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eddog 14th March 2006 03:53 PM

Numbnut builds chipamp..success!!
First thanks for all the great info posted on this site, without it I wouldnt have discovered this incredible little amp. In my case a LM3875 rev 3 kit. Firstly I managed to but the caps in backwards on the amp cards. After discovering this mistake my amp was clipping very badly, after much anguish I found that my "regulated" DC power supply was malfunctioning and giving me incorrect voltages for the rails. Then I had my signal ground inputs wired incorrectly(not to ground). Even after all this(including one exploding cap)the amp is now running and making great sounds. I really can't believe it after the abuse I put it through. I have one question concerning what I percieve to be a slight "tsk,tsk" yness to cymbals. Is thier anyone else'samp with this quality? It may be my speakers tweeters though as they are cheap goldwoods that replaced the OEM's that got blown up by the Evil Powers of Rock and Roll!

Nordic 14th March 2006 03:58 PM

Give it a week or so, they sometimes sound less than nice right at the start, but with some burn in, you and the amp will get more used to each other.

Garnett 14th March 2006 05:29 PM

This is great news!

There's hope for me yet. My kit arrives any day, and I'm looking forward to a similarly seamless build.

Well done. Have you enclosed it yet? Any chance of some pics?

Are there any additional instructions you found particularly useful that you can recommend? Or any top tips (other than those you've already mentioned) for fellow electrically hindered newbies?

kmj 14th March 2006 05:41 PM

Congratulations Numbnut!!

Sorry, couldn't resist :D

eddog 14th March 2006 05:42 PM

Sorry, no digital camera. Imagine a cardboard box with a bunch of wires coming out of it and you have my current enclousure:D I am using some old heatsinks from an old RCA stereo about 2.5" X 6" X 1/4" and it seems to be enough for my low volume needs. The best build advice I can give is "relax and have a homebrew" and if you have enough batteries to = 24volts, use those as the amp is completely silent that way. Dont worry too much about the feedback resistor and mount it on the PCboard if you feel uncomfortable soldering it to the pins. I know I was worried about the whole grounding issues, but if you check and double check your wiring you will be alright. These chips seems to be able to handle lots of brainfarts and still work. Good Luck. By the way, I was able to visit London last summer with a group of high school kids(prior to the bombing) and really had a great time there. Great city and great beer!!

eddog 14th March 2006 05:48 PM


Originally posted by kmj
Congratulations Numbnut!!

Sorry, couldn't resist :D

Absolutely! Glad to see it's a global expression:cool:

eddog 17th March 2006 05:20 PM


Originally posted by Nordic
Give it a week or so, they sometimes sound less than nice right at the start, but with some burn in, you and the amp will get more used to each other.

What you said!! The amp has exceeded all expectations, the treble seems to have mellowed yet still retain it's clarity and the bottom end just floors me. I was listening to an old Blue Oyster Cult track "I love the night" today and was just amazed at the detail. For 35 bucks these amps are the worlds best bargain.
Good luck to all who build these, hope yours turns out as well as mine did.

airframe 19th March 2006 05:19 AM

LM3875 rev 3 kit
Where was the kit purchased from?


neutron7 19th March 2006 05:46 AM

from the sound of it it was a brianGT kit from
i have a couple of the first version ones running and they are great. better than anything i ever bought :)

eddog 20th March 2006 02:07 PM

Yep it was Brians kit.

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