Holographic imaging

Having worked with a good number of master tapes, I might be able to help with the terms here.

Bloom: a function of harmonic distortion, part of a spectrum: neutral, warmth, bloom, thick or fat, bloated, muddy all describe distortion, usually lacking odd orders, so it is more of a coloration than an irritant (generally associated but with not limited to tubes). Odd-ordered colorations are harsh, chalky, clinical, bright, etc (generally associated with but not limited to transistors).

Thus an amp that is transparent will lack bloom (although it can sound natural), as transparency comes from a lack of distortion.

Holographic imaging is a function of soundstage. It comes from the ability to reproduce low level detail and maintaining phase relationships, so it requires wide bandwidth for the latter and low distortion at low levels for the former.

Transistors have traditionally had difficulty with retrieving low level detail, and so the slight ambient cues that exist around an individual image in a soundstage are less likely to get reproduced. This will give the image a 2D quality in the soundfield, and simultaneously cause it to stand out more. Newbee correctly identified this phenomena, although I would like to add that as the slight ambient cues that exist around each image get added, there will be the effect of a more 3D image, but also a more homogenous overall effect in the soundstage as the relative size of the 3D image will be larger than that of the 2D image of the same thing.

Tubes are better at doing low level detail, and so are more likely to have 3D images and greater ambient information, adding to the holographic effect. Any processing in the signal chain that is not part of the original recording can be regarded as a form of distortion, as most imaging systems rely on altering phase relationships to obtain 'holographic' effects. Tubes are not so great at keeping phase relationships correct, as often tube amps have less high frequency bandwidth, owing to the presence of an output transformer, but there are nowadays amps with wide bandwidth OPTs and of course OTLs :) that overcome this issue.

If phase issues exists at or very near the upper limits of human hearing, some interesting imaging effects can occur that seem to enhance the 'holographic' effect and I would not doubt that this has served as an inspiration to some processor designers! At any rate this accounts for why some tube amplifiers that are not great performers in the bandwidth department can have some apparently 'enhanced' imaging effects.

If there are no phase anomalies and low level detail is maintained, many 2-mic recordings will exhibit a height phenomena, which is a function of the mic placement in the soundfield.

Having master tapes so you **know** what the recording is supposed to be like is paramount to sorting this stuff out!

Sorry for the diatribe...

Mapman, my experience has been that anywhere you can involve tubes in audio will help, as long as the tubes are in a competent circuit :)

Doppler effect??! I would think that if there is any doppler effect in the recording, you would certainly **not** want to compensate for it. Otherwise you would not be playing it back right :)

I get the feeling that a lot of these holography systems that have appeared over the years are aimed at those who have a lack of resolution in their systems- and can stand listening to an effect, rather than the music.

Sorry for the criticism, but I've always felt bad for people who've laid out the cash over the years for such things. IMO/IME the best performance in the audio system will be when there are as few processors/audio building blocks between the recording microphones and the playback speakers as possible.

Tbg, sorry, but, **there is no doppler effect in an amplifier**! If a designer of a 'holographic processor' tells you something like that, turn around and run as hard as you can!

You have propagation delay in any amplifier circuit but that does not create doppler effect, in either an amplifier or a preamp. It is possible to get some in a loudspeaker driver that has wide range and high excursion, but that can be dealt with by proper speaker design. IOW, if 'doppler effect' is really the reason, its at best a fix for a problem that does not exist. At worst--? Certainly such a 'process' can be considered a distortion in the overall output...

Roger, I have many times had test tones being played through loudspeakers with microphones and frequency counters in use- never in the years of working in and out of the recording studio have I ever observed a connection between gain and pitch as you assert, nor have I until now, known anyone to make such an assertion. How have you measured this effect to prove or disprove your hypothesis and add what outcomes does it suggest?

I have also been able to alter the speed of the amplifier circuit (speed in this case being equal to slew rate) and again seen no measurable effect on pitch. How were you able to test your hypothesis in these conditions?

