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In Reply to: RE: Modifying capacitor leads posted by banpuku on September 13, 2016 at 08:02:52
That's not a "grid stopper" cap; it's a screen bypass. If there were any factual benefit to this, commercial manufacturers would have done it years ago.
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But, even if it is a "placebo effect"... as long as the patient (or listener, in this case) feels the positive effect --- all should be okay?
In medicine, we see this all the time. A patient is screaming he has excruciating pain. He is given a pain med. He immediately feels better. Not only that, but his once high BP (while in pain) instantly drops to normal.
Now, pharmaceutics data shows that the pain med takes 15-20 minutes to dissolve and another 30 minutes to 1 hour to reach therapeutic levels in the blood. But, as long as the patient feel better --- 10 seconds after taking the med --- everyone is fine with it. No one is going to say, "It's impossible for the med to work that fast."
Just a thought...
8^)
"the planned therapeutic effect will be greater if the nurse believes the placebo efficacious as well"Psychosomatic or not ... that is powerful stuff.
The Mind has No Firewall~ U.S. Army War College.
Edits: 09/13/16
so neither the investigator nor the subject knows which is placebo and which is the good stuff. (I don't wish to dredge up the old arguments on the subject of double-blind testing of audio equipment. It's a good idea, if practical, but it is not usually practical.) I'm just pointing out that the concept has an important place in scientific methods.
LOL...while it would be useful, to go and get two sets of output Iron, and power/filter iron just so I can build two identical amps and double blind test some resistor/capacitor/grid choke... It is rather impractical.
This impracticality gives rise to placebo-ists who claim one must use 4.3 runs of some specific colour and manufacturer wire between the 100kOhm plate load and the 12AX7's plate in order to get a properly 'efficient transfer' of musical energy so a 2A3 can put out power that sounds like it is coming from an amp with two orders of magnitude more power.
One test I like involves leaving the system alone for a bit, and then come back and listen. And have other folks drop in for a listen. Dropping in on a system 'cold' will give you the, 'it needs work', or, 'I like it much' response...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
What I do is to listen to the system with the new device for at least several weeks and then go back to the "before" condition for several more weeks. And ideally, you (or I) should go back to the new device, to see if you (or I) still love it so much or so little. But in practice, I am lazy. Seat of the pants rules. Which is why I am loathe to trumpet my conclusions. My data are usually bad. Thus I sometimes marvel at the degree of certainty about anything, often seen here.
Edits: 09/26/16
I have observed a lot of 'bad' data myself. I have seen a few good results, and my most certain confirmation comes from other sets of ears, preferably on an absolutely 'cold' basis...either they like it or not.
I'll try and stick to building what I like to listen to...:) The basis of a good amp has always started with good engineering.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"Now, pharmaceutics data shows that the pain med takes 15-20 minutes to dissolve and another 30 minutes to 1 hour to reach therapeutic levels in the blood"
Does a patient's BP go back up and does he start complaining of pain immediately once this is explained to him?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
As most RNs will be happy the patient is not complaining and his BP is within normal limits. The physiology of how it is impossible that the med is working, is not explained. For whatever reason, the med is "working."
There are patients that are on chronic pain meds. Say, one tablet every 3 hours as needed for pain. Some of these patients will sleep all day. EXCEPT, the 3 hour period when the med is due. They wake up exactly at or just before each med can be given. In bad pain.
They are given the med and can be sound asleep in less than a few minutes. There is no physiological reason that their internal timers are so precise and that the meds work so quickly --- except the mental aspect.
The brain plays such a strong influence on how we process our internal senses and external stimuli --- it can overcome science, at times.
8^)
"The brain plays such a strong influence on how we process"... what we think we hear.
If a person is trying to really understand (and build) a music playback system that IS really properly reproducing the input signal...I would say they need to know what is and what is not "placebo effect".
That isn't going to happen if we just repeat "But, even if it is a "placebo effect"... as long as the patient (or listener, in this case) feels the positive effect --- all should be okay? "
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Problem is... it can be hard to separate the two.
8^)
Yes! It's very hard not to get fooled.Even professional listeners have a hard time not being fooled.
This is why it's so important that good scientific method has to be followed before proclaiming that X is "better" than Z.
Otherwise the claimant could just be "fooling" himself (and by extension, trying to fool you and me) when there is, in fact, no actual basis for the claim to start with.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 09/13/16
Reproducibility is the word!
