Electro Harmonix Bad Stone clone built

[Marcos - Munky]

Built it from Topopiccione's layout and schematic, and I didn't had to debug it since it worked at the first attempt (I love when this happens ). Tested it this morning, and got sweet and warm phase sounds, very similar to the soundclips at Topopiccione, cool for clean stuff. Also, at high Rate settings, it become a kind of pseudo ring modulator. Didn't tried it with distortion, because it's unboxed yet, and I don't like to put an unboxed effect on the ground, and my amp doesn't have an effects loop, so I can't use distortion from it. But it worked great with the PT-80 between the BS and the amp. The only thing I did was remove the Manual/Automatic switch and hard wire it to Automatic setting. I will try to do some enclosure etching work after the weekend (when my vacation will start), and if everything goes alright I will try to post a picture of it.

Also, anybody knows how to add a LED to the LFO to see how's the Rate? It would be a nice thing to add to the enclosure.

[sta63bmx]

Is the LM324 the LFO?  I would set it to maybe 1 Hz or so, a pretty slow rate, and then set your DMM on DC volts and probe the LM324 pins to see if you can pick up a signal somewhere.  I'm ASS-suming that the 324 is giving a square wave LFO, but I don't know.  If it is, you may be able to find a pin on it where the output flips back and forth between high and low.  And then you could tee off that line to drive the base of a transistor and use that transistor to turn an LED on and off.  I did that with my Electric Mistress build

I used a 360k base resistor, a 360k pulldown on the base (may have to fiddle with this value), and then a 4.7k current limiting resistor, a bright blue LED, and a 2N5088 NPN transistor as my "switch".  It was set up in low side switching, with 9V connected to the high side of the resistor, then the resistor connected to the anoed of the LED, the cathode of the LED connected to the collector of the 2N5088, and the emitter of the 2N5088 connected to ground.  The 360k base resistor was in series with the signal coming from the LM324 to make sure it was real high impedance and the base didn't drag that pin down.  I had to fiddle with the pulldown resistor on the base to get it fully OFF when the LFO is low.

With a scope you could pick it up pretty easy, but if the rate is low AND there is an "on-off" signal somewhere, you could probably see it with a DMM, too.  Good luck.  Try pin 7 where it comes out to the rate pot wiper.

[Marcos - Munky]

Thanks for the suggestion. I don't have a scope, hope it won't be too hard to use a DMM. Here's a picture of the LFO wave:

[sta63bmx]

I bet you could use that.  If you can find what pin it's on, I'd just run that signal to the transistor deal like so...



Feel free to laugh at the schematic all you want. lol  The bigger the pulldown, the brighter the "off" light was.  Dunno if it's current leakage or what.  But too small of a pulldown and the thing stayed OFF all the time.  Without that 360k base resistor it just pulled the LFO signal down and I got no flashing light.  I wasn't listening to the circuit, but I bet it would have killed the LFO, too.  I think that base was just sinking all the current to ground.  Anyways, that's how I rigged it.  I just put the parts on perf.  I also put the current limiting resistor for the "regular" LED on there and just ran wires to my LEDs.  A 3904 ought to work, too, I just used what was at hand.

Let us know how it works!  Don't be a dummy like me and forget the base resistor.   If you get no reading with the meter on DC volts, and it acts like the voltage is flipping around too fast, just back off the rate pot as much as you can.  Hopefully you'll be able to find a pin that's going back and forth.  I dunno if the DMM will give you a reading, but if you see a likely pin, just drive that transistor base with it.