This is a question about hooking two different radios to the same speaker set. I have an original Sapphire XI radio that is convenient for getting the news. I also bought a really inexpensive bluetooth receiver that pounds out 50 watts (in theory) so I can play the iPad. Replaced the original speakers with more modern - mice had chewed what they could reach of the old uns.

So, can I hook the radio AND the bluetooth to the same pair of speakers without damaging the electronics when one is playing and the other turned off? I don't care about cooking the bluetooth unit that much other than the inconvenience, but the original radios can be hard to find.

Thanks. Not snowing and it is October, so I have that going for me which is nice.

My suggestion would be a simple relay setup with a pair of DPDT relays you can use to toggle back and forth. Set the NC position to the Sapphire and have the relays set to energize when you turn on the BT module. You can use a couple inexpensive relays, probably buy on line or at Frys. There is probably an off the shelf choice too, if you want to go that way. You MIGHT be okay just leaving both connected but I would be worried about 1) the change in output impedance seen by the amplifier(s) and 2) back biasing the output sections with power from the opposing unit, power on or off.

Morrie
(AE, not EE, sorry)

Thanks. I was thinking that a double pole double throw switch would work as well. But your solution is slicker and less prone to my mistakes.

Yeah, you probably don't want to back drive an amplifier except at very low levels. The output stage of the off amplifier will likely provide a very poor load (low, non-linear impedance). Bear in mind the switch or relay needs to be able to handle some current. Driving 50W into 8 ohms requires over 2A.

I have a stock stereo that I want to put back in the dash but wanted Bluetooth and better sound. I found a unit that is an amp and a Bluetooth tgat is designed to be set up inline from the radio, so it has an input from the wires that would have gone from the radio to tge speakers. When the Bluetooth receives a signal, it takes over and cuts off the radio. I ended up just putting in a radio delete plate and just using the phone for my tunes. It sounds great and has a pretty good range on it. I can get about 40 ft from the car before it starts cutting out. On my truck I pretty much have to be within touching distance.

We will be selling these units in the near future if your interested.

This is a good solution: http://www.tech-retro.com/Aurora_Design/Automotive_Home.html

I've installed a good handful of these, it keeps the radio looking stock and does everything you want. It's a well designed module from a very talented EE.

Due to time and complexity, I don't install them anymore. However, there are dealers that do.

Can these ‘guts’ be installed in Vintage Blaupunkts? Seems like it would be the best of all worlds.

Does anyone on the Forum have one to give a review?

It can be installed into most all radios. All original knobs and buttons are still functional and can be used as intended. I did a conversion for a old corvette radio that had the wonderbar button, even that worked after the conversion. It's really a cool solution for those that want the look and functionality of a old stock radio.

The cons, these modules are expensive. Also, the time needed to convert one takes over 20 hours, atleast it did for me. I didn't like the heat sink that came with the main module, so I had a custom heatsink machined to fit the radio chassis. This conversion puts out a bit of power, so it is a good idea to improve the heatsink to help keep everything cool.

Sounds like adding another Bluetooth enabled module hidden under the dash may be much easier! I did make an adapter to be able to run my iPod or iPhone through the amplifier section of my Blaupunkt Frankfurt that works well enough that I can hear it when the top is in place. Running with the top stowed makes it a lesson in futility over the engine and road noise.

just use a four pole two position switch known as 4PDT as mentioned above.

Wow, that is awesome! Thanks for posting it! I may have to go out and find a stock radio now.