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xrk971 Pocket Class A Headamp GB
xrk971 Pocket Class A Headamp GB
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Old 29th January 2017, 12:58 AM   #21
agdr is offline agdr  United States
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Join Date: Sep 2010
xrk971 Pocket Class A Headamp GB
xrk971 - 2 boards
pcgab - 2 boards
zman01 - 2 boards
stellarelephant - 2 boards
samoloko - 1 pcb
lui04 - 2 boards
Morde - 2 board
cyteen - 2 boards
funch - 2 boards
syyma - 2 boards
av-trouvaille - 2 boards
Mituisho - 2 boards
bogde - 2 boards
faltinsen - 2 boards
vanofmonks - 1 board
M_Balou - 2 boards
dwpeterson - 1 board
agdr - 1 board
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Old 29th January 2017, 05:44 AM   #22
xrk971 is online now xrk971  United States
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Join Date: Oct 2012
Location: Metro DC area
xrk971 Pocket Class A Headamp GB
Default Schematic

As requested, here is the full schematic for this amp. Not shown is the electrical connections for the two batteries in series for 18v.

Click the image to open in full size.

Again, thanks to BDHM for the schematic and layout.
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File Type: png Pocket-Class-A-Schematic.png (39.8 KB, 6277 views)
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Old 29th January 2017, 06:09 AM   #23
walangalam is offline walangalam  United States
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Join Date: Jun 2004
Location: Bay Area, CA
xrk971 - 2 boards
pcgab - 2 boards
zman01 - 2 boards
stellarelephant - 2 boards
samoloko - 1 pcb
lui04 - 2 boards
Morde - 2 board
cyteen - 2 boards
funch - 2 boards
syyma - 2 boards
av-trouvaille - 2 boards
Mituisho - 2 boards
bogde - 2 boards
faltinsen - 2 boards
vanofmonks - 1 board
M_Balou - 2 boards
dwpeterson - 1 board
agdr - 1 board
walangalam - 2 boards
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Old 29th January 2017, 10:01 AM   #24
Morde is offline Morde  Finland
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Join Date: Oct 2014
@xrk971: Thanks for the schematics! What is the meaning and value of R8/R16? I thought it was just a load value for the LTspice model to represent the headphone impedance. Do I need to connect it? Sorry for the noob questions?

Edit: I'm going to use this mainly with 70 ohm headphones. I suppose the 390uF output caps provided in the bom are sufficient for low frequency extension?

Last edited by Morde; 29th January 2017 at 10:07 AM.
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Old 29th January 2017, 10:16 AM   #25
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Morde View Post
...................I'm going to use this mainly with 70 ohm headphones. I suppose the 390uF output caps provided in the bom are sufficient for low frequency extension?
It's a passive single pole filter. Calculate the F-3dB
It will have virtually no roll off @ 60Hz and probably no more than about -0.5dB @ 20Hz
F-3dB = 1 / 2PiRC = ~6Hz
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regards Andrew T.
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Old 29th January 2017, 01:02 PM   #26
xrk971 is online now xrk971  United States
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xrk971 Pocket Class A Headamp GB
I use 270R as RL even when headphones not plugged in mainly to allow me to test the amp so it simulates my headphone. It could be a higher impedance like 600R or 1k even.
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Old 29th January 2017, 01:27 PM   #27
gwrskien is offline gwrskien  Norway
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Join Date: Feb 2014
Location: skien
xrk971 Pocket Class A Headamp GB
xrk971 - 2 boards
pcgab - 2 boards
zman01 - 2 boards
stellarelephant - 2 boards
samoloko - 1 pcb
lui04 - 2 boards
Morde - 2 board
cyteen - 2 boards
funch - 2 boards
syyma - 2 boards
av-trouvaille - 2 boards
Mituisho - 2 boards
bogde - 2 boards
faltinsen - 2 boards
vanofmonks - 1 board
M_Balou - 2 boards
dwpeterson - 1 board
agdr - 1 board
walangalam - 2 boards
gwrskien - 2 boards
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Old 30th January 2017, 02:20 AM   #28
redarc12 is offline redarc12  United States
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Join Date: Jul 2012
Location: houston tx.
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Quote:
Originally Posted by gwrskien View Post
xrk971 - 2 boards
pcgab - 2 boards
zman01 - 2 boards
stellarelephant - 2 boards
samoloko - 1 pcb
lui04 - 2 boards
Morde - 2 board
cyteen - 2 boards
funch - 2 boards
syyma - 2 boards
av-trouvaille - 2 boards
Mituisho - 2 boards
bogde - 2 boards
faltinsen - 2 boards
vanofmonks - 1 board
M_Balou - 2 boards
dwpeterson - 1 board
agdr - 1 board
walangalam - 2 boards
gwrskien - 2 boards
redarc12- 2 boards
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Old 31st January 2017, 12:24 AM   #29
xrk971 is online now xrk971  United States
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Location: Metro DC area
xrk971 Pocket Class A Headamp GB
Ok I have triple checked the layout vs the schematic. All looks good and I am almost ready to order boards. However, the fab houses in China will not open until Feb 3 after the Lunar New Year celebrations are over. So I will leave GB open for a few more days. In the meantime, please send me a PM with your PayPal email and where you are located (Country). I will send you an invoice.

Thanks,
X

We are currently at 38 boards:

Quote:
xrk971 - 2 boards
pcgab - 2 boards
zman01 - 2 boards
stellarelephant - 2 boards
samoloko - 1 pcb
lui04 - 2 boards
Morde - 2 board
cyteen - 2 boards
funch - 2 boards
syyma - 2 boards
av-trouvaille - 2 boards
Mituisho - 2 boards
bogde - 2 boards
faltinsen - 2 boards
vanofmonks - 1 board
M_Balou - 2 boards
dwpeterson - 1 board
agdr - 1 board
walangalam - 2 boards
gwrskien - 2 boards
redarc12- 2 boards
To make ordering the BOM easy, here is a Mouser shopping cart for everything except the SMT resistors, SMT caps, and battery terminals.

http://www.mouser.com/ProjectManager...sID=f8bb47c63f

Last edited by xrk971; 31st January 2017 at 12:30 AM.
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Old 31st January 2017, 04:11 PM   #30
xrk971 is online now xrk971  United States
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Join Date: Oct 2012
Location: Metro DC area
xrk971 Pocket Class A Headamp GB
Update:

Thank to the folks who have provided me their email and payment!

Quote:
xrk971 - 2 boards
pcgab - 2 boards - INVOICE SENT & PAYMENT RECEIVED
zman01 - 2 boards
stellarelephant - 2 boards
samoloko - 1 pcb
lui04 - 2 boards
Morde - 2 board - INVOICE SENT & PAYMENT RECEIVED
cyteen - 2 boards
funch - 2 boards
syyma - 2 boards - INVOICE SENT & PAYMENT RECEIVED
av-trouvaille - 2 boards
Mituisho - 2 boards - INVOICE SENT & PAYMENT RECEIVED
bogde - 2 boards
faltinsen - 2 boards - INVOICE SENT & PAYMENT RECEIVED
vanofmonks - 1 board
M_Balou - 2 boards
dwpeterson - 1 board
agdr - 1 board
walangalam - 2 boards
gwrskien - 2 boards
redarc12- 2 boards
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