Description:

This is the latest version of the revolutionary preamp. It has only been used as a dealer demo. This is an attempt to make the H-CAT™ amplifier method more understandable to the average audiophile reader and to clear up any misconceptions about the nature of H-CAT™. It has been difficult thus far to introduce a product so radically different in its operation to the audio industry. All I ask is that you be open-minded when it comes to learning about H-CAT™ and how it deals with amplification.

It has come to my attention that many audiophiles visiting my web site believe that H-CAT™ is using special circuitry to manipulate the audio signal and somehow generate the illusion of 3D imaging. This could not be farther from the truth. In fact it is just the opposite.

It is understandable that many would come to this conclusion because the only exposure of 3D type circuitry thus far has been introduced by designers who feel that they have the solution to dimension and space cues found in recorded material. They do not.

Several “holographic” products come to mind - all of which rely on the introduction of signals added to the original stereo channels to produce a phenomenon of dimension to the listener.

Here is text taken directly from literature on such a product…

“This is accomplished by sending a complex crosstalk signal from the left and right speakers in addition to the normal program. These extra signals are virtually identical to the unwanted second sound arrivals but they are out-of-phase with them and they cancel each other out. The result is a more three dimensional and wider soundstage, where the positioning clues are restored.”

This was a clever circuit arrangement that was designed to “overcome a problem in obtaining accurate sound reproduction”

Here are the facts as plain as possible:

H-CAT™ does not operate this way nor does it involve the use of opposite channel information or phase inversion or crosstalk or anything even remotely close to this.

H-CAT™ does not take any portion of the left channel information and introduced it into the right channel

H-CAT™ does not take any portion of the right channel information and introduced it into the left channel

H-CAT™ does not use any phase shift to create the illusion of dimension or space. Zero.

H-CAT™ does not use negative feed back (NFB) to remove distortion.

H-CAT™ channels are totally isolated from each other and are completely independent.

H-CAT™ uses common controls for volume settings (but still independent)

H-CAT™ is 100% pure analog and has no sampling or digitizing or processing of any kind.

Up to this point there does not seem to be anything special or unique about a simple 2 channel amplifier circuit. Except for one thing – the H-CAT™ method of amplification – the circuit itself - is virtually distortion free and does not rely on conventional NFB to suppress harmonic distortion. Everyone knows that doesn’t work.

Another misconception about H-CAT™ is that the Wavefront Timing Control is the gadget that somehow manipulates the audio signals in such a way as to CREATE the illusion of space and dimension. It does not.

By now you probably saying “wait a minute, the users who have posted to web threads all report adjusting the WTC and having the soungstage and instruments "pop out" at one particular setting (therefore) the WTC control MUST be the gadget or circuit responsible for creating the illusion of a transparent soundstage”

No actually it is not. In fact you can omit the WTC control completely and still have transparent 3D imaging. The only problem is in order to make this happen it would require that you have a power amplifier and DAC (or phono stage) of the same distortion free caliber as the H-CAT™ preamplifier. Since you don’t – it has become necessary to implement the Wavefront Timing Control. This control allows the output of the H-CAT™ preamplifier to successfully interface with the rest of your system.

Defining the problem

Electrical amplifier circuits whether solid state or tube design have imperfections in the way they handle the simple task of taking an input signal and delivering a larger (amplified) version at the output end of the circuit. It is essential to first grasp the concept of how a signal “travels” through a circuit. The idea that a signal enters the input terminal and leaves at the output terminal is just not true. The output signal is merely a suggested rendering of the input signal – not the same signal.

The output signal is typically a voltage potential that is changed by applying a corresponding change to the input (potential). It can be seen therefore that the signal itself does not travel through the stage but rather the influence of the input changes are passed along (from device to device) until the output is taken from the final device in the stage.

This is true even under the simplest of circuits like a single triode. The input signal voltage is applied to the grid (resistor), which in turn varies (influences) the plate current causing the plate voltage to vary in a larger fashion thus producing voltage gain. The output signal does not share the same current as the input signal but represents an isolated bigger “copy” of the input signal. In this case it is also phase inverted.

