Dynamics..

[0XI0]

Next time you ChatGPT "difference between latency and time constant", at least try paying attention to the whole thing. The last sentence in particular is pretty fucking important.

"essentially, latency focuses on the delay in a single event, while time constant describes the overall response time of a system to a change."

this is pretty important

 

[DLC86]

No, terms are not interchangeable at all in this case.
Latency is what is produced by a delay effect, time constant is e.g. the attack time of a compressor.
You wouldn't call the attack time "compressor delay" or "comp latency", would you?

 

[0XI0]

if I'm referencing one single gain stage inside a whole other thing, the time it takes for that stage to do its thing, is its own latency. separate from that single gain stage's own time constant (the shape of its thing). but whatever. you could slow the recto cold clipping down so much that it's 10ms behind the fundamental if you wanted. that's a deliberate latency in a parallel signal path

 

[Boudoir Guitar]

I thought possibly the google search string "time constant DC vs AC circuit" might move the discussion forward. Keeping in mind that guitar pickups produce fairly complex AC signals with low E fundamental frequency of about ~90Hz (period of ~12ms) and higher notes and harmonics all having higher frequency and shorter periods. Two parts seem very relevant.

First is the simple AI description:

"In a DC circuit, the time constant represents the time it takes for a capacitor or inductor to reach approximately 63.2% of its final voltage or current value when a voltage is applied, while in an AC circuit, the time constant is still calculated the same way, but its meaning is less straightforward"

Next, the Quora thread that came up on first page of hits to that search does a pretty decent job of qualitatively explaining this "less straightforward" meaning of time constant in an AC circuit:

In the case of AC circuits, the RC time constant tells you which signals the circuit passes through and which signals the circuit filters out. An RC circuit acts as a high pass filter which passes high frequency signals and blocks low frequency signals.

When you apply an AC current to a capacitor you are basically sticking some charge onto the capacitor and then taking it off. If you do this at a low rate, smaller than the time constant, then the capacitor has time to discharge. But if you put the charge there rapidly, at a speed much greater than the time constant, the capacitor doesn't have time to discharge. In this way, you can pass high frequency signals through the capacitor.

The point at which half of the power you are applying to the circuit is transmitted is typically referred to as the 3 dB frequency. For an RC circuit, this 3 dB frequency is given by this expression.

 

[Lysander]

I thought possibly the google search string "time constant DC vs AC circuit" might move the discussion forward.

Man, don't bother. It's like trying to discuss EE with a pigeon.

I've seen people confused about latency before, but no one being so confidently wrong.

 

[Ed DeGenaro]

Maybe this might be interesting to some on the conversation…

 

[Boudoir Guitar]

Maybe this might be interesting to some on the conversation…

View attachment 35805

View attachment 35806

My take on what is being said in these chunks of text: Tube amps are non-linear, and the nature of that non-linearity varies with time over 20ms or so. That is, tube amps introduce compression, and the manner in which they compress changes over time.

That is not delay though. It's like a guitar amp acting like a compressor with a robot on the control knobs of the compressor and adjusting those knobs over a ~20ms window.

It seems you are using the terms "fast" and "slow" in the same way that Jay was using "hard" and "soft".

 

[Ed DeGenaro]

My take on what is being said in these chunks of text: Tube amps are non-linear, and the nature of that non-linearity varies with time over 20ms or so. That is, tube amps introduce compression, and the manner in which they compress changes over time.

That is not delay though. It's like a guitar amp acting like a compressor with a robot on the control knobs of the compressor and adjusting those knobs over a ~20ms window.

It seems you are using the terms "fast" and "slow" in the same way that Jay was using "hard" and "soft".

Read my previous post about coupling caps discharging (in the pre-amp).
Although correct it isn’t a delay but there’s a hiccup in rise of the attack.
And yes obviously there’s compression and sag as a power amp.

But all that really falls under how it feels. And that used to get to me, but then I was still of the opinion that an amp should conform to my playing.
Whereas these days I see things as me having to adjust to the amp.

 

[Boudoir Guitar]

Read my previous post about coupling caps discharging (in the pre-amp).
Although correct it isn’t a delay but there’s a hiccup in rise of the attack.
And yes obviously there’s compression and sag as a power amp.

But all that really falls under how it feels. And that used to get to me, but then I was still of the opinion that an amp should conform to my playing.
Whereas these days I see things as me having to adjust to the amp.

I’ve read everything you’ve written and it all reads to me like an attempt to over complicate the objective technical phenomenon to better comport with what I agree is a fairly complex subjective experience.

 

[EOengineer]

Overall dynamics will be a function of how the model handles input, and then the capabilities of your playback system. I do think there are limitations in the digital realm but most of us struggling with dynamics are most hamstrung by our playback systems.

 

[Orvillain]

Man, don't bother. It's like trying to discuss EE with a pigeon.

One of those 1 legged ones in Leicester Square? The ones who hop around, vaping grapefruit juice or whatever?

 

[Lysander]

One of those 1 legged ones in Leicester Square?

If only. That'd be interesting.

 

[Boudoir Guitar]

Man, don't bother. It's like trying to discuss EE with a pigeon.

I've seen people confused about latency before, but no one being so confidently wrong.

I’m no engineer, either, tbf.

 

[DLC86]

I love when people with very basic knowledge about electronics believe they can find something missing in amp modeling before someone who has spent a couple decades doing that as his main job.

 

[DrewJD82]

Oh boy, I can feel those Mt Stupid/Dunning Kruger memes warming up.

 

[the swede]

How nerdy can things get? Really?

 

[mercifulfuzziness]

 

[FractalAudio]

Latency:
Latency is a simple, one-dimensional parameter that indicates the time delay between the input and output of a system. If a signal is input to a system, latency is the amount of time it takes for that signal to appear at the output.

