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Microphony III

Steven Toy said:
You tested the material not the structure.
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I hope Tonies moderating activity permits this brief post.

Steven you will be interested to know I have ordered today a ReSponse mini (not of the same shape as you well know I am sure) but of the material which it's claimed If your hi fi component is resting on a high priced hi fi rack, or on a basic piece of furniture (or even on the floor), a ReSponse mini can make a substantial improvement to the performance.

So await some reactions next week when it has arrived. I shall of course be trying it in several ways
 
BE718 said:
Why didnt they just show the voltage difference against time?:confused::confused::confused:
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My memory may be playing tricks on me but I seem to recall they didn't.I think that the point is they wanted to measure the timing improvement, which as audiophiles know is quite different from playing the wrong thing at the right time. It's like having a different performance.
 
Werner said:
Never say never.

The high induced hum in the upper trace is cause for concern. It may well be that curing it also cures the speaker-induced signal in the lower trace.

Was the silent amp's input open or shorted?
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Yes it is a concern, didn't have a lot of time to bottom out. The input was connected to the tag processor out

However I totally agree it seems very odd, so I willl investigate more. Your right, never say never. :)

Easiest thing to do is use a totally separate amp to confirm.
 
It does seem to me that we listen to a hifi system as a complete system. If connecting the loudspeakers has produced a spurious result, that is nevertheless how the system will be operating when we perceive whatever it is that we perceive.

Unless we measure the performance of the entire system, under the conditions we are interested in measuring, can we be satisfied that we have performed a sufficiently rigorous test of what is going on?
 
Sue Pertwee-Tyr said:
It does seem to me that we listen to a hifi system as a complete system. If connecting the loudspeakers has produced a spurious result, that is nevertheless how the system will be operating when we perceive whatever it is that we perceive.

Unless we measure the performance of the entire system, under the conditions we are interested in measuring, can we be satisfied that we have performed a sufficiently rigorous test of what is going on?
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You can still break into into sections, and don't forget this result I had could be spurious measurement and not what is happening normally in the system. I made the measurement a few days ago but didn't mention it because of my own doubts. It's just that the recent conversation led me down the path of mentioning it.

In fact I think the only way do do this is to break it into sections otherwise it's impossible to establish where any issue resides. Yes ultimately test as a complete system, interactions can happen.

I don't think that microphony issues are something that whole system testing is necessary to diagnose. Any individual component will be sensitive to it, or not.
 
Werner said:
… Das war night nur nicht richtig, es war nicht einmal falsch! …
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... OH that’s GOLD; ;)… I haven’t heard that since I was at high school where our Chemistry teacher (a very austere German) had it printed above the blackboard in German with an English transliteration underneath. Thanks for reminding me…:D


Hi Guys;
While it is admirable to try and measure the effects of vibration born interference, the results of one single test cannot be considered conclusive with out fully understanding and considering all other possible inputs.

Looking at the data set, there is apparent interaction between the channels. However, if we draw an averaging line through the graph, (ignoring the initial noise spikes caused by the unshielded cable) the apparent interaction is already 96 dB down at its worst case. Allot of amplifiers already struggle to achieve this.

BE718 said:
… BTW there is no crosstalk between the power amp channels; they are 5 totally separate amps in the same case with separate transformers, power supplies and grounds…
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Before accepting the dataset we need to confirm that there is no cross talk between the channels. I don’t quite believe that you can achieve complete isolation in the real world. Even with separate power-supplies for each channel stray capacitances, induction between leads or even leakage between apparently isolated power-supplies can happen, it as also a possibility that the crosstalk may be coming from the pre-amp.

I would use a fully shielded cable to feed the amplifier used to generate the test signal then try to eliminate any noise, also try to get a dummy load for the signal amplifier, short the input for the amplifier under test and disconnect all other equipment (including speakers) from any other unused channels on the amplifier. Run the test again and measure the inherent crosstalk within the test scenario, then record the results.

Once this is done you can be a little more certain of just how much crosstalk there is in the system. Only then can you replace the dummy load with a speaker, re-run the test then subtract the known crosstalk from your new test results. You can now be a little more certain that what you are measuring is actual interference caused by vibration/micro-phonic activity with the amplifier.

