Empress Compressor side chain variable HPF idea

[labeledbass]

Sorry for the crude photo, but I was thinking after reading about adding capacitors to the side chain, with something like this with variable capacitance work like an adjustable filter? The frequency could obviously be dialed in, but if it worked it would be worth a shot.

 

[NKBassman]

Sorry, I don't know enough about circuit design to answer your question directly.
As a reliable option, you could just buy a Broughton HPF for less than $100 and be done with it.

 

[labeledbass]

Sorry, I don't know enough about circuit design to answer your question directly.
As a reliable option, you could just buy a Broughton HPF for less than $100 and be done with it.

Yeah, I was just thinking about an option under 15 bucks, maybe even remove the 1/4" side chain jack and replace with a knob, no drilling necessary, could return to stock with little effort, and have a broad range of filter.

Really just need someone to check my math, its been a bit since I did any DC theory..

 

[labeledbass]

Sorry, I don't know enough about circuit design to answer your question directly.
As a reliable option, you could just buy a Broughton HPF for less than $100 and be done with it.

Wait are you saying that this will control the HPF in a Empress via side chain? or is this a filter for a signal path? looks like a straight signal filter.
https://www.broughtonaudio.com/product-page/always-on-high-pass-filter

 

[inchoate]

Wait are you saying that this will control the HPF in a Empress via side chain? or is this a filter for a signal path? looks like a straight signal filter.
https://www.broughtonaudio.com/product-page/always-on-high-pass-filter

I bought an always on HPF to control the side chain on my Empress but I've never gotten around to using it that way. Great little box though.

 

[labeledbass]

I bought an always on HPF to control the side chain on my Empress but I've never gotten around to using it that way. Great little box though.

I'm just trying to wrap my head around the wiring, I was under the impression that the side chain was TRS, but the ring and tip were two different directions. Does a Y/split make this possible with the broughton?

 

[Wasnex]

Sorry for the crude photo, but I was thinking after reading about adding capacitors to the side chain, with something like this with variable capacitance work like an adjustable filter? The frequency could obviously be dialed in, but if it worked it would be worth a shot.View attachment 3627408

I believe with that wiring, adjusting the pot is going to have a significant impact on the signal level that passes from the input to the output of the sidechain. I don't think it will vary the knee of the HPF the way you imagine.

With the setup you proposed, when the pot is closed, the capacitor sees the full 10K ohms and no signal passes to the wiper. As you open the pot, the capacitor starts to see a proportion of the input impedance of the sidechain return in parallel with 10K. If the input impedance of the return is high enough I believe the capacitance and the resistance of the pot is the primary factor that sets the knee of the HPF. So if you want to shift the frequency of the HPF you need to use a different capacitor.

I have an amp with a weird master volume (see below). With this setup, adjusting the master volume is also like a tone control. More volume, more bass.

Normally a master volume is wired like your sidechain idea, and changing the volume has no perceived effect on low end response.

 

[inchoate]

I'm just trying to wrap my head around the wiring, I was under the impression that the side chain was TRS, but the ring and tip were two different directions. Does a Y/split make this possible with the broughton?

yes. the tip is the send and the ring is the return.

 

[Wasnex]

Here is a related thread on the Empress; there are more threads.
Empress Compressor Sidechain

My understanding is putting a capacitor in the sidechain creates a frequency contour to the compressor key, so more lows pass before the compressor engages. I suggest watching the video in post #18.

 

[labeledbass]

Normally a master volume is wired like your sidechain idea, and changing the volume has no perceived effect on low end response.

Ok, so what about just a simple variable capacitor?

 

[labeledbass]

Here is a related thread on the Empress; there are more threads.
Empress Compressor Sidechain

My understanding is putting a capacitor in the sidechain creates a frequency contour to the compressor key, so more lows pass before the compressor engages. I suggest watching the video in post #18.

Yes I've watched everything I can find, and read that thread, I'm trying to figure up a way to have variable capacitance so you can adjust your range, instead of having a handful of modded cable ends, which I'm not opposed to making but for dialing in exactly what frequency works for you could be much easier. Imagine if Empress owners could even pass something like this around in the community until they found what cap would be the best for their rig and make exactly what they need/want.

