Chip amps few ?'s

[matt36887]

With the recent talk of chip amps, I am getting quite interested. But I have a few questions. How much out put does the 3886 stereo have? Also where can you find the cases for the amps? How much does it usually cost to complete on of these amps?

Thanks,
Matt

[cjd]

Power output depends entirely on a few things: speaker impedance, amp gain (something you have some control over within a certain range), power supply rail voltage being the big ones. They're capable of up to 68W into 4ohm steady state, and higher peak delivery capability. For details check out the datasheet (google search will pretty much bring you right to the National Semi page).

Cost can run you up to ~$150 if you buy a case somewhere. Specifc cases for these amps don't always exist, but something like a basic rack-mount case or one of the many kit-boxes can work quite well. The one I have entirely complete, I built a box of cherry and maple with dovetail corners.

If you snag parts like power supply, etc. on sale and have some parts handy you can do them for quite a bit less.

If you need more power you can do other things. I'm working on a variation that should crank about 200W - it's being matched to a specific pre-amp as well. Cost will be more per W than a basic kit for a few reasons (and for me, since I'm developing some of the PCB's, that alone will be more than many of the available kits offered - low count parts runs don't help my case there).

C

[matt36887]

can someone post a website where they found a chassis for an amp. Just want something plan and simple.

[Hdale85]

http://www.par-metal.com seems to have some nice stuff you can get it custom sized and anodized and all kinds of stuff the 20 series is their amp enclosures and they do cod thats where i'll be ordering chassis for my hypex amps. They will even stamp holes that you need and stuff im sure you would have to have a decent pdf of the schematics myne are just going to be blank but its possible if you wanted lol

[Vikash]

How much does it usually cost to complete on of these amps?

http://www.vikash.info/audio/gainclone02/costs.asp

That was for two amps built in DIY chassis'. Might give you an idea of the things you'll need and costs involved.

[knifeinthesink]

mine cost about $50 for two mono amps. I bought transformers and good pots at a local surplus place and everything else at a little electronics shop. For a case i put them in a shoe box temporarily, and then salvaged some cases from various things i found. If you want to keep you case on the cheap look at computer surplus places or use wood. You could pick up data switch boxes and use one for PS and one for amp. Nice and cheap since they are everywhere.

By the way, splurge abit on a good pot, its worth it, but its fun to use a cheapo pot and then swap in a good one. I was amazed at the difference.

Good luck

[TimRawson]

I have 4780 (2 3886 on one chip i believe) running parallel mode. Works very well, nice clean open sound.

Also, at least swith the 4780's, take care to electrically isolate the chip from the heat sink as the metal on back of the chip is at V-. I practically exploded a chip touching my tuner case, grounded chassis, to it. Cooked my tuner as well (dang shame as it was a great sounding one). I picked up an assortment of sil-pad, kapton and mica from local electronic surplus store for a couple bucks.

Transformer is usually the killer... I have an overkill toroid in my 4780 stereo amp, but building a mini amp (single 4780 as a stereo rather than bridge or parallel) with a 40vct 4amp transformer that I picked up 12 bucks from surplus.

I'm going to try using a diy pcb method to cut my own pcb (laser toner ironed onto copper blank then etched) for this task. If really desparate, can point to point wire it, but that is fragile in my opinion. Easiest to order the kit rather than pcb's from one place, then parts from another as shipping overhead ads up. Also, as with much of DIY, endeavors like make your own pcb ends up being more costly in tool aquisition than the boards themselves.

Been doing more diy electronics lately as garage too cold to spend long hours wood crafting, more so, cannot apply nice finish at this temp (great lake region).

IMO, the sound quality easily competes with any 500 and under amp even on used market. But of course, a matter of taste. Very balanced sound quality.

[cjd]

A good regulated supply can help a lot on the transformer requirements, but adds to the cost and of course un-does the "super simple circuit" concept.

I'm not convinced the magic lies in the lack of components (or not entirely) though.

C