Split power rail from single supply. - Page 1
Forum section: electronics / projects

author: Gintoki
author_rank: Newbie
timestamp: November 05, 2013, 06:05:38 am
content: Hi, I'm currently working on a discrete Class-A headphone apmplifier that I want to supply from a single supply e.g. a 12-15VDC wall wart.I have searched alot on the net but couldn't find something that worked properly for my case. The specifications is minimum +/-5VDC and about 100 mA. I don't want to use a switching power supply, so only linearThanks in advance.~GintokiBtw. I'm new to the forum, so hello all ^^

author: ddavidebor
author_rank: Super Contributor
timestamp: November 05, 2013, 06:34:09 am
content: You're welcome, it was my pleasure.

author: johansen
author_rank: Super Contributor
timestamp: November 05, 2013, 06:39:48 am
content: class A doesn't require a split power supply.for a head phone amplifier you could split the rails with two 6.8v 1/2watt zeners and two 470uF caps and call it good.edit:forgot to mention... if you don't want to hear the zenar diodes, make sure to wrap them in cotton cloth and use oxygen free copper wires between the zenars and the capacitors, also, you'll need 1 ohm resistors inline with the 1uf polypropylene capacitors to de-couple the 470uF cap.

author: Unknown
author_rank: Unknown
timestamp: November 05, 2013, 06:45:28 am
content: This page discusses some options with a minimum of audiofool nonsense:http://tangentsoft.net/elec/vgrounds.htmlThe circuit with the buffer and the discrete circuit should work fine for 100 mA, although you might need beefier transistors that can dissipate more (eg. DPAK, TO-220) in the discrete circuit, since you might be dissipating over half a Watt worst case.

author: Jon86
author_rank: Frequent Contributor
timestamp: November 05, 2013, 09:47:19 am
content: For something as low power as a headphone amplifier, I'd say just go with the resistor divider option. There's going to be barely any current flowing into your ground, so it'll probably be fine. But I guess if you want a better, more clean supply you could go with another option.

author: calexanian
author_rank: Super Contributor
timestamp: November 07, 2013, 03:45:28 am
content: Why do you have to use a wall wart? And at that low amt of power use a 9 or 12 volt AC wall wart and use a voltage doubler and connect the ground to the center of the doubler. Its isolated anyways and you can ground later in the system. Also many brick power supplies have +/- 12 volt now in that power range and can be had for under 20 bucks.

author: olsenn
author_rank: Frequent Contributor
timestamp: November 07, 2013, 03:59:15 am
content: 100mA may work for the majority of headphones, but you might want to increase it a bit to accommodate for insensitive, low impedance headphones such as planar magnetic headphones. 200mA - 400mA should do the trick.You are definitely NOT going to want to use a resistive divider as Jon86 said, and TLE2426 can only source around 20mA per side. You could use a high-current op-amp to buffer Vin/2 which would become your virtual ground.Is this device going to be battery operated, or only wall connected? Look at the very respectable O2 amplifier schematic for another possibility (although the power section is kind-of sketchy in my opinion, so consider other options first)

author: deth502
author_rank: Frequent Contributor
timestamp: November 07, 2013, 05:27:47 am
content: charge pump

author: chasxmd
author_rank: Contributor
timestamp: November 10, 2013, 12:55:32 am
content: Any problem with soldering on a power supply? You could always throw in a DC to DC power supply.. pretty small, not to bad of a price (unless this is going to mass market)http://www.digikey.com/product-search/en/power-supplies-board-mount/dc-dc-converters/4325599

author: dannyf
author_rank: Super Contributor
timestamp: November 10, 2013, 01:12:46 am
content: 1. try not to split the rail; use output capacitors or transformers or balanced output, etc. rail spliters are at least as evil as any of the approaches mentioned above;2. if you have to split the rail, use at least as good of an amp as your headphone amp to split the rail: configure it as a follower;3. if anything else fails, you a linear regulator to create the virtual ground.QuoteYour wall wart is likely a smps.