Discrete 4x1.5V Battery Headphone Amp, Lowpower

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lineup

lineup

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Joined 2005
#1
It works down to +/-2.0V.
Distortion is low and current consumption is only like 3-4mA depending on the status of the batteries.
Has been tested in simulation with 32ohm and 300ohm load.

I challenge everybody to try to design a real lowpower headphone amp for +/-2.0V.
Post your schematic here.

Lowvolt Battery Headphone_03.jpg
 
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#2
My old abandoned thread. The tricky part is to bias it in class B.
J

Thread 'Amplifier with 2 AA battery'

Output swing: +-1V
Output current: >500mA

I was amazed my 5 inches shelf speaker can play pretty loud with just 2 AA battery.

This kind of out put stage seems to work pretty well with full swing of power supplier. I am thinking about to up scale it to larger power.

PS: It is able to work in Class B, with extremely low distortion.
 
#5
@lineup , thank you. However, I don't really the circuit. I built 4, and hooked them in btl for 2 channels just for the prove of concept.

Here is another design, not from me. It could work in very low voltage too.
G

Post in thread 'Common emitter / source amplifiers, rail to rail output voltage swing'

jxdking said:
Your attachment seems not working.
Click to expand...


You are right. Here is the circuit again for the +/- 1.2 V head phone common emitter amplifier.

hp_amp.jpg
The long tail from LTP can be swapped out with a trimmable current source for bias stability.
 
#9
lineup said:
I challenge everybody to try to design a real lowpower headphone amp for +/-2.0V.
Click to expand...
Many CMOS opamps can do that I suspect. For instance the AD8656 can drive +/-75mA and run from +/-1.35V supplies upto +/-2.5V supplies. You could do a bridge-tied version if your headphones are 4 wire rather than 3 wire for more volume, though that might be stretching the output stage too far. Current consumption 3.7mA per channel.
 
#10
I have described a number of low-voltage, low-power amplifiers.
Here is a example:
Elvee

Thread 'A small, low-voltage, battery operated amplifier'

Hi,

Here is a small, low-voltage (3V or less) amplifier.

I wanted a signal-tracer amplifier, very small, and battery operated to be used in completely floating situations: like typically to measure the noise across a component.

This amplifier fits the bill. It is rather crude, but has some interesting features: it uses same-sex output transistors, operates efficiently at ridiculously low voltage levels, and yet offers a decent quality: here, it is shown at max output power, and the THD is well under 2%, with a nice harmonic profile.
At lower power, the distortion is even lower.
Also...
This one operates from an even lower voltage, and is frugal enough to dispense with a power switch:
https://www.diyaudio.com/community/...ovative-in-line-amplifier.385011/post-6991150
Another one:
Elvee

Thread 'The X-FoBooster is a transformer-like in-line booster'

Here is another project inspired by Danny: it is based on the same principles as the BoosterPhone, low supply requirements, rail-to-rail output on a low impedance, in this case 600 ohm and decent audio quality without too much complications.
It is designed to match older sources, delivering 150~200mV to modern equipments requiring 700mV or more. It thus mimics a passive step-up transformer, but without the impedance penalty: a 1:4 step-up transformer increases the impedance by a factor of 16, which can be problematic. Instead, the output impedance is much lower than the input...
 
#13
The CD4049 doesn't do much at 5V, but one could use the 74HCU04 (25mA@5V) instead. It may also be necessary to keep an eye on the supply current. Further, with the VCC/GND connections common anyway, all gates on a chip could be paralleled to boost the output.
 
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