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Old 11th September 2008, 02:00 AM   #1
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Default My first Chipamp

well after doing a fair amount of reading i purchased a lm4780 kit from audiosector. after sitting around with the kit for some time now i finaly started it tonight. i'm not really all that good with a soldering iron but i did try my best.

has any one built this kit? i am afraid i do not know what cz, rz, and rm are. i could not find them in any of my packets of parts. maybe they are optional? any insight would be great.

also i still am undecided if i am going to run the chips bridged, parallel, or just make 2 stereo amps.

see the pic for whats done so far and the heatsink i plan on using.
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Old 11th September 2008, 02:05 AM   #2
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start with making one stereo
this is the standard and will have less problems/issues
then later you can try bridge/parallel

i also do not know what those cz, rz, and rm are
did you consult The Manual?

Peter Daniel has put together a very good builder instruction called
User Guide or something like that
you can download this PDF from the website KIT page
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Old 11th September 2008, 02:14 AM   #3
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Default Re: My first Chipamp

Quote:
Originally posted by Trooper46
well after doing a fair amount of reading i purchased a lm4780 kit from audiosector. after sitting around with the kit for some time now i finaly started it tonight. i'm not really all that good with a soldering iron but i did try my best.

has any one built this kit? i am afraid i do not know what cz, rz, and rm are. i could not find them in any of my packets of parts. maybe they are optional? any insight would be great.

also i still am undecided if i am going to run the chips bridged, parallel, or just make 2 stereo amps.

You can find more specific info about that particular kit here: http://www.diyaudio.com/forums/showt...565#post636565

Also, LM3875 online user gide is quite useful as well, as both kits are very similar: Commercial Gainclone kit- building instructions

Rz and Cz are Zoble parts and I personally don't recommend using them, that's why those parts are not included with a kit.

Rm is mute resistor (10k). It is tiny SMD part and should be inluded with a kit; the amp will not work without it.

For bridged application you need to provide balanced signal to the amp. Parallel and stereo option will work with all standard sources.

Your heatsink looks very good, don't forget to isolate the chip; the yellow plastic strip (inside the schematic) was provided for that purpose.
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Old 11th September 2008, 02:24 AM   #4
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thanks for the quick response. i think i will build this first one stereo. hey that way i can have two amps right!?! so i do not have to source the zobel components, but i do need to install the mute resistor. sounds good. i'll keep this thread updated until i have a working gainclone! once again thanks for the help guys!
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Old 11th September 2008, 02:36 AM   #5
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Yes, with a stereo setup you will get 4 separate channels from one kit.
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“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
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Old 12th September 2008, 02:44 AM   #6
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board is pretty much done. need to get that led and resistor for it still. i also seem to be running into issues trying to find a suitable transformer. parts express seems to be out of every one that i've heard of people using. they do however have a 250 VA 2x18V. would this be suitable? i'm still trying to push the 60 watts a channel out of this thing.
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Old 12th September 2008, 09:35 AM   #7
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Check this graph for power output vs transformer voltage:
http://www.diyaudio.com/forums/showt...92#post1508992

Divide the voltages in the graph (DC) by 1.4 to get the transformer secondary voltage (AC). For 60W into 8 ohm, you need 35V DC. Which would require a 25V transfomer.
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Old 12th September 2008, 01:05 PM   #8
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thanks, guess im just going to have to wait for 25v secondary toroids to come back in stock.
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Old 12th September 2008, 09:50 PM   #9
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well its all soldered up, with led and everything, but i had to use a 100k resistor because i didnt have any 62k. hope the led still works. well i guess my question is, is there any way to test the amp before my toroid gets in?
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Old 13th September 2008, 12:43 AM   #10
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Well,the only way to test your amp is with the transformer.Be patient and do not rush your work.make sure to check and re-check all connections before you plug it in. You can use a light bulb to be in the safe side.Good luck.
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