Time Constant:
One of the basic laws of the universe is that many systems obey a first-order differential behavior. The rate of change of the state is proportional to the difference between the state and the input and inversely proportional to the product of the inertia and the resistance.

Since this is a cold winter day an appropriate example is a bowl of soup. If we heat the soup up and then remove the heat source the soup cools rapidly at first and then more and more slowly as the temperature approaches the ambient temperature. The larger the volume of soup the greater its inertia or "thermal mass". The better insulated the container the greater the "thermal resistance". A quart of soup in a thermos will cool much slower than a cup of soup in a metal cup.

Mathematically we write this as:

dT/dt = (T - Ta) / (R * C)

This is a linear, first-order Ordinary Differential Equation (ODE). The rate of change of the state (temperature, T), dT/dt, is proportional to the difference between the temperature and the ambient temperature (Ta) and inversely proportional to the thermal mass, C, and the thermal resistance, R.

We can obtain an explicit solution to this equation by integrating both sides and using some substitution tricks (chain rule). We end up with:

T = (Ti - Ta) exp(-t/(RC)) + Ta

At time t = 0 this evaluates to Ti, which is the initial temperature. As t -> infinity the exponential approaches 0 and T approaches Ta, the ambient temperature.

This is known as exponential decay. The rate of the decay is given by the time constant, R*C. The larger the time constant the slower the state decays. This time constant is often denoted by the Greek letter tau.

The basic form of exponential response is therefore written as:

y = A exp(-t/tau)

When t = tau the expression evaluates to y = A exp(-1) = A * 0.368. So we say that the time constant is the amount of time for the state to decay to 36.8%.

Many systems exhibit this basic behavior. A hockey puck sliding on the ice. The puck slows down rapidly at first and slower as it's velocity approaches zero. The greater the mass of the puck the longer it takes to slow down. The less friction (resistance) the longer it takes to slow down.

Incidentally thermal mass and thermal resistance are directly analogous to capacitance and resistance in an electric circuit and use the same symbols, R and C. One of the building blocks of electronic circuits is the RC network. It exhibits exponential decay with a time constant defined by R * C.

If we write the ODE for an RC circuit using Ohm's and Kirchoff's laws we get the mesh equation:

C dV/dt = (V - Vin) / R

Rearranging we get

dV/dt = (V - Vin) / (R * C)

which is the exact same form as our bowl of soup equation.

As we see latency and time constant are two completely unrelated terms.

The internet has given everyone a voice. So you have two choices: talk or listen. The problem is that many people want to talk but they don't want to listen. They spout nonsense and drop technical terms while being oblivious to what those terms even mean. If you don't understand the above, which is literally Differential Equations 101, then perhaps you should listen for a change.

 

[djd100]

Thanks Cliff, much appreciated!

 

[Orvillain]

Latency:
Latency is a simple, one-dimensional parameter that indicates the time delay between the input and output of a system. If a signal is input to a system, latency is the amount of time it takes for that signal to appear at the output.

Time Constant:
One of the basic laws of the universe is that many systems obey a first-order differential behavior. The rate of change of the state is proportional to the difference between the state and the input and inversely proportional to the product of the inertia and the resistance.

Since this is a cold winter day an appropriate example is a bowl of soup. If we heat the soup up and then remove the heat source the soup cools rapidly at first and then more and more slowly as the temperature approaches the ambient temperature. The larger the volume of soup the greater its inertia or "thermal mass". The better insulated the container the greater the "thermal resistance". A quart of soup in a thermos will cool much slower than a cup of soup in a metal cup.

Mathematically we write this as:

dT/dt = (T - Ta) / (R * C)

This is a linear, first-order Ordinary Differential Equation (ODE). The rate of change of the state (temperature, T), dT/dt, is proportional to the difference between the temperature and the ambient temperature (Ta) and inversely proportional to the thermal mass, C, and the thermal resistance, R.

We can obtain an explicit solution to this equation by integrating both sides and using some substitution tricks (chain rule). We end up with:

T = (Ti - Ta) exp(-t/(RC)) + Ta

At time t = 0 this evaluates to Ti, which is the initial temperature. As t -> infinity the exponential approaches 0 and T approaches Ta, the ambient temperature.

This is known as exponential decay. The rate of the decay is given by the time constant, R*C. The larger the time constant the slower the state decays. This time constant is often denoted by the Greek letter tau.

The basic form of exponential response is therefore written as:

y = A exp(-t/tau)

When t = tau the expression evaluates to y = A exp(-1) = A * 0.368. So we say that the time constant is the amount of time for the state to decay to 36.8%.

Many systems exhibit this basic behavior. A hockey puck sliding on the ice. The puck slows down rapidly at first and slower as it's velocity approaches zero. The greater the mass of the puck the longer it takes to slow down. The less friction (resistance) the longer it takes to slow down.

Incidentally thermal mass and thermal resistance are directly analogous to capacitance and resistance in an electric circuit and use the same symbols, R and C. One of the building blocks of electronic circuits is the RC network. It exhibits exponential decay with a time constant defined by R * C.

If we write the ODE for an RC circuit using Ohm's and Kirchoff's laws we get the mesh equation:

C dV/dt = (V - Vin) / R

Rearranging we get

dV/dt = (V - Vin) / (R * C)

which is the exact same form as our bowl of soup equation.

As we see latency and time constant are two completely unrelated terms.

The internet has given everyone a voice. So you have two choices: talk or listen. The problem is that many people want to talk but they don't want to listen. They spout nonsense and drop technical terms while being oblivious to what those terms even mean. If you don't understand the above, which is literally Differential Equations 101, then perhaps you should listen for a change.

Yeah but do you like Tool and ISIS??

<ducks>