 

[Wasnex]

Yes I've watched everything I can find, and read that thread, I'm trying to figure up a way to have variable capacitance so you can adjust your range, instead of having a handful of modded cable ends, which I'm not opposed to making but for dialing in exactly what frequency works for you could be much easier. Imagine if Empress owners could even pass something like this around in the community until they found what cap would be the best for their rig and make exactly what they need/want.

The video I reference in the other thread included a chart with recommended capacitors and the HPF knee they would produce. The lowest knee was 100hz. For the chart, see 2:41 in the video:


If you want a lower knee, try a bigger capacitor. If you want multiple knees, probably the easiest thing would be to get multiple TRS pancake jacks and wire up the various value of the capacitors you want.

 

[labeledbass]

The video I reference in the other thread included a chart with recommended capacitors and the HPF knee they would produce. The lowest knee was 100hz. For the chart, see 2:41 in the video:


If you want a lower knee, try a bigger capacitor. If you want multiple knees, probably the easiest thing would be to get multiple TRS pancake jacks and wire up the various value of the capacitors you want.

Yeah I get it, 3.9nF = 100hz, 1.2nF=145hz, and so forth BUT just imagine if you had a POT that could control your capacitance from say, 3.7nF all the way up to 220pF, you would have hundreds of options on control. Just think the HPF POT on a Cali CB, THIS is what I'm trying to figure out with the side chain input.

 

[NKBassman]

Wait are you saying that this will control the HPF in a Empress via side chain? or is this a filter for a signal path? looks like a straight signal filter.
https://www.broughtonaudio.com/product-page/always-on-high-pass-filter

sorry I’m operating on assumptions here. I don’t own the Empress comp and have never looked at it that closely. However I do know how a side chain HPF works.
If you’d put the Broughton (or any other) variable HPF in the side chain using an insert cable, that will allow you to apply HPF on the sidechain signal only. Very useful for fine tuning the compressor response.

 

[labeledbass]

sorry I’m operating on assumptions here. I don’t own the Empress comp and have never looked at it that closely. However I do know how a side chain HPF works.
If you’d put the Broughton (or any other) variable HPF in the side chain using an insert cable, that will allow you to apply HPF on the sidechain signal only. Very useful for fine tuning the compressor response.

Yes, basically this, or like I mention above just adding the HPF feature on the Cali CB. If its simple as I think you could literally replace the jack with a POT, done, less than 15 bucks. But maybe this is more complex than I'm thinking. I've made variable High pass Filters in the past and it wasn't a problem in a mono signal path.

 

[Wasnex]

Yeah I get it, 3.9nF = 100hz, 1.2nF=145hz, and so forth BUT just imagine if you had a POT that could control your capacitance from say, 3.7nF all the way up to 220pF, you would have hundreds of options on control. Just think the HPF POT on a Cali CB, THIS is what I'm trying to figure out with the side chain input.

Here is the variable HPF from a Matamp GT120

Old radios used variable capacitors that looked like this, but I believe the capacitance is too low for your application.

 

[Wasnex]

Yes, basically this, or like I mention above just adding the HPF feature on the Cali CB. If its simple as I think you could literally replace the jack with a POT, done, less than 15 bucks. But maybe this is more complex than I'm thinking. I've made variable High pass Filters in the past and it wasn't a problem in a mono signal path.

You might like this page Invalid Link Removed

Note this is basically the Master Volume circuit from the amp I listed above. The problem here is the circuit controls two parameters volume and HPF knee instead of just HPF knee.

 

[JKos]

imagine if you had a POT that could control your capacitance from say, 3.7nF all the way up to 220pF

You're talking about a variable capacitor. Unfortunately, they tend to be in the pF range and quite large. Google "variable capacitor" and you'll see.

- John

 

[labeledbass]

You're talking about a variable capacitor. Unfortunately, they tend to be in the pF range and quite large. Google "variable capacitor" and you'll see.

- John

Yeah, stinks lol - something so simple, has to be a small alternative

 

[labeledbass]

Here is the variable HPF from a Matamp GT120
View attachment 3627563

Old radios used variable capacitors that looked like this, but I believe the capacitance is too low for your application.
View attachment 3627565

That second one is basically a 6 position switch right?