BAJA Small Clone
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Just finished my build utilizing this board. It sounds great! I combined it with a 1776 Effects Rub-A-Dub Reverb and Opto-tron. Sorry for the crappy iPhone photos!
Loe Sounds
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bajaman
- Old Solderhand
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On original Small Clones, the 47n cap goes from pin 2 (the wiper) of the rate pot to ground. The 47n cap on pin3 of the LM358 in the "EHX" schematic is an error.plesur wrote:I've been doing a bit of work on the Small Clone and compared the Tonepad schematic to an EHX schematic I found here: http://sites.google.com/site/electrocon ... ctoryE.pdf
There's a couple of differences:
The 10n cap that joins to pin 2 of the 4558 through the the 6k8 resistor has other end to ground in EHX schematic and 4.5V in the Tonepad
The 47n cap goes to ground from pin 3 of the LM358 in the EHX but from the rate pot in the Tonepad
Can anyone with a original unit help me confirm which is right?
Thanks!
Oy, what a pain. I recently have been trying to build a BAJA Small Clone, and finally got it working. This was not without several issues that I think others have had to deal with.
1) I built mine on PCB revision 160815. This board has two errors on it. First, the diode going to pin 2 on the 4047 is backwards on the silkscreen. You will have to ignore the silkscreen and install it the other direction. Second, there is a missing trace from pin 3 of the 4047 to the capacitor that spans pins 1 to 3. Pin 3 needs to be connected to the capacitor.
2) I've never heard this mentioned on any other site, but apparently this circuit is very picky about the forward voltage of the diode going to the 4047. I was using a 2N4148 with a forward voltage of .664, and the circuit did not work. When I swapped it for a 2N914 with a forward voltage of .542, the circuit worked. People always say the 4148 and 914 diodes are interchangeable...WRONG.
----Mods-----
There have been several mods made to this circuit that are unnecessary, or that change the tone needlessly.
-First, the 220uf and 10uf capacitors coming off the 9v supply line are a mod that was added in at some point, and does nothing. Original small clones did not have these capacitors, and I noticed zero difference between having them in or out, regardless if I'm using a battery or wall wart. Leave them out.
-Second, the 150p capacitor on pins 1 and 3 of the 4047 is a mod value, not the original. This slows the clock down and isn't true to the original sound. 100p is the original value.
-Third, there is a 20k resistor on most schematics that connects between the 1uf cap and 22k resistor where the FET switching was in the originals. The original value of this resistor is 27k, and it affects the wet/dry mix of the two signals. Obviously, adjusting this value changes the sound of the pedal. Use the original value of 27k, not 20k.
-"the depth pot" mod
. I don't understand why this mod has been perpetuated as a "must have" for any Small Clone diy build. It greatly changes the functionality and tone of the pedal...for the worse. The two depth settings chosen by EHX decades ago for this circuit are the definitive best settings. If there was a magical setting that could be achieved through a potentiometer, EHX would have used a pot, since pots are cheaper than switches. Putting a potentiometer in there actually messes up the circuit because it always connects the LFO to ground, which eliminates the correct subtle chorus setting, and makes it impossible to dial in the original settings at all (the 4.7k resistance value should always be in the LFO signal path, which does not happen with a pot in there, it can go down to a couple ohms). When you add to that the 150p cap that slows down the clock, and the increased wet mix from the 20k resistor above; it's no wonder clones don't sound like the originals.
1) I built mine on PCB revision 160815. This board has two errors on it. First, the diode going to pin 2 on the 4047 is backwards on the silkscreen. You will have to ignore the silkscreen and install it the other direction. Second, there is a missing trace from pin 3 of the 4047 to the capacitor that spans pins 1 to 3. Pin 3 needs to be connected to the capacitor.
2) I've never heard this mentioned on any other site, but apparently this circuit is very picky about the forward voltage of the diode going to the 4047. I was using a 2N4148 with a forward voltage of .664, and the circuit did not work. When I swapped it for a 2N914 with a forward voltage of .542, the circuit worked. People always say the 4148 and 914 diodes are interchangeable...WRONG.
----Mods-----
There have been several mods made to this circuit that are unnecessary, or that change the tone needlessly.
-First, the 220uf and 10uf capacitors coming off the 9v supply line are a mod that was added in at some point, and does nothing. Original small clones did not have these capacitors, and I noticed zero difference between having them in or out, regardless if I'm using a battery or wall wart. Leave them out.
-Second, the 150p capacitor on pins 1 and 3 of the 4047 is a mod value, not the original. This slows the clock down and isn't true to the original sound. 100p is the original value.
-Third, there is a 20k resistor on most schematics that connects between the 1uf cap and 22k resistor where the FET switching was in the originals. The original value of this resistor is 27k, and it affects the wet/dry mix of the two signals. Obviously, adjusting this value changes the sound of the pedal. Use the original value of 27k, not 20k.
-"the depth pot" mod
. I don't understand why this mod has been perpetuated as a "must have" for any Small Clone diy build. It greatly changes the functionality and tone of the pedal...for the worse. The two depth settings chosen by EHX decades ago for this circuit are the definitive best settings. If there was a magical setting that could be achieved through a potentiometer, EHX would have used a pot, since pots are cheaper than switches. Putting a potentiometer in there actually messes up the circuit because it always connects the LFO to ground, which eliminates the correct subtle chorus setting, and makes it impossible to dial in the original settings at all (the 4.7k resistance value should always be in the LFO signal path, which does not happen with a pot in there, it can go down to a couple ohms). When you add to that the 150p cap that slows down the clock, and the increased wet mix from the 20k resistor above; it's no wonder clones don't sound like the originals.