Jump to content
Electronics-Lab.com Community

LM384N/NOPB-IC amplifier with heatsink


Guest abador08

Recommended Posts

Guest abador08

Hey everyone, I am trying to build an amplifier that I can hook up to some floor speakers that a friend gave me. They have an 8 ohm load and they're rated for 65 watts. The ic that I'm putting in the circuit is rated for 5.5 watts so there's plenty of room before it gets to the rated wattage. My main question is about the heat sink. The datasheet says it needs a staver v7 heatsink but I can't find it anywhere and I can't find anything with the right dimensions. Is the heatsink really necessary or is there a good alternative? Also my next question is this, how loud can 5.5 watts get? Is it pretty loud?

Link to comment
Share on other sites


The LM384 is VERY old and needs the obsolete heatsink to survive. Use a newer amplifier IC.
With the obsolete heatsink its output was 5.5W with horrible sounding 10% clipping distortion. Its output before clipping was about 4W which sounds only a little louder than a cheap clock radio.

A modern LM3886 IC can be mounted on a real heatsink and produce 50W into 8 ohms at very low distortion.

Link to comment
Share on other sites

Guest abador08

The LM384 is VERY old and needs the obsolete heatsink to survive. Use a newer amplifier IC.
With the obsolete heatsink its output was 5.5W with horrible sounding 10% clipping distortion. Its output before clipping was about 4W which sounds only a little louder than a cheap clock radio.

A modern LM3886 IC can be mounted on a real heatsink and produce 50W into 8 ohms at very low distortion.


What is the input power on this one. I would like to keep the input voltage below 20 volts so I can use a wall adapter or maybe a laptop charger to power it but I am open to suggestions on other power sources. Also is this surface mount or is it through hole? I am planning on getting my IC through radio shack so it will need to fit in those holes if possible. Is there a place that can print a circuit board for me for around $5 or is that unreasonably low? I'm getting my supplies through Newark right now.
Link to comment
Share on other sites

The datasheet for an LM384 amplifier IC shows that with a 20V supply its output is about 3W into 8 ohms before clipping. It heats with about 2.5W so it will need a pretty good heatsink that is not available anymore. How will you cool it? The maximum 20V current is (3W + 2.5W)/20V= 275mA.

Radio Shack online does not have an LM384. They have a low power (0.45W) LM386 instead.

An LM1875 amplifier IC is available at Digikey and many other places (not at Radio Crap). It can be bolted to a modern finned heatsink. With a 16V supply its output is about 2.5W into 8 ohms and with a 60V supply its output is 32W.

A modern amplifier IC (might not be made anymore, 10 years ago there were 76 amplifier ICs available made for car radios) uses two amplifiers in a bridge. Each amplifier drives each wire of a speaker out-of-phase so that the effective voltage is doubled which also doubles the current resulting in about 3.5 times more output power.
Today many amplifier ICs are in tiny surface-mount packages and use class- D (PWM) so they do not get hot.

Link to comment
Share on other sites

You'll never be able to drive those speakers from with a power supply voltage of 20V is 25W but in reality the usable power will be half that so don't worry about blowing those speakers.

How many channels do you need? If it's just mono, then I'd recommend the TDA2009 bridged, if it's stereo, there are plenty of bridge stereo amplifier ICs to choose from.
http://docs-europe.electrocomponents.com/webdocs/0acf/0900766b80acf1b0.pdf

Link to comment
Share on other sites

Guest abador08

I would like to have stereo sound so each speaker has its own input. Also I would like to ad a bass knob if possible so I can crank the bass if I want. Would a low pass filter be suffice or would it need to have a whole circuit dedicated to the function? I would also like to have a space for a sub woofer if possible though I don't have a sub woofer right now. At the same time I would like to keep the circuit as simple as possible since my experience with electronics is limited.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
  • Create New...