Have you seen that guy? another little diy synth (Rockit)

still kickstarter…


From the demo it sounds good. From the schematics there’s some really, really wacky stuff going on! OTAs for volume and VCA gain (applied before the filter?) on what appear to be PWM outputs and… digital pots in the filter core! I assume the exponential response is done through one of those “put a resistor between the wiper and one end of the pot to get audio taper”. The world’s turned upside down!

From the blog posts, the guy is understanding what he is doing, which is becoming a rare thing these days…

Doesn’t look like he’s going to get anywhere near his $10,000 though…


yeah that’s a lot of dough.
would be cool though.

Is the hissing sound in the sound clips and video encoder related? Seems to be there whenever some deep bass is going on, really anoying… and makes it pretty useless in my book.

hmmm, just listened to the clips again, but i couldn’t hear any hissing. with both headphones and speakers, really loud.
what i do hear is some clicks here and there.
at what time does the hissing sound appear?

Probably always, and above your hearing range :slight_smile:

yeah thanks to heavy metal
so i could still have fun with it while annoying the audience hehehe

Oki, either it’s my computer or my hearing is too good, and that’s a new one… Still as I read it a kit with PCB and programmed MCU is going for 25. 10000/25=400 sold kits before he will commit… is that not a little much?

Or 80 full kits.

that’s just the pcb and mcu, no kit for $25. the full diy kit with all parts is $125.

still seems much, when i think of the lot of people who are required to take one, but on the other hand in terms of money i think the prices (are ok, no?) depend on quantity and would rather be higher with less boards. imagine a board at that size plus mcu (programmed probably) for just 25 bux.
and then the development cost that he must have had…

@Lindeborg any chance you could check that again with different gear? it would be a bummer to annoy listeners and oneself not even noticing. it’s more than likely my hearing is not the best after all that crap at full volume as a little kid, but at least it was vinyl back then and no mp3 :wink:

I loaded one of the .aif files on SoundCloud and there’s some whine around 7.4kHz, ~12dB above the noise floor. At best, it could be aliasing from a very bad soundcard, or power supply hiss. Sprinkling 20pF caps here and there on op-amp feedback loops might solve it if it’s a PWM harmonic getting aliased. At worst, a bad board layout choice…

Oki, I missed the full kits… will check the audio on another computer tomorrow… To me it sounds like some sort of aliasing as it is only evident in the more bassey sound clips and in the video…

Strange, seems like it was something in the MME drivers of my EliteBook, With DirectSound on the same computer it sounds fine if just a little noisy. On my Atom driven HP Mini as well. Never noticed that before, sorry!

cool, thanks! that’s good news.
boards and hearing wise (still reason for doubt on that one)
and if the rest hissing pichenettes spotted can possibly get rid of by some caps that’s ok. i couldn’t hear it anyway

I asked Matt Heins, that’s the guy behind the RockIt, what the dimensions are and what shipping for Europe would cost. The PCB is 8,6" (~22cm) x 5,125" (~13cm) and internatinonal shipping is $10.

looks good to me!

Really good…

up that, backed it sealion.

and he doesn’t know how to calculate shipping so when he does cut him some slack