Turn it around the other way.... In order to confirm you were referring to Joe Rasmussen say nothing. Otherwise state that you weren't. 😉
I may kindly remind that the subject/discussion in this thread should actually focus on and around the cap, and its effect/consequences when use it as described in the circuits, but not about one or another person.
Can we please get away from discussing about individuals?
Can we please get away from discussing about individuals?
Coris,
You may have already hit on the explanation; Phase!
Back in the 70's, Aphex invented what they called an Aural Exciter. This was a rack unit used in the studio recording process (but could be used for audio restoration) to "enhance" certain audio tracks or the over all stereo mix. The process involved amplitude dependent harmonic generation, and frequency dependent phase shifting. There were other companies that followed with their own versions of "audio enhancers".
Perhaps the capacitor is simply introducing frequency dependent phase shift?
I would suggest building a box with two tracking channels of all-pass filter with an adjustable frequency, placed between the preamp and amplifier, and see if this produces a similar effect.
Maybe this is what is really happening?
You may have already hit on the explanation; Phase!
Back in the 70's, Aphex invented what they called an Aural Exciter. This was a rack unit used in the studio recording process (but could be used for audio restoration) to "enhance" certain audio tracks or the over all stereo mix. The process involved amplitude dependent harmonic generation, and frequency dependent phase shifting. There were other companies that followed with their own versions of "audio enhancers".
Perhaps the capacitor is simply introducing frequency dependent phase shift?
I would suggest building a box with two tracking channels of all-pass filter with an adjustable frequency, placed between the preamp and amplifier, and see if this produces a similar effect.
Maybe this is what is really happening?
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Poynt99, very interesting! I hadnt come across this enhancing article before. Almost sounds like the SS equivalent to the Lampizator.
Any cap will do that, it's in the nature of filtering. The question still remains, is that filtering audible, and if so, is there anything special about putting it in that spot in the circuit? Have any of the proponents of this "effect" done any experimental work yet to answer either of these questions?
a the fundamental problem for the hobbyist tweaker is the requirement for at least 2 units to compare
audio memory is poor for small differences - before and after a mod is not a Psychoacoustic Science acceptable method due to the sighted aspect and the delay
if you think the quality difference survives recording then you could capture, normalize, compare the analog output of the before and after cases in foobar200 ABX plugin or similar
but the Psychoaousitc/Perceptual Science test requirements are needed because of human limitation - not lack of "intellectual honesty" - we do perceive differences when we listen for them in uncontrolled settings - the conscious perceptions without experimental controls, blinding protocol just have too loose a correlation with the sound waves hitting our ears to be useful for audio Engineering
audio memory is poor for small differences - before and after a mod is not a Psychoacoustic Science acceptable method due to the sighted aspect and the delay
if you think the quality difference survives recording then you could capture, normalize, compare the analog output of the before and after cases in foobar200 ABX plugin or similar
but the Psychoaousitc/Perceptual Science test requirements are needed because of human limitation - not lack of "intellectual honesty" - we do perceive differences when we listen for them in uncontrolled settings - the conscious perceptions without experimental controls, blinding protocol just have too loose a correlation with the sound waves hitting our ears to be useful for audio Engineering
Actually, you cannot say anything meaningful about that capacitor unless you know the impedance it is paralleled to. On the one (left) hand, you have the DAC I-output which is high impedance. In and on itself, a 1uF cap would just draw down any signal into the noise.
BUT, on the other (right) hand is the input impedance of the I/V converter which can be expected to be very low. In the ideal case, where the I/V presents a zero input impedance, the cap has no effect at all of course. But since the I/V most probably is not ideal, not having zero Zin, we need to know what that I/V really represents. THEN we can say something meaningful about what the cap effect is on the signal.
Otherwise it is all wild speculation into the blue yonder.
Edit: as an example, assume an I/V with 1 ohm Zin, then a 1uF cap would cause a roll-off of the highs at approximately 159kHz. Personally, I would consider that as 'useless' and 'waste of money'.
Jan
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But this isn't an all-pass, it's a plain old pole.
Aphex's "trick" was adding level-dependent distortion.
Aphex's "trick" was adding level-dependent distortion.
http://www.diyaudio.com/forums/lounge/249418-dac-filtering-rasmussen-effect-58.html#post4221192
The intended response being flat @ 1KHz, -0.5dB @ 10KHz and -2dB @ 20KHertz.
The intended response being flat @ 1KHz, -0.5dB @ 10KHz and -2dB @ 20KHertz.
