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xrk971 Pocket Class A Headamp GB

Getting there :D

DCA v4.png

Edit: yes, the heatsinks look like they're on the bottom of the board. You can ignore that, I put the outline there cos it's irritating when working on the layout.
 
Founder of XSA-Labs
Joined 2012
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You might find that a standard 2.5mm pitch 3-position screw terminal socket (green ones) are more secure and will let you fit even wider diameter transistor legs. IRF510 is higher current, but I think signal quality of 610 is better. If you have rare Toshiba 2SK2013, they will work well too. Just bend legs 90 def and even weight of heatsink could be supported with screws.
 
Any luck finding a suitable inductor? I am especially interested since I presume they might really help this amp to cleanly drive low impedance, low sensitivity cans, like my Fostex planars. :)

I really love the onboard power management. If I understand correctly, now we can just plug in a suitable power brick, and voilà!
 
Any luck finding a suitable inductor? I am especially interested since I presume they might really help this amp to cleanly drive low impedance, low sensitivity cans, like my Fostex planars. :)

I really love the onboard power management. If I understand correctly, now we can just plug in a suitable power brick, and voilà!

Dont konw which parameter is more important here, large inductance or low DCR (means high current ?)

??? 40MH 1.5A ?? ??? ??? ?????? I572412-???

40MH 1.5A,DCR 2.8R

USD 7.18
 
Szpunk,
Thanks for that link. You want low DCR but hat usually means big fat wire and heavy. For a headphone amp, the 2.8R value for DCR is acceptable. The price on this is excellent. Have you seen the same item listed on aliexpress?

It's hard to found this even in TAOBAO Chinese site, i must include "Tube" in keywords "Choke Coils" (Sure all means Chinese words) to search it. Then search in the relevant store manually.

I try this on Aliexpress and just found something but not same as i put the link:

Tube Amplifier Choke Coils - Shop Cheap Tube Amplifier Choke Coils from China Tube Amplifier Choke Coils Suppliers at IWISTAO HIFI Components Store on Aliexpress.com

Good Luck!:D
 
I've sorted some MOSFET models suitable for use here (MOSFET Source Follower), for "suitable", it's based on:

1. Vdss > 30v, Id > 1A;
2. High Gfs, Low Ciss, Low Qgs and Qg, and Low Vgs(th);
3. TO-220 and SOT-223 Only;
4. Live on Digi-Key or Mouser, so something like 2SK213 is ignore.

So, if this basic theory is wrong, please point it out and ignore the whole post.:eek:

MOSFET_for_Source_Follower.png

MODEL Gfs Ciss Qg Qgs Qgd Vgs(th)
TO-220
FQP4N20L 3.2 240 4.0 1.0 1.9 1.0-2.0
IRL510A 3.2 180 5.5 0.9 3.5 1.0-2.0
IRL510 1.9 250 6.1 2.6 3.3 1.0-2.0
IRF510 1.3 180 8.3 2.3 3.8 2.0-4.0
IRF610 0.8 140 8.2 1.8 4.5 2.0-4.0
STP16NF06L 17 345 7.3 2.1 3.1 1.0-2.5
BUK75150 2.1 322 5.5 1.0 2.7 2.0-4.0
IRLZ14PBF 3.5 400 8.4 3.5 6.0 1.0-2.0
IRLZ24NPBF 8.3 480 15 3.7 8.5 1.0-2.0
IRFZ24N 4.5 370 20 5.3 7.6 2.0-4.0
MTP3055V 5.0 410 7.8 1.7 3.2 1.0-2.0
C2M0280120D 2.8 259 20.4 5.6 7.6 2.0-4.0


SOT-223
ZVN4306G 0.7 350 ? ? ? 1.3-3.0
ZXMN7A11G 4.66 298 4.35 1.06 1.8 1.0-?
IRFM120A 3.12 370 16 2.7 7.8 2.0-4.0
BSP296N 2.66 114.8 4.5 0.27 1.45 0.8-1.8
FDT86246L 7.3 238 2.3 0.7 1.0 0.8-2.5
FDT86106LZ 8 234 2.4 0.7 0.9 1.0-2.2
auirll014n 2.3 230 9.5 1.0 3.0 1.0-2.0
NDT014L 4.2 214 3.6 0.8 1.4 1.0-3.0
FDT457N 5 235 4.2 1.3 1.7 1.0-3.0

IPAK (TO-251)
IRFU220B 3.7 300 12 2.0 5.5 2.0-4.0

DPAK (TO-252)
B35N04 19 527 13.7 2.1 4.2 1.5-3.2
 
It seems like the chokes may add significantly to components cost and layout difficulty. If you think it is not worth it, X, or BDHM, I certainly don't want to steer the conversation in an unproductive direction. Nobody is here because they are chasing vanishingly-low THD.

As of last night, I may have found my endgame solution for my Fostex planars. After much fear of destroying my nicest cans I took the advice of the resident experts on Head-Fi and connected them to the speaker taps of my 100wpc Onkyo Class AB receiver. Holy cow. It transformed the sound so beautifully.

All this to say, I am intrigued by the performance possibilites of the MoFo trick but it isn't a sticking point for me. The PCA powers my other headphones wonderfully, and this new variant (DCA?) can only be better!