Aleph headphone amp

jwb · 28th May 2003, 06:08 AM

Just about the only way to improve on <a href="http://www.diyaudio.com/forums/showthread.php?s=&threadid=2451">tortello's beautiful Zen headphone amp</a> is to go for an Aleph headphone amp. The advantages are the balanced FET front-end and the DC-coupled output. This design is specified to put 500mW into Grado headphones, or other phones with about 32Ω impedance. It should also drive a small speaker, and indeed has done so in a breadboard incarnation.

Right now the only thing I'm not liking is the high value of the current sense resistor. I used it in my breadboard mockup but I might change it for something smaller.

One channel shown.

Nicke · 28th May 2003, 09:10 AM

Shouldn´t there be a resistor between R14 & R15 coupled to ground ?

Nicke

akira · 28th May 2003, 09:45 AM

Would it be OK to drive HD580 Sennheiser Headphones with this amp ? The input inmpedance is much higher ... 300 Ohms.

jwb · 28th May 2003, 01:16 PM

Quote:

Originally posted by Nicke
Shouldn´t there be a resistor between R14 & R15 coupled to ground ?

All that junk on the left is for the input coupling. I didn't draw it because it isn't that interesting.

paulb · 28th May 2003, 02:08 PM

Quote:

Originally posted by Nicke
Shouldn´t there be a resistor between R14 & R15 coupled to ground ?

Nicke

What Nicke means is, you're showing 100% feedback. A resistor where he suggests would reduce feedback, adding actual gain.

Nicke · 28th May 2003, 03:09 PM

Quote:

Originally posted by paulb

What Nicke means is, you're showing 100% feedback. A resistor where he suggests would reduce feedback, adding actual gain.

Thats right ...
Is it unity gain stable as drawn ?

jwb · 28th May 2003, 07:00 PM

"As drawn" is incomplete. Trust me, those resistors over on the left really do go in the circuit. I just got tired of clicking the mouse. You obviously get the idea.

jwb · 1st June 2003, 01:12 AM

Take 2. The front-end doesn't have enough headroom with that 9.1V reference, so reduce to 5.7V via an LED string. Switch to 2sj109 monolithic FET pair. Increase idle current to about 220mA. DIscard C3 and C4.

Edwin Dorre · 15th June 2003, 10:00 PM

How is it going?

I have some kristian PCB boards lying around for an Aleph 4 which I like to turn into a headphone amp for my Sennheiser 580!

Edwin

jwb · 16th June 2003, 12:00 AM

Hi Edwin. It's going well. I got a Sun 411 SCSI case to put the amp in and modified it for XLR connectors. I'm still in the process of drawing the printed circuit board. Hopefully I will finish it next weekend.

I also increased the design rail voltage to 14V.

28th May 2003, 09:10 AM	#2
Nicke diyAudio Member Join Date: Jun 2001 Location: Sweden	Missing component ? Shouldn´t there be a resistor between R14 & R15 coupled to ground ? Nicke

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28th May 2003, 09:45 AM	#3
akira diyAudio Member Join Date: Jan 2002 Location: Paris France	Would it be OK to drive HD580 Sennheiser Headphones with this amp ? The input inmpedance is much higher ... 300 Ohms.

28th May 2003, 07:00 PM	#7
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	"As drawn" is incomplete. Trust me, those resistors over on the left really do go in the circuit. I just got tired of clicking the mouse. You obviously get the idea.

15th June 2003, 10:00 PM	#9
Edwin Dorre diyAudio Member Join Date: Apr 2002 Location: Netherlands	How is it going? I have some kristian PCB boards lying around for an Aleph 4 which I like to turn into a headphone amp for my Sennheiser 580! Edwin

16th June 2003, 12:00 AM	#10
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	Hi Edwin. It's going well. I got a Sun 411 SCSI case to put the amp in and modified it for XLR connectors. I'm still in the process of drawing the printed circuit board. Hopefully I will finish it next weekend. I also increased the design rail voltage to 14V.

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