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Old 15th October 2011, 02:56 PM   #11
oshifis is offline oshifis  Hungary
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Sorry, no offense was intended. My comment was not concerning your design, that seems very professional. Good to see the integrated circuits are in sockets, so they are upgradeable if needed.
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Old 17th October 2011, 03:41 AM   #12
kawo is offline kawo  China
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Welcome to the discussion
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Old 17th October 2011, 03:55 AM   #13
kawo is offline kawo  China
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HPA-2 is a headphone amplifier that uses operational amplifier and transistor to compose Class A amplification. Its simple circuits design and double side PCB board minimize the signal path. O type transformer strengthens the linear power supply. At the result, all of these high-end components make such a brilliant headphone amplifier.
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Old 18th October 2011, 11:56 AM   #14
oshifis is offline oshifis  Hungary
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Kawo,

Do you intend to produce a two-stage model in the future? My other question: what is the input impedance of the unit? Thanks
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Old 18th October 2011, 02:00 PM   #15
kawo is offline kawo  China
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In fact, this is the other two models. Before one is HPA-1, it may be expensive, about USD1000, this is the economic version, just USD200, but do 98% of HPA-1

33K Ohm.
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Old 30th October 2011, 02:37 PM   #16
kawo is offline kawo  China
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The WSC resistance on jeff rowland model 10 .
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Old 11th November 2011, 03:01 PM   #17
kawo is offline kawo  China
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After revisions, the new version of the 10Hz → 100KHz is -0.3 and-0.2dbm, up to 295KHz,-1.2dbm
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Old 11th November 2011, 06:13 PM   #18
Electrons are yellow and more is better!
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Quote:
Originally Posted by oshifis View Post
Those AD OP27s are a bit suspect... I have TDA1541As similarly engraved not painted that are fakes.
Nowadays they use laser and then you'll get a marking with very little contrast. It's not a sign of fake.
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Old 12th November 2011, 12:09 PM   #19
kawo is offline kawo  China
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Thankyou.
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Old 12th November 2011, 12:36 PM   #20
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Nice little touch there with the LED behind the volume knob.
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