22 November 2009

The Hip Bass Drum (Part 1)

Today I build a very nice project called 'The Hip Bass Drum'. I it found in an old article from the Polyphony Magazine published in 1983. I had all components except for the 4739 opamp. I replaced that one by two LM741's. I decided to build this one right away on an experiment PCB. As you can see in the pictures it is full with holes and islands. You can solder them together to create the necessary wiring between the components. It is just a matter of looking at the schematic and making all the connections manually. The advantage over the bread board I use earlier is that you don't have to take it apart afterward and build it anyway on a board like this. It is only less easy to correct mistakes. But since this is a very small module I took the risk :)

Here you see a picture of the PCB from the top with most components installed. Since this module has a lot of external potmeters I decided to wire it right away with wires long enough to reach a front panel that I will eventually make for this module. I only mounted the Led on the PCB, but that one will go on the front as well. It lights up when to modules receives a trigger. After this I hooked up the power from my lab power supply to do the famous smoke test and it all looked OK. After that I got some potmeters from the stack I received from Mouser last week.

After hooking the potmeters up I attached a mini jack to get some audio from it. The first thing I noticed it that the trigger wasn't really working. Well I forgot to attach a resistor to ground. That was an easy fix. Then it sounded like only one of the two audio generating circuits was working. It sounded like the impact module worked, since I recognized that sound from the Snare Drum Module I'm building, but I couldn't hear the oscillator that should create the kick sound. After some debugging I found a resistor that I forgot to hook up on one end. And yes then It sounded like a kick :) I fiddled a bit with the potmeters and it sound very nice. A very usable module. I'll start making a front panel for it and I will also add a manual gate option and maybe a output level potmeter. If you are interested in the article, just send me an E-mail.

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