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Old 21st September 2009, 10:22 PM   #1
diyAudio Member
 
Join Date: Sep 2009
Location: Jönköping, Sweden
Default My first project --> lm3886

Hello everyone!

I'm new to this and would like some guidance from you

So, I've got this project work for school and decided to build myself an Gainclone.

I've been looking around for parts, and I found the cheapest ones on ebay (ofc).

Since the difference in price is quite big I'd rather stick to the ebay ones.

The one I've been looking on in particular is http://cgi.ebay.com/LM3886-Hi-End-AM...d=p3286.c0.m14

Is it any good, or is just a waste of money?

Also, what specs would you recommend on a transformer? 2x24v, 250VA enought to power the GC I linked above?

If it turns out that this GC kit isnt any good, what would you recommend for a newbie like me, that have a very limited budget?

Thanks

Maxhax
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Old 22nd September 2009, 12:52 AM   #2
Minion is offline Minion  Canada
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Join Date: May 2006
Location: Cowican Bay , vancouver island
Ive used those kits and simular ones with mixed results... they really scrimp on the Parts , mainly the bypass caps on the LM3886 boards , I believe they were 220uF caps that came with the kit when a minimum of 1000uF is really needed , the PCB"s were ok though so Now I just buy the PCB"s and source my own parts which is considerably cheaper , at least for me ...

but yes they will make a working amp that should sound good , if you upgrade some of the parts they should better ....

I haven"t used the Power supply kit but I have used the PCB"s for the Power supply and they are good ......

As for the Power transformer, 225Va is fine for a stereo amp but the Voltage really depends on the Load it will be driveing (yer speaker impedance) so if you are doing strictly 8 ohm speakers a 2 x 24v Transformer is suitable , if you are running 4 ohm speakers a 2 x 18v Transformer would be better , also a 2 x18v one would also be fine for 8 ohms but with less power than a 2 x 24v transformer ......


Good luck
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Old 22nd September 2009, 01:13 AM   #3
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Join Date: Feb 2009
Quote:
Originally Posted by Minion View Post
As for the Power transformer, 225Va is fine for a stereo amp but the Voltage really depends on the Load it will be driveing (yer speaker impedance) so if you are doing strictly 8 ohm speakers a 2 x 24v Transformer is suitable , if you are running 4 ohm speakers a 2 x 18v Transformer would be better
i presume this had been discussed so much, but i'm asking anyway, sorry
could you describe me why better?
i'm running such a kind of dual-mono gc, 4x24Vac transformers, 120VA each, and 4ohm speakers..
something relating to LM's current limits, which doesn't allow to use all these volts?
only more unuseful heating?

Last edited by madqwerty; 22nd September 2009 at 01:18 AM.
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Old 22nd September 2009, 03:22 AM   #4
Minion is offline Minion  Canada
diyAudio Member
 
Join Date: May 2006
Location: Cowican Bay , vancouver island
The IC Package only can dissapate so much heat , at 4 ohms and +/-35vDC the chip will try to deliver more current which means the chip has to dissapate more heat and eventually go into thermal shutdown due to it"s thermal protection , the datasheet shows this stuff....
You might get away with it at lower volume levels but you risk it overheating ......


Cheers
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