Building a chip amp

Rybow · Jul 29, 2011

I know that most of the projects here focus on pro audio recording/mixing/mastering gear, but I just finished a chip amp, and I would like to share it with you guys! After building it, I am seriously considering building another to power some passive monitors in my little studio.

It all started when my Dad sent me an email asking me to look at some little Pyle amp. He wanted an amp to power some small 6Ω bookshelf speakers in his home office for music listening, and he wanted the price tag to be under $100. I looked at the amp in question, sent my Dad a reply that it would be less than awesome, and jumped head first into building him one for the price tag of $100. Of course, it ended up costing 4 times that to build, so Merry Christmas, Happy Birthday, and Happy Father's day Dad. I just gave the amp to my Dad a week ago. It spent one day powering the bookshelf speakers before being moved upstairs and connected to his Kef Hi fi's. I think I went overboard.

LM3886 chip amp stereo kit from chip amp.com, Rod Elliotts P88 OPA2134 pre amp, 225VA Hammond 22V toroid, ALPS blue velvet pot and a 12"x8"x3" Hammond aluminum chassis. The sound is soooooooo good! Optimized to deliver 60+ watts into 6Ω, 40 Watts into 8Ω. Tested on my Kef C40's, 100 watt towers, showed that 40 watts from a chip amp is a silly amount of power. No hum, no buzz, no electrocution, no speaker short protection, no slow start and no mute circuitry. Kept it simple to increase chance of success. The power light is a blue LED mounted on the PS board. It can be seen through the vents. I wanted to keep the look clean and classy.

Enough talk. Picture time!

Front graphics

Back connections. Slight Dremel slip on the IEC. Whoops!

A little too ambitious on the top vent. I don't have a drill press, so just a hand held power drill. Despite centre punching, the drill slid around a bit. You can see where I start and then get better at it

Here is what I should have done on the top

The guts pre-paint. You can see it's a tight fit. Despite the close proximity, there is no hum from AC leakage.

I tried to think of ways to tell my Dad that I couldn't do it so I could keep it for myself, and then buy him a $100 amp. He was like a kid on christmas day when he pulled it out of the box, so it was more than worth it in the end.

erikb1971 · Jul 29, 2011

Looks like a nice build Ryan! I've build one as well using the premium kit from audiosector http://www.audiosector.com/lm3875.shtml. I love the sound as well. Mine drives a pair of Anthony Gallo Nucleus speakers and I have a line out that drives a small closed active 8" dayton subwoofer. I have a passive "pre" though, just a 4pot to select input. I assume the board between the alps and the rectifier is the pre-amp? And what is the little board attached to the back? The only gaget in my opamp is a remote volume control from dantimax with an alps motorized pot.

I read a lot of different opinions on using the chipamp as a monitor amp. Iam thinking of using a chipamp to drive my to be build DaveP's auratones...
Iam wondering if there are people here with an opinion on that.

anyway, nice build, hope your dad enjoys them!

abechap024 · Jul 29, 2011

Nice! Thanks for sharing. I built one too and enjoy the sound. Does sound good.

tchgtr · Jul 29, 2011

Fun thread and nice story. I like the change from the usual, and it's nice DIY!

Rybow · Jul 29, 2011

Thanks Erik! Yeah, the board between the rectifier and the alps is the pre amp. I haven't done any testing with and without the pre amp t determine it's effect on the sound. If I had more time, I would have bypassed it for testing. Oh well, I'll do that on the next one. The board on the back is the power amp supply. I used separate supplies for the pre and power amps. A remote control pot sounds so cool!

I still need to do a bit more research about the monitoring idea, but to my ears, differences in recording stood out when run through this amp. Plus the bass is killer. I had my ipod on random when a track came on with a sub drop. It wasn't just that it was bassy, it was the sound pressure squeezing my skull in another room that got my attention. Crazy!

Hey Abe! Thanks. I remember you were thinking about it a bit ago, but I didn't know you had built it already. Did you post pics anywhere?

Thanks tchgtr! Took awhile to get done, but it was worth it. I am just hoping that nothing starts smoking or burning up now that it's out of my hands. My customer service department is pretty crappy. ;D

If you guys have pics of chip amps you are itching to post, feel free to share!