Antique radio bluetooth mod - stereo/mono conversion

[woodyp]

Hello all

I have got an antique radio with a nice casing, and volume knob that I am thinking of repurposing.
I would like it to have a line-in, and a bluetooth function. Unfortunately the radio can only accommodate one speaker, and I think i will look for a 5.25 inch driver.

I want to power it with a suitable board. I found many, with the appropriate power, line in, and bluetooth, and volume control (which i intend to interface with the original knob).


Here is a good example of a board I'm considering


But these are all stereo. I am a little at a loss as to how best to convert to drive a single speaker. I see advice about combining the line-level signal using simple resistor Y-shaped configs, but not clear about how to combine a class D L/R output to mono.

Any tips would be greatly appreciated.

 

[pboser]

Edcor makes nice little transformers to combine stereo to mono, both at line level and speaker level. I can’t find the latter on their site, but I know they exist because I have one at home! This might be easier and smaller- you could use the line-level and just one amp channel.

 

[pboser]

I misremembered- the speaker level one is the Speco TSM-30.

 

[MarcelvdG]

Pity that you are going to spoil an antique radio. Why not connect a Bluetooth receiver to its phono input? Antique phono inputs are usually meant for ceramic or crystal cartridges and can be used for line level signals.

 

[oon_the_kid]

You can consider one of these from tinysine. You have option of mono when you order the board mixed digitally inside the chip.

2 x 20W Class D Bluetooth Audio Amplifier Board - TSA9840B (TWS/Apt-X)

You might want to retain the original driver if it is still in good condition. I would also recommend adding in a simple first order coil low pass filter at 5-10 kHz. Reduces the break up in cone. It gives a really nice antique sound if you are playing songs from the 60s...

Oon

 

[woodyp]

Thanks for those who provided helpful comments. I will explore the tinysine suggestion. Should have mentioned my location is the UK so not sure about how to source it.


And for the passionate conservationists - the radio which i picked up in a boot sale has its original driver removed, and most of the internals missing too. the back plate is badly cracked which i will have to restore. So I am not really butchering something nice, just reusing a decent looking housing.

 

[ubergeeknz]

I think the mixing board is the best option.

Please don't try putting 50 or 100w into the original speaker, you'll turn it to molten slag [emoji16]

 

[seantkezm]

I've used these to do similar projects to what you're describing. Wired well for me.

Dayton Audio KAB-100M 1x100W Class D Audio Amplifier Board with Bluetooth 4.0

 

[Pano]

I've used the Tinysine and other Dayton KAB boards. Both worked well for me, tho I haven't tried mono vesrions