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2 x irf640 headamp(p2p)

post #1 of 14
4/28/10 at 12:30am
Thread Starter 
Greg J inspire me by building the mosfet headamp so simple.i made it point to point,i like its sweet sound.
zang





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post #2 of 14
4/29/10 at 5:12am
Thread Starter 
it is a headphone amplifier.the active device is irf640.
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post #3 of 14
4/29/10 at 5:58am
neat work. How high is your bias current set? What are your output capacitors?
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post #4 of 14
4/29/10 at 6:14am
Thread Starter 
the bias is 0.26A.i use NTK capacitor and remove the plastic skin for better looking and better sound.
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post #5 of 14
4/29/10 at 6:19am
wow..that is pretty hot..what's the rail voltage?

Any schematic for this?
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post #6 of 14
4/29/10 at 10:59am
I like the case-sink

Quote:
Originally Posted by sachu View Post
Any schematic for this?
Unless he changed it:
link

I have been meaning to build one of these little guys for some time now.
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post #7 of 14
4/29/10 at 10:47pm
Thread Starter 
yes,it is Greg J. Szekeres design.the url is correct.
i think this is a good project for solid state amp beginner.it cost under $10usd.
chassis - $4
2 x irf640 - $0.8
resistors & caps - $2
socket & pot - $ 3
handcraft work - one weekend

all parts is standard,nothing is hard to buy.it use a 12VDC 4A switch power block.the hot is a issue to care about it.it is not very hot.touch the chassis with fingers,the surface is around 40 degree during running.
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post #8 of 14
4/29/10 at 11:43pm
I see the 640 has much higher numbers for input and output capacitance (granted @ 1MHz) than the 510. Anyone know -would this have any negative effect in this particular design?
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post #9 of 14
4/30/10 at 2:28am
Quote:
Originally Posted by IcantHearU View Post
I see the 640 has much higher numbers for input and output capacitance (granted @ 1MHz) than the 510. Anyone know -would this have any negative effect in this particular design?
Either way I wouldn't want to have a passive preamp or potentiometer driving the mofsets. If you use an active preamp you should be fine. The input capacitance forms a low pass filter -3dB Freq = 1 divided by 2 x pi x Rout (preamp) x capacitance.

Run the numbers with a 50k potentiometer and you will see what I mean about the loss in high frequency.
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post #10 of 14
4/30/10 at 2:54am
Thread Starter 
yes,the irf510 is better than irf640.i just use handy stuffs.
i use pc audio interface with +4dB output level,50k potentiometer,so it is ok.a decent preamp would be fine.

zang
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post #11 of 14
4/30/10 at 5:39am
You can put anything there,ex. opamp,tube,passive preamp,etc.I've put NE5534 and I'm happy with sound.It's very punchy and energetic,and lacks coloration
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post #12 of 14
4/30/10 at 7:19am
Beats a c-moy IMO, but I want to try to find a way to rid it of the electroctrolytic coupling caps on the output.
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post #13 of 14
4/30/10 at 7:23am
Good stuff!
What type of R4's are those? Wirewound?
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post #14 of 14
4/30/10 at 8:38am
Quote:
Originally Posted by regal View Post
Beats a c-moy IMO, but I want to try to find a way to rid it of the electroctrolytic coupling caps on the output.
Take a look at this

Very nice work Digi I really like the looks of your p2p projects!
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