I wanted to make the whole thing Eurorack friendly, so it would interact with the rest of the Eurorack system. It’s a nice addition to the voice mixer and certainly a useful mod. I added that signal to the mixing section with it’s own level control. Whether that was necessary or not, I have nu freaking clue. I simply took that signal, put it through an opamp configured as a voltage follower, so It wouldn’t interfere with whatever was going on in the sub octave modulator. The CD4013 used to divide the incoming frequency and thus achieve a sub octave. Pin 2 of the CD4013 (A17) output a square wave an octave below the guitar input. The Square Sub oscillator works on the same principle. I’ve added a level control as well so one could blend, say some noise, into the signal before it enters the filter. So you could easily add an external input to the mixer by making an input over a 10K resistor to the summing point on the mixer. It might not be that obvious from the schematics, but the voice mixer is set up as a simple mixer where A10 is the summing opamp. I also suspect different units to behave slightly different here so you might need to adjust to taste. You should try out a bit of other resistor values, 47K will allow for a bit more extreme sounds. I also added a switch to disable this mod. What I’ve did was simply connect the output of A12 (pin6) back to the input of A10 (pin 2) over a 56K resistor. It has the tendency to start going ape-shit and turn into an overdriven mess, so a bit of subtlety is at it’s place to find the right resistor. This one is again a fairly simple one to implement and extends the resonance control up to the point of oscillation. I’ve ordered a few CA3094’s to replace it, we’ll see whether that works or not. Luckily it can be replaced (at least in the filter) by an LM13700 and work fine. I managed to kill one two while working on the filter. I didn’t pursued this issue any further as I didn’t really found it that big of a problem, and I feared trying to solve this would really be quite an undertaking.īe careful with the EH1040 IC’s though. At short rates the filters drops lower then on long rates. That fixed the issue but now the ‘rate’ control also has an influence on the filter range. To counter that I used an opamp (non-inverting) to amplify the control voltage going to A10,A11,A12 over the 3.3k resistors and coming from A13. The filter consists of 3 identical stages, changing capacitors c25, c26, c27 from 33nF to 68nF shifted down the range, however, not only the bottom end, also the top end. IMHO it really needed to go down a lot deeper, especially if you want to use it with synths. Sending white noise through it I found out it’s range was about 700Hz-18KHz. I did like the quirky filter but it just hadn’t enough ‘Oomph’ to it. I found the filter a bit lacking in range when used for synths. This one is a bit more invasive to the machine, so it might not be for everyone. Just install a switch between this and the filter output and you’re good to go. As you can see in the pic, output 6 from A11 provides a band pass output. I don’t know whether it’s useful for a bass guitar, but it sure is for running synths through the thing. This is a really simple mod to perform and opens up a whole new range of sounds. The filter really can get some 303-like action going on, especially when you use the square wave generator. It should give an idea what the unit is capable of when applied to synths. I recorded some tweaking and went through more or less all the settings except the external inputs and triggers. It starts with a clean version of a saw wave riff generated with a Korg Gadget app. I’ll try to address the implementation of some mods in this article. You’ll can find the schematics of the EHX Bass Micro Synth easily enough on the web, but for the lazy, click here. Things could do with a bit of tweaking here or there, but that’s up to personal taste. But I’m pretty happy with the results so far. Replaced the internal power supply with an external adapter (I really didn’t trust that thing).Added trigger/filterCV leds (the thing could use more leds).So, here’s a brief list of things I ended up doing to it: So I decided to transplant the pedal’s guts into a 19″ rack casing from an old and broken M-Audio firewire audio interface and at the same time see how I could make it more synth/modular friendly. Sourcing 10 100K linear sliders with the right dimensions turned out to be rather difficult and costly. After bringing it back to life I noticed all the sliders were far from performing well and should be replaced. My ‘broken’ EHX Bass Micro Synth was gathering a ton of dust.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |