Modding a Glitchee for more sensitivity on the sub and low

[felipesareas]

Hey guys;

I've been using the Glitchee for a while now and purely loving it. Today a friend came by and noticed something I hadn't noticed so far:

The Low and Sub (specially the second) tend disappear when the input signal is not strong enough. When playing more softly and using the octaves in more pronounced settings this becomes a true issue. Using a booster before Glitchee's Input improves this significantly. I don't understand well how the CD4024 works but I was wondering if there's a way to increase the signal being sent to the octave part of the circuit. Maybe lowering R5 would do the trick?

I mean, the pedal is absolutely fantastic, my favorite among all the 80+ pedals I've built so far in my lifetime. If I could calibrate the input sensitivity to the octave part of the circuit it'd be perfect for pick-less soft players like myself :))

[thomasha]

My guess is that R5 is part of some tone shaping filter.
Since the gain of the 386 is already maxed I would play with R9.
Both R9 and R10 are 220k, so that the gain of the following OpAmp is 1.
Try reducing R9 to 100k, and you have twice as much gain for the low/sub signal.

[Aleph Null]

There's some very heavy low pass filtering going on before the signal from the LM386 reaches the CD4024. Are you playing way up on the neck when the octaves drop out, or does it happen in lower registers too?

[felipesareas]

There's some very heavy low pass filtering going on before the signal from the LM386 reaches the CD4024. Are you playing way up on the neck when the octaves drop out, or does it happen in lower registers too?

In the high register of the guitar, the dropout is happening much quicker, but overall, the octaves are dropping out sooner than desired. My picking is quite gentle so, specially in the long notes, the dropout gets really noticeable and rough.

I'll take a look at the filtering section to see if maybe I can mod something there to let more of the higher notes be sent to the 4024

I thought of replacing R9 and R10 too... I'll let you guys know if I get good results.

Thanks a lot!!

[felipesareas]

It didn't work... soldered a 500k pot for R9 so I tried  all possible different resistances for it. The result is that only the final volume of the octaves changed; the dropout time kept being short.

I also tried the same strategy for R5 but nothing happened at all, which seemed very weird.

After giving up on messing with the circuitry, I put an overdrive pedal with maxed volume and gain before Glitchee and tested it. The results were very interesting: Glitchee behave in a 8-Bit glitching way with no dropout. Depending on the guitar pickup and tone it would rather keep glitching for sustained notes or just sustain it normally. Despite the huge gain being fed into Glitchee after the overdrive, it's output was pretty normal, so in the end, just the sustain of the "Sub" and "Low" was affected, which is pretty much what I wanted.

Does anyone know if it'd be possible to do all this inside Glitchee (so no external pedal would be needed)? If thomasha is right about 386 being maxed out, I'd guess it can't be done...

[thomasha]

Based on your description, my suggestion was in the wrong direction.
I thought the octave was too low in volume. What you actually want is more stability.

Maybe you can achieve that by adding a transistor or jfet gain stage at the input.

[felipesareas]

That's it I was thinking of right now... Not so sure where to add this since I'd like to make just the detection of the octaves be more responsive. When I add a booster pedal before the input it affects the filter part of the circuit and drive the drive too which is not ideal...

I still don't understand why reducing R5 didn't work. I mean, I guessed 4024pin 1 would be the input of IC2 but I got it wrong?

Where in the circuit would you put that JFET?

[thomasha]

You can try adding it before the two low pass filters that go to the 4024 (after C5).

I'm not sure what the function of R5 actually is. Input capacitance of the clock input is only 7.5 pF, so any low pass filter would be at a really high frequency. I don't think the signal is attenuated there, so reducing it will not help much.