[Hutnicks]

Woot woot! DIYAudio member Raptorlightning has successfully implemented a USB-charging single cell lithium battery pack in the Pocket Class A! The amp can also run directly off USB power with this setup--a major benefit IMO.

He used a LiPo cell and three small circuits: an off-the-shelf boost converter board, a custom load-sharing board with a micro USB power input, and a tiny custom cap multiplier board that keeps the battery from going into auto-protect when the big capacitors charge up at turn on.

I'm hoping to do the same for my builds as soon as I fully understand his approach.

Hoo Yah. That is what I have been awaiting. Need to explore this big time.

On insane clown mode. I have an almost irresistible urge to go old school with this design and do a point to point wired version. I will consult a therapist obviously before going there, but still....

On heat dissipation. There are several great choices out there readily available at most large hardware retailers. Begining with aluminum paint available at Home depot, to hammertone copper, Krylon Silve and gold plate. A lot of the above mentioned were pioneered in the laptop trade as coatings to inhibit rf interference and somewhat alleviate the heat generated by high clocked cpu's in an enclosed space.

 

[xrk971]

Well this was almost hand made P2P for the serial number Zero:

 

[Hutnicks]

Hmm not seeing an image there.

 

[xrk971]

Ok I had to re upload as it was on DIYA server and you probably don't have an account there.

Here it is...

 

[Hutnicks]

Actually I do, which is all the more puzzling.

 

[stellarelephant]

Raptorlightning kindly shared Gerbers for the two custom PCBs that enable his battery mod, as well as a BOM, schematics, and some instructions.

For folks without a DIYA account, you can also grab them here:
https://www.dropbox.com/s/y5hk5w1mlvtjya2/Raptorlightning Mod.zip?dl=0

I ordered several of each board from OSH Park a few days ago. The two zipped folders within the main folder I've linked worked perfectly for me when I uploaded them for printing. If you order from OSH Park, as Raptor and I did, expect to get a warning that they can't do slot drills. According to Raptor, this is fine and just means you'll have to use wire cutters to trim the micro USB jack somehow. I assume this will make sense once I see the part and the board.

To do the mod, you'll also need a MT3608 boost module and a 2600mAh 3.7V tablet battery that measures 7.8x52x51mm.
Both items are all over eBay and AliExpress. They look like this:

Anybody have tips for cutting PCB traces? X-acto knife?

 

[funch]

X-acto would be my weapon of choice.

 

[macky112]

Raptorlightning kindly shared Gerbers for the two custom PCBs that enable his battery mod, as well as a BOM, schematics, and some instructions.

For folks without a DIYA account, you can also grab them here:
https://www.dropbox.com/s/y5hk5w1mlvtjya2/Raptorlightning Mod.zip?dl=0

I ordered several of each board from OSH Park a few days ago. The two zipped folders within the main folder I've linked worked perfectly for me when I uploaded them for printing. If you order from OSH Park, as Raptor and I did, expect to get a warning that they can't do slot drills. According to Raptor, this is fine and just means you'll have to use wire cutters to trim the micro USB jack somehow. I assume this will make sense once I see the part and the board.

To do the mod, you'll also need a MT3608 boost module and a 2600mAh 3.7V tablet battery that measures 7.8x52x51mm.
Both items are all over eBay and AliExpress. They look like this:

Anybody have tips for cutting PCB traces? X-acto knife?

May I know an estimate of the total cost to do this mod?

 

[stellarelephant]

Pretty cheap. The three boards can each be had for less than a dollar. Battery is like $10. I haven't made a Mouser/Digikey cart with the BOM yet, but I am hoping the assorted parts needed to populate the load sharing board and cap mx board will total $5 or so plus shipping. Ballpark $20, all shipped? About the same as buying some rechargeable 9V batteries and a charger.

 

[xrk971]

Hi StellarE, would you mind running a GB for us? I am in for 4 sets of boards.

 

[funch]

Me too.

 

[stellarelephant]

Hi StellarE, would you mind running a GB for us? I am in for 4 sets of boards.

I'd love to, but man, I am covered up with work and house projects for the foreseeable future. I'll be lucky if I find time to get the mod done! With free shipping available for all the parts, I'm not sure it would really help much anyhow. Except maybe for folks outside the US.

 

[xrk971]

That's cool StellarE - we have all have been there, and totally know that family and "yes, Honey" duties always come first if one wants longevity with diy.

 

[stellarelephant]

Just filled up a Digi-Key cart with parts for the RaptorLightning mod. All the components for one mod add up to about $9.50 plus shipping (cheapest shipping option is $3.50). Adding in the battery and the 3 boards, I'm at about $26 total cost for the mod, not including the few cents worth of extra wire I'll need to connect all the boards together. X, can you recommend a certain wire gauge?

I had to substitute a different 1uF cap and 47R resistor, as the ones on the BOM were not available.
Also, here is the 47uF cap that Raptor used (this replaces the 100uF on the BOM): https://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=238395325&uq=636409334171526774
Other than those three parts, I'm ordering using the exact part numbers on the BOM Raptor provided.

 

[stellarelephant]

I soldered up my first cap MX but failed my first attempt at the USB load sharing board. Tiny pins under that micro USB jack... Must buy a fine solder tip and liquid flux!


In the meantime...I bought some new planar Mayflower V1 cans. These are a T50RP v3 modded for accurate frequency response.



I was worried that the Pocket Class A wouldn't have enough juice for them, but alas, it seems this amp fears no headphone. According to X, it helps that I'm running the amp at full 18V. It probably also helps that I boosted bias further with my resistor values. And thank goodness my x3 player puts out a generous 1.5v line out signal. First impressions tell me that I have headroom to spare (pot set at about 2:00 is loud) with good dynamics and more detail than I have ever gotten from a headphone before.