Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 23rd August 2003, 07:05 AM   #1
diyAudio Member
 
Join Date: Aug 2003
Location: Bacolod City, Neg. Occ., Philippines
Send a message via Yahoo to mozikluv
Unhappy how to compute the rms output of audio amp

does anyone know how to compute the rms output of an audio amplifier in the class A or AB? thanks.
__________________
"none but the brave deserves the fair" shakespeare
  Reply With Quote
Old 23rd August 2003, 06:50 PM   #2
diyAudio Member
 
Sch3mat1c's Avatar
 
Join Date: Jan 2003
Location: Milwaukee, WI
Send a message via ICQ to Sch3mat1c Send a message via AIM to Sch3mat1c
It depends on the devices used, load resistance, supply voltage and available current. Can you be more specific?

Tim
__________________
Seven Transistor Labs
Projects and Resources
  Reply With Quote
Old 28th August 2003, 01:20 PM   #3
PassFan is offline PassFan  United States
diyAudio Member
 
Join Date: Aug 2001
Location: Central FL
A rough calculation would be output voltage squared divided by speaker resistance. If your meter gives an rms measurment your done if not, multiply by .707.
Use a dummy load and an adjustable input source for more accuracy. Input to amp should be around .775v to 1v. This method does not simulate a real world load but will give you a good idea of what you have. Good Luck
  Reply With Quote
Old 28th August 2003, 02:43 PM   #4
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Unless you want to buy an Agilent or Bird wattmeter, this is simple and really works -- get a decent thermometer, a thermos of at least 1 litre capacity, fill with 1 litre of distilled water, place an 8 ohm resistor (insulate the leads with heat shrink tubing) of sufficient wattage to handle the load in the thermos.

Measure the temperature temperature at rest, crank up the amplifier and measure the temperature again. 1 calorie is the amount of energy needed to raise 1 liter of water 1 degree C -- you can convert to watt-hours by just figuring in the constants.

Yes, I did the graduate labs in physical chemistry --
  Reply With Quote
Old 28th August 2003, 03:04 PM   #5
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
That reminds me of the student who was asked how he could compute the height of a building with the aid of a barometer. Answer: climb to the top of the building, drop the barometer, time how long it takes until impact, then using the normal formulas for accelaration under 1 gravity, calculate the height of the building....


Jan Didden
  Reply With Quote
Old 28th August 2003, 03:09 PM   #6
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Quote:
Originally posted by janneman
That reminds me of the student who was asked how he could compute the height of a building with the aid of a barometer. Answer: climb to the top of the building, drop the barometer, time how long it takes until impact, then using the normal formulas for accelaration under 1 gravity, calculate the height of the building....


Jan Didden
At least you won't have to purchase a bunch of polystyrene caps to integrate the measurements with your AD536 !

btw, at one time I did ask the people in the labs at CPC (they make salad and cooking oil) for the thermal transfer constants for this application on one of my ham band transmitters -- they actually know this stuff if you are diligent enough to look.
  Reply With Quote
Old 28th August 2003, 03:25 PM   #7
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Default ...another one:

Climb the stairs in the building, and put marks on the walls for every "barometer height" as you climb. At the top, go back down and count the marks. Multiply with the barometer length, gives you the building height.

Another one, anyone (yes, this is a challenge)?

jan Didden
  Reply With Quote
Old 28th August 2003, 03:34 PM   #8
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Stand far enough away so that the barometer covers the height of the building when held at arms length. Measure the actual height of the barometer, and the length or your arm, and as long as you know how far away from the building you are, simple geometry does the rest.
__________________
Al
I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort
  Reply With Quote
Old 28th August 2003, 03:41 PM   #9
diyAudio Moderator
 
pinkmouse's Avatar
 
Join Date: Apr 2002
Location: Chatham, England
Or...

Go to the top of the building and tie the barometer to a length of string and lower it down until it is just suspended off the ground. Start the barometer swinging, and measure it's frequency. You can then compute the height from the mass of the pendulum, and the time it takes for a full cycle.

al/should probably stop now...
__________________
Al
I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort
  Reply With Quote
Old 28th August 2003, 04:06 PM   #10
diyAudio Member
 
Join Date: Nov 2002
Location: North Herts, UK
How about measure the air pressure at the base of the building then measure the air pressure at the ... No don't bother it would never work...
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
TV Horz. Output Tubes used as Output Audio ppl Tubes / Valves 90 27th August 2009 02:21 PM
how to compute for fuse amperage? jarthel Parts 32 2nd August 2006 01:06 PM
Compute D for dipole speaker DougL Multi-Way 16 23rd September 2005 04:57 AM
DIY stepped attenuator (how to compute resistor values?) jarthel Solid State 8 16th June 2002 09:54 AM


New To Site? Need Help?

All times are GMT. The time now is 03:14 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2