Headphone amp idea.... - Page 3

Russ White · 27th May 2005, 02:08 PM

higher available current and lower impedance to gnd are two reasons I can thinks of. Also no quiescent current draw for virtual ground. its a "real" ground.

tobias_svensk · 27th May 2005, 04:52 PM

If your not worried about one of the batteries getting discharged faster than the other i can't se any reason to have the 2426 (i maybe wrong)

00940 · 27th May 2005, 05:14 PM

http://tangentsoft.net/elec/vgrounds.html

The designer of the pimeta explains at the beginning why he doesn't trust two batteries to discharge equally. The main concern is that when batteries near zero, which coud happen if you let the amp on with music playing too long (getting asleep, leaving the room, and so on), DC offset could go through the roof and destroy the headphones. There are some posts about that on headwize.

Lovan · 27th May 2005, 06:43 PM

Yes DC offset is a big problem but only if one rail is A LOt higher voltage-vise i.e. one rail is disconnected. I have found that the effekt is not killing if your using a high impedance headphone(300ohm).
The dc output is about one rail at worst.

I think it´s still usable but with cauton. Somehow you have to monitor the batteries status.
If your using big sealed lead-acid batteries(4-7 Ah) the dc-offset is not a really big problem either. The amp draws about 40mA per batteri. That´s stereo. So with the 4Ah batteries you still have 100 hours use without any problem.

Caution though, my experience is limited to high impedance phones. But if DC is a problem you can use output caps.

27th May 2005, 05:14 PM	#23
00940 diyAudio Member Join Date: Sep 2003 Location: Paris	http://tangentsoft.net/elec/vgrounds.html The designer of the pimeta explains at the beginning why he doesn't trust two batteries to discharge equally. The main concern is that when batteries near zero, which coud happen if you let the amp on with music playing too long (getting asleep, leaving the room, and so on), DC offset could go through the roof and destroy the headphones. There are some posts about that on headwize. __________________ Ben.

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27th May 2005, 02:08 PM	#21
Russ White diyAudio Member Join Date: Jan 2005 Location: Nashville, TN, USA	higher available current and lower impedance to gnd are two reasons I can thinks of. Also no quiescent current draw for virtual ground. its a "real" ground.

27th May 2005, 04:52 PM	#22
tobias_svensk diyAudio Member Join Date: Jan 2004 Location: Hudiksvall	If your not worried about one of the batteries getting discharged faster than the other i can't se any reason to have the 2426 (i maybe wrong)

27th May 2005, 06:43 PM	#24
Lovan diyAudio Member Join Date: Oct 2003 Location: Sweden	Yes DC offset is a big problem but only if one rail is A LOt higher voltage-vise i.e. one rail is disconnected. I have found that the effekt is not killing if your using a high impedance headphone(300ohm). The dc output is about one rail at worst. I think it´s still usable but with cauton. Somehow you have to monitor the batteries status. If your using big sealed lead-acid batteries(4-7 Ah) the dc-offset is not a really big problem either. The amp draws about 40mA per batteri. That´s stereo. So with the 4Ah batteries you still have 100 hours use without any problem. Caution though, my experience is limited to high impedance phones. But if DC is a problem you can use output caps.