Miniature of the power amplifier LM4766 preferred

[ljm_ljm]

All of the power amplifier IC I like this.

Not many people like LM1875, or LM3886, more is not the TDA8920 and a digital TA2020.


Previously done much of this IC amplifiers, LM4766 is the most good. And the most simple, power can achieve +-33 V 50 W RMS 8 R. Very appropriate.

LM1875 than a much wider, close to the LM3886. And lasting appeal and the voice was very good.

DESIGN BY LJM

[martingolder]

I have just built this amp and hooked it to my Iphone. Serious distortion as the volume goes up past half. Any ideas

[!]

^ You might want to elaborate martingolder, like what supply voltage you used, whether the gain was the same (did you actually build exactly this amp or just use the same schematic with different values or ???), and whether you mean the volume on the iPhone or the amp itself (if not fixed value like it would be if only using the PCB).

Offhand guess is your gain is too high for the PSU voltage, or there was an assembly error or component flaw.

While there seems to be some English translation issues, I tend to disagree with the statement that "Not many people like LM1875, or LM3886, more is not the TDA8920 and a digital TA2020." Some like class D amps, some like A/B and higher output with LM3886, and some prefer more detail at lower output levels with LM1875.

Of course, some may like the tradeoff of increase in output power while retaining more definition that LM4766 provides. Otherwise they are very similar, the circuit you build around them can make more of a difference.

[abraxalito]

Originally Posted by martingolder

Any ideas

If the PCB is connected strictly according to the schematic shown then the problem could be that there's no connection between input (AG) and output/power supply (ignd) grounds.

[martingolder]

I built exactly that amp. I am using 24VAc/1.6Amp transformer. I am using the Iphone volume control. I have tried connecting the input output grounds. I note that the amp seems to work at high volume for about 15 seconds from start and then distorts heavily. the LM4766T heats up quite a bit. I have a pentium heatsink with fan but it is not glued on yet.

[benb]

LM4766 - Overture Audio Power Amplifier Series Dual 40-Watt Audio Power Amplifier with Mute

Features SPiKe Protection

Apparently it takes the thing 15 seconds to heat up to where the "SPIKE" protection kicks in for the output power it's running at. What it's doing (the oversimplified version) is keeping the chip from destroying itself. When you properly mount it to a heat sink it won't get so hot and it won't do that.

[martingolder]

It's hard to imagine that the heat sink is going to clear this up. I have held it tightly to the IC but with no heat transfer gel or cement. I am thinking that for some reason it is reaching overload too quickly because of some component value being wrong and so kicking in the Spike. I will recheck all the values and mount the sink on monday when I can get the cement. Then I will post again. Thanks everyone for your comments so far. What an amazing group of people who actually know about all this stuff in technical detail.
cheers till monday or tuesday

[ljm_ljm]

There are photos can see it, this is a most simple IC AMP

There are so many people in the use of it.

[ljm_ljm]

THD + N at 1 kHz at continuous average output power of 2 x 30 W into 8 0.009% (typ)

Very, very low distortion.

[!]

^ Every semi modern chipamp has very low distortion within a certain wattage limit... given the datasheet/spec'd/ideal power for it.