LM4780 SS Pcb - Page 6

pinkmouse · 11th December 2006, 03:32 PM

I've never bothered, I just use 5% for outputs

mhennessy · 11th December 2006, 03:32 PM

Quote:

Originally posted by CarlosT
Da**! I've never seen .1% resistors...you guys sure you're not talking about 1%?

Yes, they exist - for example the RC55Y series. And they're expensive - nearly a pound each. But the point is, you don't need to buy them - you'll be able to find enough in a batch of standard 1% components that are well-enough matched.

Quote:

Originally posted by jaste
So the low-value output resistor is hard to meashure, maybe I´ll get that one from 0.1% department rigth away tehn, or do the even exist in that tolerance?

I've never seen better than 5% for those, but who knows what's out there given enough cash? Trouble is, at those values, the component leads and PCB tracks have a comparable resistance. I was able to match up components quite well from a batch of 5% parts... I used a current source and voltmeter to make the measurements

jaste · 11th December 2006, 04:23 PM

so how important are the matching of the output resistors, should be as important as any?

CarlosT · 11th December 2006, 04:24 PM

What's an output resistor?

gmphadte · 12th December 2006, 09:57 AM

Refer sch at post #34
R11 and R12 are output resistors and u will use them for parallel mode operation only. If you want to make a stereo version do not install them.
At no time u should connect all the 3 speakers even if it is shown. U either connect the middle only with R11 and R12 installed or connect the top and bottom speakers(Left and Right) without R11 and R12.

Gajanan Phadte

pinkmouse · 12th December 2006, 10:04 AM

Quote:

Originally posted by gmphadte
At no time u should connect all the 3 speakers even if it is shown.

Indeed.

jaste · 12th December 2006, 10:56 AM

Just making sure I got it right, the thing called "J" in the scheme is just a wire to connect the two sides if you wanna go parallel?

pinkmouse · 19th March 2007, 01:24 PM

Discussion of pirate SW removed to Texas

baskiria · 19th March 2007, 01:25 PM

Thanks pinkmouse

superR · 26th January 2011, 05:23 PM

I today verified that pinkmouse's design still works

Made a pcb and at first it didn't work. Turned out the chip/input-ground was not connected to the power supply ground. Maybe I did something wrong with the "ratnest" function but after connecting both power and signal ground, presto, music from my loudspeaker.
I used no zobel due to the fact I didn't have the parts available.
Other parts used;
resistor between input and +in 1 k
resistor between inout and gnd 20k
feedback resistor 20k
-in to gnd 1k
mute resitors, 10k each
mute elco 100uf
psu elco (on pcb) 1000uf and 0.1uf
http://www.zelfbouwaudio.nl/forum/do...5222&mode=view
http://www.zelfbouwaudio.nl/forum/do...5223&mode=view

11th December 2006, 03:32 PM	#51
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	I've never bothered, I just use 5% for outputs __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

19th March 2007, 01:24 PM	#58
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	Discussion of pirate SW removed to Texas __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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11th December 2006, 04:23 PM	#53
jaste diyAudio Member Join Date: Dec 2005 Location: Stockholm	so how important are the matching of the output resistors, should be as important as any?

11th December 2006, 04:24 PM	#54
CarlosT diyAudio Member Join Date: Oct 2006	What's an output resistor?

12th December 2006, 10:56 AM	#57
jaste diyAudio Member Join Date: Dec 2005 Location: Stockholm	Just making sure I got it right, the thing called "J" in the scheme is just a wire to connect the two sides if you wanna go parallel?

19th March 2007, 01:25 PM	#59
baskiria diyAudio Member Join Date: Jan 2006 Location: budapest	Thanks pinkmouse

26th January 2011, 05:23 PM	#60
superR diyAudio Member Join Date: Nov 2006	I today verified that pinkmouse's design still works Made a pcb and at first it didn't work. Turned out the chip/input-ground was not connected to the power supply ground. Maybe I did something wrong with the "ratnest" function but after connecting both power and signal ground, presto, music from my loudspeaker. I used no zobel due to the fact I didn't have the parts available. Other parts used; resistor between input and +in 1 k resistor between inout and gnd 20k feedback resistor 20k -in to gnd 1k mute resitors, 10k each mute elco 100uf psu elco (on pcb) 1000uf and 0.1uf http://www.zelfbouwaudio.nl/forum/do...5222&mode=view http://www.zelfbouwaudio.nl/forum/do...5223&mode=view

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