For a given change in gain, say 20 db, how much change in pitch will be measured?

So- how do you measure Doppler effect in an amplifier?
What is the unit of measure? What test equipment do you use for this? How much DE is reduced by your circuit?

Guitar and synthesizer players often use a tuning device that mutes the output of the guitar so the musician can tune the instrument silently, then after that, regardless of volume, the pitch will be found to be in tune. This does not seem to matter whether there are tube or transistor amps in the signal chain.

IME again, I have found that the measurable propagation delay in an amplifier circuit does not change with the input level. How do you square this with your hypothesis? Do you have a different meaning for the word 'speed'? If so, could you define it?

Again IME by changing the volume in my system, I've never experienced a change in the soundstage perspective- that of being in the 10th row as opposed to the 2nd row for example. I would describe sound as seeming the same 'distance' away, just not as loud -certainly not a change in perspective! Does your hypothesis support exceptions or does it predict that the experience of perspective is universal?

Since when listening I am usually seated, why exactly should I care if there is Doppler effect if I move? In a real life situation, would you not also experience Doppler? It seems to me that you would want to preserve the Doppler effects of real life music. What am I missing?

Roger, the term for the time it takes a signal to pass through an amplifier is called Propagation Delay. It is usually a constant at all frequencies within the pass band of the amplifier circuit. But- has nothing to do with Doppler Effect.

I noticed that you did not answer any of my questions. Do you have intention of doing so?

Alright Roger, how do you square:

Yes I am familiar with Propagation Delay and all the classic textbook terms that pertain to amplifiers.
None of which was helpful in troubleshooting the real issues facing a relatively simple task of making a small signal larger.

with

What I am referring to with velocity is the lateral or horizontal speed of the circuit. IOW my interest is in the manner that a given input signal travels from input to output and more importantly is it (the velocity) constant.

Not to put words in your mouth, but it looks very much to me from the second comment (which is a description of Propagation Delay) that you are contradicting the first. Am I missing something?

I'm really interested in seeing the answers to my questions!

Roger,

What happens in-between is not monitored - it is assumed.

This is not true; this is in fact what Propagation Delay **is**. Any opamp designer and any amplifier designer worth his salt will be quite concerned about that number!

So- its only when volume is *changed* that pitch is affected? So as long as we don't change the volume, there's no worries.

It must be a subtle effect as there are Voltage Control Amplifiers on my synthesizer that I routinely use to modulate my volume with a Low Frequency Oscillator (as an effect), but I've never associated that with a pitch change nor has anyone mentioned it on the various synthesizer groups I monitor (and they talk about a lot of stuff like this). My instrument tuner can't detect a difference either!

So- you did not answer the question- over a 20db range, how much pitch change will be observed? Let's assume that the volume is being changed by 20db over a period of 1/2 second.
I assume you must have documented effects like this in order to prove or disprove your hypothesis, so you must also therefore be able to predict the pitch change if you know the volume change over time. there must be a formula? Like Pitch=something something X frequency divided by time :)

Roger, 1/100th of a db? Really? So if the change in pitch cannot be detected by **musical instrument** tuning devices (which are quite sensitive, much more so that any frequency counter I've seen), it follows that it cannot also be heard by the human ear, but you say it can. How do you square your apparently contradictory statement?

The **amplifier** is changing gain? What is the mechanism for that?

You've still not answered any of my previous questions yet. I've distilled them below:

1) How have you measured this effect to prove or disprove your hypothesis and add what outcomes does it suggest?

2)Given that a change in the speed of the amplifier has produce no measurable result, how were you able to test your hypothesis?

3)For a given change in gain, say 20 db, over a period of 1/2 second how much change in pitch will be measured?

4)How do you measure Doppler effect in an amplifier?

5)What is the unit of measure?

6)What test equipment do you use for this?

7)How much DE is reduced by your circuit?

