beginers guide

[laki101]

Hi guys great forum

so I'm new here a have 14 years (today exactly) I do have experience with electronics but no experience with amplifiers.

So what I need is some circuit for beginning something like 2 way mono amp low powered

But just one thing because I'm not really into 220v AC I would love something that I can power by a pre-fabricated power supply like a AC converter for lighting or computer power supply or something like that

[danielwritesbac]

Got a surplus laptop 15vdc Regulated power supply handy? LA4628 can provide a considerable amount of entertainment when powered by such a resource.

And, you don't have to worry about temporarily waiting around until the next project in order to achieve a powerful amplifier. Caveat: LA4628 is a small size, so do use some rather good CPU thermal paste between it and a nice heatsink.

[tomchr]

Actually, my first electronics projects were lab power supplies. I designed and built a couple back when I was 10-12 years old. You do have to be careful with the 220 V, though. Make sure you unplug the equipment before working on it, and verify with a voltmeter that there really is no voltage present before you work. Building a simple, unregulated, dual supply would be a nice project for a beginner with some experience. The 220 V is contained on the primary side and all you need to wire on that side is a power switch and a fuse. Maybe an in-rush limiter. Easy. But be careful.

For an amplifier, I suggest an LM3886. Follow the typical application schematic in the data sheet. With +/-35 V rails you should be able to get output powers on the order of 50-60 W into 8 ohms.

I would not recommend using a computer power supply. They tend to be rather noisy (both acoustically and electrically) and often they require a minimum load on one of the low-voltage outputs in order to provide regulation. Maybe you can dig out a medical switcher at a scrap yard. But in lieu of that, I think building your own supply will be easiest. Laptop supplies (as suggested above) may be another solution.

~Tom

[laki101]

Ok thanks guys

do you just have some circuit that works to suggest or anything with the LM3886 could do?

[tomchr]

Currently, I have a large heat sink with two channels of LM3886 built according to the "typical application" schematic on page one of the data sheet running in my living room. I'm using an old HP lab supply as a power source. It's a sweet amp! Mine is not a pretty implementation, but it does work. And it'll only be in its raw state until I get the chassis for my tube amp done. Then it's back up to the lab bench to get cleaned up.

I have to say that getting the LM3886 to run was quite possibly the easiest amplifier build I have ever done and I've done a good handful. You do have to pay attention to the grounding (use star grounding - google it if you aren't already familiar with this), but aside from that it's basically plug&play. You can see my implementation in this thread.

I think Panson Audio (pansonhk or panson_hk I think his username is here) out of Hong Kong sells LM3886 kits. Unless you want the thrill of point-to-point wiring (like I did), a kit is probably a good way to go. But a piece of perf board (aka Vector board or Vero board) or a simple PCB made by hand would work as well. I have no personal experience with Panson's kits but I have talked a bit with him through the forum and watched his posts. He definitely seems to have his brain plugged in and he has the test equipment to thoroughly test what he sells so I wouldn't hesitate to buy from him if I wanted to go the kit route.

Other keywords to search for: gainclone.

~Tom

[danielwritesbac]

Originally Posted by laki101

Ok thanks guys
do you just have some circuit that works to suggest or anything with the LM3886 could do?

It can do less than half as much power as LA4628 on a 17vdc regulated (or smaller) power supply.

In fact, on power supplies less than 55 volts dc (27-0-27 vdc), the LM1875 can beat the LM3886 on both quality and efficiency. The little chip is also easier to wire--with only 5 pins, it takes only minutes.

Now, up at higher voltages than these is where the LM3886 is used to good effect.

So, what power supply did you have in mind and how much power did you want from the requested "low power amp" ?

[laki101]

well cause its my first project I was thinking on something that is easy to make but runs good so I dont have any special power needs for now

And power supply I think I will make my own

[laki101]

Ok
I made up my mind

So I have 2 70w speakers (bass, mid and high tones) currently I have an 40 years old 50w amp, has great sound but it is starting to die

So I want a good sound quality 2x80w (70-100w is ok) and I will make my own power supply just *** little as possible 220v work. So something like 220v connector than an fuse and the coil and thats that with the 220v

cause I'm a total beginner with this I would like something with the complete circuit diagram and PCB design. So 1,2 links with complete design

Thanks guys

[laki101]

http://diyaudioprojects.com/Chip/LM3...886-manual.pdf
found this looks great sounds great also

now I just cant find hos much W output does it have so can you can tell me

[gootee]

Originally Posted by laki101

http://diyaudioprojects.com/Chip/LM3...886-manual.pdf
found this looks great sounds great also

now I just cant find hos much W output does it have so can you can tell me

It depends on the impedance of your speakers and the secondary voltage(s) of your power transformer. See paragraph 3 of section 2.1 of the pdf document from your link, and the LM3886 datasheet.