My headphone amp is the ''All-Fet Line Amp'' EB-107/309 + ''All-FET Low Noise Regs'' EB-704/418, all dual mono with CRC filter before the Regs... According to the Line amp documentation it can drives 30 ohms in Class-A, enough for an headphone amplifier 
As per the doc I added a 10ohms resistor in series with the output.
Volume pot is a Noble AP25.
SB
As per the doc I added a 10ohms resistor in series with the output.Volume pot is a Noble AP25.
SB
Hi,
Would you have reference to the circuit you used?
I have Dimitri Danyuk's Electronics World August 2005 article but that is 'fully' variable.
See also :
http://www.linearsystems.com/lsdata/others/Headphone_Amplifier_Evaluation_Board.pdf
Ref 4,5.
Patrick
http://www.linearsystems.com/lsdata/others/Headphone_Amplifier_Evaluation_Board.pdf
Ref 4,5.
Patrick
There is a discussion in the Pass forum J2 thread about the MCS version discussed here in post #5.
You can easily turn this into a power amp by changing the MOSFETs to 2SJ618.
And change R10 to 0R47, R13a to 0R24, and R13b to 0R26, using 20~24V rails.
Bias will be around 1.2A.
All components are acrively available, no unobtaniums required.
And it will have a very similar signature to the J2, dominanted by H2.
Cheers,
Patrick
You can easily turn this into a power amp by changing the MOSFETs to 2SJ618.
And change R10 to 0R47, R13a to 0R24, and R13b to 0R26, using 20~24V rails.
Bias will be around 1.2A.
All components are acrively available, no unobtaniums required.
And it will have a very similar signature to the J2, dominanted by H2.
Cheers,
Patrick
I looked at that schema from linear systems. I have no clue how it works - the input drain references to a LED - that is, AC zero ohms, so no amplification - and goes to the gate of the next stage (Q102/Q112);
while the inverted pair does see 270 ohms in the drain so there is amplification there but it goes to the source of the next stage (again Q102/Q112);
unless the next stage pair (Q102/Q112) is in fact wired as a cascoded pair.
And there is a high impedance DC feedback to the same next stage via the sources of (Q102/Q112).
Not really fit for 32 ohms Fostex Planar that are on my list, I'm afraid . .
done
Adding a 4-transistor Wilson Mirror
In EUVL's document about this project, Post #2, he mentions, and I'm paraphrasing here:
The use of a 4-transistor Wilson mirror will not only reduce distortion, but will also improve DC offset.
I am very, very close to convincing myself to give this project a try and improved DC offset is of particular interest to me. Google shows a number of 4-transistor mirrors, but I cannot envision how to adapt them to this particular circuit.
If anybody would like to help, I would be thankful for a quick sketch showing the addition of a 4-transistor Wilson Mirror to this circuit.
In EUVL's document about this project, Post #2, he mentions, and I'm paraphrasing here:
The use of a 4-transistor Wilson mirror will not only reduce distortion, but will also improve DC offset.
I am very, very close to convincing myself to give this project a try and improved DC offset is of particular interest to me. Google shows a number of 4-transistor mirrors, but I cannot envision how to adapt them to this particular circuit.
If anybody would like to help, I would be thankful for a quick sketch showing the addition of a 4-transistor Wilson Mirror to this circuit.
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