8^)
That's for sure.
Case in point, if there was a clear reason why changing the leads on the cap would make a big difference then OK, but the fact is a screen grid bypass cap merely holds the screed grid at AC ground.
There is no way mathematically that the tiny difference in the resistance, inductance, capacitance, dielectric absorption, etc.. between the stock lead wires and the new added lead wires would hold the screen grid enough closer to ground to make the claimed difference. "dynamics just soared with the modified caps"
In this case one would have to do a DBT. If a claimant and/or other listeners could show statistically significant results in a DBT then we would need to look for a different reason for the change.
In the mean time, expectation bias is more likely the cause of what is being "heard".
If someone secretly undid the change I don't believe the listener would notice that the system had lost the perceived added dynamics.
The listener would assume that the modified leads were still in place and the expectation would remain, so the perceived improvement would remain.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
You've touched on a major question that is always worthy of consideration. One wonders if perhaps the OP replaced a 2.8uF capacitor, the value called for in the schematic, with the 4.7uF Clarity MR cap that he had modified, in which case, the improvement he heard could have been due more to increasing the value of the capacitor than to adding wire to the leads. I am sure he can answer that question.
I am a doctor, too, albeit a non-practicing one. Today I visited a dental surgeon who placed an implant in my lower jaw. During the procedure, he numbed me up very effectively, but of course the local anesthesia started to wear off by mid-afternoon, and I really began to suffer. Thereupon, I took a codeine tablet, which did nothing for me until at least 45 minutes had passed. Why don't doctors experience the placebo effect?
One huge placebo effect for audiophiles is brought to bear after one spends a great deal of money on a component or some other less obviously functional element of a system. There is a strong subconscious bias to favor that which is new or expensive. Just check out Tweaker's Asylum some time, for proof of that.
"See the attached schematic which calls for a 2.8uF cap, but it currently has the 4.7uF cap with the modified leads."
I kind of missed that. That is to say, it didn't dawn on me that banpuka might have meant that he replaced a 2.8uf cap with a modified 4.7uf cap.
That might explain a lot.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Driven by an AC supply, a capacitor will only accumulate a limited amount of charge before the potential difference changes sign and the charge dissipates. The higher the frequency, the less charge will accumulate and the smaller the opposition to the current, therefore; higher frequencies MAY improve with a larger value capacitor in that position.
The Mind has No Firewall~ U.S. Army War College.
Yes, the reactance of a larger cap is lower than the reactance of a smaller cap.In this application that would make a better connection to ground at all frequencies (not just the higher frequencies) for the screen grid.
If it is the case that the OP replaced a 2.8uf cap with a 4.7uf cap and then reported that he heard a difference, then that would be completely understandable.
On the other hand if the original poster had already changed (at a previous time) the 2.8uf for a 4.7uf (or built the amp with a 4.7uf to start with) and is not reporting on that change in sound but is reporting on a change in sound having do to with the modified leads on the 4.7uf, he might be fooling himself (through expectation bias or whatever) and some proof of a real change in the sound will need to be proven through a DBT or a better explanation of the science involved.
Update; in the post linked below the OP has confirmed that he is indeed reporting that the perceived change in sound was between a 4.7uf without the leads modified and the same 4.7uf cap with the leads modified.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 09/14/16
!
The Mind has No Firewall~ U.S. Army War College.
You may not have felt relief for 45 min because you understand the kinetics. Which may or may not be a good thing, in the short term. But, best in the long run... Maybe.
Edits: 09/13/16
To bring this back to audio, if the goal is to advance the audio reproduction state of the art.....it's always a good thing to not be influenced by anything but actual physical reality.
I think we are all in agreement that that is hard to do because we are all so easily fooled when it comes to what we see and hear. It's built into our brains to work that way.
All the more reason to be cautious.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
...We certainly are. Even Richard Feynman realized this and made a big deal of it. This is partly why great claims must be independently reproducible by parties not directly involved with the "discovery". Not a frequent occurance in tweak audio.
Yah...Feynman was indeed on to something...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
This is why reproducing results under controlled conditions is so important. Ideally, with error factors included.Subjective views are hard to quantify, but they play a role in audio. Just look at all the adjectives used to describe what you hear. Most are subjective, not objective or quantifiable. I'd say this is impossible to completely eliminate.
Edits: 09/13/16
...that may be so for now but we shouldn't stop trying.
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