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Headphone Systems Everything to do with Headphones

Mosfet class A headphone amplifier
Mosfet class A headphone amplifier
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Old 11th December 2017, 05:16 AM   #21
sevenup2278 is offline sevenup2278  Netherlands
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When using a high impedance headphone (250-300 ohm) the extra voltage would be usefull.
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Old 11th December 2017, 02:42 PM   #22
BesPav is offline BesPav  Russian Federation
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Default Mosfet class A headphone amplifier

Quote:
Originally Posted by tomchr View Post
That will greatly increase the supply impedance compared to the regulated supply. It will also result in worse filtering, in particular when the parasitics of the supply caps are factored in.

Hi, Tom!
Yes.
But caps will be a real reservoir of the energy, not a “feedback’ed ventile on the pipe”.
Mosfet class A headphone amplifier
If we would be in need for a best possible supply - than shunt regulation must be applied. Something like this will be good enough:
IMG_6872.JPG
But this circuit likely not need this.
Just place something like 4700 uF + 10 Ohm + 1000 uF (latter should be decoupled with small sized 100/47 uF and good > 100nF NP0).

Quote:
Originally Posted by tomchr View Post
As for inverting vs non-inverting: I'm assuming you're concerned about common-mode distortion. That's not really a thing anymore with modern opamps. I'm sure you can find one opamp out there somewhere that shows common-mode distortion, but amps like the LME49710, OPA1611, etc. perform better non-inverting than inverting, at least for buffer applications, due to the 6 dB higher loop gain of the non-inverting configuration.

Yes, you are mostly right!
Common mode distortion are nonlinear to the common-mode itself.
But next i want to have as deep as possible feedback depth at least up to third harmonic of the 20 kHz.
And there is no chance to override THS4021 with one chip at this task:
IMG_6868.JPG

OPA1611 for compare:
IMG_6870.JPG

And, of course, we can afford 6 dB drop there.

Simultaneously, we need to concern about HF common mode error. Just check:
IMG_6873.JPG
At 10 MHz range there are a good receiving antenn is present - headphone cable.
So, we must go for balanced 4-wire headphones with splitted ground, or use somethind like Murata 78602/2c choke.

Last edited by BesPav; 11th December 2017 at 02:45 PM.
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Old 11th December 2017, 03:00 PM   #23
cumbb is offline cumbb
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What are your sources?

Use just the MosFet; no input-op: build an amp, not a buffer -sounds much better than op and buffer.
Use just one psu für both channels -or connect the psus later;-)
Build a p-channel-MosFet-amp. Sounds a little bit cleaner and clearer.
For the now residual 4 or 5 e-parts you do not need a board, a "sound-destroyer"-)
...

LG
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Old 11th December 2017, 03:03 PM   #24
Mark Johnson is offline Mark Johnson  United States
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Mosfet class A headphone amplifier
Quote:
Originally Posted by PRR View Post
I don't know why you would want +/-15V and 200mA for any headphone.
There's a very useful table of headphone characteristics (HERE).

According to that table, the headphones that need the biggest voltage swing are (a) low sensitivity, and also (b) high impedance.

The "winner" (largest required voltage swing of them all) is the Beyerdynamic DT770 Pro, with a sensitivity of 98 dB SPL @ 1V, and an impedance of 251 ohms. They require a voltage of 3.981 volts RMS to reach the target SPL which 110dB. That's plus or minus 5.63 volts, peak to peak. If the amplifier's maximum undistorted output voltage is 7V less than the rails, you'd want a power supply of +/- 12.6 volts. {7V might not be enough if using a MOSFET output stage}

Also according to that table, the headphones that require the biggest current to achieve the 110dB target SPL, are weirdo outliers made by Hifiman. The HE-4 requires 159mA and the HE-6 requires 261mA. If we ignore/discard those, then the headphones with the third biggest current requirement are the Fostex TH-900: 63.4 mA RMS, per channel. Input impedance is 25 ohms and sensitivity is 108 dB SPL @ 1V input.

To summarize: +/- 13V supplies at 150 mA, will let you drive all but two of the headphones in that table. It is probably a good idea to include big filter capacitors that let you ride out the difference between RMS and peak, when delivering a full amplitude 20 Hz sinewave.
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Old 11th December 2017, 03:12 PM   #25
cumbb is offline cumbb
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You all have to modify the/your "reference-headphones". They all sound very ugly - capsules to big, suspension, cables ... all;-P
The most headhones do "win" per ADDITION of "rough and dull" sound, per separate headhoneamps: these counter the diffuse and noisy and gray headphone-sound;-)
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Old 11th December 2017, 08:03 PM   #26
sevenup2278 is offline sevenup2278  Netherlands
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Quote:
Originally Posted by BesPav View Post
But this circuit likely not need this.
Just place something like 4700 uF + 10 Ohm + 1000 uF (latter should be decoupled with small sized 100/47 uF and good > 100nF NP0).
I have C-R-C on the pcb before the voltage regulators

First C: up to 10,000uF
Resistors: pitch 18mm for each channel
Second C: up to 1,000uF for each channel
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Old 13th December 2017, 08:40 PM   #27
sevenup2278 is offline sevenup2278  Netherlands
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Quote:
Originally Posted by tomchr View Post
If you have a volume pot soldered to the input of the amp board, the volume pot will drain the cap.

Tom
Thanks for your reply.
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Old 16th December 2017, 11:02 AM   #28
sevenup2278 is offline sevenup2278  Netherlands
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Layout based on the circuit in post 17.

Removed one set of voltage regulators, now there is one set of regulators for both channels.
Attached Images
File Type: jpg 3.JPG (166.1 KB, 274 views)
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Old 16th December 2017, 11:22 AM   #29
BuckarooBanzai is offline BuckarooBanzai
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Quote:
Originally Posted by sevenup2278 View Post
Layout based on the circuit in post 17.

Removed one set of voltage regulators, now there is one set of regulators for both channels.
Looks great ! What is the part number of the heatsink you're using?
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Old 16th December 2017, 11:24 AM   #30
sevenup2278 is offline sevenup2278  Netherlands
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Quote:
Originally Posted by BuckarooBanzai View Post
Looks great ! What is the part number of the heatsink you're using?
It's this one: SK 68, Extruded heatsinks for PCB mounting, Heatsinks f.cool, Fischer Elektronik

100mm length
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