Dynamic Performance and Transient "Speed" are Improved (continued)

 

The dynamic performance of virtually any component will benefit from reduced levels of electrical noise. In particular, any such artifacts that make their way into the circuitry of an amplifying stage or power amplifier carry with them the potential to reduce the stability thereof. Specifically, such a condition risks altering the total negative feedback-loop profile of the amplifier, such that new and unintended secondary loops will have been created. In that event, depending on the phase relationship of the noise signals with respect to whole, it is possible and likely that the circuit stage being contaminated thereby will develop some level of oscillation.

If the oscillation is only minor we say that it is "damped," which produces a "ringing" type effect not unlike that of a bell that has been "rung," with the sound thereof slowly decaying in amplitude over time. Such ringing may well work to reduce the affected amplifying stage or power amplifier's ability to accurately respond with sufficient speed to the desired input signal - especially signals that contain abrupt changes of amplitude and/or high frequencies. Examples thereof would be percussive instruments like drums and bells, the initial hammer strike of a piano note or the pluck of a stringed instrument, etc. In such a case, the resulting sound of these and other instruments will suffer a loss of dynamic impact and realism.

In the event that the magnitude of the oscillation is more severe, the circuit can even become unstable and/or worse... eventually fail altogether. This scenario is often the cause behind power amplifier failures, particularly those of the Class-D/Switching types. Therefore, if for no other reason every effort should be made to protect any and all circuits from exposure to noise... especially high frequency noise that has the potential to induce oscillation and ringing within a given circuit or amplifier, etc.

It would seem reasonable at this point to wonder just where such high levels of high frequency noise might originate? Basic engineering and design practices almost always involve the use of a metal chassis "Faraday Cage" to protect a given component's internal circuits from exposure to environmental sources thereof, so what's the big deal?

Well, the fact is that modern digital audio components such as DACs and Class-D / PWM / Switching Power Amplifiers employ circuitry that often operates at extreme high frequency. Worse yet, the signals they generate and use are "Square Waves," and a "Fourier Analysis" of square waves tell us that they are composed of even higher frequencies that, in those applications, extend well into the Mega-hertz bands. At this point we are talking VHF & UHF Radio Frequencies (RF) that exhibit very short "wavelengths."

OK then. As it turns out the corresponding wavelengths associate with these frequencies are often equal to or are some large percentage of the lengths encountered in the wiring and cables often used INSIDE these types of audio components.That being the case, the same wiring and cables that are employed to route the various signals around from point-to-point inside a given digital or switching component can act as either Transmitting antennas, Receiving Antennas... or both - often at almost the same time.

So now we find that our beloved component has become its own "worst enemy" by actually contaminating itself. One wire WITHIN transmits an RF signal artifact from one part of the circuitry and another wire WITHIN picks that same signal up and injects it right back into the circuitry at some other point. NOT GOOD!!! None of this behavior was ever intended or factored into the product's design, so "all bets are off" as to what the ultimate effects thereof may be.

Again... will an unintended oscillation to occur? Maybe. Will it cause an increase in distortion and/or work to limit the component's transient/dynamic response? Probably. Will it cause the component (most likely in the case of a Switching Amplifier) to become unstable and less reliable? Possibly. Will it do so to the point that the component will eventually become unstable enough to self-destruct? It very darn-well could.

Everybody knows that these newer Class-D/Switching amps can be "finicky" at times. Now we know one very good reason why, and that's because while their designers may be well-versed in Switching circuit design, few are actually trained in the field of RF Engineering and Electro-Magnetic (EM) Wave theory and practices. As a result, their circuits often work great, but their "implementations' into a final product... sometimes not so much.

In light of these facts, it is the proper shielding and grounding of all wires and cables within a given audio component that is the cornerstone of TDSS D.R.R.T. treatment.

Please NOTE:

An important process that also has the potential to greatly limit a component's ability to accurately reproduce transient signals and dynamic performance is that of circuit "SATURATION" effects. Among other reasons, the Saturation of a circuit can take place as a result of being subjected to extreme high frequency signals or oscillations as described above. For the sake of brevity and to avoid repetition though, we will not list that information here. For a more in-depth review of the matter and how circuit saturation works to reduce dynamic performance, please reference the High Frequency Switching Noise section of this website.

 

INDUCTANCE - THE BANE OF GOOD TRANSIENT PERFORMANCE:

TDSS has discovered that, due to the relatively low source-impedance of most generally well-designed driving stages that make up the different sections within various audio components (Power Supplies, Filter Sections, Amplifier Stage Outputs, etc.), our custom ribbon-foil conductors actually outperform and are superior to the often highly praised "Litz Wire" cables/wires that seem to have been quite "en vogue" for many years now. Why is this important? We will explain further below.

In simplest terms, Inductance is a property of electricity that resists or attempts to limit the rate at which current flow is able to change. As a very similar analogy, Inductance is similar to mass and how inertia tends to resist a massive body as an applied force attempts to cause it to speed up or slow down (i.e., accelerate or decelerate). A heavy object like a locomotive sitting still can be made to move if enough force is applied, but the faster you want to make it move from its rest position, the more force you'll need to supply.

The same is true when trying to bring the same locomotive to a stop when it is already moving along at a given speed. Trains just can't stop very quickly (so when crossing a set of railroad tracks with one approaching it's best not to try and outrun it). Conversely, a small mass such as a .22 caliber bullet can be made to move very fast with a relatively small amount of force. In either case, the amount of mass is similar to the amount of Inductance in an electrical circuit.

So as we can see, a small amount of Inductance is a good thing when we are trying to get current to flow very quickly - as in current flowing through a wire or circuit when that current represents a fast changing audio signal. If we want the fast transient signals that are always present in music to be accurately reproduced, then ideally the circuits and wires they flow through would exhibit no Inductance whatsoever. Unfortunately (at least in this case), all wires and other electrical conductors will exhibit some amount of Inductance, even though that amount may be quite small.

Therefore, our goal is to "minimize" any Inductance as much as we can in the wires and cables that we use to transport current from one location to another inside an amplifier. Similarly, that means it would be best if the speaker cables we use in our stereo system were to exhibit a very small amount of Inductance as well. Very simple.