Aion Xenotron : Vactrol Instead of LDR

[klausmo]

Good Morning,
has anyone tried using vactrol (VTL5C3) instead of LDR for flange with no name from Aion Fx ?

I am aware that the manual does not recommend this, but for experimentation purposes, I tried it and, unsurprisingly, it does not sound like the original.

However, I was wondering if changing some resistance values, such as R73 or R81, it is possible to achieve a similar sound.

Any suggestions would be greatly appreciated

 

[Giorfida]

Good Morning,
has anyone tried using vactrol (VTL5C3) instead of LDR for flange with no name from Aion Fx ?

I am aware that the manual does not recommend this, but for experimentation purposes, I tried it and, unsurprisingly, it does not sound like the original.

However, I was wondering if changing some resistance values, such as R73 or R81, it is possible to achieve a similar sound.

Any suggestions would be greatly appreciated


View attachment 73863View attachment 73864

Not all vactrols are created equal, just like not all LDR are created equal. Vactrol is simply an LDR and LED in a sealed package. Factors you need to consider is the light and dark resistances (and to some extent LED color as that can change the response somewhat).
Can you add resistors to make a non-specified vactrol to work? Depends. If the circuit is expecting an LDR with a small range (100ohm-1k), and the vactrol is wider range (100ohm-1M), you could likely get it to work by changing resistors. But if it’s the other way around, where it’s looking for a wide range LDR and you try to use a shorter range LDR/Vactrol, it simply won’t work.

 

[klausmo]

Hi Giorfida and thank you for your answer.
As you mentioned, light and dark resistances need to be considered. In fact, the vactrol VTL5C3 (the one I want to use) has an on resistance of 30KOhm (1mA) and a dark resistance of 10M. Aion Fx suggests using the LDR NSL-19M51, which has a range of 20 KOhm - 20 MOhm, so it's a wider range but almost comparable. Therefore, the dark resistance is neglected by the parallel resistance R81. In my opinion, one could use a vactrol for this project, but I'm still waiting to see if someone has tried it.

Thank you anyway, I appreciate it

 

[comradehoser]

If I recall correctly (I think in the Spectron build docs), Aion noted that the original circuits used open LED/LDR as opposed to vactrols. He tested circuits with and without vactrols and came to the conclusion that vactrols changed the behavior of the pedal too much. He hypothesized that there are array-wide effects in the original circuits resulting from the open LEDs leaking light into neighboring LDRs. Changing resistors I don't think will be able to address that.