making Headphone Amp -- ChuMoy Amp2 --


Japanese version here.


I had enough aidio parts to make headphone amp.
So I tyied to make ChuMoy amp again.
I designed a amp for Dual Bipolar OpAmp.


Circuit is almost as the same as the one of the amp using FET OpAmp.
The different points are folowing.
1: changing the resistor which decides bias current (100kohm to 2kohm)
2: increasing the capacity of coupling capacitor
3: determining the values of negative return circuit in order to cancel input bias current

1: is because bias current of Bipolar OpAmp is larger than that of FET OpAmp.
2: is for preventing from increasing cut-off frequency of High Pass Filter.
3: is that if we adjust the impedance of a parallel circuit, which are return resistor and negative input resistor, and the impedance of positive input resistor, input bias current will get minimum.

ChuMoyAmp Bipoloar input circuit
(If you click, the figure will expand.)


ChuMoyAmp2 making1

I put sockets in order to be able to exchange OpAmp and resistances easily.

Capacitors of MUSE series are so huge.
But they sound very nice, so I can't help selecting MUSE.
They are looked as if they were shouldering tanks.

ChuMoyAmp2 making2

OpAmp that I chose was NJM2114D.
It is designed for very low noise and sounds powerful.
The only negative point is big POP noise.

ChuMoyAmp2 making3

I chose SW-100 by TAKACHI.

ChuMoyAmp2 making4

I put peach colored LED for indication lump.
Diode stablized current as 15mA passing through LED.
It looks beautiful.

ChuMoyAmp2 making5

This sounds very powerful and deep.
I like this rather than CMoyAmp of FET OpAmp.

But thanks to NJM2114D, POP noise is big.

Now it is exhibited in Yahoo!Auction.
It was sold out, thank you.

Closing: 22:36 - 10 - March - 2007

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