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Old 22nd August 2013, 02:09 PM   #1
Vigo is offline Vigo  Sweden
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Default MOSFET follower to my phone

Hi everyone

I am considering to build a no gain head amplifier to use together with my phone.

I was planing to test this design Class A MOSFET Headphone Driver | HeadWize.

Do you think it will improve the sound from my headphones?

I use my phone as source (Nokia 920) and a couple of Denon headphones.
Thinking of buying some new headphones if the headamp turns out good.
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Old 22nd August 2013, 02:29 PM   #2
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If you decide to build this circuit, diyAudio members can suggest a few ways to improve the circuit design. For example, the PSRR* can be improved dramatically by modifying the R2/R3/D1/D2 network.

*Power Supply Rejection Ratio
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Old 23rd August 2013, 12:20 PM   #3
JimT is offline JimT  Canada
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I like mine. It needs a quiet power supply. In the future you could change R4 to a ccs.

Jim
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Old 28th August 2013, 09:16 AM   #4
Vigo is offline Vigo  Sweden
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Hi

I have decided to move on with this project.

I have only a basic understanding of electronics so there are some question that i hope someone can help me with.

First it seams that the MOSFET used in the design IRF 513 is no longer available.
I think i have some IRF 610 at in a box somewhere, would these be possible to use?
Or can anyone suggest a good replacement for IRF 513?

I plan to replace the R4 with a CCS according to the sugestion from JimT.
Would it be possible to use a LM317 CCS with a potentiometer?
I am not sure if it could deliver enough current.

What other modifications is recommended?
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Old 28th August 2013, 01:11 PM   #5
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Here is something I built. Works great!
You can eliminate the virtual ground and use output caps if you wish.
Attached Images
File Type: png 3 Channel Szekeres.png (4.3 KB, 332 views)
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Old 28th August 2013, 02:13 PM   #6
Vigo is offline Vigo  Sweden
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That looks interesting, i am thinking doing something similar together with IRF610. What kind of OP-amp do i need for this, is more or less anyone ok or do it need some special characteristics.

Found this website of a head amp with IRF610, DIY IRF610 MOSFET Class-A Headphone Amplifier Project
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Old 28th August 2013, 02:41 PM   #7
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Quote:
Originally Posted by Avro Arrow View Post
Here is something I built. Works great!
You can eliminate the virtual ground and use output caps if you wish.
Input capacitors are probably a good idea too, since "Lin" and "Rin" are biased at +10 volts.
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Old 28th August 2013, 04:39 PM   #8
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Quote:
Originally Posted by transistormarkj View Post
Input capacitors are probably a good idea too, since "Lin" and "Rin" are biased at +10 volts.
I know it isn't noted on the schematic, but input ground
and output ground are the same. With output/input ground
being virtual and the inputs being referenced to virtual
ground, there is no offset voltage at the inputs
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Old 28th August 2013, 04:40 PM   #9
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Quote:
Originally Posted by Vigo View Post
That looks interesting, i am thinking doing something similar together with IRF610. What kind of OP-amp do i need for this, is more or less anyone ok or do it need some special characteristics.

Found this website of a head amp with IRF610, DIY IRF610 MOSFET Class-A Headphone Amplifier Project
There is no op amp.

There is a TLE2426 rail splitter...is that what you mean?
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Old 29th August 2013, 06:33 PM   #10
JimT is offline JimT  Canada
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Quote:
Originally Posted by Vigo View Post
That looks interesting, i am thinking doing something similar together with IRF610. What kind of OP-amp do i need for this, is more or less anyone ok or do it need some special characteristics.

Found this website of a head amp with IRF610, DIY IRF610 MOSFET Class-A Headphone Amplifier Project
You will be happy with Giovanni Militano's improvement over the original Szekeres. Remember that class A does take a large heatsink. The second post mentions an improvement to the biasing network for the mosfet. I do have this on mine, but it would not be needed with a regulated supply. I plan to build a Salas SSLV for mine, but have been spending my time outside enjoying the summer.

Have fun
Jim

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