Univibe LDR's

[Coony]

Hi!

My univibe-clone still doesn't sound like I'd want it to. Firstly, when turning the effect of, it takes some time (5 sec) until the sound is back to 'normal'. During those 5 seconds the sound is phased slowly. Secondly, the vibe effect isn't really deep, it's almost no more than a sort of tremolo-effect, depending on the amp-settings.

I'm convinced it has to do with the LDR's; in the datasheets I found that the recovery time is 200kOhms/sec. I think this isn't fast enough to make the vibe work well, the lamp flashes too fast for the LDR's to follow. On the other hand, at very slow settings, the intensity is good because the LDR's can follow then.

I tried various things.
I removed the diodes in the oscillation-circuit so that the difference between dark and bright is bigger. This is audible, however not really enough.
I removed the resistors before the bulbdriver transistor so that the signal at the base is bigger. This didn't change much.

The only good solution would be to sub the LDR's with others. However I have no idea where to get them (they don't sell mouser parts over here!).
Is there a way to modify the circuit so that these LDR's would work?

Best Regards,
Koen

[R.G.]

I'm convinced it has to do with the LDR's

You are correct. The LDRs are too slow.

Is there a way to modify the circuit so that these LDR's would work?

No. The LDRs you have are simply too slow. There is no good way to mess with the LDR light drive to speed them up. The worst thing is the slow turn off. There's just no way to make the light bulb be darker than dark and suck light back out of the LDRs to make them go dark faster.

Sorry - you gotta get faster LDRs.

[Coony]

Thanks RG!

I looked at the mouser-catalog again and it seems that the LDR with partnumber 338-54C679 (=the suggested part) isn't available anymore. Any suggestions you can make?

Thanks,
Koen

[RedHouse]

Small Bear had 'em last time I looked.

[Coony]

Are there any other suppliers in Europe? Anybody build it with other LDR's?
Thanks!

Koen

[Lithium_Grim]

Ok, reviving this thread. The NOS LDR's are out of stock and /or you can find them for crazy amounts of money. Does anyone know of new (still in production) alternatives for Univibe LDR's?

I found that there are still 9203 LDR and NSL-7530, but I do not know their production status or if they are EOL.

To be short. Do you know and tested still in production LDR's that make a lush Univibe (Neovibe, Habinger x)?