Neovibe - phasing sound is a bit unusual

[yeeshkul]

In my last build, the vibe doesn't go "wooo-weee" but more like "wo-wo - weee". I mean it sort "hiccups" when passing to the deep side if the phase.
Anyone experienced the same thing? Any idea where i shall start looking?

[Papa_lazerous]

just a stab in the dark, check the LDR's are all a similar distance from the light source, and if they are I would also check that they all have comparable values both light and dark.

Failing this its entirely possible that you have a resistor or cap somewhere thats off on 1 of phasing parts of the circuit to cause that portion of phase to be off to ther others, if that makes sense

[yeeshkul]

I handpicked the LDR's from bunch of 10. I'll check for the misplaced res in the phasing chain. Thanks.

[SteveB]

Does the bulb also hiccup in brightness? May be hard to see, but does the sound coincide with the bulb swing?

[yeeshkul]

No , the bulb blinking was smooth. Also all the parts were placed correctly. The hiccup was happening at the deep part of the swing and it was getting more prominent as i was adjusting the bulb to shine brighter (500R trim pot). So in the end i turned the bulb to shine a bit dimmer (to get a bit bigger resistance than my usual 200 ohms on the Darlington emitter - ground). The hiccup was scary though, it hasn't happened to me yet and i have no idea what could have been the cause ... all 4 LDR's hand-picked, almost the same dark/light resistance.
I made the following changes to the well known RG's Neo:
1. JC's driver bias mod
2. 100k on the output vibe/chorus divider instead of 47k to get similar volume levels on both
3. Darlington device as the bulb driver
4. speed up mod
5. no power supply components on the PCB
6. 18V/1.3A (Switched Mode Power) stabilised power supply
7. All ground wires wired to one spot on the output jack
8. Blinking LEDs for both Vibe and Chorus (2mA)

But i did all these on my two builds before and the swing was smooth  , the only really new thing was the 18V wallwart ... that may have been it.