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Old 2nd March 2014, 11:57 PM   #1
jscovie is offline jscovie  United States
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Default Best LM4780 plans or kit??

I built two LM386 circuits into a 9v battery-operated stereo to play my Android phone's MP3s through small loudspeakers. It sounds surprisingly great -- especially considering that my last LM386 project, built around 1976 for a crystal radio, was full of distortion. (Today's digital source = unbelievable difference.) But, now that I've played it daily for two months, I'd like more power. Does anyone know the best plans or kits available for the LM4780? It looks like a lot of power with very low distortion.
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Old 3rd March 2014, 06:55 AM   #2
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There's one here
DIY Chip Amplifier Kits, PCB's, Components and Information.

A bit pricey for a full blown stereo kit *BUT* 1) It will probably be the only one you ever need and 2) Good quality components and reputable seller.

Then there is always eBay. You will save about half but occasionally run into QC problems.
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Old 3rd March 2014, 08:24 PM   #3
jscovie is offline jscovie  United States
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Default Transformer for LM4870

Thanks! Pricey, but looks like this would include almost everything except the dual-gang attenuator (or potentiometer), switches, I/O hardware and of course PSU transformer. Does the LM4870 need a torroidal transformer in a small enclosure? Has anyone built one of these using a switch-mode PSU transformer? Appreciate any input. My input source is MP3 from headphone jack of Android phone.
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Old 4th March 2014, 04:51 AM   #4
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The output level of an Android phone will be quite less than required to drive the chipamp.

Gajanan Phadte
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Old 4th March 2014, 05:20 AM   #5
sangram is offline sangram  India
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Quote:
Originally Posted by jscovie View Post
small loudspeakers.
That's the issue, small speakers are usually very inefficient.

A single 4780 is two LM3886 dies in a single package and derated, so unless you bridge the chip and use one per channel (assuming your speakers are 8 ohm or greater and you have a sufficiently beefy power supply) you aren't getting more usable sound level. And then, you risk blowing the speakers across the room. You can configure Peter's kit for bridge, parallel or stereo. Parallel will not give you any extra usable power.

Bigger and more efficient speakers will go a longer way in improving your experience, as will a touch more gain on the amplifier. You can get a 7dB boost in volume output by using Poweramp music player (~$1 from the Play store), which goes a long way. Tweaking the feedback ratios on the chip will also help.

When I do use a phone, a single 3886 per channel with Poweramp is louder than I can stand, playing into pretty much any speaker. The only time I wish for a bit more, is when I'm using the Aurasound NS3, which are 80dB/w. Mirrors your experience almost perfectly...

Last edited by sangram; 4th March 2014 at 05:24 AM.
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Old 4th March 2014, 07:53 PM   #6
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Quote:
Originally Posted by jscovie View Post
Thanks! Pricey, but looks like this would include almost everything except the dual-gang attenuator (or potentiometer), switches, I/O hardware and of course PSU transformer. Does the LM4870 need a torroidal transformer in a small enclosure? Has anyone built one of these using a switch-mode PSU transformer? Appreciate any input. My input source is MP3 from headphone jack of Android phone.
It doesn't need a toroidal transformer. People chose them for several reasons but even high quality commercial amps don't necessarily use them.

If you do have a problem with your Android not having enough drive, the gain of the LM4780 can be changed fairly easily: Just a couple of $.08 resistors.

Just me, switchers are great for a lot of applications but I have a tendency to shy away from them in audio amps except for single ended power supply designs. It would depend on the failure mode of the switcher i.e. shuts down or channels 170 V to the amp until all the smoke is gone.
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Old 5th March 2014, 03:39 AM   #7
sangram is offline sangram  India
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Doh, I read 386 as 3886. You can ignore that bit of my post!
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Old 8th March 2014, 03:55 AM   #8
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I have a few LM 4780 chips laying around and am thinking of buying this board. Has any one tried this one out yet or have any opinions about this amp?

LM4780 X2 Tube Buffered Amplifier SPK Protect PCB | eBay

I like the fact that it has a tube pre amp and that the power supply and speaker protecter is all on the same board.

Im not sure if it will be the best sounding amp on the market, but it could be a neat build.

Dale P.
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