Thursday, August 15, 2019

Super Sounding, Super Low Parts Count DIY Balanced Modulator: Burr Brown 4214RM

Does the world have enough Balanced Modulators? Maybe and yet, I'm still building them.

This time it's a super low parts count--wait! check that, ridiculously low parts count B-Mer--courtesy maven mvcl.

Turns out mvcl is a neighbor, living only a few blocks away from me in sunny California, US of A; we began trading emails and meeting up at our local Modular Synth electronics meet up.  And! MVCL has access to some great chip pulls from the old days, some coming from video boards he built in the late 1970's.

One chip of interest to DIY audio is the Burr Brown analog multiplier, the BB4214:

mvcl asked me if I was interested in messing with this chip and after looking at the datasheet--the chip has tremendously good specs--I said sure!! and so he dropped one off at my house.

Before too long I had its "connection diagram" on a breadboard, super simple--literally NO external parts! Wait, no additional parts?  YES! NO ADDITIONAL PARTS!  Just +/- 15V DC power (note to Eurorack/Doepfer-smokers--this should work fine with +/- 12V as well!), 2 audio waveform sources, some jumpers, a scope and audio amp/speakers to test:

I grounded X2 and Y2--but if you want to use balanced audio coming in, it's good to go!  Pin 11 can be open or grounded, and from my experiments the 100K resistor is not necessary.

It sounded--GREAT! Clear, crisp, clean, with little to no feed through, no hiss, no cross-tweeze, just as the specs would indicate.

So it's on to the next step--perf board!! Readers of this blog know I hate (and am very crappy at) perf-boarding and strip-boarding, but this one is so simple even I can't screw it up. I added a simple 4x unity gain buffer board--get info on the buffer board I used on my website, here: 2 buffers for the inputs, 2 buffers for the outputs. Again super easy.

The board on the left is the 4x unity gain buffer PCB I created a few years ago. 

It was a piece of cake to wire this mishpucha to a Frac 1U Panel, add a few jacks and so on, the whole thing took maybe a couple of hours, including breadboard and test time. Yeh!!!

I built this thing as fast as I could and it still worked first time!

Ready to test. Works!  FPE front panel has been ordered...UPDATE 9-17-19 ha! Back and in!

Here's a MOV-ie of the board being tested. This is 2x VCO's (ramp), VCO1 modulated by an LFO and then fed into the X input, VCO2 fed right into the BM's Y input; BM output to my near field monitors. That's it.

In case you want to hear more: bonus sound clip is here.

OK could anything be easier? This chip can still be found on Ebay ($10-$25 each, worth it!), I am not sure if different flavors of the chip sound different, but if you want to mess with a super easy to build balanced modulator, I mean it can't possibly get any easier than this, the BB4214 is highly recommended.  

Many thanks to mvcl for turning me onto this great old chip and all his encouragement and enthusiasm.  Until next time, happy BMing!

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