Aspen Headphone Amp - Page 2

Bigun · 22nd September 2009, 01:36 AM

Quote:

Originally Posted by MJL21193

Nice one Hugh!
Simple, easy to build and I'd guess as good (or better) than most out there.

Will Gareth work up a board for this?

As you know I've enjoyed designed a few boards in the past, but I think Hugh needs something professional here so I'm going to lean on Aspen for some help with boards, take advantage of their supply chain

MJL21193 · 22nd September 2009, 01:41 AM

Could be a group buy in the offing? Sign me up!

GK · 22nd September 2009, 02:15 AM

Quote:

Originally Posted by AKSA

This small amp has lots of phase margin, 75 degrees at 12MHz, the dominant pole.

12MHz??

The unity loop gain frequency is actually closer to 1.1MHz and the dominant pole frequency is a bit under 50kHz.

Bigun · 22nd September 2009, 02:20 AM

Let's see if a simulation file is helpful here (attached - my recreation of the schematic - Hugh, perhaps you can post your original file including the device models). I've opted for the infamous Vbe multiplier for now - can swap out for diode's later.

To use the sim, download it and change the file extension from .txt to .asc (LTspice). You may need to go into file options to view the file extensions.

Bigun · 22nd September 2009, 02:29 AM

I see this as a desktop unit so my first thought was not batteries despite the noise benefits because I don't want to be worrying about re-charging etc.

If we want to keep this simple I'm leaning towards a 20VA trafo, anything too small will have poor regulation ? IF it is to drive small monitor speakers as well, I'd want 50VA.

Current draw on the rails is small, perhaps we can get away without dual supplies, put some fairly stiff CRC or CLC filtering in place on the rails if current draw is limited to headphone use only.

Another option would be a capacitance multiplier. It's a bit crude, but does the job well. The downside is some loss in headroom since you have not just the Vbe drop but Vce under load and the drop across the base resistor.

I'd like to keep it really simple - my dream would be a single pcb for both channels and power supply - how fussy should we be, can we achieve -100dB cross-talk on a single pcb ?

What are you thoughts ?

ikoflexer · 22nd September 2009, 02:32 AM

Quote:

Originally Posted by AKSA

Hi Ikoflexer (should that be Harley, or Buell?),

It's just a plebeian wee-strom, but I love it.

GK · 22nd September 2009, 02:36 AM

.

MJL21193 · 22nd September 2009, 02:43 AM

Quote:

Originally Posted by Bigun

I'd like to keep it really simple - my dream would be a single pcb for both channels and power supply - how fussy should we be, can we achieve -100dB cross-talk on a single pcb ?

What are you thoughts ?

I think so but where the amp itself is simple, I'd like to see extra effort on the PS. For a low current draw amp like this going with a fully regulated supply makes sense.

AKSA · 22nd September 2009, 03:06 AM

Here's the Bode plot from LTSpice:

Looks like unity gain is at 11.6MHz, 3dB point is at 1.6MHz.

I noticed GK's plot showed a gain of near on 34dB, which is very different to the CLG of 15dB.

?

Hugh

MJL21193 · 22nd September 2009, 03:07 AM

Maybe a variation on the Jung super reg. Make things a bit more challenging for us older hands.

22nd September 2009, 02:29 AM	#15
Bigun diyAudio Member Join Date: Jan 2009 Location: K-W Ontario Blog Entries: 2	Power supply I see this as a desktop unit so my first thought was not batteries despite the noise benefits because I don't want to be worrying about re-charging etc. If we want to keep this simple I'm leaning towards a 20VA trafo, anything too small will have poor regulation ? IF it is to drive small monitor speakers as well, I'd want 50VA. Current draw on the rails is small, perhaps we can get away without dual supplies, put some fairly stiff CRC or CLC filtering in place on the rails if current draw is limited to headphone use only. Another option would be a capacitance multiplier. It's a bit crude, but does the job well. The downside is some loss in headroom since you have not just the Vbe drop but Vce under load and the drop across the base resistor. I'd like to keep it really simple - my dream would be a single pcb for both channels and power supply - how fussy should we be, can we achieve -100dB cross-talk on a single pcb ? What are you thoughts ? __________________ "The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

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MJL21193 Account disabled at member's request Join Date: Mar 2007	Maybe a variation on the Jung super reg. Make things a bit more challenging for us older hands.

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