This one started out as a stupid idea when coming across a cheap bluetooth module on ali-express. Why not build it in an Eurorack module? Could be fun, maybe even useful for that odd field recording or weird voice message.

So I went out and got this. A Bluetooth receiver under 2$. All I had to do was to add some supporting circuitry to make it compatible with the Eurorack ways of doing things. Now I can connect my phone or computer wireless to my modular 😀

So I can:

Use field recordings, or whatever audio is on my phone without the need to drag files around.

Youtube is full of incredibly dull relaxation yoga pants soundscapes that beg to be filtered and abused in every possible way.

Use the modular as a very impressive bluetooth speaker. If that doesn’t impress, I don’t know what does anymore.

I can confuse the hell out of my audiophile friends by using incredibly expensive gear for mediocre results.

I can finally fulfil that lifelong dream of becoming a telephone switchboard operator.

Fake that live modular performance as never before.

I can keep twiddling knobs while on the phone, and at the same time make dull conversations a lot more interesting.

In short.. have lots of fun.

Now, don’t expect low-latency performance here. Bluetooth connections have a high latency, and this is cheap chinese electronics after all. Syncing up beatboxes and virtual synths from your phone to your modular is not going to yield great results I’m afraid.

Schematics

Fit a bluetooth module in your modular.

As you can see, there is not much going on. A simple 5V voltage regulator (78L05) makes sure the Bluetooth module gets its power how it likes it and even the moderate TO-92 package can provide enough current to get it running. No need for big voltage regulators and cooling. A single op-amp is used to mix the left and right channel together and amplify the signal to modular signal levels. The module outputs line-levels signals, so it needs quite a push up to get up to modular levels. You could make a stereo version easily by duplicating the amplification stage for each signal instead of mixing them together. If you find it needs more amplification, just increase the value of R1 to something higher.

It can easily be fitted in a very small module so it won’t take up much room in the modular.

Links