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Old 20th March 2015, 10:21 PM   #1
Coris is offline Coris  Norway
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Default The Joe`s capacitor...

Well, I think this subject it may be fortunate to discuss it further, but not so as before, to conflict with the forums rules.

I think too, that Joe Rasmussen have a merit in this area, as the one who pointed out for all of us, the effect of this capacitor placed over a DAC chip differential outputs. As I have learned already, calling this effect as "Rasmussen effect" it seen as enough provocative for someone, and it can easily leads to off topic discussions. So I will suggest to call it "Joe`s capacitor/cap".

What it do this capacitor as effect? Well, to use only few words for description, it improve the soundscene. To observe these improvements is only enough simple listening tests (available to everybody who may want to experiment). The differences before/after are obvious. How to quantify/measure such? Well, here is a big challenge. What to measure, and how, is up to you to comment, but I`m personally quite sceptic that what is to hear is always measurable...
What is the role of this capacitor, or what actually is this capacitor placed so in the circuits?
Here is a controversy, which in my opinion it may be beneficial to discuss about it further.

In the former (closed) thread dedicated to this subject (DAC Filtering - the "Rasmussen Effect") it was a quite hot and long enough discussion, trying to be found the right explanation for what actually is going on about this cap.
It is a filter, or what it may be?
It looks enough obvious that is a filter, or it have a filtering function. But what is more than obvious, this cap it have an effect or a big impact on the soundscene, improving it a lot. Why is like this, I will suggest to discuss it further here. But let`s discuss about the cap and not about the persons who participate to discussion..

Last edited by Coris; 21st March 2015 at 09:40 AM.
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Old 20th March 2015, 11:30 PM   #2
Coris is offline Coris  Norway
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So, my first "contribution" to this thread...

Joe Rasmussen made it us known about, and he used this cap over the DAC outputs differential lines, or at the input of the I/V stage (as we know so far...).
I have followed this idea and I used it too so, and I could confirm at that time the Joe`s statements. Then for some particular reasons, I got bad results when using this cap, and I abandoned the idea. I found out later on about the causes of my negative results. So, I came back to this idea, and use it the cap on my new designed post DAC processing stage. The result was immediate and more than positive. So, my definitely conclusion is: this works! The effect of this cap is very real, even though is enough unclear the explanation of this effect.
They who only deny the existence of this effect, sorry, but they do not know (yet) what is actually about, or never try it.

Recently I was thinking and asking myself what it may be the effect of a such capacitor, or how it may works if is placed somewhere else than just on the DAC chip outputs.
Let`s say placed over the differential lines at the inputs of an pre-amplifier circuit. Well, the answer is: IT WORKS!
But what it may happen if heaving a such cap already placed on the DAC outputs (and working well as effect), if another one it will be placed in the same processing chain, at the input of the pre-amplifier device?
Well, this was actually the reason I decided to start again the discussion about this effect, in this new thread.

When using the samme approach with this cap over diferential lines, both on DAC outputs or I/V inputs, and at an pre-amplifier inputs, then it is possible to control the "shape" of the soundscene, or how it may "looks like" the soundscene.
I used for first experiment the same value of the cap on both DAC outputs, and at the preamp inputs. I got a distorted soundscene. Please do not misunderstand. The audio signal was not distorted at all, but always just exceptional fidelity. The soundscene itself was unreal wide, so that some instruments was positioned in unreal positions, while the another ones was in right places. Just unbelievable effect!
It was very obvious that was far from natural. I have appreciated to lower the cap value, quite by chance. Another big surprise: the soundscene became very real, with everything in its right place, and the position of the instruments became just amazing precise. The volume/space of the soundscene it were very large both left/right, and far/near, so to permit an extreme well definition in space of the sound elements. Instruments placed very near each other could be very well and easy located. I never heard a such realism in a audio playback.
This effect and the improvement is not to be obtained only by using the cap at the DAC outputs, but using it in two places in the chain. The effect obtained by placing the cap on the DAC outputs it define somehow a soundstage. The another one cap placed at the preamp stage inputs it multiply the precision and the volume of that "predefined" soundstage, and it can modified (by the used cap`s value), to obtain an optimum of an even more increased/improved sound quality, than only using this cap on DAC outputs.
What happen is just and only amazing!

I have tested playing back some old Tangerine dream albums (standard CDs). After so many years I was used with this band works. it was for the first time I have experienced the real way Tangerine dream was created and recorded. The sounds was flowing in the room, moving it far and near, from the left to right in a very large like area, with an extreme precision in space. The speakers became completely transparent or non existent in the room, but only the sounds coming right from their precise places. Very easy to locate multiple sounds in the same time in very different or very near positions. Undeliverable is a quite poor word to express such experience.

Well, as a conclusion so far, here we have an very real effect of improved soundscene in different levels as using this cap in different places into the processing audio chain.
It looks like a such cap it have filtering function here, but the effect is quite far from only a filtering result. There is something more than only filtering, which happen when this simple cap is placed over differential lines. I do not know so far, what it may be, but is very right in my opinion, to call it this as an effect. I can also hardly define this effect too...

