Designing a super low distortion headphone amp.

Rainwulf · 12:20 PM

So - decided to build myself an insane headphone amp.

Im going to build it using the guidelines on this site for low distortion, low noise construction, no C-in, film caps etc.

So far, my choice of chip is an LM1875 power amp. I know its massively overkill for an headphone amp, but i do plan on winding down the gain, and putting in a attenuator using non wire wound resistors to reduce noise.

So, is LM1875 a good chip for headphone amps?

wahab · 15th March 2010, 12:40 PM

Will work, undoubtly, but will lag considerably compared
to a smple op amp + Class A biaised discrete devices.
A simple NE5532 + a pair of sanken darlingtons will blow it away..

Rainwulf · 15th March 2010, 12:44 PM

thank you for your input.
Im going to google for some circuit diagrams.

wakibaki · 15th March 2010, 12:54 PM

John Conover: Direct Coupled Stereo Headphone Amplifier

You'll be hard pressed to better this.

w

Rainwulf · 15th March 2010, 12:56 PM

Portable 9V Headphone Amplifier by NE5532 | Circuit Project Electronic is something i just found.

Rainwulf · 15th March 2010, 12:57 PM

Quote:

Originally Posted by wakibaki

John Conover: Direct Coupled Stereo Headphone Amplifier

You'll be hard pressed to better this.

w

holy crap, i dont think im going to go this far, i only have a 60 dollar set of Phillips SBC-HP250 headphones!

wahab · 15th March 2010, 01:20 PM

found something that look like this one..

high current discrete audio buffer

Rainwulf · 15th March 2010, 01:24 PM

wahab, i love that circuit, clean.
However, no way to adjust bias current, and diodes have variable forward drop due to temperature. Are you relying on the op-amp to minimize crossover distortion?

wahab · 15th March 2010, 01:36 PM

To adjust the bias, a pot in serial with one of the diodes will
be enough., although it s useless as the strip of 6 diodes makes the
amp biased in class A.
The current is limited by the power devices emitter resistors.
You can also change these resistors to choose your bias.
It is very stable anyway.
also, you can use two darlingtons as power devices, this will make the
circuit even more simple, and that s what i made mysef.

Rainwulf · 15th March 2010, 01:51 PM

so its more of a class A amp.
I like it!

Thats why you warn to mount the transistors on heatsinks, power dissipation.

15th March 2010, 12:16 PM	#1
Rainwulf diyAudio Member Join Date: Feb 2009	Designing a super low distortion headphone amp. So - decided to build myself an insane headphone amp. Im going to build it using the guidelines on this site for low distortion, low noise construction, no C-in, film caps etc. So far, my choice of chip is an LM1875 power amp. I know its massively overkill for an headphone amp, but i do plan on winding down the gain, and putting in a attenuator using non wire wound resistors to reduce noise. So, is LM1875 a good chip for headphone amps? Last edited by Rainwulf; 15th March 2010 at 12:20 PM.

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15th March 2010, 12:40 PM	#2
wahab diyAudio Member Join Date: Nov 2009 Location: algeria/france	Will work, undoubtly, but will lag considerably compared to a smple op amp + Class A biaised discrete devices. A simple NE5532 + a pair of sanken darlingtons will blow it away..

15th March 2010, 12:44 PM	#3
Rainwulf diyAudio Member Join Date: Feb 2009	thank you for your input. Im going to google for some circuit diagrams.

15th March 2010, 12:54 PM	#4
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	John Conover: Direct Coupled Stereo Headphone Amplifier You'll be hard pressed to better this. w

15th March 2010, 12:56 PM	#5
Rainwulf diyAudio Member Join Date: Feb 2009	Portable 9V Headphone Amplifier by NE5532 \| Circuit Project Electronic is something i just found.

15th March 2010, 01:20 PM	#7
wahab diyAudio Member Join Date: Nov 2009 Location: algeria/france	found something that look like this one.. high current discrete audio buffer

15th March 2010, 01:24 PM	#8
Rainwulf diyAudio Member Join Date: Feb 2009	wahab, i love that circuit, clean. However, no way to adjust bias current, and diodes have variable forward drop due to temperature. Are you relying on the op-amp to minimize crossover distortion?

15th March 2010, 01:36 PM	#9
wahab diyAudio Member Join Date: Nov 2009 Location: algeria/france	To adjust the bias, a pot in serial with one of the diodes will be enough., although it s useless as the strip of 6 diodes makes the amp biased in class A. The current is limited by the power devices emitter resistors. You can also change these resistors to choose your bias. It is very stable anyway. also, you can use two darlingtons as power devices, this will make the circuit even more simple, and that s what i made mysef.

15th March 2010, 01:51 PM	#10
Rainwulf diyAudio Member Join Date: Feb 2009	so its more of a class A amp. I like it! Thats why you warn to mount the transistors on heatsinks, power dissipation.

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