This being the intended response for a "raw DAC" + cap at the output of a I/V without LPF. The effect is supposedly still audible if you correct this response back to flat at 20khz, with either digital correction or an analog post filter.
As I said:
Actually, you cannot say anything meaningful about that capacitor unless you know the impedance it is paralleled to. On the one (left) hand, you have the DAC I-output which is high impedance. In and on itself, a 1uF cap would just draw down any signal into the noise.
BUT, on the other (right) hand is the input impedance of the I/V converter which can be expected to be very low. In the ideal case, where the I/V presents a zero input impedance, the cap has no effect at all of course. But since the I/V most probably is not ideal, not having zero Zin, we need to know what that I/V really represents. THEN we can say something meaningful about what the cap effect is on the signal.
Otherwise it is all wild speculation into the blue yonder.
Edit: as an example, assume an I/V with 1 ohm Zin, then a 1uF cap would cause a roll-off of the highs at approximately 159kHz. Personally, I would consider that as 'useless' and 'waste of money'.
So far, all wild speculation into the blue yonder....🙂
Jan
Actually, you cannot say anything meaningful about that capacitor unless you know the impedance it is paralleled to. On the one (left) hand, you have the DAC I-output which is high impedance. In and on itself, a 1uF cap would just draw down any signal into the noise.
BUT, on the other (right) hand is the input impedance of the I/V converter which can be expected to be very low. In the ideal case, where the I/V presents a zero input impedance, the cap has no effect at all of course. But since the I/V most probably is not ideal, not having zero Zin, we need to know what that I/V really represents. THEN we can say something meaningful about what the cap effect is on the signal.
Otherwise it is all wild speculation into the blue yonder.
Edit: as an example, assume an I/V with 1 ohm Zin, then a 1uF cap would cause a roll-off of the highs at approximately 159kHz. Personally, I would consider that as 'useless' and 'waste of money'.
So far, all wild speculation into the blue yonder....🙂
Jan
Yes!!! In fact, the whole assembly, whole audio chain needs to replicated, and very meticulously adjusted so that in nominally identical form the differences between the two setups are not audible.
If the differences survive recording, then far preferable is to use a far more sophisticated, and competent version of DiffMaker, to isolate the meaningful differences. Then those difference elements can be added back in a separate test environment, with just waveform editing doing the job, to rigorously confirm audibility.
Do you or anyone else expect that I or somebody else who state about this effect, it will work so hard to demonstrate to sceptics that the effect is real?
Should you organize/proceed to such test sessions? And what happen after all these carefully tests?
Who will invest in such sophisticated or "simple" way to find out if is a difference or not?
What may be the goals with such tremendous work and the very high price to pay for it?
If it may be supported by a million devices production, maybe it can be profitable...
As I can see, someone may show quite huge amount of fantasy in this case...
Can we be a little bit more with the feet on the ground?
Should you organize/proceed to such test sessions? And what happen after all these carefully tests?
Who will invest in such sophisticated or "simple" way to find out if is a difference or not?
What may be the goals with such tremendous work and the very high price to pay for it?
If it may be supported by a million devices production, maybe it can be profitable...
As I can see, someone may show quite huge amount of fantasy in this case...
Can we be a little bit more with the feet on the ground?
As an alternative, why not try to demonstrate that the cap does something other than just add a low pass filter?Coris said:
When claiming an implausible effect there are two useful approaches: demonstrate that it really happens (listening tests), make it more plausible (reasonable explanation of the circuit mechanism of the effect). Anything which does not contribute to either of these aims does not really contribute. Repeating an assertion does not make it more likely to be true, although it may make it more likely to be believed by some people.
Unless you have no curiosity, or have a deep love of wasting time on something that could be sheer fantasy, you need to demonstrate it to yourself. It will take less effort than typing numerous posts.
Well, I worked a little bit on this approach. Then I demonstrated to my self. So, I confirmed to others, So, I made it know about...
I do not do an apology of this effect here, and I do not intend to convince anybody that it works. I just came out with the information about the improvements this way of filtering (or what it is) it may bring for audio environment. That`s it.
P.S. Thanks for your efforts to read/answer to, my "numerous typed posts"...
I think you misunderstood a little bit the approach with this thread. I do not pretend that this (low pass) filter does something else, or does something magic. I`m not very sure also about what it does...
I just shared the information that the effect of this low pass filter, or the way it is filter something in the circuit, it improve the resulted audio environment.
The question/discussion about this (low pass) filtering, is what it may be (low pass) filtered out/in so to get the improvements mentioned. I think this question still be yet unanswered...
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