Some questions on the Gilmore headphone amp.

Artie · 21st April 2009, 09:05 PM

I think I'm going to build this Gilmore headphone amp, but have a couple questions:

1. I'm not sure I understand why he's using eight output transistors per channel. Each of those transistors can handle up to 150ma. Seems excessive for a headphone amp. Since I'm going to use this to drive 250-ohm Beyerdynamic DT-770 Pro's, (20ma/100mW max), could I get by with just one transistor pair per channel?

2. Is there any particular reason for +/- 16-volts per se? +/- 15-volt supplies are fairly common. (I have a few lying around.) Is that 1-volt going to matter?

Btw: I would have asked this over at Headwise, but their forum is down. Thanks all.

LineSource · 22nd April 2009, 01:08 AM

1. I think Glimore used 4-output pairs because: a) he believes using one pair of large output transistors does not sound as good as multiple pairs of small signal transistors; b) the outputs are the same 2SC1815/2SA1014 transistors used in other stages - its already in his parts bin; c) multiple outputs means very modest Tj temperature changes and this removes the need for a Vbe temp comp circuit(diodes or Vbe multiplier) and the need for heatsinks; e) these are only 400 mW transistors

2) I think this circuit would work fine at +/- 15V without any component changes. You can always run a Spice sim if you want to fine tune any resistor values.

This Gilmore headphone amp gets consistent excellent reviews, and I would try to copy it as closely as possible. The main cost is the power supply.

Artie · 22nd April 2009, 01:21 AM

Thanks LS. And I agree, it would probably be best to build it verbatim, and make sure it works right, before I start messing with changes.

21st April 2009, 09:05 PM	#1
Artie diyAudio Member Join Date: Jul 2007	Some questions on the Gilmore headphone amp. I think I'm going to build this Gilmore headphone amp, but have a couple questions: 1. I'm not sure I understand why he's using eight output transistors per channel. Each of those transistors can handle up to 150ma. Seems excessive for a headphone amp. Since I'm going to use this to drive 250-ohm Beyerdynamic DT-770 Pro's, (20ma/100mW max), could I get by with just one transistor pair per channel? 2. Is there any particular reason for +/- 16-volts per se? +/- 15-volt supplies are fairly common. (I have a few lying around.) Is that 1-volt going to matter? Btw: I would have asked this over at Headwise, but their forum is down. Thanks all.

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22nd April 2009, 01:08 AM	#2
LineSource diyAudio Member Join Date: Sep 2003 Location: SiliconValley	1. I think Glimore used 4-output pairs because: a) he believes using one pair of large output transistors does not sound as good as multiple pairs of small signal transistors; b) the outputs are the same 2SC1815/2SA1014 transistors used in other stages - its already in his parts bin; c) multiple outputs means very modest Tj temperature changes and this removes the need for a Vbe temp comp circuit(diodes or Vbe multiplier) and the need for heatsinks; e) these are only 400 mW transistors 2) I think this circuit would work fine at +/- 15V without any component changes. You can always run a Spice sim if you want to fine tune any resistor values. This Gilmore headphone amp gets consistent excellent reviews, and I would try to copy it as closely as possible. The main cost is the power supply.

22nd April 2009, 01:21 AM	#3
Artie diyAudio Member Join Date: Jul 2007	Thanks LS. And I agree, it would probably be best to build it verbatim, and make sure it works right, before I start messing with changes.

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