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R/E/P => R/E/P Archives => Brad Blackwood => Topic started by: Alécio Costa - Brazil on June 05, 2010, 05:50:57 pm

Title: Choosing Sidechain frequencies for the OCL-2
Post by: Alécio Costa - Brazil on June 05, 2010, 05:50:57 pm
Hi, folks

Which are the most used side chain frequencies you guys select for the Pendulum OCL2?

I intend to build a small box, so it is time to thing about frequency selection...

I was thinking of :
1 - 40
2 - 60
3 - 90
4 - 120
5 - 150

There was a thread at GS where something like 320 was also chosen. Seems a bit high, right?

Thanks

Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Andrew Hamilton on June 07, 2010, 03:58:43 am
Bom dia, Al
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Alécio Costa - Brazil on June 08, 2010, 01:20:05 am
Thanks, Andrew!
BTW I used to be an electrical engineeer
LOL
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Alécio Costa - Brazil on June 08, 2010, 01:24:20 am
p.s: If you come to Brazil, drop me a call and I may take you to visit some of the 43 beaches we have here!

Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Andrew Hamilton on June 08, 2010, 11:30:08 am
I'll let you know if I make it there.  Thanks.  By the way, I meant to say that the frequency column in my list contained the _non_-integers, and the capacitance column, the integers...

Memristically, yours,







Andrew
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Alécio Costa - Brazil on June 10, 2010, 09:32:25 am
Cool
Let us Keep In contaqct!
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: The Buzz on June 13, 2010, 02:22:25 am
From listening experience, changing a HPF in the side chain of a compressor has to be quite radical to notice any real change.  If the filter is only a 6dB slope, then yes, starting roll off at 300Hz is not as silly as it sounds.  The thread you mention might have been about the Atlas compressor I designed, which has such a filter in the sidechain.  But if the filter has a steeper slope then lower cutoff freq's will work.

Tim
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Alécio Costa - Brazil on June 16, 2010, 12:23:20 am
Interesting, Tim.
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: bblackwood on June 16, 2010, 12:45:28 am
Honestly, while one would think the lower freqs were too subtle, I find myself using all five selections on mine with some regularity. The one thing I'll likely do is add a '2x' switch to the side to make higher freqs available.

But yah, I find even the lower freqs useful.

http://www.euphonicmasters.com/misc/OCL2_SC_HPF.JPG
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Viitalahde on June 16, 2010, 06:12:25 am
Yeah, my Knif compressor has SC cutoffs at 30, 50, 70, 100, 150 and I often find myself using 50 and 70, sometimes the upper ones.

Brad: I think that 2x switch could be done by putting a toggle switch at the output, shunting a resistor equal to the input Z of the OCL2 to ground. 10k?
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: bblackwood on June 16, 2010, 08:51:16 am
Viitalahde wrote on Wed, 16 June 2010 05:12

Brad: I think that 2x switch could be done by putting a toggle switch at the output, shunting a resistor equal to the input Z of the OCL2 to ground. 10k?

Yah, that's what I'm thinking. Should be a simple 'mod', and making some even higher freqs available can't hurt.
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Alécio Costa - Brazil on June 17, 2010, 01:30:58 am
Brad, are your filters 6dB/octave, 12...?

Have you felt the need to go  into the low mid area with the side chain frequencies? (300 for example)
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: bblackwood on June 17, 2010, 08:31:54 am
Al
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: dcollins on June 17, 2010, 01:50:28 pm
I guess it's worth mentioning that the OCL-2 has a 15Hz S/C filter internally so any external rolloffs are in addition to this.


DC
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Andrew Hamilton on June 18, 2010, 06:26:55 am
dcollins wrote on Thu, 17 June 2010 13:50

I guess it's worth mentioning that the OCL-2 has a 15Hz S/C filter internally so any external rolloffs are in addition to this.


DC


Wouldn't that mean that the quality of the s/c-hp filter becomes 2nd order (when using the Blackwood mod - or even swappable TRS connectors with caps soldered on, for those s/c inserts)?   If so, then perhaps the Buzz would object less to the notion of the efficacy of selectable low end corner frequencies for the side chain.







Andrew
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Viitalahde on June 18, 2010, 07:22:02 am
Andrew Hamilton wrote on Fri, 18 June 2010 13:26

Wouldn't that mean that the quality of the s/c-hp filter becomes 2nd order


If the added cutoff was also 15Hz. I'd think that around 50-75Hz it'd look like some sort of a shelving response with rolloff. Above that it starts at 6dB/oct and towards lower frequencies it approaches 12dB/oct. All guessing.


Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: dcollins on June 18, 2010, 01:51:16 pm
Viitalahde wrote on Fri, 18 June 2010 04:22


If the added cutoff was also 15Hz. I'd think that around 50-75Hz it'd look like some sort of a shelving response with rolloff. Above that it starts at 6dB/oct and towards lower frequencies it approaches 12dB/oct. All guessing.



I'll have to look at the schematic again, I think it's 12dB/oct at around 15Hz.

DC
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Andrew Hamilton on June 19, 2010, 02:26:25 am
So, you're saying that the existing 15 Hz s/c hpfs are not in series with the side chain filters?  ...are buffered in some way from the inserts, but the filtering is still cumulative - just not to the point of affecting the order of the cascaded networks?





Andrew
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: dcollins on June 19, 2010, 12:53:27 pm
Andrew Hamilton wrote on Fri, 18 June 2010 23:26

So, you're saying that the existing 15 Hz s/c hpfs are not in series with the side chain filters?  ...are buffered in some way from the inserts, but the filtering is still cumulative - just not to the point of affecting the order of the cascaded networks?



There is a side-chain filter built in the OCL-2.  Any external networks are in addition to this.


DC
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Andrew Hamilton on June 21, 2010, 08:32:20 am
If the on-board s/c filter is not buffered from the side chain insert (TRS) filters one might apply, I wondered if that meant it would result in a single, sharper filter, or if that nascent network is buffered from the TRS ports and, as Viitalahde wrote, therefore the resultant s/c filtering would be in two, different, but concurrent slopes (of non compression)....



Thanks,
    Andrew




P.S., this is the "net" action I was wondering about possibly going on...

index.php/fa/14979/0/



Also, if you have a step on your s/c switch that is open, rather than through a cap or jumper, then the audio will only be passed through the compressor with make-up gain, but no compression...  could be a convenient step for comparisons...
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: dcollins on June 21, 2010, 12:53:53 pm
Andrew Hamilton wrote on Mon, 21 June 2010 05:32

If the on-board s/c filter is not buffered from the side chain insert (TRS) filters one might apply, I wondered if that meant it would result in a single, sharper filter, or if that nascent network is buffered from the TRS ports and, as Viitalahde wrote, therefore the resultant s/c filtering would be in two, different, but concurrent



The internal filter is buffered.


DC
Title: Re: Choosing Sidechain frequencies for the OCL-2
Post by: Alécio Costa - Brazil on June 27, 2010, 12:01:24 am
15 Hz only?  ( for free)
Rolling Eyes