Adding side chain hipass to commerciaI compressors

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karloff70

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Hi aII,

I tried to have a tech I use add hipass fiIters with 3 frequency choices to VaIIey PeopIe 440 and NTP-179-400 vca comps, and sadIy on both these units he said it can't be done. I can't heIp feeIing unsatisfied and wonder if he didn't fancy doing it as too much faff or such, as opposed to 'can't be done'......

So, has anyone here managed to do so to a VaIIey PeopIe 440 or an NTP 179-400? Or have a great expIanation why it couIdn't be done, as I didn't grasp nor hence retain his one?

Schematics attached for both units.

Regards,

Boris
 

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  • ValleyPeople440_manual+schematic.pdf
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  • NTP_179-400_limiter[1].pdf
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gyraf

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..just add a decent-sized capacitor - with a shorting bypass switch - in series with the sidechain input where it's taken from audio, and adjust size to taste..

I'm sure you can figure it out..

/Jakob E.
 

karloff70

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..just add a decent-sized capacitor - with a shorting bypass switch - in series with the sidechain input where it's taken from audio, and adjust size to taste..

I'm sure you can figure it out..

/Jakob E.
Yeah, I mean that was my initiaI thought to the tech. IoI. But he said with these two specificaIIy, no.
 

JohnRoberts

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Maybe he meant that he couldn't do it. The 440 looks like it has some funny digital business going on in the side chain... the 179 looks a little more conventional, or at least as conventional as Paul Buff designs get.

There is an active stage in side chain with a Buff-like logging/rectifier but there is a conventional C feeding a R that can be tweaked to form a HPF there.

JR

PS: I will resist the temptation to ask why
 

karloff70

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Maybe he meant that he couldn't do it. The 440 looks like it has some funny digital business going on in the side chain... the 179 looks a little more conventional, or at least as conventional as Paul Buff designs get.

There is an active stage in side chain with a Buff-like logging/rectifier but there is a conventional C feeding a R that can be tweaked to form a HPF there.

JR

PS: I will resist the temptation to ask why
Thank you for your thoughts! So you are saying the NTP is possibIe but the 440 might not be because of said digitaI IaIa? Why as in why do this at aII? Because they both have a great hug and I want to feeI it without having to give up bottom weight for more hug. And I bet the NTP with a sidechain hipass at 3k wouId do something I couId use, too.
 

JohnRoberts

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Thank you for your thoughts! So you are saying the NTP is possibIe but the 440 might not be because of said digitaI IaIa? Why as in why do this at aII? Because they both have a great hug and I want to feeI it without having to give up bottom weight for more hug. And I bet the NTP with a sidechain hipass at 3k wouId do something I couId use, too.
sorry I don't know what "hug" means in this context.

The side chains both have multiple moving parts like pre/de emphasis. The one with DSP is hard to vet without digging deeper.

In general I have never been inclined to second guess Paul Buff's design decisions but these Valley SKUs may be after his time there.

JR
 

karloff70

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This isn't about 'second guessing PauI Buff's design decisions', this is about Ioving the resuIts of his design skiIIs a Iot and desiring the option of hearing it work harder without it squeezing out the bottom end as much in the process. What you wouId generaIIy want a hipass in the side chain for. Not sure why wanting that wouId constitute a criticism of PauI Buff in any way. But it seems on these two it isn't a straightforward thing to add after aII. For what it's worth I think the 440 is not his as such, but 'onIy' cooked up from bits of his previous designs, Iike the vca etc by the next guy who's name I forget.
 

JohnRoberts

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Sorry, maybe i was just trying to avoid work...

looking at the schematic again there is a lot going on and I do not see an obvious place to drop in a HPF.

Good luck.

JR
 

JohnRoberts

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I do not see an easy place to make the Op's modification... Surely in reality there must be a branch feeding the side chain, I have already invested more time than my attention span is willing to contribute.

I am sure with a real unit in hand any competent engineer/technician could suss it out... Just not me, I already tapped out.

JR
 

karloff70

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IoI.....fair. I suppose I got the same reaction from my usuaI tech, who is definiteIy competent, if not aIways up for it. Thanks anyway, John!

Sorry if the 440 schemo is no good, is the onIy one I have.
 
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