i just built an amp useing the lm3886. it sounds amazing. it starts to clip at 32 volts. so i figure e=i*r... 32=i*8...32/8=4......p=v*i.... so .....p= 32*4.....that means 128 watts? thats a lot of power for that little amp. my question i why on the data sheet does it say 38 watts at 8 ohms and 28 volts? i come up with 98 watts
You need to calculate the RMS output voltage of the chip, and use that - NOT the peak to peak output. For a sinewave you divide the p-p output by 2.828 to get RMS.
The LM3886 is rated to deliver 68W RMS to a 4 ohm load when it has a positive 28VDC and a negative 28VDC supply. The total supply voltage is 56VDC and the sine-wave output is 16.5V RMS which is 46.6V peak-to-peak. So it has a loss of 56V- 46.6V= 9.4VDC.
It is rated to deliver 38W RMS to an 8 ohm load when it has a positive 28VDC and a negative 28VDC supply. Again the total supply voltage is 56VDC. The sine-wave output is 17.4V RMS which is 49.3V peak-to-peak.
So its loss is reduced to 56V-49.3V= 6.7VDC because the current is lower.
It gets very hot when its output is 68W. Any higher output would fry it even if it has a huge heatsink with a fan.
What is your "32V"? Is it 32V peak-to-peak across 4 ohms? Then the power is only 32W RMS.
Look in Google for The Gain Clone Amplifier. It is made with the LM3886 and LM3875 power amps. One guy makes and sells a stereo amp for $4000.00US!
i have two transformers.after being rectfied and filtered they each put out 38volts. i use on for positive and one for negative. the output starts to clip at about 32 volts peak. i have had it spike up to just about 38 without clipping though. iv'e run it wide open just under clipping for a while and it is loud as hell. it went past the threashold of pain for me. i had to put my ear protection on. and i am used to loud music.
As you've now changed your signal to peak, then the output power will be 60/64W in to 8 ohms.
Bear in mind you need ten times the power to be twice as loud, so it's twice as loud as a 6W amplifier!, and only half as loud as a 600W amplifier.
I seem to remember reading that the 'gain clone' chips are very sensitive about their supply voltages, and exceeding it soon kills the chip, I'm not sure what the spec is?, have you checked it?.
iv'e got a problem now. when i take the scope lead off of the output the sound goes away and all i get is a loud hum. i can put a single lead on the negative but if i put a single lead on the positive side it almost blew my brain out of my skull. it sounded like an extremely loud pop..pop..pop.............. any ideas as to what could be causing this?
It's called a gainclone because the orignal design was called Gaincard, the parts were about 100 bucks, but they sold them for like 3 grand, and people bought them (audiophiles are a different breed) or at least obsessed with numbers that don't mean anything and willing to shell out a buck or two for those numbers.
i can take a pic this evening when i get home. so you think c5 and six could be the problem? i didn't have any caps that could take the voltage. i might have to pull one off of a scrap board if i can find one. what time is it in england right now. im at american central time and it 10:40am. is it nightime over there?
i can take a pic this evening when i get home. so you think c5 and six could be the problem? i didn't have any caps that could take the voltage. i might have to pull one off of a scrap board if i can find one. what time is it in england right now. im at american central time and it 10:40am. is it nightime over there?