting to flash slightly, soft clip with the 0db tone. I hooked a speaker up and it dropped to 24.8v The speakers read 3ohms. I am guessing that's between 150 and 203 watts.

An amp with no speakers connected has an infinite load (Mega-ohm range).

Your voltage dipped when you added speakers because of the lower resistance load and the internal resistance of the amp.

Theoretically, 24.8Vrms at 3ohms would give 205W (V*V/R) BUT speakers have varying loads with frequency so it would depend on what frequency you played and what the resulting actual load the speaker would give...

LOTS of variables.

[SnowDrifter]

Like what wicks said. Lots of things to consider, lots of variables.

In theory, it might give you some sort of a general idea, but... See my sig

[Jessica]

Just curious, If you put a volt meter on an amp without speakers hooked up, what do you assume the ohm load is?

I ask because I put my volt meter on my 4 channel today and was getting 25.1v with the clipping light just starting to flash slightly, soft clip with the 0db tone. I hooked a speaker up and it dropped to 24.8v The speakers read 3ohms. I am guessing that's between 150 and 203 watts.

An amp with no speakers connected has an infinite load (Mega-ohm range).

Your voltage dipped when you added speakers because of the lower resistance load and the internal resistance of the amp.

Theoretically, 24.8Vrms at 3ohms would give 205W (V*V/R) BUT speakers have varying loads with frequency so it would depend on what frequency you played and what the resulting actual load the speaker would give...

LOTS of variables.

Well, I understand impedance rise and all that. But shouldn't a lower load give higher voltage? Or does it only effect amperage. I know that (Volts X Volts) / Impedance = Wattage.

Wouldn't high resistance give lower voltage? Or does it effect only amperage. I figured in a 4ohm load for rise to get the 150 watt as the lowball number, but that's just a guess of course since I can't prove it without a clamp meter.

Anyway, thanks for the reply.

edit, Why did i ask that twice? Proofread duck, Proofread.

[Wicks]

Just curious, If you put a volt meter on an amp without speakers hooked up, what do you assume the ohm load is?

I ask because I put my volt meter on my 4 channel today and was getting 25.1v with the clipping light just starting to flash slightly, soft clip with the 0db tone. I hooked a speaker up and it dropped to 24.8v The speakers read 3ohms. I am guessing that's between 150 and 203 watts.

An amp with no speakers connected has an infinite load (Mega-ohm range).

Your voltage dipped when you added speakers because of the lower resistance load and the internal resistance of the amp.

Theoretically, 24.8Vrms at 3ohms would give 205W (V*V/R) BUT speakers have varying loads with frequency so it would depend on what frequency you played and what the resulting actual load the speaker would give...

LOTS of variables.

Well, I understand impedance rise and all that. But shouldn't a lower load give higher voltage? Or does it only effect amperage. I know that (Volts X Volts) / Impedance = Wattage.

Wouldn't high resistance give lower voltage? Or does it effect only amperage. I figured in a 4ohm load for rise to get the 150 watt as the lowball number, but that's just a guess of course since I can't prove it without a clamp meter.

Anyway, thanks for the reply.

edit, Why did i ask that twice? Proofread duck, Proofread.

When you measure the voltage on your amp output terminals with no load attached, you're looking at the actual voltage on the power rails.

When you start to draw current the internal resistance in the amp will reduce the output voltage. If you have a "lesser" power supply in the amp it may also droop as it i can't maintain the power rails. A perfect amp will have zero internal losses and an infinite current supply so it wouldn't droop.

Think about this: You said that a lower load might give a higher voltage... Take that to the extreme and lower the load all the way to zero ohms (dead short). V=I*R=I*0=0Volts.

[Jessica]

OK, that makes sense, I guess i will clamp when i can, It's not a big deal i'm just curious what i am sending to my mids just to satisfy my own curiosity. I just one of those people that want to know exactly what everything in my car is doing.