You could also re-run the test with, then without a speaker attached to the test channel to see if the passive speaker is behaving like a microphone and feeding a signal back into the amplifier channel under test.

Accuracy and consistency in the method is just as important as knowing how to read the results and understanding what mechanism have been eliminated or allowed for, all this is necessary for interpreting the results correctly. Anybody can make a graph, its knowing how to read and interpret the data contained in the graph that makes all the difference.

Well done for having a crack at it though...

LPSpinner.
 
Werner said:
Chance. Or cherry picking. Yes, that is a grave accusation.

At any rate, the very few quantitative details that could be gleaned from the graphs suggested error magnitudes, even in the best case, of such an order as to beggar any belief.



Pauli. You know, the bloke who explains why some sodium vapor lamps make orange light, and others near-white light.




The ripped data they use as a reference contains unreconstructed sample data points.

Upon replay these points get reconstructed in the, erm, reconstruction (oversampling, anti-imaging, whatever) filter, resulting in a smooth curve in the analogue domain. This signal is then sampled by their measurement ADC. The replay and record clocks are not related, so they feature mutual temporal offset, drift, and jitter.

In other words, even with a perfect/ideal replay DAC and a perfect/ideal record ADC the chances of hitting the very same data points, and keeping hitting them, are zero.
So whatever comes out of the ADC must not ever be compared to the ripped unreconstructed data. Such comparison is meaningless.




Such difference tests are very hard to do properly. This helps:

-use only reconstructed signal as reference

-lock the playback and record clocks together

-assess any impact of anti-imaging and anti-aliasing filters, and move them out of harm's way, if possible

-characterise the jitter for the entire loop. Learn from this what sort of differences to expect even when nothing changes

-test the entire setup for known zero-difference cases and for known big-difference cases. Is it reliable?
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Thanks for trying to explain. However this is all clearly beyond my knowledge of digital audio, and I don't wish to spend further time trying to understand it. I'd rather listen to music.

In fact I'm going to trial the Vertex Grounding Block. I don't expect it to do anything as I reckon I've dealt with most of the problems they identify with a power regenerator and anti-vibration products, but we'll see. I'll judge by what I hear.
 
I wouldnt expect it to do anything either, if you really want better sq I would look at how your room and loudspeakers interact.
Keith.
 
Oh yes, best thing I ever did.

I've seen pictures of your setup... oh dear, oh dear, oh dear.

;-)

P.S If your syatem sounds so good, why are you constantly tinkering with it?
 
Purite Audio said:
I wouldnt expect it to do anything either, if you really want better sq I would look at how your room and loudspeakers interact.
Keith.
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You are of course correct. That should be the number one consideration after buying the gear, and before checking out cabling and other peripherals.

After buying equipment, I advocate the following:

1. Find the best location for speakers and ears (listening chair). The best way is to use frequency response (FR) measurements from say 0-500Hz using something like REW software.

2. Room treatment, particular bass traps. The FR software will tell you the sort of problems you have.

3. Complete the speaker/room corrections with an equaliser (it works for me anyway, before the naysayers jump in).

4. Consider cables, anti-vibration, power products. The last two won't change the FR but offer other qualities as described on this thread.

5. Consider CD cleaning and other CD treatment.
 
OK, perspex test

MDAC sat on perspex headphone stand. Same test as with the rubber feet and metal bolts. Phone on vibrate on the glass stand.

Did the perspex stop the vibration. No, in fact probably added some of its own natural frequencies into the mix.

By now I'm not sure anyone should be surprised by this result.

perspex%20test_zpseeoatlge.jpg


Stand accel below, perspex on top.

perspex_zpsxtdc7t1i.jpg
 
Hipper said:
In fact I'm going to trial the Vertex Grounding Block. . I'll judge by what I hear.
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Please, please dont spend your money on this.

From the literature

In the module itself the ground of each socket is connected to a feed wire which enters the acoustic labyrinth, providing a low impedance acoustic route into an advanced labyrinth structure.

I have absolutely no idea what this acoustic labyrinth has to do with any electrical theory or grounding issues a system might have. I really dont need to say anymore
 
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