Forum Vibe Demo And Question

[Slade]

Hi,
I've just finished the Forum Vibe with all the mods and wanted to know what do you think of the sound I'm getting from it.
I think that the LFO is not doing his work as good as it should, it's more like a triangular LFO than the Univibe LFO wich is more irregular. Listening to John Lyons's great demos I have compared them and don't seem to do the same thing. Could it be the LDR's I'm using? I'm using the CDS LDRs from Small Bear and ultra bright orange led for the bulb (it worked way better than red led, green led and light bulb from SB).

Here's a short demo I've recorded of the pedal, only to show the LFO waveform at different speeds:

Forum Vibe Demo

Any opinions will be much appreciated. I think this is a fantastic proyect, I'm very grateful to his creator and all the contributors.

Regards,

Fernando.-

EDIT: Here's the demo from John Lyons I was talking about (thanks for that): http://www.mrdwab.com/john/neo-vibe1.mp3

[John Lyons]

The bulb is what you want and what the
circuit is designed around.
The way an bulb turns on and off is WAY different
than with an LED.
An LED does not illuminate on it's sides.
It mainly illuminates from the top.
The Photo cells are probably not getting
enough light, or at least enough to give
the "swing" you need.
Have you adjusted the bulb bias?

[Slade]

Thanks, John.
Yes, I've adjusted the bias and I've tried it with a bulb, but the results became on a not deep sweep. I've used all the mods from the Forum Vibe article and layout. Could I be using much light in the bright side so it's getting a too brilliant sound?

[John Lyons]

The bulb does not need to be very bright.
Are you using the light shield?
The LDR/Bulb assembly needs to be completely
dark in order to work correctly.
Even covering the bottom of the PCB from
room light will help.

John

[Slade]

Yes, I used a reflectant shield though, and I protected the bottom with black paint to avoid the light coming through the PCB. The thing is that with the bulb the bright part was not very notorious, the effect became flat, not really deep. Anyway, I'll try again tweaking the light bulb with the trimmers and see if it helps.

[Slade]

Well, I've tried the bulb and it's still not getting the "irregular" LFO waveform, I still have the "triangular" LFO, and not as rich and deep sweep like with the orange led...

Any ideas?

[Slade]

Ok, so I put the led back in position and I added the speed led through a 100k trimmer at the base of Q12 (in both layouts). I adjusted it until I get it working and sounding good, and then I noted this:

Forum Vibe Speed Led issue... (I thought before that you could listen to the other demo for free, I was wrong so I uploaded the demo to other server, it's only a 1MB file)

The fact is that at high speed ranges the waveform of the LFO is as it should be but at slower speeds the "irregular" waveform is gone and I still have a "triangular" waveform...


HERE IS THE FIRST DEMO.

[Eb7+9]

I think that the LFO is not doing his work as good as it should, it's more like a triangular LFO than the Univibe LFO wich is more irregular.

yours is close to what it should be - just need to work on the offset a bit
you might be referring to the double-bounce effect that can happen when the bulb driver isn't biased right - you're not getting that ...

[Slade]

Ok, thanks for your opinion

I'll keep working on this.