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xrk971 Desktop Class A (DCA) Headphone Amp
xrk971 Desktop Class A (DCA) Headphone Amp
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Old 14th May 2018, 08:39 PM   #11
xrk971 is online now xrk971  United States
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xrk971 Desktop Class A (DCA) Headphone Amp
The Aksa Lender HPA has lower THD but similar sonic profile of SE Class A. The Aksa Lender also has more gain, if that’s what you like. But I would say that a no global feedback SE Class A like the DCA, will have better soundstage and imaging. The DCA can be driven to very high bias (tested to 150mA which means it can drive 300mA peak current) as it has provision for larger heatsink. So can drive lower impedance cans with more power. I think you will find that both sound similar in that they are very dynamic and natural sounding with smooth response and low low noise. They are cheap enough to enjoy many times. Don’t need to settle on one. DCG3 is a great amp but I have not listened to it side by side so can’t compare.
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Old 15th May 2018, 02:30 PM   #12
xrk971 is online now xrk971  United States
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xrk971 Desktop Class A (DCA) Headphone Amp
For a limited time, I am including a pair of BF862 JFETs for free with every DCA PCB. Some folks are having a hard time sourcing these. The JFETs are in a tape reel next to each other, but otherwise unmatched. They will play pretty good music nonetheless.
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Old 15th May 2018, 04:39 PM   #13
xrk971 is online now xrk971  United States
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xrk971 Desktop Class A (DCA) Headphone Amp
Here is the BOM:

Quote:
xrk971 Desktop Class A HPA v2 May 9, 2018
BOM

Part Value Device Package Description
C101 100 CPOL-EUE3.5-8 E3,5-8 POLARIZED CAPACITOR, European symbol
C101A C22/10 C22.5B10 CAPACITOR
C101B C27/17 C27.5B17 CAPACITOR
C101C 01 MKC1860-0U1 MKC1860-0U1
C101D 100 MCAP250V10U MCAP250V10U Fidelity Component MCap
C102 100 CPOL-EUE3.5-8 E3,5-8 POLARIZED CAPACITOR, European symbol
C102A C22/10 C22.5B10 CAPACITOR
C102B C27/17 C27.5B17 CAPACITOR
C102C 01 MKC1860-0U1 MKC1860-0U1
C102D 100 MCAP250V10U MCAP250V10U Fidelity Component MCap
C111 10 C5/5 C5B5 CAPACITOR
C111A C10/6 C10B6 CAPACITOR
C111B C15/8 C15B8 CAPACITOR
C112 10 C5/5 C5B5 CAPACITOR
C112A C10/6 C10B6 CAPACITOR
C112B C15/8 C15B8 CAPACITOR
C113 2200uF CPOL-EUE7.5-18 E7,5-18 POLARIZED CAPACITOR, European symbol
C113A CPOL-EUE5-10.5 E5-10,5 POLARIZED CAPACITOR, European symbol
C114 2200uF CPOL-EUE7.5-18 E7,5-18 POLARIZED CAPACITOR, European symbol
C114A CPOL-EUE5-10.5 E5-10,5 POLARIZED CAPACITOR, European symbol
C131 220 CPOL-EUE5-13 E5-13 POLARIZED CAPACITOR, European symbol
C133 10 C5/5 C5B5 CAPACITOR
C134 2200 CPOL-EUE5-13 E5-13 POLARIZED CAPACITOR, European symbol
C135 2200 CPOL-EUE5-13 E5-13 POLARIZED CAPACITOR, European symbol
C141 2200 CPOL-EUE5-13 E5-13 POLARIZED CAPACITOR, European symbol
C142 2200 CPOL-EUE5-13 E5-13 POLARIZED CAPACITOR, European symbol
C143 10 C5/5 C5B5 CAPACITOR
C144 10 C5/5 C5B5 CAPACITOR
R101 RK09L12B RK09L12B
R102 100k CMF-55 CMF-55
R103 100k CMF-55 CMF-55
R104 22k0 CMF-55 CMF-55
R105 22k0 CMF-55 CMF-55
R106 1k1 CMF-55 CMF-55
R107 68R0 CMF-55 CMF-55
R108 250R CMF-55 CMF-55
R109 1k1 CMF-55 CMF-55
R111 68R0 CMF-55 CMF-55
R112 250R CMF-55 CMF-55
R113 47R0 CMF-55 CMF-55
R114 47R0 CMF-55 CMF-55
R115 270R CMF60 CMF60 (for R115 to R123 recommended to use 1w parts here and elevate above board 5mm or more for cooling)
R116 270R CMF60 CMF60
R117 270R CMF60 CMF60
R118 270R CMF60 CMF60
R119 270R CMF60 CMF60
R121 270R CMF60 CMF60
R122 270R CMF60 CMF60
R123 270R CMF60 CMF60
R124 270R CMF-55 CMF-55 (can be up to 1k if using 600ohm cans)
R125 270R CMF-55 CMF-55 (can be up to 1k if using 600ohm cans)
R131 10k0 R-EU_0207/10 0207/10 RESISTOR, European symbol
R132 220R R-EU_0207/10 0207/10 RESISTOR, European symbol
R133 1R5 R-EU_0207/10 0207/10 RESISTOR, European symbol
R134 0R47 R-EU_0309/12 0309/12 RESISTOR, European symbol
R135 0R47 R-EU_0309/12 0309/12 RESISTOR, European symbol
V101 BF862 SST201 SOT23 TEMIC / Siliconix N-Channel JFET
V102 BF862 SST201 SOT23 TEMIC / Siliconix N-Channel JFET
V103 JFET 2SK170 TO92-DGS Field Effect Transistor Silicon N Channel Junction Type 2SK170 Audio Grade (optional instead of BF862)
V104 JFET 2SK170 TO92-DGS Field Effect Transistor Silicon N Channel Junction Type 2SK170 Audio Grade (optional instead of BF862)
V111 IRF610 IRF512 TO220BV N-CHANNEL MOS FET
V112 IRF610 IRF512 TO220BV N-CHANNEL MOS FET
V131 1N4004 1N4004 DO41-10 DIODE
V132 IRF610 IRF512 TO220BV N-CHANNEL MOS FET
X101 22-27-2021-02 22-27-2021-02 6410-02 CONNECTOR unknown unknown
X102 22-27-2021-02 22-27-2021-02 6410-02 CONNECTOR unknown unknown
X111 22-27-2021-02 22-27-2021-02 6410-02 CONNECTOR unknown unknown
X112 22-27-2021-02 22-27-2021-02 6410-02 CONNECTOR unknown unknown
X131 22-27-2021-02 22-27-2021-02 6410-02 CONNECTOR unknown unknown
X132 AK500/2 AK500/2 CONNECTOR unknown unknown
X1011 SK104 SK104 SK104 HEATSINK manufacturer Fischer/distributor Buerklin
X1012 SK104 SK104 SK104 HEATSINK manufacturer Fischer/distributor Buerklin
X1031 SK104 SK104 SK104 HEATSINK manufacturer Fischer/distributor Buerklin
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Old 15th May 2018, 07:04 PM   #14
pelayostyle is offline pelayostyle  United States
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RK09L12B-LOG10K or RK09L12B-LOG100K ?
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Old 15th May 2018, 07:10 PM   #15
xrk971 is online now xrk971  United States
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xrk971 Desktop Class A (DCA) Headphone Amp
I use a linear 10k myself, not a fan of log pots. But anything from 10k to 100k can work. Just make sure it fits the pads and two extra pads for brace.
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Old 15th May 2018, 07:12 PM   #16
xrk971 is online now xrk971  United States
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These look like nice heatsinks and will handle the thermal load just fine.

