Now for some bright/treble cap snakeoil trials

[Fischerman]

When doing listening (or taste) tests people might claim "sounds the same" or "tastes the same" at first listen/taste; but then when someone points out the difference eg - "listen for the sibilance" or "taste for that slight metallic flavor" then they can't unhear it (or un-taste it). It's often going to be very subtle. Also, your senses are generally the sharpest in the morning.

I use those NOS 47pF red dogbone caps as bright caps a lot. To quote Frank's Red Hot sauce; "I put that shit in everything". But it's not like I've triple blind tested it ever.

Lastly, be aware of the Pepsi sip test effect. It led to Coke doing extensive 'sip testing' and then creating New Coke. New Coke beat Pepsi in 'sip tests' more soundly than Pepsi beat original Coke in sip tests. But when Coke released New Coke everybody hated it, it was too sweet. In sip tests people tended to choose the sweeter one. But when they drank a whole can of it...too sweet. When we typ do listening tests they are often more like 'sip tests' and very well could lead you astray.

[martin manning]

All of these elemental circuit components are measurable. Put them on a suitable analyzer that measures their parameters in depth and you'll find there are differences, even between polyester and polypropylene or mica vs. styrene vs. ceramic. You can model those in circuits to determine what, if any, deltas they create in the circuit performance.

Differences in dielectric behavior can be measured for sure, but not by ordinary means. An LCR meter or VNA will typically get only R and L parasitics. Scanning caps in the LTSpice library I find ca. 0.14 ohm and 0.85 nH for typical treble cap value and voltage rating. These R and L values are not going to impact the audio range in any way and don't show up in Bode plots until you get well into RF.

[martin manning]

Here is a high pass filter with ideal and real 270p C0G cap and 470k shunt resistor. The real cap has 0.167 mohm Rs and 0.85 nH Ls, from the cap library. The resistor is ideal in both cases.

[nuke]

Differences in dielectric behavior can be measured for sure, but not by ordinary means. An LCR meter or VNA will typically get only R and L parasitics. Scanning caps in the LTSpice library I find ca. 0.14 ohm and 0.85 nH for typical treble cap value and voltage rating. These R and L values are not going to impact the audio range in any way and don't show up in Bode plots until you get well into RF.

Indeed, one can measure anything if he spends enough money.

Curiously, some of the properties that do affect audio, are not part of the electrical characterization, but often a result electromechanical properties of the dielectric. Introducing microphonic distortion is often overlooked in designs. It isn't a parameter listed in the capacitor catalog datasheet. But it does truly exist, and it definitely can insert itself noticeably into audio systems.

So, I'd say, while taste-testing, definitely mechanically tap on the capacitor under test.

We like/dislike unpotted humbuckers for their microphonics or lack thereof, depending on how loudly one plays.

There are some really good papers on the topic of choosing capacitors in audio circuits.

https://www.ti.com/lit/an/slyt796a/slyt ... 8426834349

Mostly focused on SMD range selections, but still a good paper nonetheless.

This is a good one from an audio enthusiast:

https://conradhoffman.com/cap_measurements_100606.html

Then we get into other things, like aging:

https://www.knowlescapacitors.com/getme ... a3a/an0006

Then my post some time ago about "boutique" tone caps in guitars, like the Luxe Bumble-Bee paper-in-oil tone caps that are $20 each in 0.022 uf. These are very leaky, brand new, right out of the package. Pretty much measure out like a .022 with a 5-7 megohm resistor in parallel with it. You should never, ever use these in an amp, but guitarists are very fond of them as tone caps for whatever reason, real or imagined.

The truth, we humans tend to fool ourselves into hearing or seeing things that might not be there. That's double-blind testing, including the null-test, is so important. Testing A:B, B:A, A:A, B:B, in a double blind manner can be very interesting indeed.

[pjd3]

Yep, was just talking about that to my engineering manager and the "component engineer" tonight, how it's a well-known fact that even moderately effective A/B testing needs to be done with A/B very close together in time or the comparison becomes moot and unreliable. Hell, I was just woodshedding my stereo amp with an actual A/B switch so to be able to compare channels with nearly no break in time. It is still very hard to assess differences even with that level of "seamlessness" but, in this amp I strive to get each channel as close as I can within reason - really looking to the effects rendering of the stereo-ness".

Well, with a whole day between listens, I can say that its nice to have a nice notable amount of "Zing" back in my amp. It was very apparent that I had to increase the treble and presence by 70% of the knobs "turn angle" to achieve a sense of highs that were satisfying and reminded me of how I usually set the EQ. It was if a sparkle was there that had gone away, and I was indeed let down about that. Its all back, and I consider that a big achievement for me. I hate playing when I'm not inspired because of some sonic characteristic I've come to be fond of that is no longer there -just want to go home. But it is a great joy and can't get enough when all of the sonic items are present.

A few of you have left some obviously relevant technical coverage on caps. I'll have to get to all of that over a cup of coffee.

Final thought, you could give me a million dollars and I couldn't tell you what the characteristics of one cap to the next is that I've traded out, but, I'm happy with the sonic quality of my amp now, and confident to go out gigging and be inspired to play. Thank for chiming in, this sheete is actually quite fun and rewarding for this constantly gigging 69-year-old weekend warrior.

Best
{PHil D