Good circuit diagram for LM3886

[koljosli]

First of all, hi too all of you. This is my first post, and i'd like to ask does anyone of you have a good circuit diagram (or schematic) for the LM3886. I found several of them on the internet, but i don't know which of those are good.
I would really like to make one really high quality sounding amp..

Some prepositions ? ?

 

[firechief]

Start with the National Semiconductor data sheet. Look for the schematic that thet call "typical application". Spend some time reading the text. Google their web site, much to learn grasshopper.

 

[AndrewT]

the LM3886 typical NS schematic omits too many components. Look at Fig and read functional description on p8 very carefully to see some of the extra components that all beginners should fit. Unfortunately Fig2 is specifically for single supply and includes a few components/wiring specific to this PSU.


I suggest you build a mono AC coupled amplifier using all the optional components and using all the passive filters and listen. You can then decide if you need better and move on with some experience under your belt.

 

[koljosli]

Thank you for the quick respond. I've been searching and searching, reading how people built the curcuit from the NS and how they got offset like V- on the output. I got many custom schemes, and many comments... But i'm wondering is this circuit workable http://www.diyaudio.com/forums/chip-amps/163034-another-single-sided-diy-pcb-lm3886-power-supply.html

 

[AndrewT]

Single sided is different from single supply.
Most modern Solid State power amps use a dual polarity supply.
A single sided PCB allows for easier home DIY of the PCB.

 

[koljosli]

Anyone with some other circuit recommendations ??

 

[jackinnj]

Bob Cordell auditioned his LM3886 "Super GainClone" amplifier at the New Jersey Audio Society DIY meeting in October -- page 539ff his book. Sounded wonderful. His design buffered and inverted the input signal to the LM3666 "inverting" input using an OPA2604 -- reduces common mode distortion. I'm sure the folks at National wish he'd used the LME49880 -- but it's only available in PSOP!

 

[aandre2200]

Hello, everyone,

This also my first post and, as luck would have it, I am also about to start putting together a chip amp using two LM3886. I am just beginning to get my feet wet in this field. Therefore, I bought a PCB on ebay, all the way from China. The PCB has everything on it: preamp (NE5532), PSU, and power amp. The circuit is somewhat different than the NS “typical application”. Instead of the parallel 10R+0.7uH in series with the output, it has 10R+ 100n (in series) installed in parallel with the output. Frankly, I don’t know what difference does it make and how good the circuit is, but I will build and test it. I will also post here the results of my experience.

I have all parts, except for the heatsink, which brings me to the question for the more experienced contributors of this forum: Has anyone experimented with a CPU heatsink (including the fan)? This is right now my option at hand, and I would greatly appreciate any comments on the issue. Thanks in advance.

 

[gideon]

Hi aandre2200,

My gainclone is using two realy small graphics card cpu heatsinks that i got for a bargain.
i ported out one of my PS transformers' secondaries and regulated it to 12v with an lm317.

This run the amp super cool, it did introduce a little hum which only if the volume is a high without music you can hear if your ear is close to the speaker.
The fans also make noise themselves, so its ok if you are not sitting next to the amp.

good luck

 

[aandre2200]

Thanks, gideon.
It sounds like a P4 copper heatsink could do the job even without a fan. Who knows, if I add the fan, I may be able to attach two LM3886 to the same heatsink. It's worth trying, provided I monitor closely the temperature.