| joecool85 |
| Thats right, not lm3886, but lm386. I'd like to drive a pretty small 4 ohm speaker with a couple lm386's. I know that they are good for 8 ohms, so running them in parallel should be fine for 4 ohms. Problem is, I don't know how to parallel chips lol. Any ideas? |
|
|
| neutron7 |
well it can power 4 ohms by itself. not very well or anything but it can do it. just try one and hook it up to the 4 ohm and see if it will go loud enough for your application.
if you want to try to parallel them try to just build 2 the same and connect each output to the speaker output capacitor through a resistor. I am not sure what value yiou need for a little amp like that. 0.1 ohm is common for lm3886 in parallel . they may run a bit wermer though you might want to stick some ramsinks on there.
|
|
|
| neutron7 |
little heatsinks that PC modding stores sell to stick to the RAM chips on video cards. they are of questionable use in that aplications but can cool any IC a bit.
any chunk of aluminium that fits on there ought to help. |
|
|
| EWorkshop1708 |
With paralleling LM386 chips, you can use 0.1-0.5 ohm output resistors with no problem. But LM386 is rather weak chip for any real power, but they still go nice and loud.
***However, DON'T bridge LM386***
I did that using 5 and 12V to run the 2 LM386 IC chips. Used an 8 ohm speaker and bridged. Even with only 5V, it played very loud, but ran warm. When I bridged with 12V it played extremely loud, but after 15 seconds the chips got hot and blew! lol :hot:
Instead of LM386, why not use a better chip that can safely drive 4 ohms with a decent amount of power? Even if you are using 6V or so of supply, a typical car audio IC will do fine.
Most car radio IC can drive 2 ohms/channel, or 4 ohms bridged. Much better IMO. |
|
|
| joecool85 |
Do you have a good example of a car audio IC that I could easily get a hold of?
Also, this thing doesn't need to be a screamer, just enough sound to play an electric bass through at low levels. Roughly speaking level. Using one lm386 on an 8 ohm load proved plenty loud for guitar. |
|
|
| EWorkshop1708 |
A chip I'm about to use for an amp project is the AN7147 which is 5W/channel @ 12V 3 ohms. I'm using this to boost the output of my soundcard for a stereo headphone amp :eek: and to drive small computer speakers too. The IC manufacturer says you can run without a heatsink if not putting out much power, but I'd still recommend a heatsink, even if it's just a flat piece of metal.
AN7147 DATASHEET: http://www.datasheets.org.uk/search...&ExactDS=Starts
This website has them for $1.40 a piece:
http://www.futurlec.com/Sanyo/AN7147pr.shtml
Also, since it's a 2 channel chip, you can parallel the two channels on the chip to drive 1.5 ohms :D
|
|
|
| N-Channel |
Joe,
Try NEC's mPC1230H2. I use to use this chip until I graduated SMPS-powered discrete Amplifiers.
I believe the old Alpine3505 (2-channel)and 3510 (4-channel)Amps used this chip. It is rated at 13W into 4W at 14.2V. Many of Alpine's old-old school (1980s) head units also used this chip. It is has BTL (Bridged Transformer-Less) output that enables the 13W rating.
I used a number of them to drive some Radio Shack Minimus-7s with exceptional results. The bass was strong and tight, the highs were crisp but not too bright, and the midrange was very full of presence- an all-around great chip to use.
I think they can still be ordered from Parts Express or MCM Electronics. for about $5-7 each.
Hope this helps,
Steve |
|
|
| N-Channel |
| Well, I just looked at MCM's catalon-online, and they're........discontinued. :bawling: too bad. These were great chips. NTE's version (NTE1389) might still be available somewhere.... |
|
|
| EWorkshop1708 |
| quote: | Originally posted by N-Channel
Well, I just looked at MCM's catalon-online, and they're........discontinued. :bawling: too bad. These were great chips. NTE's version (NTE1389) might still be available somewhere.... |
NTE is overpriced.................
Being that he's only playing with simple chips, that's why I told him to go with AN7147, because it's just as easy to hook up as a LM386, nearly as cheap too, and they are still available, and it does not require much heatsinking. Also does not need any resistors other than 2.2ohm/0.1uf zobel network.
If he's wanting some real power from 12V, he could always get one of those 50W max BTL Car radio chips :eek: :hot: |
|
|
| triden |
| What I would probably do instead of paralelling the chips is make a simple push-pull current gain stage on the output using 2 bjt transistors. This way you are limited only to the amount of current that the transistors can provide. Adding a small single output stage would be a fairly easy to do. |
|
|
|
