Replacing VTL5C1/VTL5C2/VTL5C3 with photocell + LED

[POTL]

Hello
I want to know if it makes sense to change the ready-made solutions in the form of VTL5C2 / VTL5C3 to photocell + LED.
The replacement looks cheaper and more affordable in the store, but I am confused that there are no photocell that fit within the technical specifications of the optocouplers.
However, I often saw photocell + LED from boutique manufacturers like EQD (Warden), Mad Professor (Forest Green), 3Leaf Audio (Proton / Wonderlove) etc.
At the same time, large manufacturers produce their products with optocouplers EHX (Q-Tron), DOD (280 Compressor), Diamond (Compressor).
I have doubts whether it makes sense to save time and money and put a photocell + LED or better to put a ready optocoupler?
Will there be a marked difference in the operation of optical effects or the difference in the extreme characteristics of the parameters do not play a role?

[Kevin Mitchell]

In most cases you can easily get by rolling your own optocouplers. However some circuits require the resistance, current or speed rating that only the VTL type can accommodate. But I doubt you'll be needing those requirements for anything stompbox related.

-KM

[POTL]

Thank you
In fact, I'm interested in the following projects.
Q-tron
Dod 280 / Diamond Compressor
Optical tremolo

[Kipper4]

You could likely look up the data for the said VTL's
Find out their respective resistances and use this info as a basis for a roll your own vactrol.

Ldr kits are available on auction sites. That way you can auditions some ldr's
Assume the led in said vatrols are red or orange.
As someone said already play around with the current limiting resistor to suit your circuits.
Rich

Some other ready rolled vactrols are also available.
E.g. NSL32

My local mom and pop electronics shop had some surplus alarm system ldrs that are nice.

[ElectricDruid]

The Druid optical trem schematic you posted above will be fine with a LED/LDR, no need for a VTL vactrol.

It's based on the Tremulus Lune, and if you were cloning that more directly, you could use a LED/LDR too - it's not a complicated enough circuit to need a specific value, and in many ways these tremolos are better "tuned" for a specific LDR/vactrol anyway. If you get the LED current too high, they often start to tick. So you increase the LED resistor until the ticking stops, and then adjust the gain resistor until you get an output which is similar to the input.

HTH,
Tom

[MetalGuy]

Also check Aliexpress for cheap VTL relpacements (not exactly the same of course).

[POTL]

You could likely look up the data for the said VTL's
Find out their respective resistances and use this info as a basis for a roll your own vactrol.

Ldr kits are available on auction sites. That way you can auditions some ldr's
Assume the led in said vatrols are red or orange.
As someone said already play around with the current limiting resistor to suit your circuits.
Rich

Some other ready rolled vactrols are also available.
E.g. NSL32

My local mom and pop electronics shop had some surplus alarm system ldrs that are nice.

I saw the documentation of the optocouplers, but I could not find suitable photoresistors, their extreme values ​​in darkness or light differ from those of the optocouplers.
Either I get the results I need in the dark, but the light resistance is too high, or I get the proper resistance under light, but in the dark the resistance is lower than that of the optocoupler.


I will look for information about NSL32

[POTL]

The Druid optical trem schematic you posted above will be fine with a LED/LDR, no need for a VTL vactrol.

It's based on the Tremulus Lune, and if you were cloning that more directly, you could use a LED/LDR too - it's not a complicated enough circuit to need a specific value, and in many ways these tremolos are better "tuned" for a specific LDR/vactrol anyway. If you get the LED current too high, they often start to tick. So you increase the LED resistor until the ticking stops, and then adjust the gain resistor until you get an output which is similar to the input.

HTH,
Tom

Thank you
This is an interesting idea

[POTL]

Also check Aliexpress for cheap VTL relpacements (not exactly the same of course).

I know that Ali has a lot of fakes, in general this is a lottery, I will look for feedback from those who bought optocouplers on Ali.
Thanks.

[PRR]

> their extreme values ​​in darkness or light differ from those of the optocouplers.

You don't need "extreme values" for a trem.

What you need is some range of "middle" values. This is not well specified in the VTL parts, and may be very different in non-VTL parts. You trim this by changing the LED current; and possibly adapting the audio-gain resistors.

So is some hour(s) of time worth the $7 savings?

As genuine VTL parts go extinct, we may all be cobbling-up optos from strange parts.

[POTL]

> their extreme values ​​in darkness or light differ from those of the optocouplers.

You don't need "extreme values" for a trem.

What you need is some range of "middle" values. This is not well specified in the VTL parts, and may be very different in non-VTL parts. You trim this by changing the LED current; and possibly adapting the audio-gain resistors.

So is some hour(s) of time worth the $7 savings?

As genuine VTL parts go extinct, we may all be cobbling-up optos from strange parts.

7 dollars an adequate price,
shipping from Small Bear is expensive =)
But gradually it seems to me that it's better to buy a suitable component and just install it on the board than to look for a suitable photoresistor.
I'll think about it.

[Marcos - Munky]

I'd say just go for a ldr + led and check how it wents. In all my builds using optocouplers, that's what I did, and I didn't even had to adjust the current limiting resistor.

Well, some envelope filters are picky with the ldrs. But most of the other effectswill work with cheap ldrs.