One-knob Magnavibe

[mcallisterra]

I had a 125B drilled for one knob sitting around, so a while back I started a thread asking everyone's favorite one-knob pedals, or pedals that could be good as one-knob versions with some trimmers inside. I like simplicity

I got loads of great suggestions, but the one I went with in the end was Hogharry's suggestion of a Magnavibe with a trimmer for the depth (this is the other one - Thanks TreeSlayer ), and the single outside knob being speed. I built it from the Tagboard Effects layout, and it fired up first time! Some pics:



I always like to try to do things I haven't before, so a couple of firsts for this one:
- First vero build!
- First time using a trimmer for a normally external control
- First time alcohol inks went on and stayed on successfully 

The last time I tried the alcohol inks, I used purple, and the mod podge turned it into a nasty burgundy color. I did it again and just used polycrylic, and it just didn't last. This time, since the colors were greens and blues, the mod podge didn't affect the colors negatively. I then finished it with rattle can polyurethane which can also amber colors, but again it's not noticeable.

I need to find a better LDR because the one in there currently doesn't have a high enough dark resistance, so the effect is still quite subtle even with the depth maxed. I socketed the LED and LDR though and it's easy to get to so I'll try some others at a later date.

One last thing - is it ok to ground the pot like that? I didn't want to run another wire round if I could avoid it, so I just soldered a jumper to the pot case. It seems to work fine, but I just wondered if there was a reason you shouldn't do that?

[Luke51411]

Cool build! I've been thinking about building this one as well. Shouldn't be a problem with grounding the pot that way as long as the pot and jacks stay tight, especially for your own pedal. I probably wouldn't do that for a build that's going to someone else but that may be more out of paranoia than anything else. How do you like vero? Tagboard is a cool site and I've built dozens of their layouts.

[LJangel]

cool, I like the ink job.  never tried those

[mcallisterra]

Cool build! I've been thinking about building this one as well. Shouldn't be a problem with grounding the pot that way as long as the pot and jacks stay tight, especially for your own pedal. I probably wouldn't do that for a build that's going to someone else but that may be more out of paranoia than anything else. How do you like vero? Tagboard is a cool site and I've built dozens of their layouts.

Thanks! Yea I doubt this one will even get gigged. The singer in my band always complains about any pitch shifting effects

I do prefer PCBs!

I guess vero is ok but I was getting frustrated at one point. Maybe my iron tip is too thick, because I was getting lots of solder bridges. At one point I was thinking it would be a miracle if it worked

[Luke51411]

Vero is nice because there are so many verified layouts. I preferred it to pcbs for a while because of the extra flexibility for modding but I haven't had as much luck with them lately.

[mcallisterra]

Yea. I'm already thinking of other ones I can do with the remaining vero I have haha.

[Guitarmageddon]

Nice build!
I have a one knob magnavibe too, love it, great circuit.

[Cortexturizer]

Looking great, good work!

I really like this circuit from the demos I've heard, sounds awesome. Unfortunatelly I am unable to get any depth from mine. It's barely perceptible when the effect is on. I have tried everything from half a dollar LDRs to vtl5c2 and in between. I expected a lot from a certain Silonex model that raulduke recommended that has a 20M dark res but whatever I tried didn't sound amywhere near the demos. It is so frustrating and slowly heading to my box of fail I'm afraid...

[mcallisterra]

Hmm maybe it's not as simple as just sticking in a new LDR then. Mine is definitely noticeable when it's on, and I was only looking for a subtle warble anyway, but it would be nice to get a bit more out of it.

I measured the LDR in there and it only gets to about 1.2M fully dark. The doc called for 20M so I have to think it would get a bit more pronounced with a different one or a vactrol.

[jubal81]

I found the cheap Tayda LDR actually works really well in it.

[nzCdog]

that enclosure is amazing.  Just awesome dude, love it

[Hogharry]

Looks great!

Hmm maybe it's not as simple as just sticking in a new LDR then. Mine is definitely noticeable when it's on, and I was only looking for a subtle warble anyway, but it would be nice to get a bit more out of it.

I measured the LDR in there and it only gets to about 1.2M fully dark. The doc called for 20M so I have to think it would get a bit more pronounced with a different one or a vactrol.

I used the Tagboard layout and mine sounds pretty good to me. I certainly didn't use anything special, just a cheap eBay LDR and (I think) a standard 5mm red LED with the top bent towards the LDR. I will try to measure the LDR when I get a chance and report back.

[mcallisterra]

Looks great!

Hmm maybe it's not as simple as just sticking in a new LDR then. Mine is definitely noticeable when it's on, and I was only looking for a subtle warble anyway, but it would be nice to get a bit more out of it.

I measured the LDR in there and it only gets to about 1.2M fully dark. The doc called for 20M so I have to think it would get a bit more pronounced with a different one or a vactrol.

I used the Tagboard layout and mine sounds pretty good to me. I certainly didn't use anything special, just a cheap eBay LDR and (I think) a standard 5mm red LED with the top bent towards the LDR. I will try to measure the LDR when I get a chance and report back.

Thanks!

Yea I have them pointed at each other as well but I used a yellow diffused 5mm LED. It was just a RadioShack LDR but I picked the one with the highest dark resistance of the lot.