Good radio shack amp ?

[wolf08]

i want to build an amp for my iPod, i want two Channels which i think is called an "op amp" i would like to put it in an enclosure and power it with a battery (9v or anything suitable)i no radio shack carries op amps but i dont no which one to get and i cant seem to find any good circuits. If you could help choosing an ic and a good circuit that would be big help.

Thanks

 

[ben7]

I built an LM386 amp for my ipod before, it costs $70 at RadioShack-no-I mean cellphone shack.

Buy stuff cheaper on the internet!

You can use a low power amp chip, such as the TBA820 or the LM386.

**broken link removed**
**broken link removed**

-Ben7

 

[audioguru]

But Wolf forgot to tell us if he wants to drive headphones or little speakers.
The output power of an LM386 into 8 ohms with a 9V supply is only 0.45W at clipping and a little 9V battery will not last long.

I would use two TDA2822M bridged little amp ICs which have an output power of 1.1W per channel into 8 ohms at clipping with a 6V supply.
Four AA alkaline battery cells make 6V and will power the amplifier for a fairly long time.

 

[transistor495]

I thought iPod already has built in headphone amp, so anyone wish to build external amp drives a speaker only.

Both LM386 and TDA2822M exhibits severe no signal noise properties that tells perfectionists to go in search of other versatile chips like say -a TA7368P.

Drive them with a pack of modern eneloop batteries instead of costly alkalines(would anyone use disposable batteries anymore?) for ever.

 

[audioguru]

Drive them with a pack of modern eneloop batteries instead of costly alkalines(would anyone use disposable batteries anymore?) for ever.

The Sanyo Ni-MH rechargeable cells are 1.25V each. Four make only 5V instead of 6V so the power from the little amplifier ICs will be lower.

I use alkaline AA cells in the radio transmitter for my electric RC airplanes because they last for a very long time and do not suddenly stop.
I use Ni-MH cells in the charger for my electric RC airplanes.

 

[Dragon Tamer]

Radio Shack is famous for charging way too much money for simple things, but it is a good place to go if you want general electronics parts very quickly. In the case of an audio amp, I know that the radio shack closest to me only carries 3 types of op-amps. The LM741, LM324, and TL082.
http://www.datasheetcatalog.org/datasheet/fairchild/LM741.pdf, http://www.datasheetcatalog.org/datasheet/fairchild/LM324.pdf, http://www.datasheetcatalog.org/datasheet/stmicroelectronics/2300.pdf
All of which are no good for an audio amp that meets your requirements. To start, all 3 are dual rail op-amps and you would need 2 9V batteries connected in series just to meet the power requirements. I tried using all 3 to amplify a very small audio signal from my iPod and they all caused sever clipping with a 1.5Vp-p output from my iPod and a gain of 2 using ±9V then ±15V. I would recommend using 2 LM386 because they are specificly designed as an audio amp.

My little iPod amp has a single LM386 that drives 1 speaker at roughly 0.5W, the 9V battery can only power it for about 6 hours before it's officially "dead". Using a battery with larger cells would last longer like AG said. I would also use the quad amp version of the TDA2822M which AG mentioned, it's the TDA2822 that would slightly improve the efficiency of your circuit.

This is what the audio trace from an iPod looks like;

it has a carrier frequency of about 100Hz combined with the actual audio signal.

 

[transistor495]

The Sanyo Ni-MH rechargeable cells are 1.25V each. Four make only 5V instead of 6V so the power from the little amplifier ICs will be lower.

But voltage level of a disposable battery goes down quickly during operation(see the 9v pp3 battery- its 1/2USD here losses its voltage so quickly that needs immediate replacement), but I agree that alkaline cells got a high capacity that helps it for keeping a high voltage level. But considering consistent 1.2v of a Ni-MH is rather impressive and all in all which is good?

Normally voltage dependent loads(eg, torch) are packed with 5x1.2v rechargeable battery that is much cost effective.

Sanyo eneloop batteries are claimed to be designed for over 1500 recharge cycles.

 

[audioguru]

In the case of an audio amp, I know that the radio shack closest to me only carries 3 types of op-amps. The LM741, LM324, and TL082.
... all 3 are dual rail op-amps and you would need 2 9V batteries connected in series just to meet the power requirements.

No.
Any opamp works fine with a single supply if its input is biased at half the supply voltage.
the 741 is spec'd with only a 30V supply. Some do not work if the supply is less than 10V.
The LM324 has a 3V minimum supply.
The TL081 has a 7V minimum supply but many work fine at 5V.

I tried using all 3 to amplify a very small audio signal from my iPod and they all caused sever clipping with a 1.5Vp-p output from my iPod and a gain of 2 using ±9V then ±15V.

They are opamps that are made to drive a minimum load of 2k ohms, not power amps that drive 8 ohm speakers.