The final signal contains a degree of distortion (errors) that is based on the instantaneous efficiency of the “influential” part of the circuit. In short, it is how the circuit behaves when asked to “move”.

Take the case where a given circuit has 6db of gain and is non-inverting. This would mean that a 1V peak-to-peak input signal would provide a 2V peak-to-peak output signal or a 2:1 ratio. Let us for the moment assume it is perfect in performance and has no distortion.You should be able to take a snapshot in time of the output voltage – then divide it by 2 and know the exact input voltage. For example, at a frozen moment in time you measure +1.40V out (divide by 2) and you expect the input voltage to be exactly +0.70V and so on.

In the real world there will be times when the output divided by the input will not equal (in this case) exactly 2. If you apply exactly 1V in and you measure 1.999V out – then your instantaneous gain is 1.999 (not 2) therefore it has less than 6db of gain AT THAT MOMENT when the ability of the input to influence the output has become weaker. This is an indication that the apparent speed or velocity of the “traveling” signal has slowed down since the output has fallen short of the theoretical potential of 2.0. This in turn changes the shape of the output slightly altering its “pitch”. Yes, with no moving parts – it is possible to alter the speed and therefore the “pitch” of the traveling signal. This minor deviation from the true shape has caused the original signal to alias itself as a different frequency – at least for the short period of time when THAT segment of the signal did not comply with the ideal 2:1 ratio. This is a form of velocity induced "shape shifting" that produces harmonics. It can also pass through a region where the gain is slightly higher than 6db thus causing a slight acceleration in velocity. As these minor fluctuations in speed occur, the listener is exposed to a sonic effect impressed upon each sound object that is essentially out of focus and "wobbling". This is Doppler. This is what happens in virtually ALL playback systems.

Defining the solution

H-CAT™ is the only amplifying method that can monitor and maintain constant velocity. It is accomplished by special built-in detectors. Unlike NFB which does a crude comparison of input and output signals, these “Doppler” detectors are placed in strategic areas of the circuit to validate the exact velocity of the circuit and ensure that it does not vary. In other words if you expect a gain of 6db or an amplification factor of 2 - the Doppler detector coupled with an exact velocity countermeasure will maintain an ampification factor of exactly 2 at all points along the swinging output voltage. In other words through 360 degrees of operation. This Doppler Control System is not only extremely sensitive but reacts in real time. The solution or “correction” is applied by way of either red shift (de-acceleration) or blue shift (acceleration) circuits that are linked directly to the Doppler detectors. Therefore, since the correction happens internally, prior to the signal appearing at the output terminal - you never experience distorted output even for a brief moment. With the use of a proprietary control technique found only in H-CAT™, the gain can be maintained at exactly 2.0 with a tolerance better than +/- 0.000000001

This gives you the mathematical stability of a digital domain but in the pure analog world. The output of H-CAT™ is metered at a constant velocity and finite changes in pitch are omitted. Everything is in focus, with unlimited depth of field.

There is only one other place in nature where this caliber of accuracy occurs - and that is when sound waves travel through air at constant speed of Mach One. Your brain recognizes the Doppler free property and is convinced it is air - not electronics. If you can cause your hi fi system to also have a fixed gain with the tolerance you see above - then your electronic segment of the entire chain takes on the property of air and your electronics are “cloaked”. The electronics will appear to have nothing to do with the music in front of you. The recording venue is exposed as original air space and is coupled to the air space in your listening room. Sound from voices and instruments appear to be coming directly from the object to you through a medium of nothing but air.

Developing the Wavefront Timing Control

Earlier versions of H-CAT™ like the P-12A did not have a means to adjust the wavefront. It meant that if you were lucky and your system synergy was such that H-CAT was a good “match” then you would be able to hear the benefits of its Doppler free nature. If it did not mate well with your power amp or CD player / phono stage then unfortunately you would experience a strange phenomenon. It would sound totally “electric” and irritating. This is due to the left over Doppler that is caused by the sum of your other components. This is why early feed back from the field has been mixed. Some audiophiles loved it and some hated it depending on their system.

