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#1 Posted : Monday, July 30, 2007 9:19:30 PM(UTC)

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Joined: 7/30/2007(UTC)
Posts: 3
Location: Canada

Just thought I'd put in here some of the modifications I have done to the basic Kookaburra kit. I don't have the most recent PCB revision (might even be the first PCB rev) so some of this may not apply to new Kookaburra boards. The first thing I did was jumper a wire from pin4 to pin1 on the PGA2311 because the PIC used for this project cannot set pin1 high on it's own. This enables the zero-crossing detector and is supposed to reduce the switching noise when changing the volume, although I can't say that I could notice any difference at all.

The next thing I did was replace the 1n4004 diodes with MUR140 fast recovery diodes. I did this the same time I changed the rectifier on my Mauro My_Ref amp to MUR820 diodes. I also don't have the latest rev of PCB for the My_Ref, so I didn't have nice proper pads to solder the MUR820's to the My_Ref, so it was a bit of work, but fairly easy as the diodes are a big part and easy to solder.

The hard soldering came with replacing the OPA2227 with LM4562. I had to remove the 100nF caps on the power supply rails next to the op-amps, and even then it was fairly difficult replacing the SOICs because I had to hold the iron vertical as to not melt anything.

Next on the agenda is the regulators. I plan to replace the 7812/7912 regulators with LM317/337 optimized for low noise. I will construct the regulator on veroboard, and solder the veroboard in place of the 7812/7912. If all goes will it should end up being only slightly chunkier than the current regulators. I'll replace the 12V zeners on the My_Ref with these as well if they turn out okay. Here's what I have for low noise regulator design. I think it's about as good as you can ask for with the LM317/337 regulators:

Edited by user Wednesday, August 1, 2007 10:41:50 AM(UTC)  | Reason: Not specified

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