Possible modifications to the Baja Limiter/Holy Roller

[Snodgrass]

I apologize in advance if these questions are elementary or well worn but I am not in much the habit of dealing with circuits like this and have been unable to find the information necessary to answer them myself. Questions are regarding the following schematic:

1.  Would placing a switch around R5 have a similar effect of the similarly placed switch on an LA2A, which is to change between a more extreme leveling (open) to a less extreme compression (closed)?
2. Would it be feasible to modify the attack of the compression on the above circuit?  If not exactly feasible, what would be required to do so? Side chain rectification, perhaps?

[blackcorvo]

1. R5 is there to keep the gain of the op-amp in front of it so that you get (roughly) unity-level output.
Add a trimpot in series with the LDR instead, and adjust it till you get your desired less harsh effect, then add the switch in parallel with it for the functionality you were looking for. You can even measure the adjusted trimpot's value to sub it for a fixed resistor if you don't want to keep the adjustability.

2. The attack depends on how bright D1 lights up, which is already adjustable by the "limit" pot, but you could always experiment with adding a trimpot between R19 and D1 and seeing if a series resistance can give a more desirable control over the attack.

[Snodgrass]

A series pot with the LDR does not sound like it would ape the effect of the switch on the LA2A which basically seems to switch between feedback operation to something else. As well I am pretty sure R5 is there to form a voltage divider with the LDR for attenuation and that the gain of the op amp is set by (1+R6/R7). This is my understanding and I could be wrong as I do not deal wit op amps regularly.
I do not believe that turning down the input gain into the sidechain is the same as changing the attack time. That would lower the overall gain reduction when I would prefer to just delay its onset a little. The same with adding an LED trim.

[PRR]

If you want time-control, don't use an LDR. The timing is all in the chemistry.

THAT Corp makes a range of designable VCAs and has documented many sidechains.

R5 does not get unity gain; you don't want that. A FB limiter's control signal goes very small at high gain reduction. R5 keeps it from vanishing altogether, forcing the LDR to do deep limiting.

[Snodgrass]

R5 does not get unity gain; you don't want that. A FB limiter's control signal goes very small at high gain reduction. R5 keeps it from vanishing altogether, forcing the LDR to do deep limiting.

So a shorting switch across R5 would in this case not have the same effect as the one on the LA2A seen below? Actually I think I am misunderstanding what you are saying for which I apologize.
And the only way to change attack/delay characteristics would be swapping between hand-selected LDRs?

[r080]

I thought there was a way to increase either the attack or release of an LDR with a capacitor, but I can't remember where it would go. If you are looking to speed it up, that would come down to selecting a different LDR.

[Snodgrass]

Nah I was more interested in delaying it.  I would imagine this thing acts pretty fast.

[Snodgrass]

I'm just going to add an addendum here that the LA-Light does exactly what I speaking of regarding the Comp/Limit switch. After spending a regrettably long time in Kicad, I intend on having a PCB made of this circuit instead, my perf/vero fabrication skills being even worse than my Kicad knowledge.