8)IME again, I have found that the measurable propagation delay in an amplifier circuit does not change with the input level. How do you square this with your hypothesis?

9)Does your hypothesis support exceptions or does it predict that the experience of perspective is universal?

10)Since when listening I am usually seated, why exactly should I care if there is Doppler effect if I move?

11)In a real life situation, would you not also experience Doppler?

12)It seems to me that you would want to preserve the Doppler effects of real life music. true/false?

Roger,

The reason you can’t see it with a THD analyzer is because it is way too subtle to show up. If somehow you alter the gain/velocity by a factor of 2:1 double the velocity! Then your 1khz signal will shift up to 2khz. A full octave away! That is represented by the spike you see on a spectrum analyzer at the 2khz mark. The length of time it spends at this accelerated velocity will determine the size of the spike.

Within the statement above occurs a contradiction. This one (the 3rd I have encountered since I began engaging in this conversation), has the spike "too subtle to show up" while in nearly the same breath is apparently visible at "the 2KHz mark". So which is it- really?

Roger, you don't seem interested in answering my questions. Its been a while since I first posted them and you have made a number of posts in the meantime.

So: I don't think you have any intention and that is borne out by your actions.

You have contradicted yourself at nearly every turn, I could pass that off as poor writing skills but re-reading them has brought me to a different conclusion.

http://en.wikipedia.org/wiki/Occam's_Razor

The explanation of a circuit that does something, based on a principle that cannot be measured in any way by any type of test or laboratory equipment, cannot be quantified, verified, with no mathematical relation or formula, cannot be heard and can only be explained yet contradicted by the designer of the circuit is a complex explanation.

The simple (correct) explanation is a circuit that either does nothing, or does something, and the principle behind it is simple (for example, a tonal coloration), and whatever it is really doing is something that the designer refuses to divulge or is clueless about.

IMO we are dealing with a case of the Emperor's New Clothes. IOW I'm with Tvad on this one.

Roger, obviously you have spent no time with these musical instrument tuners. I have. They are so sensitive that they can show variation in pitch that is really hard to hear. The one I have is a rack mount unit and can show a deviation in pitch of one whole note over nearly that entire width. Its when you get to the center that its hard to hear what its telling you.

It is a fact that some people hear pitch better than others, but from what you are saying, none of this has any bearing on your 'phenomena'.

So: we still have an unquantifiable phenomena, no math to support its existence (whereas there is math to support the existance of anything else real in audio). On this point I should point out that as a manufacturer I have heard plenty that did not seem to show up on the 'scope- until I got a better scope that is... and while I agree that test equipment comes well short of what we hear, it is only because it is measuring the wrong things, not because those things can't be measured! They all do, after all, exist within the medium of electronics.

So it can't be measured, no math, no proofs of hypothesis nor any sought, if I get the previous posts, the pitch variation so slight as to be well below audibility, therefore the 'gain variation' caused by an amplifier's distortion is also too slight to be audible or measurable (since in any amplifier the gain is something we **do** measure)... conceded by a comment about 100th of a db (or less), and apparently, other than listening, no other way to explain that this is the right hypothesis. IOW, because an effect is heard, therefore it **must** be Doppler Effect! -and can't possibly be anything else...

Occam's Razor is still suggesting a simpler explanation: the whole thing is a made up story and the actual truth of the matter is something far simpler. For example I know that slight tonal enhancement at certain frequencies can cause the image to jump out, and we are talking here about 'Doppler Effect sensors' that are sensitive to a '100th of a db', yet the effect cannot be measured by any test equipment- but it can by the 'special' sensors! So I will point to this as another glaring contradiction.

If it were me, and in the face of the Occam's Razor, the amazingly far more complex explanation I knew to be the right one, I would have hooked these 'detectors' up to some sort of device to measure their output (they are affecting the circuitry in the audio path anyway, so they have an output...). This has not happened, and yet is the blatantly obvious thing to have been done a long time ago, and I think the explanation for why that has not happened is also obvious.

