Feeling amazed with myself for pulling this retrofit off! I bought a Bluetooth receiver pcb, a sterio amp pcb, a little speaker and an isolator (waiting for delivery). Fitted it into an old Roberts Radio in the space where the big battery would go, and blow me it blimmin worked! Now this sweet little radio not only looks great, but it can also take on the new boys;
Brilliant tinkering! What were the components you used? Nice to see something be repurposed like that. I took an old Bose Wave and turned it into a home pod by using an Apple Express adapter. Does the job though.
Here are the links, but there are loads of versions. Ebay cheaper, but usually requires more patience! Bluetooth; https://www.amazon.co.uk/dp/B07KPTX...imm_K3VQP2S3A4SGWJK932ZH?_encoding=UTF8&psc=1 Amp; https://www.amazon.co.uk/dp/B07LG35...imm_ESA9M8V2PGCTCS5Y7TAJ?_encoding=UTF8&psc=1 Speaker; https://www.amazon.co.uk/dp/B07TP99...imm_J5FQ70C89FHF7B62Q8BJ?_encoding=UTF8&psc=1 I found it harder to find an isolator (probably because I don't know the right things to search). I am waiting for this one to come from EBay so putting up with a little bit of background noise (I think it is called ground loop) in the meantime. Isolator; https://www.ebay.co.uk/itm/B1212S-1...6?pageci=e0bf6958-9051-469c-a016-0f839838cd24
oh interesting, I wondered it there was an input audio Jack you had used, or maybe intercepted the original circuitry between radio receiver and amp to connect the BT received audio. Nice clean power will make all the difference. Often a Vo and Vi capacitor to ground can help smooth it and stabilise it. This may not be necessary with your component (I haven’t had time to check). This circuit (below) is for LD1117 (I use them a lot in Bike projects). The principle is the same.
That's great, thanks. I would love to have used the original amp, but working that out is beyond me, or at least it would take a long time. I am having to learn each step as I go.
It will be interesting to see if the isolator has enough power. I couldn’t find the tech specs on the amp and BT boards but would have guessed they’d draw more than the isolator provides. If I’m actually looking at the specs of the one you are getting. It isn’t clear how it amplifies (linear good and switch mode bad for audio). Poor input power (and other injected harmonics say from the radio board) may cause harmonic distortion which will get worse as the signal is amplified to the speaker. It does however depend on the frequency of the switching and THD as if outside the frequency range of the amp/speaker/ear then won’t be heard even if amplified. You can add high pass/low pass filters but then it starts getting complicated.
You know your onions! I will try the isolator and see but will order those parts on your message in the meantime. I was planning to power the BT on the output of the isolator so was thinking it wouldn't need much, but apparently it draws 250mA at 5V though so just over the 1 Watt limit, I probably should have ordered the 2 watt verion...
