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xrk971 Pocket Class A Headamp GB

here's the board, do not judge the soldering it was my first time soldering SMTs,
I did not settled down for Altoids box, i m making my own, but since i m in the middle of moving , it's gonna take a while until i can finish the box ;)
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Founder of XSA-Labs
Joined 2012
Paid Member
Thanks for sharing photos. In case you did not see the revised BOM, replace the 100uF rail caps with 2200uF caps (25v since you can afford the size) and that will improve stereo separation/imaging and improve bass response. Also, if you are using headphones lower than 250ohms, use 1000uF 16v oscons x 2 as output caps, or a single 1000uF Panasonic FR.
 
Founder of XSA-Labs
Joined 2012
Paid Member
You don't need a transformer. I suggest against it in fact. You will just get hum if you are not careful. SE Class A amps have no PSRR so the power supply must be absolutely clean and free of ripple (<500uV AC under load). So use a SMPS followed by some filtering like CRCRC or a capacitance multiplier. Or if you want to use a linear transformer and bridge - follow it with a cap multiplier and CRCRC.

I think some people have used an LM317 regulator with good results. Higher performance ones from Linear Technologies also work. But in my experience, a good 19v laptop SMPS frommmajor brand (HP, Dell, etc) will be superior to a transformer bridge and caps.
 
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You don't need a transformer. I suggest against it in fact. You will just get hum if you are not careful. SE Class A amps have no PSRR so the power supply must be absolutely clean and free of ripple (<500uV AC under load). So use a SMPS followed by some filtering like CRCRC or a capacitance multiplier. Or if you want to use a linear transformer and bridge - follow it with a cap multiplier and CRCRC.

I think some people have used an LM317 regulator with good results. Higher performance ones from Linear Technologies also work. But in my experience, a good 19v laptop SMPS frommmajor brand (HP, Dell, etc) will be superior to a transformer bridge and caps.

thanks for the input, laptop ac adapter with filtering it is ;).
 
So this is what I did with the cap multiplier board and the step up converter:
Now there is a choice of running it off batteries or off USB (via step up converter board). I used a leaded cap for the 100uF on the cap mx instead.
Haven't figured out an elegant way to mount the step up so the USB port is accessible from outside, but then again this particular build just sits on my desk/around the house. Will have to work something out for the one in an actual altoids tin.

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Thanks :) it's just a quick project since i want to listen to this amp and i do not like it hanging on a piece of scrap wood or something.
yeah i do have a laser engraver. the box needs a little more work but i ll probably let this one go as it is and use what i learned for the next one using the good veneer, lol.
the box held together by glue, the bottom is removable ( held by screws ) to have access to the board and yeah as you see the battery compartment has removable cover held by magnets, wanted to make it like drawer but it would make the box a little larger.

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Finally ordered components for the RL mod. I'm going to try it upgraded with all thin film resistors on my OSH Park boards. The CRC noise filter will be Panny FCs with these tiny metal foil chip resistors soldered to the leads between caps. Hopefully this setup will get me the cleanest DC possible from a rechargeable battery in a mint tin! I found this article on resistors for audio enlightening.
 
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