last updated: Friday, 02-Apr-2004 23:22:52 EST
- audio home
- The Vifa X3
- Preamp
- Car Audio
- Shiva!
- PA Speakers
- Hafler stuff
- Phase Linear
- LM3886 amp
- lm12 amp
When Chris built his amp., he built it with the LM12CLK-80, a version of the chip whis is certified to use +/-40V supplies. Since that verson isn't available, you must use a 42VCT OR LESS transformer. Any more and you risk blowing up the LM12s when you first power the device up, which will be a $120 mistake if you build a stereo version.
It's official, my amp has been decomissioned. It developed an annoying hummmmmmm bout the same time I took delivery of my Phase Linear 700, and thus it was disassembled. It's remins now sit in a largish anti-static bag, with the heatsinks and panels finding theor way to the recycling depot, and the power trnsformer finding it's way into the perfect spot to stub my toe. The amp is dead. Long live the amp.
I will not be liable for anything relating to this project, under any circumstance and in any condition. If anything bad happens, it is not my fault
Working with hoigh power electronics and AC lines is inherantly dangerous. Everything here is provided for informational purposes only. If you build it, you take full responsibility.
Pictures!
I've got pictures of my (kinda) completed amp. It worked, and that's all that mattered to me.- Right channel, view 1. Nothing special, except that my coils are HUGE for what they have to do. They should have been 18 or less guage magnet wire. I had the 14 guage house wire laying around, so...
- Left channel, view 1. This was the first channel I biult. PAy attention to the wiring! I spent 2 weeks debugging the fact I grounded both inputs to the LM12....drove me nuts, and boy did I feel stupid when I found it.
- Right channel, view 2. This is what Joe User will see once the amp is done. Well, the RCAs will be on the back of the case, along with the binding posts, but thas is about how it will look. The heatsinks came from some kind of industrial driver. I have no idea what it was, but I also got a 200A bridge rectifier out of the beast before I tore it apart.
- Test Fixture, right channel. This is how the setup was when I was testing the channels after construction. The caps are the 'small ones', 33,000uF @ 60VDC. The transformer weighs about 30 pounds.
- Closeup, right channel. This is an up close and personal look at the inverting amp in the right channel. 17 parts per side, including the (omitted) bypass caps!
- Finished amp pic 1 Top view over the front panel. Notice there are no top or bottom panels. It's not really finished, but it's close enough for government work.
- Finished amp pic 2 Top view over the back panel. Nothing special here. The RCAs and the binding posts are rat shack specials.
- Finished amp pic 3 Back panel, low angle. A better view of the business end of the amp.
- Finished amp pic 4 Bottom view, south up. This shot plainly shows off my lack of cuttting fluid when tapping the holes for the crossbraces. Note 4 screws out of 9 holes total. What a waste.
- Finished amp pic 5 Repeat of view one. Nothing special here.
I'm planning on putting together a parts list soon. Suffice it to say that with some careful shopping and good luck you can put together a beast like this for ~$75USD. If you buy everything retail, well, I don't want to think about that. The LM12 is $32US in small quantities. Ouch. The 4 pin LM12-specific socket (!) can be ordered from Newark Electronics (www.newark.com) as Augat part number 8112-AG7, to the tune of US$12 per. Ouch. This link should take you directly to the part order page.
| Amplifier Schematic | In GIF format |
| Power Supply Schematic | In GIF format |
My costs went as follows:
| Part | Source | Cost |
|---|---|---|
| LM12CLK | Donation | Free! (~$32US) |
| Transformer | EBay | $18US |
| Filter Capacitors | Purdue Salvage | $2US |
| Discreet parts (resistors, sm. caps, diodes) | Active ELectronics | ~$25US |
| Heatsinks | salvaged | Free! |
| Everything else | junk box | Free! |