Tbg just to clarify some points, you are right, I'm not a fan of the THD spec. I feel that it does not matter how much distortion an amp or preamp makes **so long as those distortions are not found objectionable to the human ear**. By the same token I feel that it matters *a lot* about the distortions that the ear *does* care about. IOW its all about the Rules of Human Hearing, which I think are the most important things in audio- everything comes from that. For more information see

http://www.atma-sphere.com/papers/paradigm_paper2.html

The debate about 'objectivist vs. subjectivist' which has been emerging on this thread has been an aspect of the Voltage vs Power Paradigms. You might think I am objectivist due to the way I have been challenging Roger, but I feel the Rules of Human Hearing are what are important, and not trying to make an amp or preamp conform to ideals that only exist on paper.

What we are talking about here is that there can be specs on paper that don't matter to the human ear- the old argument about how you can hear things but not quantify them. What I have found in the investigation of the paradigms is that all that is really happing is that we are simply not measuring the things that are important. If we did, the specs on paper would tell us how a product would sound. Its really that simple. The point is- one way or another, it really is all measurable if you know what to look for and do not limit your investigation to the blinders of the Voltage Paradigm.

The same is true with Roger. He could *easily* measure what he is talking about. After all, did he not devise his Doppler Effect detectors? They are, according to his website, able to correct the behavior of his circuit to eliminate or substantially reduce the phenomena. If they are able to modify the operation of his preamp, then they are also a tool for measurement. Where I see his arguments failing is that anyone in possession of such devices would be *acutely* aware of this fact. That he maintains that the effect is *not* measurable: Occam's Razor then suggests that these 'detectors' do not actually exist.

The speed of sound in air is always varies depending on air pressure, elevation, temperature and humidity.

Roger, please don't argue about the speed of sound OK? If you have heat, air conditioning, humidity control or lack of it, weather, what not- the speed of sound will change. You cannot ascribe that as a constant; it is constantly changing.

Phase relationships are maintained through having bandwidth. You got bandwidth, you got imaging. Try turning off the tweeters sometime and see what happens.

FWIW, the reason recordings don't have the same perspective that you hear in the concert hall, that you have a greater holographic quality in them than in real life, has to do with the microphone placement and post processing (if any).

Try spending some time with the mics at live performances and you will see what I mean real fast. Having a recording that you have taken from the live performance to CD or LP is immensely useful in developing a reference- it makes a difference when you were there and know what it was supposed to sound like.

Tbg, some more things to point out. I've been careful not to say anything about how any of these products sound. I have only offered personal experience on what causes imaging. As far as the H-Cat goes, I'm only concerned with the explanation, not the end result.

Here is an insight. Life is. It does not care what we think of it, it simply is. Humans usually exist as reason and meaning making machines. We attach reasons and meanings to everything. In fact, we are generating stories all the time (reasons, interpretations, beliefs, etc.) about life. This is not a problem so long as we are aware of it, but when we try to live our lives as if our made-up stories are real, anywhere where life disagrees will be a source of suffering.

for more info see http://www.landmarkeducation.com -if any of this resonates with you, do not hesitate and take the class called the Landmark Forum.

My feeling through this whole thing is that Roger latched on to a 'story' or 'reason' (I use that word since he concedes that he never tried to prove or disprove its reality) to justify his actions regarding his 'phenomena'. That is not to say that whatever he's *doing* does not work, but the 'reason' does not hold water. It is a matter of **profound luck** that he has success (if you are to be believed), this bit of 'profound luck' (and contradictory explanations) led me to Occam's Razor- I doubt its coincidence, I doubt its luck and think there is a simpler explanation.

There are many products well defended by theory and science. In that conversation, I would be careful about assuming that just because that is so, that that product is a mere rehashing of old circuits. For example, we built the first fully-differential balanced preamps, which were also the first to have a direct-coupled balanced output. That's not exactly a rehash... I can point to some other examples, like the Messenger, that are not rehashed either, and they are all supported by theory and science.

