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Old 12th October 2010, 08:16 AM   #1
ampimp is offline ampimp  United Kingdom
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Join Date: Sep 2009
Location: coventry
Smile newbie needs a little direction

Hello
I built a lm3886 amplifier last year. I madel lots of mistakes but the amp worked and managed to sound very good. I have been doing lots of reading and am now ready to move on a little . I have a pair of 2sc5200 and compliment's and would like to build a class a/b amplifier approx 30- 40 watts into 8 Ohms and simple . They are genuine they where pulled from a tired old nad c320 bee lol. The reason i choose class a/b over a is down to size and cost of the psu.
My inspiration so far comes from the one and only.
Nelson Pass: wow i have just read article on finding sweetspot
Andrew t: Your guidence to others has been a great help and i have gained a lot too.
And not forgetting Peter With his fantastic looking amplifiers a great inspiration.
Im sure this list will grow over time.
many Thanks
Ian
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Old 12th October 2010, 09:33 AM   #2
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Hi,
read Leach's papers on the Low Tim.
I don't recommend building it, but he explains fairly clearly why he made some design decisions.
Worth reading D. Self, again for insight into why design decisions are arrived at. Many of his papers are in his website, or be extravagant and buy his 5th edition.
Look at ESP for possible project.
DX is another possibility.
The single pair version of the various Mongrels would be an excellent way to start. You just build a new voltage amp stage to hear what the changes have done to the sound. A really cheap and easy way to learn the art of designing.
Which closes the circle: The Art of Linear Electronics by the late John Linsley Hood (JLH on this Forum).

BTW,
your 1pair output stage of 2sa1943/c5200 is good for 50W into 8ohm speaker.
This will require a transformer of between 25Vac and 30Vac. I would tend towards the 25Vac or 28Vac end, rather than push the SOAR of the Toshibas.
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regards Andrew T.
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Old 12th October 2010, 10:40 AM   #3
ampimp is offline ampimp  United Kingdom
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Join Date: Sep 2009
Location: coventry
Smile Attention all newbies

Hi
Thankyou for the guidance Andrew it is much appreciated and very much needed.
I used to mess with hifi and pa amplifiers in the early 80,s 90's.
And read magazines inc practical electronics and elector and the awsome rs electronics catalouge of the day as it goes i remember maplins used to carry a lot of componet data too.
So i started out changing out all the carbon resistors for the new low ppm metal film resistors and upping psu caps changing electrolytic for film type on input. Now and again i got lucky and there was an improvement! I thought, or was it just diffrent im still not sure.
The Last amp i built was a maplins high power kit in the early 90,s
i used only the main output pcb and the psu board that was stabalized to feed the driver board. it used 8 mosfets on each rail at 90 volt's.
i found some massive 80'000uf 100v caps at a surplus shop i bought two cases of them at 2.00 each 24 in total i used two of these in parralell per rail each output device was hard wired through its own fuse and straight to the psu The transformer was over spec and was made by a very clever gentalman at a company called repanco apparently they used to produce world class transformers any way this thing would still play for at least 30 seconds at disco levels with no mains power before it started to distort.
Anyway sorry for the rant. Im not a total electronics newbie i have used etch resit pen and also taped direct to board and have done a little photo etching as well . And at last i think i may be best sticking with the lm 3886 for a while it may be a small ic and its circuits are simple but boy can it be made to sound diffrent. supply voltage, mains transformer not just size but type and make , the psu caps not just make but value also i found loads of uf just thrown at psu wont make it sound good and i used to love big caps as you wil have read . The layout last but no means least
And i promise for now that is it. Till next time . im off to do some reading in silence. By the way once bent the pins dont like being bent back again they will fall of now no music untill i can get some more 3886 tomorow .
Thankyou Andrew
regards Ian
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