Expander Logic Pro

[Marcelene Vasconez]

Ive never used any expander plugin, but my thoughts were always that an expander is just a compressor with an auto-gain. Is it more than that? Wouldn't we be able to achieve the same results by using a compressor and since Logic comes with several types of compressors, we would be better off with the compressor only?

"What is upward compression? Upward compression is a type of dynamic range compression that boosts the amplitude of an audio signal below a certain threshold while maintaining the amplitude above the threshold. Upward compression is available in digital plugins and via parallel compression with hardware or software."

So basically in upward compression, the audio above the threshold is ignored and the threshold now acts like a "ceiling" for the audio below it, so it compresses all the audio below (like a normal compress would) and then turns it up towards the threshold. Right?

What most people do to achieve this effect is use parallel compression - compress heavily (which brings up the low level stuff but also compresses the transient peaks), and then mix in the dry signal, which brings the transient peaks back in.

I was thinking about parallel compression as well, but if we think about it, it's not exactly the same, even though it's similar. When you add the parallel/super compressed version, you are also increasing the amplitude of the transients on the original source, whereas with upward compression it seems that the transients (when above the threshold, of course) will remain intact in terms of amplitude and only the audio below that threshold will be compressed and pushed up. Does it make sense?

I know. And the fact that I could directly recall *one* compressor plugin that has a proper upward compressor (and there's probably a few more I can't recall right now), but yet I know of probably hundreds of regular compressor plugins, should go someway to indicate my claim that "pure" upward compression is not that widely used.

I'm well aware ? and if you read my words, I deliberately didn't claim it was exactly the same (I did expect you to raise the point though ). If you google it, parallel compression is regarded as "a form of upward compression", and that it is.

And it's a very widely/commonly used method, supported by many plugins (including Logic's own), and is sufficiently similar that it's a perfectly acceptable tool to use to achieve this effect (which is all about bringing up low-level detail and density), and consequently not many people seem to bemoan the lack of upward compressors.

But go ahead and play with a compressor that has a proper upward compressor (and one that doesn't just implement a regular parallel compressor for this internally, I wouldn't be surprised if some naive implementations do) and see what you think. I think Sculpt is a pretty unique tool on things like drum loops and can bring up low level detail really nicely (you can pick it up for $6 if you're quick), but I'm sure I could do a lot of those things with regular parallel compression if necessary - it's just more convenient in the plugin as the workflow is simpler.

Again, upward compression is an approach and, like many audio processes can be implemented in many different ways, so isn't going to sound the same between plugins, just like different compressor plugins don't sound the same.

Is Logic Pro X contains such thing as downward expander ? There is expander but it's upward expander. I'm looking for a plugin, which allows to increase volume gain to the parts which are BELOW the threshold set by me. Compressor compresses everything above the threshold. I'm looking for something which will increase the volume of everything that does not reach a certain threshold, and everything above this threshold will leave intact... I'm not sure, but it seems to me that the downward expander works in such way... But if you have any better ideas, will be nice to see it

Expansion normally increases dynamic range, while compression normally reduces dynamic range. Raising the low level signals but leaving the high level signals intact will reduce the span between the extremes, i.e. reducing dynamic range.

I say "real upward compression" because you can achieve something similar sounding with a regular downward compressor set with a very low threshold and very low ratio. If this compressor has non-linear properties such as the Electro mode in Waves Renaissance (which shortens release times for gain reduction amounts below 3 dB) and a controllable or ratio-dependent gain reduction range (to avoid over-compression at such low threshold settings), then it's even closer in sound to real upward compression. Parallel compression can achieve something similar as well.

Yes, and that is indeed upward compression you're showing. The presets I did for the Syrah will do something similar via level independent parallel compression, but it's on the full signal (more similar to the 3rd picture) since it's in parallel.

My design intent is to use the port expander with Vcc at 3.3V with two of the P0-P7 ports would be set as outputs tied to 5V logic circuits and the remaining 6 would be set as outputs tied to 3.3V logic. The I2C_SCL and SDA are communicating with a Master which also operates at 3.3V.

Are you saying that you two of the ports will be used as an input for a 5V logic and the remaining 6 would be for an output (Vcc is 3.3V so the output logic high would be 3.3V minus some change due to parasitics). Is my understanding correct? Otherwise I can also interpret what you are asking as you want 2 ports on our device to output a 5V during an output high logic which is not possible (Vcc of our device is is 3.3V so it cannot output 5V).

Our device is 5V tolerant meaning if the port is designed as an input then it can handle it even at 3.3V as Vcc. You would not want to set the port to an output high logic though because you would have a low impedance path between 3.3V and 5V.

Can I get a block diagram of what you are suggesting? Our device is an I/O but you probably do not want to set the device to be an output at 3.3V into a 5V without some kind of resistance between the two voltage rails. Otherwise you would get a short circuit. The device does not use diodes to prevent the device from sinking current.

Two of the outputs at logic High (3.3V) would be controlling logic for 5V circuits. There's a 10K pull-up from the output of the port expander to 5V rail to prevent short circuit between the rails like you mentioned.

"Two of the outputs at logic High (3.3V) would be controlling logic for 5V circuits. There's a 10K pull-up from the output of the port expander to 5V rail to prevent short circuit between the rails like you mentioned.

Thank you for the additional information. Based on what you have provided, you should be fine. The 10k is more than enough to prevent a short circuit. When the I/O is an input or even output low our device is 5V tolerant so this will not be a problem.

Downward expansion: attenuating the signal at a specified ratio when it drops below a set threshold (Turning the quiet parts further down, increasing dynamic range - think of a noise gate that doesn't completely cut the signal below threshold, but turns it down gradually.)

Downward expansion works as a counterpart to compression. Whereas the compressor compresses the dynamic range of higher volume levels, the downward expander expands the dynamic range of the lower volume levels. With downward expansion, the signal is reduced in level when it falls below the threshold level. This works in a similar way to a noise gate, but rather than abruptly cutting off the sound, it smoothly fades the volume with an adjustable ratio.

OptiFlex I/O expanders deliver input and output capacity to the powerful OptiFlex BACnet Building Controllers. Up to nine OptiFlex I/O expanders can be added to an OptiFlex BACnet Building controller.

Tesira EX-LOGIC expanders must be associated (proxied) via the equipment table to a SERVER, SERVER-IO, TesiraFORT, IDH-1 and OH-1 device. EX-LOGIC Expanders have one Ethernet port and connect to the Tesira control network. Please refer to the Supported Network Topologies section for more details

Ethernet data connection. Standard RJ-45 connector for connection with minimum CAT-5e cabling. The expander must receive PoE (IEEE 802.3af) power on this connector in order for proper operation. This connection is for sending and receiving control data with the Tesira server. The expander will not operate if it is not on a network that includes a Server-Class Tesira device.

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