Converting Vintage Radio to an iPod Speaker

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markm78
 
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Converting Vintage Radio to an iPod Speaker

Post by markm78 »

I am a WWII reeancator and have a 1940's portable radio that I like to play period music through. I currently use a cheap battery powered speaker that hooks to my iPod which I hide inside the radio case. I recently came across a website that showed how to convert the radio into a speaker using an amplifier. My question is which of your amplifier's would you recommend using to do a project like this? I was taking a look at the Stereo 20W Class D Audio Amplifier - MAX9744 but unsure if this would be a fit for this type of project or not. I would like to have the ability to hook the volume control to the volume knob on the front of the radio if possible. I will also need a small speaker as well (2 or 4") since I saw that a magnetic speaker is required for amps like these. I also need a recommendation on best type of power source to use since it is a portable radio. It may be nice to use a rechargeable battery source, so didn't know if a lithium ion 3.7 volt with one of your boosters would be a good fit or not. I'm first to admit that my knowledge of electrical engineering is lacking and would appreciate any assistance you could provide and recommendation on products you would recommend for this type of project. I would be glad to purchase all of the components from your company if possible.

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Re: Converting Vintage Radio to an iPod Speaker

Post by adafruit_support_bill »

The 20W stereo amplifier should work. I don't know if your radio has room for two speakers or not. But the iPod output is in stereo. If you have only room for one speaker, it is possible to combine the left and right inputs to create a mono signal. In that case, you would use just one channel of the amplifier. Depending on the speaker choice and the volume you want to achieve, we also have a smaller 2.5W mono amplifier.

The amplifier can be powered with as little as 4.5v, so a 3.7vLiPo with a PowerBoost controller would make a good rechargeable power source.

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markm78
 
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Re: Converting Vintage Radio to an iPod Speaker

Post by markm78 »

Thank you for the insight. I appreciate your assistance. I saw the smaller version that you mention but was drawn to the 20W since it said it could be connected to a volume control. If I were to go with the 2.5W could it be connected to the volume control on the front of the radio as well? Also, I found a black Friday deal from radio shack for a 10,400mAh Portable Power Bank for $29.99 that I was thinking of using to power the amp. Would this be a suitable power pack for this type of application? http://www.radioshack.com/radioshack-po ... HfsUcmNrkc. Also, For reference the radio is 9" tall x 12" wide x 6.25" deep. This probably means I would be limited to single speaker. I tried attaching a pic of the radio but file was too large. Thanks and have a great day!

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Re: Converting Vintage Radio to an iPod Speaker

Post by adafruit_support_bill »

Any of the amps could be made to work with the volume control. And that RS powerbank should work to power the system.

A single 2.5W speaker in that cabinet is not likely to give you much volume. Given the 9x12" face, you should have enough room to fit a pair of 4" speakers. These would be a perfect match for the 20W unit: https://www.adafruit.com/products/1732

Photos are limited to 1meg in posts. If you resize to 800x600 it should upload fine.

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Re: Converting Vintage Radio to an iPod Speaker

Post by markm78 »

Thanks again for your help. I'm sorry to keep pestering about this but I want to be sure I get the proper components to make my project work and be worthwhile. I picked up the RS power bank this morning. The specs say output is 5VDC, 2.1A. Cell capacity of 10,400mAh. There is a note that total input current for deice plugged in should not exceed 2.1A which if I'm calculating correctly means 10.5 watts? I'm making the assumption then that a 20 watt amplifier and speaker is too much for the battery to power? Also, would you say I need to back down to a 2.5 Watt mono amplifier and if so do you think it would provide ample volume in my application? I appreciate any insight or recommendations you can provide.

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Re: Converting Vintage Radio to an iPod Speaker

Post by adafruit_support_bill »

20 Watts would only be at peak volume. But with stereo, that would be 2x 20 Watts.

You might be better off with one of the 3.7W stereo amplifiers and a pair of 4-ohm speakers. 2x 3.7W is 7.4W at max output - safely within the limits of your battery power. We have a detailed tutorial for this here: https://learn.adafruit.com/stereo-3-7w- ... -amplifier

The sound levels won't be wall-shaking, but will probably be about on par with what the original radio circuitry could do.

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Re: Converting Vintage Radio to an iPod Speaker

Post by markm78 »

Thanks for all your help. I just ordered the 3.7 Watt amp, 2 x 3" 4 ohm speakers, a headphone cable and some connectors. I'll have to let you know how the project turns out. Again, thanks for giving some audio knowledge to an otherwise naive person when it comes to this stuff. I will same I've gained some useful knowledge from all of this.

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