The LFO section is *very* sensitive to both voltage and current, so if your board doesn't fire up right away (which happened with my second build too), you should consider doing a little daughterboard with 9V regulator, 8V2 zener and a 10-50 trimmer to get the LFO going. That being said - this is not a project for beginners.
---
Mr. Hollis has been known for his modulation circuits. This one seemed like an interesting build so i drew it up. Once again. I'm more or less out of sources for the demos and so on. But i have a hunch that this may be 1:1 with two knob version of Copilot FX Android... Anyway. The circuit does tremolo from mild to wild and flick of a switch turns it into super mean ring modulator - with lots of good stuff on the sweep. Or so i'm told.
looks really interesting! i guess it's not yet verified? i'll build it after work and we'll se if anyone has verified it before then. built the harthrob yesterday to replace the circuit of a artec tremolo for my bandmate. let's se if this is more interesting! :D
ReplyDeleteInfo on the trimmer here:
ReplyDeletehttp://www.geofex.com/PCB_layouts/Layouts/frobn.pdf
I was planning to take a much needed break from pedal building and I dont usually try unverified projects, but I dont have a ring mod and Ive got all the parts in my spares so I'll give this one a go and feed back.
ReplyDeletejust finished the recent trem/ring you made but i can't confirm it. it sounds like a fuzz box and that is when depth is all the way up, otherwise it wont give me any signal, freq does nothing nor the switch. checked for bridges and found nothing and also checked placing of the components and found nothing wrong. any idea what could be the issue?
ReplyDelete2 of the 3 leds lights up constantly as well. https://dl.dropbox.com/u/2828668/Photo%202012-12-10%2023%2045%2037.jpg
What transistor did you use?
DeleteMPSA18 as suggested CA3080 for IC1 and TL072 for IC2 :)
DeleteThere could be something wrong with the layout too (i'll go through it tonight after work), but according to geofex documentation, the trimmer should be used to tune the modulation nearly inaudible.
DeleteI'll get back to you...
+m
There's a bad cut on the 6th row right next to bottom of 470K. That 470K should form a loop between IC1 pins two and six. I must have juggled some parts around when compacting the layout - that cut is not needed and it's just plain wrong.
DeleteI'm at the office, so i can't fix the layout for another 7 hours :(
I'll keep checking if there's anything else in there, but soldering a link over that cut *should* do it...
+m
i was so eager to try this out so i went home for lunch.
Deleteunfortunately it makes no diffrence for me really other then that it's no longer a fuzz box, it still behave the same way but without the really high fuzziness. checked the board again for bridges and can't find any. im sorry man :/
...aand there's a small copy/paste error with the output cap. It should be 1µ and not 47µ (from Q1 emitter to output row). That should explain why the modulation dies.
DeleteBut. I'll keep it on hold until i get home, commit the two fixes and build it myself.
I'll eye it through one more time, but i can't see anything else wrong in there at the moment.
+m
I used a 2n5089 and had the same results as rudeez.
ReplyDeleteIll try the link when i get back from work.
Try to swap the output cap too. I'll fix the layout once i get home.
Delete+m
Made the changed as listed above and now it trems and mods fine. Thanks mate.
DeleteI note that with the freq pot maxed out theres a high pitched whine, which I can mostly get rid off as theres a tight sweet spot which quietens things. Im going to swap out the trimmer with a multiturn trimmer and see if I can make it quieter.
I would suggest bigger value rather than just multiturn. Mine seems to whine all the time regardless of the trimmer. Should probably up it to 250K... But so many things to do.
Delete+m
It says on the R.G. Keens document that:
Delete"Adjust trimpot for lowest modulation feedthrough with zero signal. You should be able to get the modulation to be almost inaudible."
I guess i'll try that.
+m
bah, did all the fixes but now im not even getting a signal through it, all i can hear is the whine from it. used a 200k trimpot. checked again for bridges and found nothing.... i have a feeling that i mights just build another board since the enclosure for it is already made.. :D
ReplyDeleteRudeez, i had the same problem after i applied the fixes but then i found that i had soldered the 1u cap 1 row below where it should go so might be worth checking that
ReplyDeletechecked an no, right place. guess i'll go over the board and see if anything else is misplaced. hows the thing sounding and working for you?
DeleteHope you get it running. It's really nice circuit...
Delete+m
i'll just rebuild the circuit later on, need to build a skreddy lunar tonight as well as re-tube and bias my amp for a gig on saturday... im just praying that i wont end up dead doing it, never done it but read and watched several how to's haha.
Deletethanks for everything miro, i had a bad feeling because of that "thanks man" comment on FB.. it was meant in a good way but sounded sarcastic haha. came out wrong :D
It works ok. In trem mode theres some hiss when connected up to my test rig. Im wondering if that will improve once boxed. In mod mode im still trying to improve on the whine. Gonna use a larger trimmer next
ReplyDeleteVoltages from my working build:
ReplyDeleteAll pots at minimum, "p" after reading means pulsing.
Bat:7.7
IC1
0, 0, 3.4, 0
0.67, 3.2p, 7.6, 0
IC2
2-4p, 3, 3.4, 0
2-4p, 3.4, 1-5p, 7.6
Q1
e2.7, b3.2, c7.6
+m
Boxing day's boxings part 3:
ReplyDeletehttp://mirosol.kapsi.fi/varasto/boxes/fornicator.JPG
Yup. I'm calling it "The Fornicator". JH Frobnicator to MP/BJF Deep Blue Delay. This is for personal use. Mean little **ker.
+m
Where does the middle pin of the spdt switch go to? Ground? or ???. Also, the resistor that's labled LED-- What is that? What is the orientation of the trimmer?
ReplyDeleteMiddle? Upper (1) and middle (2) pins of the SPDT are connected (3 stays unconnected)- or pins 1 and 2 of SPST (there is no 3 in SPST). That means that in one position the wires are connected to each other and in second position they are apart.
DeleteLED resistor is meant to be the resistor for your indicator LED and LED+ wire is to be connected to the anode of that LED. You'll need to match the LED resistor for your LED - Different colours need different values. 1K-2K2 for diffused red is a good rule of thumb.
Orientation? Pin 1 to 9V strip, 3 to ground and 2 between those two.
I have to say that this is not a recommended build for beginners. I've build two boards - one working as it should and another with no modulation. Boards are identical to every component, but i still can't figure out why the other doesn't work.
+m
Just a note for anyone who builds this.....it sat in my failure bin for a long time as all I could get was clean signal. I came across a thread that suggested that a lower supply voltage can get the oscillator to work. I put two 1n4148's in series with the power supply and now have a working tremolo/ring mod! Something to try if you get stuck like I did.
ReplyDeleteExcellent, thanks for the tip
DeleteI did notice some similar symptoms/cures. On of my builds worked perfectly with 8,7ish V battery, but not with wall wart measuring 9.1V. My plan was to try on a little daughter board with regulator on it, but haven't got around to it yet. One thing to try would be placing 8.2V zener anode to ground and cathode to the supply rail...
DeleteThanks for bringing this info up Furdy! This information should help Rudeez too!
+m
Nope. That zener just wasn't enough. The LFO is *very* sensitive to voltage, and current, so regulator like 7809, 20K trimmer and 8V2 zener. Sad thing really. The tremolo side sounds just awesome, but sensitivity and fact that it works correct with only tuned voltage and current make this design very unstable.
DeleteI wouldn't recommend this to anyone :) Sounds golden, but beware the notes.
I think i'll update the description...
+m