SSL-Comp: switch for dry level ????

[matthias]

Hi,

I'm still looking for an easy way to mix in a certain amount of dry level to the compressed signal...

due to the fact that the ssl comp doesn't have an extra gain stage for make up gain.. there's no possibility to amplify the dry signal as well somewhere in this circuit...

mixing the signal at the input directly to the output would be a good solution for me, you can set the mix value using the makeupgain pot...

yesterday I soldered the inputs and outputs together with a switch...

first it seemed to work very well, but when I inreased the makeupgain pot, a weird noise appears... I think it's something like a feedback...
I think the output level is higher than the input level and so the current goes from the outputs again to the inputs...

so I need a solution that the current can only go from
the input to the output, and not backwards...

Is there a simple way to do it ?? maybe with diodes??

thank you
matthias

 

[Rob Flinn]

The approach that you have used in your diagram is definately not a good one, since you are applying postive feedback using the switch, which will cause problems.

The simplest way to achieve what you want is to use a mixing desk to blend the original & compressed signals. Other than that you will need some sort of external buffer/mixer circuit so that your dry signal path does not become a feedback loop.

 

[matthias]

thank you..

is there really no simple way to fix this, maybe with diodes, that let the signal only pass in one direction ??

 

[gyraf]

We've discussed a "direct-blend-in" circuit before somewhere here (schematic and all), using only a pot and some caps and resistors..

Jakob E.

 

[matthias]

yes jakob, I tried this already, but this solution is very uncomfortable, because it changes the dry/wet setting on both pots... if you increase the makeupgain, your setting on the dry/wet pot is also changed...

mat

 

[gyraf]

I see.

But I don't think there's any easy way around that..

Jakob E.

 

[Rob Flinn]

The best way has to be using your desk to blend the sounds to your taste.

 

[matthias]

would it be possible to install a second pair of output xlrs that are connected directly to the inputs??
so I can grab the original signal (like a direct out ) and lead it
back to 2 channels on my mixer ??
or will this maybe decrease the volume of the signal that goes into the compressor??

mat

 

[matthias]

another idea:

If I would just lead the signal through an op amp (without any amplification) would this prevent the feedback loop ??

mat

 

[tony dB]

if this buffers it, yes.
Still i would go for 2 more channels in a mixer. Often when wanting to use the paralelled comp/dry technique i still want to eq just a little to make it fit or to ad impact in the lows. The mixchannels come in very handy then.

Don't try to reinvent the wheel :grin:
my 0,02 ?

Good luck,

Tony