WAKEFIELD 627-15ABP Vertical Heatsink TO-220 34.9 x 12.7 x 38.1(mm) *NEW* Qty.10 | eBay

I currently use these:
To-220 Heat Sink 1 Hole 10 Pcs | eBay
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Old 16th May 2018, 01:26 PM   #17
xrk971 is online now xrk971  United States
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These Class 2 transformers have been found to be very low noise when used drive a DC step up.

GCi technoLogies AM-12800 12VDC 800mA Charger / Power Supply Amazon.com : GCi technoLogies AM-12800 12VDC 800mA Charger / Power Supply : Everything Else

Use something like this for the DC-DC step up or down.

That plus the built in cap Mx and CRCRC are all you need to have a PSU that’s as clean as a battery.
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Old 16th May 2018, 01:48 PM   #18
twocents is offline twocents  South Africa
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xrk971 Desktop Class A (DCA) Headphone Amp
Quote:
Originally Posted by xrk971 View Post
I use a linear 10k myself, not a fan of log pots.
Very interesting. I was under the impression that log pots were the goto pots for audio. Why do you prefer linear?
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Old 16th May 2018, 03:15 PM   #19
xrk971 is online now xrk971  United States
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Haha, because for me, I think of output in volts, not dB. Plus, I think a stereo linear pot is more likely to track each channel linearly.
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Old 16th May 2018, 04:49 PM   #20
DontHertzMe is offline DontHertzMe  South Africa
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xrk971 Desktop Class A (DCA) Headphone Amp
Most affordable logarithmic pots are actually a combination of two linear tracks that give a log approximation.

I've used the loading resistor method mentioned by Rod Elliott here ESP - A Better Volume Control with excellent results. High quality linear pots are easier to get and cost less . X is right about them tracking better, too.
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