Thanks to a member here who posted how he fixed the problem with these little amps. They were mistakenly manufactured with a 100ohm resistor instead of a 3K resistor, putting the amplifiers gain @300.
According to the OP, R8 is 130K instead of 120K as in the IRAUDAMP7S reference design here.
Also, according to Page 29, Gain = R8/R2. Isn't it really Gain = R8/(R2+R7)? I say this because 120,000/(3000+330) = 36.
I would like to modify the Gain to maximize this Amp's potential with an input signal of only .9Vrms. These amps are rated at 1.5Vrms with a gain of 36, according to the reference design. These China boards are closer to 40.
According to the OP, R8 is 130K instead of 120K as in the IRAUDAMP7S reference design here.
Also, according to Page 29, Gain = R8/R2. Isn't it really Gain = R8/(R2+R7)? I say this because 120,000/(3000+330) = 36.
I would like to modify the Gain to maximize this Amp's potential with an input signal of only .9Vrms. These amps are rated at 1.5Vrms with a gain of 36, according to the reference design. These China boards are closer to 40.
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Well, since no advice was given here and after talking to an EE friend, I decided to order 2.5K resistors in 0805 package. This will put the gain @ 130,000/(2500+330) = 46. I'll try to take some pre and post pics with the 'scope.
I'm with you. The R8/R2 is a misprint and should have been R8/(R7+R2) as stated earlier in the document.
Arggh. I'm not getting around to do this mod because these keep blowing out! So far I've had 4 fail. The fan stops blowing and no output. Thankfully it doesn't harm the speakers.
So taking 1 apart the FET they are using is a IRFB31N20D. Any help?
So taking 1 apart the FET they are using is a IRFB31N20D. Any help?
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