Holographic imaging

Atmasphere,

The misunderstanding is (and this is my fault) when I refer to the speed of the amplifier – I meant its velocity. IOW the speed that a signal travels through a circuit. Propagation delay refers to the amount of time the signal spends in the circuit and while it is directly related to the speed of the traveling signal – it can only indicate the AVERAGE speed since the comparison is base on the time it took a signal to enter and exit the circuit. What happens in-between is not monitored - it is assumed.

This is the area of interest to me.

As far your question..
“For a given change in gain, say 20 db, how much change in pitch will be measured?”

This is the same misunderstanding that Detlof has with his statement…
“I know however, and that for certain, that in a well set up rig, volume and pitch do not have anything to do with each other.”

Please read slowly --- It is not the volume setting you are listing at that affects the pitch. It is the CHANGE in volume that affects the pitch. Let me reverse that statement. The pitch will change as you increase or decrease the volume. Once you take you hand off the volume control, the pitch is the same no matter where you left to volume.

Hope this helps :)

Roger

Musicnoise,

Please accept my apologies. I certainly thought you were aware that I am the designer of H-CAT.
There are many references within this thread that may have indicated this earlier.
When this topic of holographic imaging started – I was very interested to read about the variety of opinions and experiences of audiophiles. After all, to me this was something that I have studied for many years. The results of my work I am willing to share with those who are interested.

Regards,

Roger

It is the CHANGE in volume that affects the pitch

Since you make no mention of frequency (group delay). I take this to mean that you suspect that the absolute signal level changes the propagation delay in the circuit. This is a non-linearity that should cause IMD distortion and it should be measureable. (Signal level or amplitude is modulating the frequency of output - creating new frequencies. For example a cymbal high frequency sound riding on top of a large oscillating bass guitar note - as the bass guitar signal goes up it changes the of pitch of the cymbal HF sound - giving side bands)

FWIW - this is already a huge problem in speakers and especially those with overhung voice coils that are not particularly linear throughout their driver excursion.

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 :)

“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.”

Atmasphere,
Now we are getting somewhere – here is the other shoe dropping.
You don’t have to manually change the volume (yourself) – your amplifier is changing the gain on the fly.
It is the unstable nature of the instantaneous gain that is constantly altering the velocity and therefore pitch.
The tiny changes in pitch also represent the shifting of the perceived location of that sound object on the stage.

Roger