Synthbox

liquids · March 14, 2012, 01:10:07 PM

Minimal to no difference from the (well regarded) shin-ei?

~arph · March 14, 2012, 03:47:14 PM

Not sure, I saw that schematic today for the first time, looked like the same to me. I briefly glanced over the input filter and trigger section and noticed the same values.

liquids · March 27, 2012, 11:14:57 AM

Now that I have a scope AND know how to use it, I've seen the waveshape of the synthbox....explains it's unique sound. Hoping to o-scope and take a picture next time I am tinkering with it on the breadboard so people can see...but if anyone else happens to be able to do that easily and quickly, please do, It would be much appreciated.

~arph · March 27, 2012, 11:31:26 AM

Cool, I'm interested.

I suspect some PWM action.. as the transistors act like schmitt triggers.
Btw, have you tried modulating the original signal with the output of the synthbox?
should give you octave sounds while retaining attack/decay

liquids · March 27, 2012, 03:18:54 PM

Quote from: ~arph on March 27, 2012, 11:31:26 AM
Cool, I'm interested.

I suspect some PWM action.. as the transistors act like schmitt triggers.
Btw, have you tried modulating the original signal with the output of the synthbox?
should give you octave sounds while retaining attack/decay

I'm not certain I understand what you mean by 'modulating the original signal with the output of the synthbox?
In my mind, I'm thinking you mean that the synthbox has no dynamics (true), but you are looking to 'return' some of the dynamics of the plucked note to the synthbox's output.
This could be done by using the guitar to create an envelope, and using that envelope to create a VCA...so that the synthbox sound has the decay characteristics of an uncompressed plucked note...

~arph · March 28, 2012, 02:15:48 AM

I mean just like a tremolo, check the colrsound octivider

liquids · March 28, 2012, 11:20:33 AM

Hmmm......http://www.aronnelson.com/gallery/main.php/v/Martys-layouts-and-photos/colorsound_octivider_v11.gif.html?g2_imageViewsIndex=1
I see that it may sort of works like the boss octave / subtractive synthesis (there is an article out there somewhere far more articulate than I) in that by some means the sub-octave generated is fed through a diode/fet/etc with the 'straight' signal...?

I'm all but sure it could be done. Might be interesting to try.

Most of those pedals utilize filtering since the sub-octave generated is harmonic-laden (this being no exception) yet a cleaner/filtered octave is the goal...but thiat approach, with or without the filtering, it might add another element of interest, with or without the post-filtering used in those schematics.

But I think I might be misunderstanding you since I don't see any common ground shared with a tremolo....

~arph · March 28, 2012, 11:24:15 AM

Well I mean instead of mixing in the sub octave sound, you mute the original signal at the rate of the sub octave. (that's why I called it tremolo) This shoudl give you an octave down sound while keeping the original envelope.

dulcetpine · August 13, 2013, 09:22:10 AM

I built one of these the other day and while I love the sounds coming out of it I liken it more to a fuzz box with an option to toggle the octave up or down. It has a synthy-ness to it's sound but I am not getting the synthy sounds I heard from the clips... The gain knob also seems to do almost nothing (it doesn't seem to decrease the amount of gain in the pedal, which is considerable) and I can't tell what the attack knob does really. The knobs that work best for me are the volume, bass & treble knobs... I play through a Gretsch 5120 with HS filtertrons so you know.

For those who have made this pedal, do you have any thoughts as to why I am not getting the organ/sax like sounds? I can post sound clips if need be.

***Update. I figured it out, i missed the post on the previous page where someonehad the same issue with the attack/gain pot. I used lugs 1&3 originally on each and I switched it to lugs 1&2, i also opted to use matched BC550B's and wow, this thing is wicked!!!! Straight to the pedal board and permanently. This makes solos sound crazy and power chords demented... simply fantastic work guys*****

ch1naski · August 13, 2013, 08:50:37 PM

Thanks for the update.....matched 550b's , huh. What were the gain on those?

dulcetpine · August 14, 2013, 08:05:58 AM

bc550b hfe i used was around 525...

has anyone else noticed that this pedal is insanely loud? unity gain for me is 9:00 on the volume knob, but the effect doesn't really start opening up until around 12:00.... is there a good way to hush this puppy?

I used TL072's as my opamps...

ch1naski · August 14, 2013, 01:07:07 PM

I don't recall how loud mine is. I need to hook it up tonight and revisit it. I wasn't satisfied with the octave on mine as compared to the shocktave, so it's been set off to the sidelines.

deadastronaut · August 14, 2013, 01:22:28 PM

is there a revised/final schemo for this?..

i now have an empty breadboard..

~arph · August 14, 2013, 01:42:48 PM

I'm going to post my contest entry now.. so that might do.

deadastronaut · August 14, 2013, 01:45:35 PM

ahhh the cats out of the bag...

cool look forward to hearing/seeing it...nice one .

dulcetpine · August 14, 2013, 04:11:40 PM

I will say that the octave on mine tracks amazing and it chunky as hell. I had in the past used a Pog2 and a fuzz pedal for a heavy low end sound, but if i can get the unity gain fixed on the synthbox i think i may end up using that instead... it is wicked.

I built mine with a PCB layout instead of vero, it was much easier...

ch1naski · August 14, 2013, 05:43:54 PM

So...did you use the synth box v2 pcb layout?
That's what I built mine from, opamp version..

Keppy · August 14, 2013, 10:46:12 PM

Quote from: dulcetpine on August 14, 2013, 08:05:58 AM
has anyone else noticed that this pedal is insanely loud? unity gain for me is 9:00 on the volume knob, but the effect doesn't really start opening up until around 12:00.... is there a good way to hush this puppy?

This thing uses a flip-flip that swings almost from rail to rail as the output wave. So yeah, crazy loud. Put a large resistor inline just ahead of the volume pot to knock it down. Also, make sure you're using an audio taper volume pot, not linear.

dulcetpine · August 15, 2013, 08:16:33 AM

Quote from: ch1naski on August 14, 2013, 05:43:54 PM
So...did you use the synth box v2 pcb layout?
That's what I built mine from, opamp version..

Yeah, the v2 pcb layout.

Quote from: Keppy on August 14, 2013, 10:46:12 PM
Quote from: dulcetpine on August 14, 2013, 08:05:58 AM
has anyone else noticed that this pedal is insanely loud? unity gain for me is 9:00 on the volume knob, but the effect doesn't really start opening up until around 12:00.... is there a good way to hush this puppy?

This thing uses a flip-flip that swings almost from rail to rail as the output wave. So yeah, crazy loud. Put a large resistor inline just ahead of the volume pot to knock it down. Also, make sure you're using an audio taper volume pot, not linear.

I put a 4.7m resister on lug 3 and it got it down to a respectable volume but robbed all the high frequencies...

Keppy · August 15, 2013, 09:57:08 PM

Try scaling down to a 470k resistor and a 50k pot. That will get you the same size signal while preserving the original pot's resistance (pretty much).

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