Introduction: Retro-Mod - Bluetooth Speaker Madness

About: I'm a design engineer, university lecturer and weekend shed goblin.

I bought this Bush DAC90a radio on ebay, broken and heavily worn. The idea being to Retro-Mod it into a funky bedroom speaker. I wanted to make my 14 year old sister a unique christmas present. She's pretty good a buying other people presents and I thought she deserved a good one back. She likes anything that looks like it's from the 50s.

This radio was in bad shape, it was far from a pristine example; I would never break an old tube radio in good condition for this purpose. I did this to give it an new lease of life (please be gentle).

Step 1: Cleaning and Stripping

I started by first detaching the main gubbins/parts from the case; this was done via the removal of three small grub screws: Two can be accessed underneath the radio and one from the back left.

I used a hover, then a soft brush and wet wipes to clean the parts. After this I then stripped back all the dried out capacitors and resistors, removed the board and looked at what was left.

Leaving the majority of the visible components seemed like the right thing to do. They're not doing any harm and the challenge of sneaking in the modern electronics seemed like fun.

Step 2: Electronics - Mock-up

For this project I will use a TPA 3116 (without bluetooth). This is because I have it to hand as it was not required for another project. You can use pretty much any small amp for this project. I will be converting this amp to bluetooth using a car usb charger a usb bluetooth stick and a ground loop isolator. Don't forget the isolator or it will hum like no tomorrow.

I will mount the main board and the aforementioned parts underneath the metal housing in place of the original board. There is plenty of ventilation and cooling as it was originally a tube amp and those things while delightful are about as efficient as a one armed rower. They produce lots of heat and not too much sound.

The speaker itself does not need to be replaced but for this purpose it will be. Speakers have moved on a bit in the last 60 odd years and my amp would quite easily cook it. So a more modern transducer is needed.

I don't want to use another single paper cone driver as in the higher frequencies things can get a bit beamy. I plan on using a two-way coaxial speaker from a car. They're inefficient but they cover a broad frequency range quite well and my amp will have no problem driving it.

I will also have to extend two of the pots and replace a switch as I plan on using the existing controls at the front of the radio. I like to make life easy for myself after all. Couldn't just go to the shops and buy something, that would be far too logical.

Step 3: Installing LEDs

I used a 100mm 12v warm white LED strip from ebay to light up the radio display, I had to drill a hole through the back of the frame so as to hide the wires from sight.

I had to extend the wires as they were to short.

Step 4: More Wiring

I was able to re-use the old mechanical switch that would have been used for the am/fm selector. To do this I wired the positive 12v input into the 2nd pin and used the 3rd for the output.

I have left in a picture of how I wired my 2.5mm barrel jack, I only used two of the pins as the other one acts a switch. This would be useful if you wanted to say have a battery turn on when the power source is removed. As i do not need this function I left it as is.

I also removed most of tabs and some of the internals of the tubes. I wanted to make sure that none of the parts touched the main board and shorted it out.

Step 5: Last Few Bits

I had to extend the 6pin 50k pot on the board so as to control the volume in its original position. I did this using male jumper wires and it was not fun! My cheap temperature controlled soldering iron just about did it without burning out to much of the board. I used a scrap of perforated steel to extend the mounting point of the pot. This was not my finest moment but it works and is still fairly hidden. Metalworking is not my strong point, with more time and resources I would have got parts laser cut of 3d printed so as to fit them better.

I used a 7mm titanium drill bit and a set of wire cutters to trim the back of the enclosure, this was done to accommodate the bigger speaker magnet.

For the output on the amp I used a stereo to mono adapter and the right channel of the amp. You could also bridge the amp L+ R-. Bridging the amp would increase distortion but give more power.

The last picture shows how much has now been crammed into this small and very shallow enclosure. I tried many ways to position it but this was the best way I found. I may yet put in some more PCB standoffs to further secure the board however at the moment is very sturdy.

Step 6: Finished - Apart From the Grille

So here is the finished boombox!

It uses all of its original controls however the radio tuner is now redundant but the slider still moves and all the mechanics are intact.

I'm very happy with finished result although I would say it was a right pain! The challenge of hiding the electronics was a good one but maybe a simpler project next time!

The sound is much better than I had hoped for and it's pretty loud and bassy!

Soon I will upload a video of it in action for you to listen for yourself. Please also take the video with a pinch of salt it was recorded on the inbuilt camera mic.

The last picture shows the grille so far. I'm just trying to find some sort of piping and fixing method for the grille. due to the massive increase in excursion old way for mounting the grille will no longer work.

I can't move the speaker back as I have no space, it will foul the frame. The only option is to move the grille forward.

Step 7: Making the Grille

I used a small section of rubber U-channel edging that would normally be used in cars for door seals and such. The piece was 10mm x 5mm and approx 1m long.

I cut the piece to length and then superglued the two ends on the underside. After I used a glue-gun to attach the grille as it provides a strong enough adhesion to stay attached but does not damage the surface. As mentioned previously I will not cut, chop or drill the external case in any way.

Step 8: Tools + Parts Required

If you have got this far thank you very much for reading my instructable!

If you have any projects you would like me to try let me know!

Here is a list of everything you need to make your own Bush DAC 90a Bluetooth radio; you can of course chop and change where necessary if you are using a different radio.


Soldering Iron - temperature controlled if you can, if not just be careful and quick!

Wire cutters - I used two different ones but you can use any really

Drill - always useful not desperately needed for this project but I did use it twice, although I'm sure you could get away without.

Hot glue gun - great for places where standard mounting is difficult - I used it on the grille and for securing some annoying jumper leads


1x broken Bush DAC 90a radio

1x 160mm coaxial car door speaker

1x TPA 3116 - or whatever you small amp you can get you hands on

6x jumper wires

1x bluetooth receiver - Like the ones without buttons!

1x car cigarette lighter to usb lead - look for usb adapters for motorbikes for ones with leads

1x stereo to mono minijack adapter - could also bridge the amp instead

1x 10mm x 5mm rubber u channel

1x ground loop isolator

1x 12v power supply - mines 6a

1x 2.5mm socket

2x component wire - I used about 1.5m meters of red and black for this project

x amount of cable ties

Epilog Contest 8

Participated in the
Epilog Contest 8

Amps and Speakers Contest 2016

Participated in the
Amps and Speakers Contest 2016