Help with the speed of a Neovibe

[lulu_joe13]

Hello, I just finished building a Neovibe. It sounds great! Lush and swirly. But, I am wondering about the speed which doesn't seem very variable. I can't get it much faster than a Leslie. Is that the way it's designed?
I have tried both the dual gang pot in the build instructions and the little circuit board that uses a dual vactrol. Also, the vactrol board takes a bit of time to ramp up to the change of speed while the dual gang pots change immediately?
It seems when I watch the lamp that the depth and the speed pots both effect the speed, too.
The build instructions have no voltages to check for, so I am really wondering how to proceed to check my build? Thanks. Joe.

[R.G.]

I am wondering about the speed which doesn't seem very variable. I can't get it much faster than a Leslie. Is that the way it's designed?

The design of the oscillator is somewhat limited in speed variation. Also, the light bulb which lights the LDRs has a limit on how fast it can heat up and cool down, so the top speed is limited for that too. This is not to say that yours doesn't have some issue, but the speed range is limited. Not much faster than a Leslie can be pretty fast. I'd need a better gauge on how fast exactly that is.

Also, the vactrol board takes a bit of time to ramp up to the change of speed while the dual gang pots change immediately?

That is normal. The LDRs inside the Vactrol change fast, but then they "coast" a little more due to the light or dark adaptation of the LDRs. Dual pots change immediately and stay there. It's normal for the difference in the two methods.

It seems when I watch the lamp that the depth and the speed pots both effect the speed, too.

A little of that is normal. The LFO in the vibe circuit is a very special case, and changing its loading can change its speed a little. There are tweaks that may or may not change this. I originally used the word "fix" instead of "change", but I believe that "change" is more appropriate. It's probably not broken.

The build instructions have no voltages to check for, so I am really wondering how to proceed to check my build?

I'd say that it's working fine. You're beyond "does it work?" and into "I wish it would do more of X". It may be that some tweaks to the LFO would make it faster, or less sensitive to loading from the depth pot, but if the sound it good as you describe, it's probably fine according to the original design.

[lulu_joe13]

Thanks RG for the response. I did find some voltages(DOH) on the build doc. And, I do think something is not right. People talk about putting these in Cry Baby shells to control the speed. With my build that would be too much work for too subtle a change. Meaning, though I can slow the pulsing of the lamp down smoothly, I lose the effect on the sound seemingly too early.
I chose to make a little foiled covered box and have my LDRs parallel to the pcb. But, because of the lead spacing I could not get them flat on the pcb. They float about 2mm above. I believe they get lots of bounce light. They are certainly lower than the lamp filament.
Assuming that my problem is with the lamp driver circuit, I checked the voltages there. I have a wall wart that's rated at 24v DC and 100ma. It's actually putting out 32VDC. So. I'm seeing 26V where I should see greater than 17VDC. That seems OK. But I am getting 5VDC volts higher at the other points then what I should see. On the build pdf I am supposed to get 11.7V before R40 and I am getting 16V. And, I am supposed to see 10V after Q12 and I'm getting 15V. Below is the schematic link. Thanks. Joe.

http://www.geofex.com/FX_images/vibeschm.pdf