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xrk971 Pocket Class A Headamp GB

Founder of XSA-Labs
Joined 2012
Paid Member
GB 2 List update.

Turbon - 1 board and 2 sets matched FETs - Payment Received
Tryptamin - 2 bords - need email for Invoice
Schlomoff - 1 built and tested board and 4 SMT populated boards with matched FETs - Payment Received
pranavkr - 1 board - Payment Received
Potatowedge - 2 boards and 1 set of matched FETs - Payment Received
pcgab - 2 boards - Payment Received
bogde - 4 boards - Payment Received - Invoice 2 sent
adn6244 - 2 boards - Invoice Sent
tcpoint - 2 boards - Payment Received
funch - 2 boards and 2 matched sets of FETs - Payment Received
Wanfai - 1 board and 1 matched sets of FETs - Payment Received
883bkong - 2 boards and 1 set of matched FETs - Invoice Sent
Kylej1015 - 2 boards - Payment Received
Jammer55 - 3 boards - need email for Invoice
 
Founder of XSA-Labs
Joined 2012
Paid Member
GB 2 List update

Turbon - 1 board and 2 sets matched FETs - Payment Received
Tryptamin - 2 boards - need email for Invoice
Schlomoff - 1 built and tested board and 4 SMT populated boards with matched FETs - Payment Received
pranavkr - 1 board - Payment Received
Potatowedge - 2 boards and 1 set of matched FETs - Payment Received
pcgab - 2 boards - Payment Received
bogde - 4 boards - Payment Received for All Invoices
adn6244 - 2 boards - Invoice Sent
tcpoint - 2 boards - Payment Received
funch - 2 boards and 2 matched sets of FETs - Payment Received
Wanfai - 1 board and 1 matched sets of FETs - Payment Received
883bkong - 2 boards and 1 set of matched FETs - Invoice Sent
Kylej1015 - 2 boards - Payment Received
Jammer55 - 4 boards - Invoice Sent

Tryptamin - have not heard from you since you indicated you were interested.
 
Founder of XSA-Labs
Joined 2012
Paid Member
GB 2 List Update:
Turbon - 1 board and 2 sets matched FETs - Payment Received
Tryptamin - 2 boards - need email for Invoice
Schlomoff - 1 built and tested board and 4 SMT populated boards with matched FETs - Payment Received
pranavkr - 1 board - Payment Received
Potatowedge - 2 boards and 1 set of matched FETs - Payment Received
pcgab - 2 boards - Payment Received
bogde - 4 boards - Payment Received for All Invoices
adn6244 - 2 boards - Invoice Sent
tcpoint - 2 boards - Payment Received
funch - 2 boards and 2 matched sets of FETs - Payment Received
Wanfai - 1 board and 1 matched sets of FETs - Payment Received
883bkong - 2 boards and 1 set of matched FETs - Invoice Sent
Kylej1015 - 2 boards - Payment Received
Jammer55 - 4 boards - Payment Received
 
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Finally got my Pocket Class A amp in the official Altoids case! It took three weeks for the mints to ship from UK to Finland. :rolleyes: Too bad they don't sell them in this corner of the globe, so I got me some extra too.
 

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Yeah, I managed to get it to look better in the pics than it really is. Input hole is a little higher than the output side, also the led is not aligned straight and the the led hole ripped while drilling. :joker: I did small pilot holes at first by using the hole guide PDF file provided in the first post and then grinded the holes larger with my cheap dremel copy.

I haven't had the time yet to test its' hand warming capabilities, but yes it could be handy here in Finland (-10 degrees Celcius this morning). I'll get to test the battery life when I get the charger delivered that was missing from the battery shipment. The mint case really fits well in my hands and no doubt the portability will be good.
 
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Diagram is confusing. Each electrolytic power cap is bypassed by two 100nF x7r's.

I didn't know what the little ceramics were for either. I'm not very skilled at reading schematics. So what exactly do they do as a bypass on the power side? Is it similar to what the WIMAs do on the output--pass high frequencies more easily? Sorry, my understanding of how circuits work is minimal.
 
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Bypass ceramic caps reduce high frequency noise by providing a low impedance path to ground (electrolytics not as low ESR at higher frequency).

That's clear, but there is 47uF MLCC and 100n MLCC on the rails already, along with 100uF OSCON (not sure what OSCON is doing there, as Panasonic FC would probaby do the same job just fine). I don't think 47uF MLCC is adding any value, imho.
 
Founder of XSA-Labs
Joined 2012
Paid Member
There is no 47uF MLCC. Look at BOM list at bottom of post 1.

Caps now recommended are Nichicon 2200uF 16v electrolytic plus 2 x 0.1uF X7R on rails per channel. On audio output coupler is now recommended 390uF OSCOn with 1uF film bypass. In audio input coupled is 2.2uF film. That's it for caps.

BOM repeated here for convenience.

All resistors 0805 package, metal thin film, 1% on specified parts, else 5%. Yageo 1% 0805 SMT from Digikey are $0.77 for 100
R1 100k (5%)
R2 47k (1%)
R3 1k (1%)
R4 33R (1%)
R5 270R (1%)
R6 47R (5%)
R7_1 470R (1%)
R7_2 470R (1%)
R7_3 470R (1%)
R7_4 470R (1%)
RL 270R (5%) User select (optional, use for higher current draw on amp)
RLED 15k (5%) Current limit for LED, 15k or value according to supply voltage

C1 Input cap 5mm pitch up to 5.5mm wide (Wima 2.2uF MKS2B042201F00JSSD)
C2_1 Output cap 3.5mm pitch, 8 dia (390uF 20v Panasonic OSCON 20SEPF390M) or Nichicon AK 470uF if you can fit it
C2_2 Output cap 5mm pitch, up to 9mm wide (Wima 1uF MKS2C041001F00KSSD)
C3 Rail cap 100uF 3.5mm pitch, diameter whatever you can fit in the tin (100uF 20v Panasonic OSCON 20SEP100MX) - or Nichicon 2200uF 16v lay on its side
C4 Rail cap 100nF 1206 package (50v X7R)
C5 Additional 100nF rail cap 1206 package (50v X7R)

Q1 BF862 (771-BF862-T/R)
M1 ZVN4306GTA

Switchcraft 3.5mm stereo jacks x2 (35RAPC4BV4)
Alps 10kOhm stereo pot with power switch (RK0971221Z05)
3mm round LED (red or green)
4-pin 2.54mm pitch power connector (see post #44)