Swapping VTL5C9 for NSL-32SR3 vactrols?

[swilliman]

Hi folks,

I've populated my Weak Joe compressor PCB and pretty close to testing but I have a couple of questions, perhaps someone who's built this before or previous vactrol projects can help!

I've used NSL-32SR3 in my build, assuming they were a like for like replacement for VTL5C9 but I've now realised I may need to change a resistor value. The question is which resistor and to what value? Or will the NSL work fine in the circuit as is?


Also, I'm unsure whether the caps around the IC should be polarised or whether standard film caps are ok. They seem to have little red marks on the layout, but don't look like electrolytics?

http://mnats.net/weak_users.html

 

[swilliman]

Also found this schematic revision with some changes: https://ibb.co/4d3GPx0

He seems to have added an extra 1k resistor and a 39uf cap in his circuit.. not sure if these are to help the NSL-32SR3 fit in the circuit?

 

[rackmonkey]

The Silonex/Luna part (NSL) isn’t a like for like replacement for the 5C9. There’s a 10x difference in both the on resistance (60 ohms vs 630 ohms) and a 5x difference in the decay time (10ms vs 50ms). No nominal typical slope value is indicated for the NSL, but from the chart it’s got a harder knee than the Vactec part. Even adding a resistor will result in different compressor performance than the original, which you may or may not like.

At about ten bucks each it’s not fun, but you can get original 5C9s from Small Bear.

 

[swilliman]

Hey rack monkey,

Just saw this, thanks for taking the time to reply. You're a real gent.

Sounds like I'll just have to shell out on some VTL5C9 from Thonk, I guess I can sell the ones I won't use on eBay to recoup some costs!

Whilst you're here, do you know if it matters whether the 1uf (bypass/decoupling I'm not sure?) caps that are next to the Opamps are nonpolarised film or electrolytics?

In the layout they have a little red mark at one end which suggests polarised, but their outline is square which suggests film.

I've used 1uf film caps - do you think I should swap them out and put some electrolytics in there?