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Gssl question
Old 12th May 2020
  #1
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Gssl question

Hello everyone, it is my first post, although I have been looking for information in this forum

I have several questions about the construction of this compressor and if someone were so kind to help me

1º Question
I am going to mount that 2181A, the question is, what resistance do I have to mount in the% in the photo that I am going to put? In the main vca I have it more or less clear but in the sidechain vca I don't

(that 2181a data)
https://www.mouser.es/datasheet/2/40...et-1602487.pdf

(web where there are various data)
http://fucanay.fischerworks.com/diy/...S3HsGsqty0DXMc

2º Question
I can't find the 22uf low ESR electrolytic capacitors of 25v and I have seen these 50v ones that seem to be 5mm in diameter the same as the 25v ones, I suppose they will wipe me out?

https://www.mouser.es/ProductDetail/667-EEU-FR1H220

3ºQuestion
Do the resistors come to change the sound a lot? Since I plan to buy from the yageo brand

4ºQuestion
to make the connectors of the main PCB and the auxiliary pcb, would it be worth awg22 cable? in xlr if I am going to put mogami cable that I have here

I leave you here a list of components in case someone is worth a reference, although I do not know if it is completely fine

https://www.mouser.es/ProjectManager...0-5f2cd7ed658a

Thank you and sorry for my English from Google translator. My native language is Spanish.
Attached Thumbnails
Gssl question-2181a.jpg  
Old 5th August 2020
  #2
rez
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rez's Avatar
Hola!

- you can use 22uf with higher voltage if they fit.
- resistors should be metal with low tolerance like 1%.
- awg22 cable should work.
I use connectors on one end of the pcb interconnections for more easy assembly of all the boards (GSSL, Turbo, dual SuperSidechain and CRC-board).


This is a question i really also like to find an answer to!

What resistor to use on the sidechain vca pin 4 if using THAT 2181 A???

I know that this high grade vca is not needed in the sidechain and a pretrimmed 2180 would be the easy route, but it so happens that i only have those 2181 A.

Nobody at THAT corporation thought of some diy guys that use the trimmable version in a circuit with no trim parts...

So how do we interpret the data from the datasheet?

Internally that pin 4 is connected to pin 2 via a 25 ohm resistor and to pin 5.

The vca works with the pin 2 at ground and a small current of -2,4mA coming into the pin 5 via resistor 3k9 from the negative 12 volt rail.

Normally the pin 4 should be connected to a high impedance current source which is created by connecting pin 4 via resistor 680k to the virtual 0v on a 50k trimmer between +15 an -15v. That means only if the trimmer is NOT at the virtual 0v there is current flowing and a small DC offset voltage is applied.

Does that in reverse mean that there is one condition when the pin 4 is connected to 0v and that is if no trim is applied?
That would mean it is okay to connect pin 4 to 0v but for safety it would be better to use a resistor?
Or can pin 4 be left floating as it is already internaly connected?
In some ic floating pins cause all sorts of problems so i really like to know how to handle this special case?
I don´t need or want to trim the thd on that sidechain vca - i just don´t want a wrong connection in that circuit.

Hope that someone can shine a light on this.

Thank you!

peace, rez
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