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.
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.
Attachments
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
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
Trooper46 said:
You can find more specific info about that particular kit here: http://www.diyaudio.com/forums/showthread.php?postid=636565#post636565
Also, LM3875 online user gide is quite useful as well, as both kits are very similar: http://www.diyaudio.com/forums/showthread.php?s=&threadid=123003&pagenumber=1
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.
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!
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.
Check this graph for power output vs transformer voltage:
http://www.diyaudio.com/forums/showthread.php?postid=1508992#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.
http://www.diyaudio.com/forums/showthread.php?postid=1508992#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.
I would recommend using them.
Why?
Answer:
1. Because some loudspeakers will REALLY need them.
Some speakers would fool you that Zobel is not needed.
Next time your amplifier will make one Burn Out in Smoke, of your new set of LoudSpeakers
Would you really like this?
2. Because they are recommended by those making these Amplifier Chips!
3. Because the designers should know better than anyone, what is safe use of LM3875 & LM3886.
4. Because some AudioPhiles are not very smart .. at least compared by
National Semiconductor worldwide big, big company Technical Engineers staff
.. and neither am I, Lineup
5. But I am actually smart enough to give people some good advice
.. to prevent unnecessary DISSASTER
Lineup
Why?
Answer:
1. Because some loudspeakers will REALLY need them.
Some speakers would fool you that Zobel is not needed.
Next time your amplifier will make one Burn Out in Smoke, of your new set of LoudSpeakers
Would you really like this?
2. Because they are recommended by those making these Amplifier Chips!
3. Because the designers should know better than anyone, what is safe use of LM3875 & LM3886.
4. Because some AudioPhiles are not very smart .. at least compared by
National Semiconductor worldwide big, big company Technical Engineers staff
.. and neither am I, Lineup
5. But I am actually smart enough to give people some good advice
.. to prevent unnecessary DISSASTER
Lineup
The zobel basically provides a low impedance path at high frequencies to counter the effects of cable and track inductance, and damp any high frequency oscillation.
http://en.wikipedia.org/wiki/Boucherot_cell
At an amp output, it should be called Boucherot cell, its function here is slightly different from a Zobel, which is used in passive crossovers. The terms are used interchangeably.
For short cable runs it may not be needed.
http://en.wikipedia.org/wiki/Boucherot_cell
At an amp output, it should be called Boucherot cell, its function here is slightly different from a Zobel, which is used in passive crossovers. The terms are used interchangeably.
For short cable runs it may not be needed.
thanks for the clarification
i finally have acquired all of parts i need. now i just need to build a case to keep it in. i was thinking about using a big Al heatsink for the front and making the rest out of mirrored acrylic. would this cause any issues with grounding? i have seen many cases made out of wood and metal, but only a few with any acrylic on them.
i finally have acquired all of parts i need. now i just need to build a case to keep it in. i was thinking about using a big Al heatsink for the front and making the rest out of mirrored acrylic. would this cause any issues with grounding? i have seen many cases made out of wood and metal, but only a few with any acrylic on them.
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