LDR and bulb neovibe?

[larsthestrat]

Hi,

I did build two neovibes, but ordered everything in Germany for parts (I live in Europe). I'm still not satisfied with the result, the intensity off the effect but also the amount of 'whobble'/depth, etc. is not enough in my opinion (compared to what I heard on youtube). I wondered if it could be the LDR's and light bulb. I now use an 18V bulb (no 15V available here) and I ordered two different kind of LDR's (the site I ordered only stated that these are the ones to be used in vibe projects). Could this be the issue? And would it be wise to use the exact LDR's and light bulb suggested in the project file?

kind regards,

Lars (all the way for the neterlands)

[larsthestrat]

used these ones:

project 1:
LDR
http://www.banzaimusic.com/Photo-Cell-150k-3M.html

project 2:
ldr
http://www.newtone-online.nl/catalog/product_info.php?products_id=1466

project 1 and 2:
bulb:
http://www.newtone-online.nl/catalog/product_info.php?products_id=1465

[Seljer]

I recently changed out all the bulbs in my cars dashboard. The smaller ones are 0.5 watt bulbs and they have leads that you can untwist and probably solder. Any they're only like 50 cents each. Might be worth a try.

[Mark Hammer]

The "proper" LDR value is partly a function of the capacitors it is being used with.  So, the sweep may not seem very strong because it is too high up to hear.  Consider playing with the capacitor values, too.

[pinkjimiphoton]

i don't know if hardware stores like we have here are in your country lars, but you can get a variety of bulb sizes at them, maybe check it out and see if a local store sells flashlight replacement bulbs? i forget, i think a "#47" is the fender amp pilot light number... been a long time!!

[larsthestrat]

I used the caps as suggested. i think I changed a couple of caps in one of the two builds, but that mod was also suggested on the internet (changing a couple of caps from 1uF to 10uF). I only wondered of the problem could occur because I use an 18V lamp instead of an 12V (as suggested) and different types of LDR's that the ones suggested (see second post for the ones I used). Thanks!

nb. 12V lamp is available!

[larsthestrat]

Anyone some insights on my question about bulb and LDR (see specs in the post before)......?

[Paul Marossy]

would it be wise to use the exact LDR's and light bulb suggested in the project file?

I say yes.

From this page here: http://www.geofex.com/article_folders/univibe/univtech.htm

"The bulb and it's time response are important to getting the right sound. The original bulb in all except one original unit I've repaired is a nominal 28V, 40ma bulb. The cold resistance is just over 100 ohms. I have sucessfully used 12V/40ma and 12V/80ma bulbs here. The bulb has a thermal time constant that means that as you try to turn it on faster and faster by twisting the speed control, it responds more and more to the average of the current through it, not the instantaneous value. This should not be a surprise, as at 60 Hz, the bulb does not respond to the instantaneous value at all, and its light output is proportional only to the average of the current through it."

Help that helps somehow...

[larsthestrat]

thanks! These bulbs are available in Europe (12V/20mA or 12V/35mA instead of the 12V/25mA, whine one?)

Now for the LDR, the print says to use:
PH CELL 50K TO 200K  (not available at mouser anymore).

Project one I used: 150K - 3M
Project two I used: 5/20K - 20M

Whiich one should I use (http://www.banzaimusic.com/Photocells/)

[Liquitone]

I have used photo cells in the 2M and even 5M range in the past but i couldn't get them to sound right (they seemed to extreme/choppy) I've tried all the mods but that didnt help with these LDR's
My latest build used 11k-500k and they got the right sound straight away,
with the lamp driver set quite low (just barely out of the dark/no effect range,when you really get the low end throb, but before it becomes too bright and clear sounding)
I used a 24V lamp, and also 24V on the LFO circuit. the lamp i used is about twice as big as the 12v ones from banzai. I got the lamp from a shop in Groningen. http://www.okaphone.com/artikel.asp?id=460997

[larsthestrat]

so 200K or 500K is better with these ones? Where did you order your LDR's?

[Liquitone]

I can not state it for a fact because I have never measured the ones from an original Uni-Vibe, but in my experience 1M or higher dark resistances doesn't sound right.
with these I got the low-end throb and wobble but not the watery phasing sound.
I think 200K will be too low. 500-600K should be ok (dark resistance that is)
I got mine from someone who sold them on synthforum, but newtone and banzai has LDR's of that range;
http://www.newtone-online.nl/catalog/product_info.php?cPath=47_80&products_id=624
http://www.banzaimusic.com/Univibe-Photo-Cell-25k-500k.html

[larsthestrat]

oke, volgens mij woon je in Nederland, haha gewoon in het Hollands dan maar -;)
Dank, ik zag ze ook bij newtone staan inderdaad. Ik heb bij newtone ook dat 18V lampje gekocht. Die zitten nu in beide pedaaltjes.
Naar jouw mening maakt het dus niet zoveel uit of je een 12V, 18V of in jouw geval 24V lampje gebruikt als ik het goed begrepen heb?
Als ik bij Banzai of in Groningen dat lampje van 12V moet kopen ben ik gelijk weer 8 euro verzendkosten kwijt, bij newtone niet....

[Paul Marossy]

thanks! These bulbs are available in Europe (12V/20mA or 12V/35mA instead of the 12V/25mA, whine one?)

Hmm... I'm not an expert on the Univibe, but I would say get both and see which one works better. I'm guessing that the 20mA would be the better way to go, less stress on the transistor and it won't be too bright like the 35mA might be.

[Liquitone]

yeah, I'm from Holland indeed, but I think it's usefull to speak english on this forum, so people who have the same questions can read it as well
I'm not sure if the voltage of the lamp matters too much, reason I chose it is that it seems to be closer to the Uni-Vibe specs, also the bigger size of the lamp might help to spread the light more even.
If i recall correctly the Neovibe runs on 15V. I haven't had any problems with using a 12V lamp on my builds running on 15v,18v or even 24v, so you should be fine.
I think the right LDR's are of bigger importance than the lamps voltage or current-draw.

[larsthestrat]

Thanks en indeed we'll talk English again, almost nobody speaks Dutch....

[Paul Marossy]

I'm not sure if the voltage of the lamp matters too much

It does if the voltage rating of the bulb you use increases the current on the transistor. It'll make it work much harder and maybe kill it over time.

I think the right LDR's are of bigger importance than the lamps voltage or current-draw.

Maybe. But you still shouldn't ignore the current used by the bulb. It's best to get it as close as possible to what is needed.