[mike j]

I completed my first Velleman chipamp this afternoon. I'm pretty impressed by the sound of it. I bought it through Parts Express. I also have a volume and tone control kit on order to complete this project. Then comes the case. I've got some nice wood scraps and some pieces of anodized steel in my garage that will work perfect for a case.
I used some speakers from a Packard Bell tube stereo console I picked up at a second-hand store. They need a little tweaking, but they're not bad.
All in all, I didn't know what to expect from an inexpensive little kit with minimal parts. However, I think I'll be doing some more chip amp kits, or looking for tweaks for this one. I'm pretty impressed by the output of this little guy. I'm looking forward to building the volume and tone control kit and seeing how much it adds to the amp.
This kit is the Velleman K4003. I'll be adding a Velleman K8084 for the volume and tone control.
I'm new to this stuff, so I hope I can get a few pointers. Do any of you DIY-ers have any suggestions for tweaks? Better caps, maybe??? Can anyone offer a quick explanation of how this thing works, beyond the rectifier.
I have a power switch to add, and I have a question about that. What do I need to do to keep the amp from "popping" when I turn it on?
Again, any advice will be greatly appreciated!
http://www.audiocircle.com/index.php?action=gallery;area=browse;album=1460&pos=0
Thanks,
Mike
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[Gordy]

   Congratulations on your first amp Mike!  Mine was a Phil Marchand chip amp. 

A couple of small suggestions, keep your signal wires as short as possible and keep that transformer as far away as possible and/or shield it with mild steel (not SS).  Iron core trannies do a good job of filtering the incoming AC but, they throw a mean magnetic field compared to toroids.  If your board uses electrolytic caps for coupling the input/output, you might consider swapping them out for inexpensive film caps like the Dantzens from PE.  If you like what you hear, you can always go upscale to something like a Sonicap or Auricap!  Just my 2 cents...

[mike j]

Thanks Gordy,
As far as toroidals go, I looked at what PE has to offer. If the voltage is the same as the iron core I'm using, what else do I need to look for? Thanks again.
Mike

[JLM]

I own Channel Island Audio chip amp monoblocks and love them with my big single driver speakers (chip amps are supposed to synergize well to single driver designs). 

One big tweak (hopefully before doing cabinetry) would be to go monoblock and separate the power supply(ies) into separate cabinets. 

Somehow my amps improved with addition of Element Cable Red Storm Power Cords (thanks to a suggestion from a fellow ACer). 

I home auditioned someone elses homebrew chip amp (with power supply in a separate cabinet) and it picked up a nearby FM station plus had a bad power supply hum.  It was bad enough that wifey made a demand (her only audio critique ever) to not buy one of "those".

The only other tweak I have in mind is to wire the monoblocks directly to the drivers so that the amps can "see" the load as directly/easily as possible.  Currently I have baffle step and zobel circuits on the speakers, but hope to replace with DEQ this year.

Chip amps have a strong reputation for being "fussy" on the tiniest tweaks, so take care.

[Gordy]

what else do I need to look for?
Mike

By all means, stick with what you have!  The iron tranny will make for a cleaner power supply.  Toroidal's are lighter and run cooler but, don't filter noise nearly as efficiently.  In fact, I just swapped in iron for toroidal's in my SKA amps.  You will definitely need to build in some ventilation into your chassis though, keep that heat away from the chips and caps!  What I ended up doing was to house the trannies in separate ventilated boxes as it was easier than modifying the amp chassis's I had already built some time ago.  Of course, if the transformer isn't getting warm to the touch under normal conditions, you needn't worry about it! 

Gordy

[mike j]

Thanks Gordy. It looks like I'll save money not buying the toroid! Cool. You mentioned shielding the tranny with mild steel, not stainless. Are you referring to using something that's somewhat ferrous to help shield the inductive field?

[Gordy]

Hi Mike, any magnetic material will work, Nickel alloys like Mu metal are the best but $$$, I mentioned mild as it's effective and dirt cheap, like me.  Galvanized will work as well, as would an old soup can.  Just keeping a good distance and very short wiring works the best, I just thought that with that small board you'd be keeping the chassis very small as well!  I always ground my shields to earth, which is necessary for RFI, dunno about mag. fields....

G

[mike j]

Thanks Gordy. Great info. 
When I get the volume/tone control built I'll be putting it with the amp in some kind of case. I haven't decided what yet. I do a little wood-playing (I wouldn't quite call it wood-WORKING!?) in spare time, so I'll see what I can come up with. Thanks for the info on grounding the shielding to earth too.
Mike

[mgalusha]

Nice place to start. In a year you'll dream up more projects than you can ever complete... DIY is a slippery slope but a good one.

I'm in the same boat - wood "working" should be used loosely with what I do... I came across this site one time. I thought it was the perfect name: The Woodbutcher's Shop.

[TF1216]

Add a relay circuit to prevent turn on pop.

[mike j]

Well, I got the Velleman volume and tone control kit in the mail today and got it assembled.  I don't know if this will work without the schematic, but I'll ask anyway. I was told by Skip at PE that I can wire both of the boards, which each use 12-0-12, off the same center tapped transformer. Can anyone shed some light on this? I can call Skip tomorrow, but I'm kind of anxious to try this out. I built some 3CR Tangbands that I'd like to hook-up to this amp, so I'm a little antsy. With that being said, I'm not in such a hurry that I'll risk damage to either of my projects. Thanks again, all!
Mike

[Jon L]

I like big Elna Cerafine PS caps with film bypass caps in my chip amp.

[Ric Schultz]

Jon,
For better sound you should lose the steel plate and bolt in the tranny.....mounting it off the chassis on a piece off wood also improves sound.  You can drill holes in the chassis around the tranny and hold it down to the wood and chassis with tie wraps.

Also drill holes underneath the binding posts and mount some rubber grommets in them and run the speaker wires outside the chassis and wrap them around the outside of the binding posts making the binding post a wire to wire clamp.  Way better sound.

Also you must damp the heatsinks......just put some constrained layer material about one inch wide across all the ribs on the top.  If it rings when you run your finger nail along the heatsinks, it will add that sound to the amp....and that sound is not good.

Cheap mods, way better sound.

[mike j]

Thanks Ric,
Sounds like good mods at the right price!
Mike

[Gordy]

For better sound you should lose the steel plate and bolt in the tranny.....

Most hardware stores carry polypropylene bolts, don't use nylon bolts as they get brittle/weak pretty quickly.

[mike j]

I think I'm being close to finished with this amp. I still have a very slight hum, so I still need to work on some grounding. Otherwise, I think it's finished!
http://www.audiocircle.com/index.php?action=gallery;area=browse;album=1460

[Gordy]

The Churchill!  I love it Mike, Congratulations