As a result I decide to create a scientific “tool” for myself to enable the microscopic trim of the final velocity so I could set it once and for all at the factory and seal the adjustment. I figured this would give me an average degree of compatibility with most systems. The control itself is actually making ultra tiny changes (in parts per billion) to the Doppler detectors internal reference. Thus “fooling” the detector into thinking it has discovered velocity errors in either the lead or lag direction. What happened next was a surprise to me. I found that I could get the velocity trimmed “perfect” in MY reference system. Then when I switched source material to a different CD - it sounded great but I was curious to know if my “trim” was still dead on. After making a slight adjustment (3 digits) - it caused the new material to “pop out” as a natural acoustic Doppler free display. Of course as a designer I had to go back to the original reference CD and verify if it is a different setting or did the velocity trim somehow drift. I did have to return it to the original setting to restore the “magic” I heard in that first recording. The result was both a disappointment and a delight. I was disappointed that I could not simply set it and forget it. But I was delighted to realize that if I were to provide this tool directly to the end user, it would virtually guarantee that it would match any system. So that’s what I did. As you may know the P-12B was designed to include a manual front panel control allowing users to trim the velocity. This gave H-CAT™ a far better track record for acceptance because more audiophiles were able to recognize the benefits of this design and understand why other audiophiles were so happy with their units. They could duplicate the results in their own system. It soon became obvious that not only is there a different setting for different record labels (due to the electronic path using different brands of mic preamps, mixers etc.) but when you switch from your CD player to your phono stage - the final trim can be quite different due to the analog stages in the DAC.

Even more interesting was the eventual verification that indeed everyone’s system was different. H-CAT™ owners would call each other and compare notes about what they found to be the “true” WTC setting in their system. These are custom settings and rarely did they match.

The Remote Control

Complaints about having no remote finally got to me and I realized I would have to develop a remote volume control circuit that would maintain the caliber of purity realized by the main line stages. The solution was a new stage containing a digitally controlled resistor ladder with taps that are fed into its own H-CAT™ “wrapper” complete with its own Doppler detectors to ensure consistent velocity management as the volume is adjusted. The result is pure analog signal path.

However, the real beauty of having a remote control was not for the volume but for the Wavefront Timing Control. Now you can sit back in your listening position and adjust the WTC on the fly for perfect trim. Having the extra control electronics on board also allowed me to store the learned “best” setting for that source in a memory slot tied to that input selection. So if your CD player sounds best at -6 and you switch to your phono input and trim it to +4, when you return to CD it will automatically reset your WTC to -6.

Home Theater Bypass + Wavefront Timing Control

The home theater bypass (HTB) is technically not a bypass since the audio feed from your video system still passes through the H-CAT™ line stage. However, in this case the volume setting as well as the WTC setting are both stored in a memory slot. Once you dedicate an input to the HTB, upon selecting that input, H-CAT™ will reset the volume to a preset level. The advantage of this is that the Wavefront Timing Control is still fully engaged in this mode. This allows you to trim the velocity of the soundtracks of your favorite movies. When switching to this mode - the letters “VOL” on the display will switch to “HTB” to remind you that the volume setting is independent for this input and is stored in memory.

Making the most of H-CAT™

It is important to note that two conditions can give you very undesirable results. One condition would be the misalignment of the Wavefront Timing Control. If the compressed and rarified images are not registered (time aligned) then you will hear a bloated and out of focus final image. The second and more common condition is the incorrect grounding of the overall system. This is one of the most difficult issues to deal with in today’s hi fi systems. Audiophiles have spent a small fortune obtaining isolation transformers, filter boxes with special power outlets for digital and separate outlets for analog and so on. Some have dedicated lines for each component in their system. Some have converted part of their system to balanced power. All of these newly added devices may help but it also makes the equation for ideal grounding more complex. The bottom line is that there should not be ANY ground loops in the system when you’re done. If a loop exists it will surely interfere with the operation of H-CAT and make it nearly impossible to use the WTC effectively. Even if you have no “noise” in your system when you (pause) the source material - this does not guarantee that you do not have ground loop(s). The manual recommends a "star" ground where the preamplifier alone is grounded to a wall outlet and everthing else is ungrounded. This is the only way to assure you have no ground loops. Please take the time to get it right - the results are worth it.

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