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DIY Stompboxes => Building your own stompbox => Topic started by: mdcmdcmdc on March 30, 2022, 01:51:29 PM

Title: Optocoupler substitution in voodolabs switching circuit...
Post by: mdcmdcmdc on March 30, 2022, 01:51:29 PM
Hi folks,

PJP started an optical switching thread last week that led me to find the schematic for voodoo labs' switching scheme:

(https://media.stinkfoot.se/2010/11/VL1.gif)

I've also seen a version that replaces the photo-FET with transistor-output:

(https://diy.thcustom.com/wp-content/uploads/2014/07/voodoo_lab_style_true_bypass.png)

Here are the respective datasheets for the two optocouplers that voodoolabs uses:
https://www.mouser.com/datasheet/2/308/FairchildSemiconductor_161480151644-1192009.pdf
https://www.mouser.ca/datasheet/2/408/TLP181_datasheet_en_20190617-708235.pdf

Seems like either a FET or transistor output device will do the job, so my question is - if I'm looking for substitutes, what are the important specs?

I was planning on ordering some stuff from Tayda sooner than later, and they have both the 4N25 and 4N26 available, which are transistor-output with an additional base connection in the 6-pin package. Would either of these do the job?






Title: Re: Optocoupler substitution in voodolabs switching circuit...
Post by: PRR on March 31, 2022, 02:19:13 PM
> what are the important specs?

1) Price.

2) Size

This is not a tough job.
Title: Re: Optocoupler substitution in voodolabs switching circuit...
Post by: mdcmdcmdc on April 01, 2022, 07:57:35 AM
I'll give it a whirl with the 4N25/26 and see what happens then. Merci!
Title: Re: Optocoupler substitution in voodolabs switching circuit...
Post by: mdcmdcmdc on April 03, 2022, 05:27:39 PM
The 4N26 works a-ok.

Ironically I'm using 2/3 of a 3PDT to test it, but it defeated a pop that I couldn't otherwise get rid of in this particular pedal so I'll take the win where I can.