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Simple High Performance DC Coupled Class A HPA with sub PPM THD

Founder of XSA-Labs
Joined 2012
Paid Member
I have assembled the Xfeed, the CLC, and the Volume pot boards. I am missing some switches which need to be ordered still. In building this, I see that JPS64 added some header pins that appear to let the user select either AC coupled or bypass with DC coupling on input. This was after I hard wired a jumper where the input cap was.

The PCBs are easy to solder but due to 2oz copper and thick 2mm board - you need a fat chisel tip to apply enough heat to flow the Pb-based solder. For SMT I used Pb-free paste and it melts at a low 155C so easy to solder with hot air gun or hot plate, or iron and regular solder if you want.

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Getting closer to a full functioning amp. Just need to install Pchannel MOSFETs and mount on heatsink. Makle a bunch of JST connectors to hook it all up. I may hardwire jumper some switches just to get verification build done.

Just want to thank Jwarch for working out the BOM for me to use - mostly correct. I am keeping a list of things that need updating and will get to you.

Also thanks to Badoygolf16v for looking into the LDOVR.com voltage regulators as a group buy or discount.

However, I just saw these ones from China on ebay and they cost less and have a pot for adjustability.

TPS7A3301 Ultralow-noise LDO Regulator -3V~ -33V Max 1A Replace LM337/7905/7912 699926319329 | eBay

TPS7A4701 Low Noise RF LDO Regulator Power Supply Module 1.5V-34V 3.3V 5V 12V 1A 699923682709 | eBay

I will order a pair and test out.
 

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Last edited:
Founder of XSA-Labs
Joined 2012
Paid Member
2mm with ENIG finish just screams quality. Going back to anything less is tough now

I can attest that I de-soldered 8 times and only pulled off one isolated pad - not connected to anything) and it was because I was rushing it. You can see how much work it took to find the diode polarity error on the silk (Eagle library problem - not JPS64's fault).

But the 2mm FRP and 2oz Cu with ENIG really holds up to abuse with a fat chisel tip 60w iron and gorilla handling. :)

I agree it is tough to go back to 1.6mm and 1oz HASL :p