To answer your previous question, yes, bandwidth is what you need for imaging. Imaging is reliant more on bandwidth than any other 'phenomena' in audio. Naturally low distortion is helpful to improve detail, but you can have quite a lot of distortion and imaging will still occur as long as there is good bandwidth. If you think Roger's design has good imaging, if you check you will find it also has good bandwidth (well beyond 20-20KHz). This happens to be one of those things that is audible and measurable. Anytime **those two** coincide, you've got something that is real.

Pubul57, I hear about timing a lot these days but its one of thoese things that I really can't say what causes it, although I do know that a lot of circuit complexity does prevent it. I don't like the word 'dynamics' as too many times I have found that audiophiles use it when what they really should have said 'distortion'. So I like to use the words 'impact' and 'authority'. Impact is the ability to respond to intense dynamic change, and authority is the ability to sustain it in the way that the source demands.

Both seem to arise more easily if the circuitry is kept simple, and certainly avoiding loop negative feedback will make the circuit more responsive to dynamic change.

As I have mentioned before, imaging and soundstage seem to derive from bandwidth, extending well beyond audibility. Oddly, what a lot of people would describe as holographic, wherein the image places *in front* of the speakers, or there seems to be unusually wide soundstage effect, nearly always seems to come from phasing anomalies near the edge of the passband. For example, as much a fan of tubes as I am, a tube amp that has poor high frequency bandwidth deriving from its output transformer can exhibit a form of this behavior. If they have good bandwidth, nearly all amps will image in a very similar way, with the variations being in how well they can render the individual images as 3D entities rather than as a cardboard-flat images, and how well the more subtle ambient cues are articulated or truncated, depending on how well the amp can reproduce detail.

Pubul57, Something fun to try is to listen to a live performance and see if you can place the mics in such a way that a 2 channel playback over speakers has the same perspective as your ears. This is usually not an easy thing to do, but when I was preparing to record Canto General, I had convinced the ensemble to rehearse for the final week in the concert hall. So I had a week to goof off with mic placement, set up a nice playback rig on location and the like.

IF you have time to do it, a recording can be made that will sound remarkably like what it sounds like if you were sitting where the mics are. In most recordings, the mics are often **above** the ensemble, which produces an odd perspective, unless you happen to know that that is where the mics are placed.

Modern mics are remarkably sensitive- with them you can hear things in the hall that you would not notice with your ears! One time I had robins chirping in the mikes- hear it as plain as day over the monitors, but stand by the mic stands and you could not hear them. I found an open door in the rear of the hall... the robins were outside.

Another thing to keep in mind that will help you understand how realistic or not a system is being, is the model of what it should sound like. Don't think for a second that the system is going to sound like the hall- it isn't. It **can** sound, and very convincingly, like your listening room is grafted onto a space (which might be a hall) wherein the music is happening. A real hall will have hall sounds beside and behind you. Your system will have the real hall sound in front, but your room sounds beside and behind you. If you keep this model in mind, you will see that we are a lot closer to the Absolute Sound than most folks think. For a long time and to this day, the bottleneck is the media, not the playback!

Detlof, in working with CD and LP mastering and with digital and analog master recordings, over and over again I am always struck and disappointed by the signal losses that occur during the mastering process, regardless of the format. If anything, the CD format seems to loose *more* during the process of going from master to produced copy than seems to happen with the LP.

When you are listening to the direct microphone feed, and then compare that to the results of a digital master file or a 1/2" analog master tape (regardless of tape speed) there is always a degradation noticable there too.

If you are familiar with this degradation, you can compensate **slightly** for its loss by microphone placement, but its tricky and most engineers will not take the time. I think this and the above phenomena is why there so few truly exceptional recordings, **especially** when you factor the performance into the equation!

When it comes down to it, I'll go for the performance nearly every time, and simple deal with whatever vulgarities the recording is otherwise. Such a world!