Maniac

So that's your excuse for editing other people's profile about double blind, which I never claim I did.

Well, don't let me hold you back.

Clearly you do not know most of those sockets available on the market will become so loose in about 20 inserts and pulls that it is no longer useful for anything other than recycling material. If you don't understand the failure mode of the parts in the middle, and how they work, then I really would suggest that you check those out and perhaps study how those could affect the test result before offering them as a solution. Since it is clearly not a solution at all but another bigger can of worms. As for Apple Newton, it is still a failure, it failed. It ushered in a lot of technology, but was not able to remain viable. And faded away in history with nothing more than some technical firsts to its name.

Socket and pins??? Are you kidding me? This is not some large filter caps that are placed far and away from the main circuit, this is decoupling cap, the contact performance is crucial here. Degrading it with a socket and pin just makes the test pointless. Design by committee is one way to fail, like Apple Newton.

I'm not about to design a product or an experiment by committee, as the result is only used for internal use, I was only sharing some info with people here and again I'm not trying to write my PHD thesis here or publish a paper on AES or some scientific journal. The full detail of the test result is only used for development, and I doubt any manufacturer would really post all details on their tuning process for everyone to critique, comment, and change the whole deal with a ton of comment from the web. Even if all those comments are good and valid, and with lots of manufacturer doing that, you'd likely end up with more than one manufacturer sounding close to the same, and the entire development cycle dragged on and on and on. That just doesn't work for any business, that only works if you got a lot of leisure time doing leisure pursuit. As for comparing the caps' difference, your suggestion will actually make the test invalid, as constant resoldering and desoldering the cap will likely damage the cap from some point on. The better method is to install another set of the same cap on the second unit, and that is when the tester reported that the difference is getting hard to tell. Yes, some may say that there can be differences between the same part, but finding out if the same batch of parts can have that much of a difference is also useful. Which we didn't find any meaningful difference between caps from the same batch.

I think I used 470uF FMs, those were physically pretty small ones. IMHO for analog stuff, stay away from caps with ultra-high high freq ripple current and almost no low freq ripple current, get ones that are somewhat more even. If you plan to try a few different caps on the amp board itself, I'd suggest soldering it more or less like SMD parts, instead of sticking it through the mounting position and solder. Less wear and tear on the PCB when you switch to different caps. And when you decided on one, then do solder them via the through hole.

Same capacitor design with different capacitance can have different response to the same frequency input, and also like many have said before, cheaper cap with large capacitance is not as good as better (often more expensive) caps at lower capacitance.

Clearly rage has overcame you...

If you don't get it, you don't get it. What's not proven is not proven, it is not wrong or non-existent. Science does not work the way you think it works. Not to mention I have proven it's consistency and accuracy while all you were really saying is FUD. If you are not able to prove or disprove anything, I'll have to ignore further similar messages from you, sorry.

I have explained how the listener is consistent, you can't explain it away as a fluke, that is your problem, not really mine. I have told you the volume are extremely consistent, and explained why, you still don't want to believe in logic and fact. Yet, as seen in the photo, the volume is extremely consistent. Now please show me some beef in proving how is it possible for the listener to be extremely consistent in identifying the amp by sound, and yet still be a fluke?

Your reasoning still does not explain how the listener is able to identify each unit by sound, as each time involves multiple listening sessions, with listener having no idea which is being listened this time around. During the entire time, the listener makes note on what is being heard, and I make note on which unit is being tested in what sequence. When we've had 5~6 (anymore is just too taxing IMHO) sessions in a row, we stop and I compare the notes. And each time, the listener was able to identify the same unit with identical comment, sometimes even commented in the note that "did I just heard this at trial number x?". And no, the pause between sessions are under 20 secs, we don't sit down and compare note before the entire test run is done. Now, can you explain how was the listener able to be extremely consistent?

Due to popular demand, the volume of the two unit with stepper are MATCHED, as shown below with both unit set to 8 notches from silent. Both results are given about 20 second for the scope to average, with measurement resetted when a different unit is being probed. Average RMS 2.09 vs 2.08 Now is someone going to complain about frequency generator's slightly different frequency average of 0.0208KHz?

Well, no. The comment from listener is extremely detailed, the listener CAN and have reliably identified the 006++ unit with FPP cap and WIMA cap. The listener actually indicated the 006++ unit with WIMA cap having some traits that was heard on the original 006+ unit (which uses WIMA in the decoupling). Now then, can you give me a hint on HOW I could have leaked any info on which machine was being listened when the listener don't even see me, don't even see the machines and was able to identify the unit out rather clearly day after day? We limited our communication to only what I have described above. When listener is not SURE about what was being heard, the listener will say so, and have done so quite a lot of times. Sometimes the listener was tired and sometimes the difference is too small. The listener will only report when it is very clearly noticeable, and won't try to hear for something that wasn't there. We also have a habit of not revealing what was being improved and what I was hoping before or during the test.

The amp's gain is set with a 1% precision resistor (0.1% on the ++ version), and in combination of a stepper, it will match to a degree that you won't believe. Since the amp work in this fashion: Input -> Volume control Pot -> Amplification circuit with feedback setting gain to a fixed setting -> output Now, there are 3 variables in this equation. Input = The same source, same cable, so there won't be any difference, since it is the same unit. Volume control pot = Since each step is extremely consistent from unit to unit, 3 steps on one will come within about 1% of the other unit's 3 steps. Normal film pot have larger channel mismatch than that. Amp's feedback setting/gain = set using 1% (006+) or 0.1% (006++) resistor, this also makes the amp's gain extremely precise from unit to unit. Now, with all three variable firmly fixed, I can't imagine how a noticeable difference in volume can be achieved when two units in question are done in that fashion. Now with the original unit using film pot, I can't say for sure. However, the listener indicates that the difference between the original unit and the upgraded unit using stepper is quite clear, sound quality difference is very noticeable. The listener like the smooth volume control of the original unit, while liking the stepper's sound.

When the listener is able to clearly identify the units day after day, comment remain the same from the first test to the last, no matter what volume (within reason of course), I was pretty convinced that the listener is not getting the placebo. All I tell the listener is "done, you can start", and all the listener tell me is "volume up/down", "I'm done". There are no visual cues, I even step back from the test area and observe the listener from a bit of distance (making sure the listener is not looking at the machines, which the listener never did look.). Now, with the listener able to identify the 3 test units consistently day after day, with no visual, verbal or even body language cues. How does it get completely invalid? I'm not planning on writing an AES report or a science project, but to get useful information when tuning. True, it is not as air-tight as would be needed by the standard of a science report, but all I need is reliable info on tuning, not something to publish paper with.