If the description of an amp circuit says "output: .5W - 10W", depending on what?

Views: 140

Reply to This

Replies to This Discussion

Hi, I don't understand the question really, but a bit of info anyway.

Some amps, speakers and hi fi music systems quote their output in "Music Power", the highest output available some of the time, just maximum peaks here and there. Others will refer to the true output which is quoted as the "RMS" power output, this is what the amplifier or speakers will handle continuously.

I'm can't remember the correct relationship between the two, maybe someone can chime in, but if one sees speakers with a 150w music power rating, its true power handling [RMS] is a lot lower than that.

For what it's worth. Taff

PMPO is the total peak power of all the channels in an amp added together. it is also calculated from max negative to max positive swing if a pure sinewave was put into the amp. RMS or root mean square is the positive half of the sine wave divided by the square root of 2 ie 1.414

for example a LM386 run from a 9V battery usually gets around a 4v swing positive and negative. so the Vrms is 4/1.414 or about 2.9V , 2.9V into a 8ohm speaker gives a max current of 0.36A, W=VA so wattage output is 2.9 x 0.36 = 1 .04W RMS output power.... PMPO on this single channel example would be 8Vx0.36A = 2.88 W PMPO  almost 3 times bigger in this example.

sorry for the math and the lecture.

Limited info, but I suspect it is using the lowest and the highest of the DC supply voltage range recommended for the circuit and giving the watts produced at these two levels so you have an idea of what you will get from the circuit.

Hi, Joe.

two things can determine the output power of an amp circuit. first is the voltage powering it. some of the ebay amps can say 12v to 24v . so with a higher power input you will get more out. but 24v will not be 2x the power output of running the amp at 12v.

the second thing that is more usual is that they will give you a different power output depending on the speaker load. like either a 8 ohm or a 4 ohm speaker.

usually the circuit will tell you what it expects as power and load. most of the cheap ebay amps are amp on chip designs like LM1875 etc... http://www.ti.com/lit/ds/symlink/lm1875.pdf

most of the ebay amps are direct copies of the test/suggested circuits from the data sheets.

pluss to confuse people more what Taffy said. some adds inflate the power output by using PMPO peak music power output. but Hi FI amps etc  usually quote RMS power ( root mean square) .

tl;dr version... use a 12v battery instead of a 9v and you will get more power. use a 4ohm instead of a 8 ohm you get more power. but only if the amp was designed for it.

Some amps have an attenuation of output.

Example:  Like a 50 watt amp that has settings to lessen that output for smaller venues or home studio/room use will have settings for 30watt - 15watt - 7watt - 5watt - 1watt or .5watt for whatever setting you want.


The Essential Pages

New to Cigar Box Nation?How to Play Cigar Box GuitarsFree Plans & How to Build Cigar Box GuitarsCigar Box Guitar Building BasicsCigar Box Guitar Parts Store

Site Sponsor


Recommended Links & Resources

Featured Instrument Video


Building to sell

Started by Mark Rinehart in Building Secrets, Tips, Advice, Discussion. Last reply by Jerry Jordan on Thursday. 4 Replies

Latest Activity

Jim Morris commented on shane wagstaff's video

Wall light banjo

11 minutes ago
Jeff 'Bones' Reilly posted photos
22 minutes ago
Spencer Lockhart commented on Uncle John's video

My Babe

"That is a phat axe and I am diggin on this song man!!!"
39 minutes ago
Spencer Lockhart liked Uncle John's video
41 minutes ago
Spencer Lockhart commented on Spencer Lockhart's photo

Robusto Rezo

"Thank you man!"
47 minutes ago
Richard Sundberg liked Uncle John's video
1 hour ago
Richard Sundberg commented on Uncle John's video

My Babe

"It might be the Choo Choo Train Lynas slide, but that train is playing on right on time! Your…"
1 hour ago
Taffy Evans replied to Paul Craig's discussion What's on your workbench?
"Hi, that's a nice conversion Darryl. Here's another small bandsaw conversion I did couple…"
1 hour ago
Derek Rose liked RTZGUITARS's photo
1 hour ago
Dave Lynas commented on Spencer Lockhart's photo

Robusto Rezo

"Worn off just right! Friendly old guitar."
1 hour ago
Dave Lynas liked Spencer Lockhart's photo
1 hour ago
Dave Lynas liked Daniel Walter's photo
1 hour ago



© 2019   Created by Ben "C. B. Gitty" Baker.   Powered by

Badges  |  Report an Issue  |  Terms of Service

\uastyle>\ud/** Scrollup **/\ud.scrollup {\ud background: url("https://storage.ning.com/topology/rest/1.0/file/get/963882636?profile=original") no-repeat scroll 0 0 transparent;\ud bottom: 25px;\ud display: inline !important;\ud height: 40px;\ud opacity: 0.3 !important;\ud position: fixed;\ud right: 30px;\ud text-indent: -9999px;\ud width: 40px;\ud z-index: 999;\ud}\ud.scrollup:hover {\ud opacity:0.99!important;\ud}\ud \uascript type="text/javascript">\ud x$(document).ready(function(){\ud x$(window).scroll(function(){\ud if (x$(this).scrollTop() > 100) {\ud x$('.scrollup').fadeIn();\ud } else {\ud x$('.scrollup').fadeOut();\ud }\ud });\ud x$('.scrollup').click(function(){\ud x$("html, body").animate({ scrollTop: 0 }, 600);\ud return false;\ud });\ud });\ud \ua!-- End Scroll Up -->