6790K Dual limiter mods?

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6790K Dual limiter mods?

Post by gaetanopellino »

Hello. I have built few 6790K Dual limiter and I’d like to make a couple of mods but I don’t have enough skill for that. By replacing C11-C12 (L/R channels) you can make the limiting release time faster (about 100 ms vs the original 500 ms or longer that causes the annoing pumping effect), much better expecially on rhythmic tracks or full program. The best value I experimented is 22mF instead of the original 100mF. Unfortunately lowering the value of those caps causes an overall increase of distortion. Any suggestions to get around this problem? The second mod I’d like to make is to have the led monitoring the limiting effect and not the input signal. Any suggestions would be really appreciated. Thanks
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Re: 6790K Dual limiter mods?

Post by toneman »

Happy Halloween Paia Phans!!
Especially gaetanopellino
buon pomeriggio

An LED to show limiter action is a good mod idea. I haven’t used my 6790 in quite some time so I had to review the schematic and reread the theory of operation. I recall that the 6750 Hyperflanger and 5760 Rocktive Dividor used the same compander IC. But neither has any LED showing compression/expansion.

Since the 6790 is a limiter, the limiting is an on/off action. I mean, once the signal level exceeds Right channels’s R9 setpoint, the opamp turns Q1 on to charge C11. You could add another transistor in parallel with Q1 to drive an LED, but it won’t change brightness, but will be on whenever the signal level exceeds the manually set threshold.

As far as the C11 thing, I think the distortion you are hearing is due to the cap value is outside the (linear)operating range of compander.
Try a compressor instead of a limiter if you want musicial distortion. The Paia Hot Lyks compressor is a good one.

For any new Paia Phans, the instruction manuals for 6750 Hyperflanger and 5760 Rocktive and, of course the 6790 Dual Limiter are in the manuals/documents section of the Paia Forum.

Hope this helps.
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Re: 6790K Dual limiter mods?

Post by PAiA-Scott »

Hello Gaetanopellino and Thanks Tone!

Sorry, but no ideas for optimizing the release action except for perhaps doing a filtered split of the input to two limiter sections, one optimized for bass and the other for treble, and mixing the output.

Below is a plan for changing the LED indication to be for limiting action vs input level sensing.

https://paia.com/wp-content/uploads/202 ... In4LED.pdf
Scott Lee
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