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JL889 31st October 2011 01:38 PM

Chipamp 4780 (1) Beta Build
Post your results for the 4780 (1) beta build here.

LM4780 amp board
R1 = 22.1K
R2 = 22.1K
R3 = 681R
R4 = 22.1K
R5 = 681R
R6 = 221R
R7 = 221R
R8 = 0.1R 3W
R9 = 0.1R 3W
C1 = 1500uF 50V
C2 = 1500uF 50V
Cz1 = 0.1uF 63V
Cz2 = 0.1uF 63V

Rodeodave 16th November 2011 08:23 AM

2 Attachment(s)
Sneak preview :D

Boscoe 17th November 2011 09:42 AM

Received mine today they look very good! I've got all the passive parts just need to wait for my samples of the LM4780 from national then will start building and testing!

JL889 17th November 2011 12:14 PM

I like the progress, good job guys!!

Rodeodave 18th November 2011 10:27 PM

1 Attachment(s)
The amps are up and running :D

I'll pull some numbers from the circuit tomorrow (I hope). So far everything is looking fine.

Boscoe 19th November 2011 05:32 PM

This may be a stupid question buts what's the mute implementation? Do I need a 5k resistor to -vee to bring it out of mute? From CHG to -vee?


Rodeodave 19th November 2011 05:48 PM

1 Attachment(s)
You'll need a 10k resistor, 1/4W will do fine. Look at the attached pic, it's at the top in the middle.
On the underside of the board there are two solder pads, a 1206 package size SMD resistor, or as in my case, a MELF resistor (MMA 0204 series) fits nicely. You could also use a regular resistor with it's leads bent accordingly.

Oh, and do yourself a favor and add coupling caps at the input. With 22k to ground it should be between 1.47uF and 2.2uF (-3dB @ 5Hz which is 2 octaves down from 20Hz).

Boscoe 19th November 2011 07:23 PM

Thanks for that I wondered why I wasn't getting any sound! I suspected the mute. What are the larger resistors used for on the underside?

Rodeodave 19th November 2011 08:07 PM

They're 2R7 2W Vishay/Phoenix PR02 metal film resistors and they are needed to complete the Zobel networks (R-C in series to ground). They're missing from the BOM, just like the muting resistor.

Boscoe 19th November 2011 08:16 PM

That's fine I didn't order any but I got some 3r3 would that be okay?

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