10 channel, PCB-free chipamp completed!!

[MikeLewis]

Well, here's my first ever electronics project. This started when I was on break from school for 6 months with spare time and a well-paying job to furnish me with parts. The goal was a 10 channel, mid-power, hi-fi quality power amp.

The design is based largely upon carlosfm's work, so mucho thanks go out to him for his ideas on both power supply as well as non-inverting 3886 amp design.

All work was done on prototyping board. Yes, I realize that this is excessive and un-necessary, but this was my first electronics project, so: a.) I wanted practice soldering (I got it!) b.) I wanted this to be as much "my own" as possible and c.) I'm really dumb and didnt realize how much easier PCB would make it and was just being a cheapskate.

Amps are 20 gain non-inverting v4 design by carlosfm, fixed volume.

The box is basically split into 2 independent circuits, a left and right, each has: 1 EMI filter, 1 625W 25-0-25 toroidal trafo (from partsexpress), 1 unregulated PSU (4,700uf + 50,000uf per rail), 5 chipamps.

The heatsinks are extruded aluminum and are probably overkill. The case is cooled by a pair of 120mm computer case fans, one in, one out. They are powered by a mini-unregged supply i threw together last minute with some spare diodes and caps to make a smooth bridge rectifier running off self-done traffo wraps with spare doorbell wire (in order to keep electrical fan noise out of the amp)

Things I feel like mentioning about the construction:
::this thing weighs like 60 lbs and is 3U rack mount.
::despite my claim of 10 channels, only 9 work now, 1 must have been crushed or a joint broken during heatsink installation. I will probably never find out the cause and will likely not even fix it. It took forever to install everything in the case. 9 channels is enough for me right now (but OCD may force me to come back and fix it later)
::fans are mechanically isolated via rubber gasket around the fan hole edge and rubber grommets between the case and the fan grill
::dabs of hot glue hold the tall 10,000uf caps together to prevent vibrations knocking them loose
::This project required well over 100 holes through 0.05" steel and another 18 holes through those heasinks. Case construction took about as long as electronics construction.
::Amp is protected by a 10A slo-blo fuse and a 15A breaker (in the switch)
::That many binding posts and isolated RCA jacks add up money wise
::soldering things to 10AWG (PSU rails) is hard as all hell
::Don't put the PSU bridge rectifier in backwards, you will have to redo it and order some new parts to replace the ones you destroyed.
::rail voltage was around 34v unloaded, I never got around to metering it loaded.

About amp operation:
::bass sounds amazing with this amp. Even with a flat EQ, this brings low frequencies to life that I had never experienced. I don't have much to compare this to, as all I've ever been able to use before this is crappy consumer grade equiptment.
::I'm running it to power a pair of vintage Essex 600 loudspeakers, each with 2 tweets, 2 mids, and a 15", all paper. It handles these wonderfully,and as I said, brings out bass that I had always blamed my speakers for lacking, turns out they're even nicer speakers than I thought, it jsut took a real amp to show me.
::My background is pro-sound, obviously different goals than hi-fi, so really apprecate their clarity in the sound image, even if power is a tad lacking.
::They respond really quickly to electronic and complex rock music and i have yet to find a song to throw at them that makes them feel "muddled"

Future:
::I am currently running the amp without a pre-amp and am controlling the volume via my computer. Yes, I know that sound card straight to a power amp is truly lacking. It will be fixed as soon as I get around to making myself a matching pre-amp. (Yes, carlos, your pre-amp is in the consideration) I may even try a tube pre.
::The reason I made so many channels was so that I could have the flexibility to bridge and parallel whatever I felt like, giving myself flexibility without having to modify the electronics.
::The ultimate goal is for this amp to be the guts of very high quality 3-way active loudspeaker setup. that is a long way down the road as I don't have time to design/make the speakers now. Also, I would prefer to make my own XO, but I suppose if time got tight I could jsut get a DCX2496. Somewhere down the line a hifi DAC would be nice as well.

Unfortunately:
::I'm back in school now (finished the amp just in time) and therefore have very little free time due to a heavy workload, so I'll just go back to trolling a bit and brainstorming my next big project, unless I can find something fairly simple and easy to do in the meantime.


sooooo... here's pics

Any and all comments, questions or concerns are welcome (positive or negative) as we're all here to learn.

Also, I'd like to note that yes, I realize the cabling is rather messy and that yes, power lines and signal lines should be farther away, but space was very tight and 10 channels is a lot. I'm glad to have got them all in and have room to solder things together. I tried my best to keep things apart, but I realize its not perfect. Regardless, you can barely discern any hiss even when you hold your ear 2" from the tweets.

[MikeLewis]

pic

[MikeLewis]

more pics

[bigwill]

I'm extremely impressed, and extremely jealous! It looks great, well done. I have yet to build a two channel chip amp, let alone a TEN channel one!

[MikeLewis]

teh piczors

[MikeLewis]

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[MikeLewis]

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[MikeLewis]

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[MikeLewis]

underside of a chipamp, missing is the 3.3uf cap that bridges between the V+ and V- lines, as it obstructed the picture. 2200uf caps are held on by zip ties.

[MikeLewis]

top of a chipamp