my rather cheap endeavour into DIY headphone amps...

[DJFender]

Feast your eyes on this prototype....


Well It is a beast I can tell you that.

Its a TDA2822M based speaker amplifier board out of one of these.

< I got the cheap knockoff from the dollar store for $2

Strapped to it with zipties are a stereo unimatch plug adaptor for hifi audio and an old salvaged lithium battery pack (I know how dangerous it is to have it without the protection circuit but it was interfering with the output)

I used this peice to power my Sony MDR-V500 headphones, specs as follows


Max. Power Handling
1000 mW
Driver Unit Size
40 mm
Frequency Response
10 Hz - 25000 kHz
Impedance
24 ohm
Sensitivity
105 dB

I'd like to design a proper 24 ohm headphone amplifier based on this TDA2822M chip and would like guidance, I have a soldering iron and I can obtain capacitors and the like from my personal salvage.

I would like the design to follow these guidelines:
Uses 9V batteries
No volume control
Power indicator light
Power switch.

I have a small 1x2x1 project box and it does indeed fit a 9V battery.

Since I'm a DJ but I like to tinker I would like to have the same punchy audio I get from my 3 channel mixer as I do from my zune...

[DJFender]

Stereo Amplifier One Watt Electronic Kit < This serves my needs but I'm not sure If this kit will put out the 24 ohms my headphones can take.

[Mooly]

The TDA2822 is great for headphones... all you need is here,
http://www.datasheetcatalog.org/data...cs/mXsrtww.pdf

just add a series resistor to the outputs to reduce the power available to the phones, say around 120 ohms.

[DJFender]

Originally Posted by Mooly

The TDA2822 is great for headphones... all you need is here,
http://www.datasheetcatalog.org/data...cs/mXsrtww.pdf

just add a series resistor to the outputs to reduce the power available to the phones, say around 120 ohms.

ok, so would I follow the TYPICAL APPLICATION CIRCUIT (STEREO) diagram?

[DJFender]

If memory serves right, a 120ohm resistor is Brown-Red-Brown-None Right?

[pacificblue]

What guidance exactly do you need? Your "prototype" seems to have everything you want. The green LED is a power indicator light, isn't it? And the switch looks like a power switch, too.
If you increase the battery voltage to 9 V, you should check whether the resistor that is in series with the LED has the correct value. >390 Ohm should be fine. The bigger the resistor, the less light you get, but also the less power is consumed.
If you don't want volume control, connect the input on the opposite pin of the potentiometer or replace the potentiometer with a jumper.

[DJFender]

Originally Posted by pacificblue

What guidance exactly do you need? Your "prototype" seems to have everything you want. The green LED is a power indicator light, isn't it? And the switch looks like a power switch, too.
If you increase the battery voltage to 9 V, you should check whether the resistor that is in series with the LED has the correct value. >390 Ohm should be fine. The bigger the resistor, the less light you get, but also the less power is consumed.
If you don't want volume control, connect the input on the opposite pin of the potentiometer or replace the potentiometer with a jumper.

the amp was premade for 4ohm use, it can drive a set of 4 ohm speakers quite well but it distorts too much when I use my headphones for a load.

[pacificblue]

A 32 Ohm load is usally easier to drive than a 4 Ohm load.
It is probably more like the amp always distorts, but your headphones are more revealing.
Or it is simply driven into clipping, because the supply voltage is too low with the batteries you are using now in relation to the listening level you want to achieve.
Another possibility is a bad connection (solder joint, headphone jack, etc.) somewhere that makes and breaks contact as you move the cable or the amp around.

[DJFender]

Originally Posted by pacificblue

A 32 Ohm load is usally easier to drive than a 4 Ohm load.
It is probably more like the amp always distorts, but your headphones are more revealing.
Or it is simply driven into clipping, because the supply voltage is too low with the batteries you are using now in relation to the listening level you want to achieve.
Another possibility is a bad connection (solder joint, headphone jack, etc.) somewhere that makes and breaks contact as you move the cable or the amp around.

I'd say its a matter of number 2, as I'm using a 3.7v 450mAh battery to power it.

[TechnoBeaver]

I also have a couple 2822, was thinking of doing something like this.

I already have a decent Cmoy, so I wanted to try something a little better.

I did not think the 2822 would sound as nice as the 5218A in my Cmoy, but maybe I will try it sometime.


Ya, you need proper voltage for this to sound clear. I made a couple of guitar amps out of these. The low battery distortion actually sounds as good or better then the diode clipping distortion using germs.