SSL mod questions.....

[j.hall]

this might help many people put a visual to some of the mods.

please look at this PDF

the blue circles:
are these the two 15k resistors i need to change to 27k for the unity gain mod?

red circle:
are these the two 47k resistors i change to a smaller value for the threshold sensitivity mod?

green circle:
can i use a molex PCB mount connector for the PSU here? the same molex connectors as used for audio I/O and control to daughter board?

 

[matthias]

can somebody please explain in which case I have to switch to the 27k resistors to get unity gain ??

(unbal -> bal ?? bal -> bal ?? unbal -> unbal ???)


thank you

 

[Greg]

As far as I understand it, the 27k substitute if for unity gain. It doesn't really have anything to do with balanced or unbalanced. With the 15k resistors in there, the unit will have 6dB gain.

 

[matthias]

@ greg :

just a short example that helps me to understand it:

when I have the 15k resistors soldered in and give a 0db signal to the input, it gets amplifeid to +6db before it reaches the vca ??

is that correct ??

 

[Greg]

I'm not looking at the schematic, so I'm not sure if it gets amplified 6dB before the VCA or not, but the unit will have 6dB gain... just meaning if you put in a signal, the output will be that signal, amplified by 6dB (assuming no compression).

I'm sure Gyraf will come along and give you a better explanation.

 

[radiance]

@ J.Hall: I will try to answer your questions.

1) yes, those are the 15k resistors.


2) Those are the resistors mentioned by forum member Matthias in this thread
I don't know if this is the right way of doing the "threshold sens" mod.
It worked for Matthias though.

3)I think you can use those connectors. Those PCB holes are on a standart "fixed distance" so standart connectors will fit.
Meassure them to make sure if in doubt....

 

[al_p]

[quote author="matthias"]@ greg :

just a short example that helps me to understand it:

when I have the 15k resistors soldered in and give a 0db signal to the input, it gets amplifeid to +6db before it reaches the vca ??

is that correct ??[/quote]

just from memory i think that resistor ir between the VCA and the output stage.

 

[matthias]

I just changed one 15k resistor to 27k to compare both channels:

with the 15k I get 0db in -> 0db out

with the 27k I get 0db in -> -6db out



I have only unbalanced insert jacks at my mixing desk, so the ssl comp is connected unbal. --> bal.

Isn't there a 6db drop due to the unbal. -> bal. connection...
so the 15k resistor compensates the 6db drop and I'm getting 0db in the end using 15k resistors???

is that possible ??

 

[j.hall]

so changing the value of the two 47k resistors i highlighted is wrong?

or will that work out?

 

[Greg]

I didn't so this mod, but Jakob suggested changing the 220K resistor going to the wiper of the threshold pot. This is the thread:

http://www.groupdiy.com/index.php?topic=2418

He said lower values give bigger threshold ranges and higher values give smaller threshold ranges. What I would do is take a pot (maybe 50k or 100k or so, I don't really know how much more resistance will effect the threshold range) from point "F" on the main PCB to the wiper of the threshold pot. Adjust the pot until you get a range your happy with.

But I would try the GSSL as is, then worry about the threshold mod if you don't like the threshold range. I find the range to be ok.