NostalgiTone Vibe Single Vibrato mod?

[Christiaan]

I recently built the NostalgiTone Vibe Single from a Musikding kit. My third attempt at building a vibe and finally one that not only works, sounds great! The one thing I’m missing from this one, however, is a “vibrato/chorus” switch. Does anyone know if such a modification is possible? I tried pulling signal from a few different points along the circuit without much luck. Would I have to lift R3?

If anyone has any insight, would be glad to know. Otherwise, I’m absolutely loving this build.

[Billy]

I don’t think it would be straightforward if you’re looking for the same as the original univibe circuit you’d need to add a few components

A vibrato switch would just cut the dry signal out I’d try a DPDT switch in place of R3 that’s the mix resistor for the dry signal I say DPDT but you could use a miniature DPST if you can find one like this

On-Off Mini Toggle Switch DPST — Switch Electronics | Your One Stop Component Shop https://share.google/4cprW0cAW3E3CAeov

 

 

 

 

[Christiaan]

Thanks for the quick answer. I’ll give that a shot and see what comes of it. Glad to know I was on the right track with R3.

[Billy]

I think it should work if you look at the forum vibe schematic here although it uses transistors and a lamp rather than op amps and an LED it’s basically the same with the chorus vibrato switch at the output the vibe should have the wet and dry signal balanced with the two 100K mix resistors R3 and 14 so you shouldn’t need the balance trimmer, voltage divider set up you see on the forum vibe

If vibrato mode is louder or quieter you could use a trimmer wired as a variable resistor in place of R14 to set it to the same level as chorus mode if it’s quieter use a 100K louder use a 250K so you can add or subtract resistance

I’m also not sure if you’ll get any switch pop with the 1u caps

https://musikding.de/docs/web/univibe-ForumVibe-final.pdf

 

[Christiaan]

Reporting back: I snipped R3 to test things out and the vibrato is sweet but fairly subtle. However, there’s a bit trade off in terms of the controls. If you turn the intensity anywhere below noon, the warble becomes almost imperceptible. The voice control doesn’t seem to have be as pronounced either, but maybe I’m imagining that.

It would be nice if the vibrato was just a little more pronounced but then I do prefer my vibrato a bit subtle and not so seasick.

Now the question is whether or not I should make this an internal or external switch. Decisions decisions. I might also test out your idea with a trim pot replacing the mix resistor while I’m in there. Could be interesting on both settings.

Funny you mention the Forum Vibe. That was my first attempt at building a uni-vibe. I thought I was extra careful when building it, but I just can’t seem to get the LFO to light the blub. It still haunts me.

Thanks again for pointing me in the right direction.

[Billy]

What transistors did you use for your forum vibe some layouts show the original Japanese transistor pinout where the collector is the centre pin it looks like the forum vibe pinout is EBC with the dot at E on the pcb image so if you’ve used Japanese 2SC types then it could be that

If I’ve had trouble with univibe builds it’s usually that where I’ve swapped transistor types to more modern easier to find replacements then forgotten about the different pinout

For the vibe I’d try a 100K trimmer in place of R14 and lower the resistance across it to see if that increases the vibrato effect

[Christiaan]

I had to dig out my little Box-of-Shame to find out but the Forum Vibe transistors are all EBCs. All 2n5088s with the exception of one 2n5210 for some reason. Again that was a Musikding kit, which is my go-to solution when I don’t want to do my own parts shopping.

If I flash a light at the LDRs I can get the classic swirling sound, I just can’t get the bulb to fire unless I send it power directly.

All good though, my freshly modded Vibe Single is scratching that itch quite nicely thanks to your help.

I’m still marveling at how much is crammed into such a small space on that PCB. Very impressive.

[Author]

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