Sorry for not coming with precise values of the caps, or the precise location of it. The values it vary quite much function of the used device, configuration, etc. The approach it have however to be customized. I only intended to share/confirm once more about the existence of this effect, adding that using this cap in two places it improve even more the final result. As I will use this approach in my further mods/improvements, I may not disclose some details.

Last edited by Coris; 20th March 2015 at 11:52 PM.
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Old 20th March 2015, 11:39 PM   #3
SY is offline SY  United States
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Quote:
Originally Posted by Coris View Post
What it do this capacitor as effect? Well, to use only few words for description, it improve the soundscene.
Before getting into a theory of operation, perhaps you could start by explaining how you determined this to be the case. Thanks!
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Old 20th March 2015, 11:43 PM   #4
infinia is offline infinia  United States
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I think the only controversy is Joe claiming it's HIS effect. This technique pre filtering the digital to analog interface is very well known years before 'joe blow' decides to plant his flag on it. We used to do this with RC filters on charge pumps for PLLs decades ago, but then we could calculate the values used and also measure the results. Did you have a question that hasn't been discussed in the closed thread?
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Old 21st March 2015, 12:09 AM   #5
Coris is offline Coris  Norway
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Quote:
Originally Posted by SY View Post
Before getting into a theory of operation, perhaps you could start by explaining how you determined this to be the case. Thanks!
How I determined the existence of this effect, it was your question?
Well, very simply. By listening before/after...
If somebody may have an idea how to measure this effect, is only welcome to develop it...
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Old 21st March 2015, 12:19 AM   #6
fas42 is offline fas42  Australia
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The measuring of such a type of effect IS difficult, because the characteristic is that the information at a much lower level than the nominal signal is "clearer", less distorted. It is not the distortion of the high level envelope of the signal, it's what's happening to the low level signals riding on top of the main, obvious time domain behaviour. And the measuring of such requires evolving measurement techniques, which people are obviously very reluctant to do ...
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Old 21st March 2015, 12:20 AM   #7
Coris is offline Coris  Norway
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Quote:
Originally Posted by infinia View Post
I think the only controversy is Joe claiming it's HIS effect. This technique pre filtering the digital to analog interface is very well known years before 'joe blow' decides to plant his flag on it. We used to do this with RC filters on charge pumps for PLLs decades ago, but then we could calculate the values used and also measure the results. Did you have a question that hasn't been discussed in the closed thread?
I think you right... But I may suggest we forget for instant what it was that "controversy", and the "flag"...

But how may you think to define a such improvement effect, from the perspective of filters and so?
My appreciation is that a such cap in that place it may improve the signal`s phases or the overall quality in this area. There is known that the human perception of the sound location is based on measuring the phase differences of the sounds which hit the ears. An improvement in reproduction of the audio signals (sound) phases, with this cap in place, it may explain the improvement of the soundscene in this case... Well a supposition, quite empiric expressed...

Last edited by Coris; 21st March 2015 at 12:25 AM.
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Old 21st March 2015, 12:22 AM   #8
Coris is offline Coris  Norway
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Originally Posted by fas42 View Post
The measuring of such a type of effect IS difficult, because the characteristic is that the information at a much lower level than the nominal signal is "clearer", less distorted. It is not the distortion of the high level envelope of the signal, it's what's happening to the low level signals riding on top of the main, obvious time domain behaviour. And the measuring of such requires evolving measurement techniques, which people are obviously very reluctant to do ...
That was actually my point too, that is very difficult to measure/quantify such effect...
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Old 21st March 2015, 09:53 AM   #9
Coris is offline Coris  Norway
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Quote:
Originally Posted by infinia View Post
I think the only controversy is Joe claiming it's HIS effect. This technique pre filtering the digital to analog interface is very well known years before 'joe blow' decides to plant his flag on it. We used to do this with RC filters on charge pumps for PLLs decades ago, but then we could calculate the values used and also measure the results. Did you have a question that hasn't been discussed in the closed thread?
I feel the need to come back to your post, with this observation:
When about to apply such cap or filtering technique to the digital to analogue interface in a DAC system, I may agree that this cap it have a full filtering function.
But the main point of my above post and motivation for opening this new thread, is that so called filtering effect or function of this cap, it is applicable (it actually works) when using it in a full analogue domain (as at an preamp stage input, or in between two analogue processing stages).
What it may be to filter here, so to be perceptible at the chain outputs a much more improved soundscene, than when not using such cap?
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Old 21st March 2015, 10:28 AM   #10
SY is offline SY  United States
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Quote:
Originally Posted by Coris View Post
How I determined the existence of this effect, it was your question?
Well, very simply. By listening before/after...
So not ears-only? You might consider trying to determine if what you perceived was real before delving into theoretical explanations.
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