Watt Meter?

[joetama]

My favorite thing about McIntosh amplifiers is the meters. But, alas for several reasons it is impractical for me do buy/use a McIntosh amplifier.

Does anyone know of an easy way that is relatively inexpensive measures output wattage.

My idea is that I would like to build a box install some decent size analog meters on the front and then have it measure my output wattage real time. I have also looked at measuring input on the amplifier instead of output but haven't had much luck looking either way.

Any input or help would be appreciated. I'm considering going to Mendelsons (big junk warehouse in Dayton Oh) sometime this week to see if they have anything that would help me. Also, accuracy isn't all that important. I don't think I am ever going to really use the box/meters for anything other than something for fun to build and play with, so it doesn't need to be all that accurate.

Thanks in advance...

-Joe

[joecarrow]

I could tell you how I would do it if I was just interested in knowing the wattage out, but I don't know how I'd do it if I was going to make something just for the sake of looking at it...

I'd take a USB DAQ fromhttp://www.measurementcomputing.com/, and log voltage and amperage out of the amp simultaneously. I'd measure voltage across the terminals of the amp, and place a resistor in series with the speaker- probably 0.05 to 0.10 ohms- and measure the resistance across that to get amperage. Volts times amps is watts, so you'd just need to scale the voltage across the current shunt to get amps and figure that out. I know that in Labview you could write a virtual instrument fairly easily that would take the input from the DAQ and move a fake "meter" in real-time.

I guess that a cheaper choice, if you have a good enough junk warehouse, would be to find an old benchtop laboratory power supply, and take the "current" meter and put that inline with the speaker. If you can get some meter to wiggle in proportion to current, that's roughly going to tell you power.

[JonP]

Did you want a "blinky light" bar graph type of display, (a la SAE amps) or are you set on meters? This guy and a few parts, LM3915 will give you a scaled LED bar graph type of display. There is also a LM3914 that does linear voltage, and a LM3916 that scales it to VU meter readout.

Check the datasheet for example schematics. They do have a speaker wattmeter example.

I think if you got a bit creative, you could run the outputs into a voltage divider network, and drive the meter to get a analog meter display.

[chasw98]

My favorite thing about McIntosh amplifiers is the meters. But, alas for several reasons it is impractical for me do buy/use a McIntosh amplifier.

It is not the meters. It is the blue McIntosh glow! :B

Does anyone know of an easy way that is relatively inexpensive measures output wattage.

Thanks in advance...

-Joe

Do a search on that auction place for VU Meters. Anything to do with meters will come up. http://cgi.ebay.com/ws/eBayISAPI.dll...ype=osi_widget

Now, you have said nothing about accuracy! Accurate wattage meters are a whole nother ballpark. Peak, Average, RMS? or all three. Do you want selectable ranges. If all you want are meters that bounce when the music gets louder almost any VU meter with a dividing network (2 resistors) will give you what you need. If you get into accuracy and meter ballistics and need Dorroughs type accuracy, then get ready to spend some money.

Chuck

[joetama]

Well, I am not really looking for anything that is really all that accurate. I have some time between my classes ending and my classes starting, so this is pretty much a see if I can build it type project.

If I get a set of VU meters do I need to build the dividing network if I run it on the Pre-Amplifier Outputs?

[chasw98]

Go here and read this....
http://sound.westhost.com/project55.htm It should get you going to see how far you want to go.