Russian Pio caps

[freefrog]

Below is the response of the pickup with 120k load + Orange Drop VS 120k load + PIO.

The Orange Drop was a 22nF cap and the PIO was... a 33nF one. Both tested close to their theoretical capacitance with a Rigol DM3058 lab meter.

The harmonic response obtained in this case is not what one would expect from such values. That's precisely why I share these examples. Vertical scale goes by steps of 3dB, BTW.

​

 

[beaubrummels]

Below is the response of the pickup with 120k load + Orange Drop VS 120k load + PIO.

The Orange Drop was a 22nF cap and the PIO was... a 33nF one. Both tested close to their theoretical capacitance with a Rigol DM3058 lab meter.

The harmonic response obtained in this case is not what one would expect from such values. That's precisely why I share these examples. Vertical scale goes by steps of 3dB, BTW.

​

Oh ok, I see. I guess what I was getting at was it would be a pretty clear answer to the legendary tone cap question if there was a PIO and Orange and both were 'exactly' 0.022uF (within 1% at least) and to see if there is a harmonic content difference through the tone caps if stimulated the same way.

Also, FWIW I'm not seeing a chart in that last post, but I see an attachment when I quote it. Not sure what's going on there.

 

[freefrog]

Oh ok, I see. I guess what I was getting at was it would be a pretty clear answer to the legendary tone cap question if there was a PIO and Orange and both were 'exactly' 0.022uF (within 1% at least) and to see if there is a harmonic content difference through the tone caps if stimulated the same way.

For me, the answer is even clearer when the higher capacitance cap, meant to make the sound darker, gives paradoxically more harmonics around 3,5khz (location of the initial resonant peak of the pickup in this case) and a more open high range (a lower Q factor) beyond 5khz... YMMV.

 

[beaubrummels]

For me, the answer is even clearer when the higher capacitance cap, meant to make the sound darker, gives paradoxically more harmonics around 3,5khz (location of the resonant peak in this case) and a more open high range (a lower Q factor) beyond 5khz... YMMV.

I saw that. Couple things: I don't know what the corner frequency is for .022uF vs .033uF. If 3.5-3.75khz is below the corner frequency of the tone network, cap value could be a red herring and it's something else going on. I noticed on the graph with just the resistor, the resistor took out 6-12db at around 3.75khz and the cap seemed to restore what was there before. Correct me if I'm wrong, but from the electronics books I have, my understanding is part of how a cap works is it changes the phase of the signal, I assume that's related to the delay of it 'filling up' and then discharging. My semi-educated guess is that could be how certain frequencies diminished by the resistor could be restored. It would be good to see a .033uF Orange cap and see if it has the same behavior as the PIO, meaning it happens to be at just the right value to restore the energy around 3.75khz

 

[freefrog]

Not easy to dig deeper when life is busy but I’ll try to share the beginning of an answer the most clearly possible…

a)About frequencies: with a typical P.A.F. style humbucker like the pickup involved in my previous posts, pickup inductance + capacitance of the tone cap (without resistance in between) sets the resonant peak around 500hz for a 22nF cap and 400hz for a 33nF one. 3.5khz to 3.75khz is the resonant frequency of the pickup as set only by its inductance + cable capacitance (when the tone control is @ 10/10 and meant to keep the tone cap out of the circuit). With a resistance of 120k, the tone network drags the maximum output of the pickup between the frequencies mentioned and more precisely, around 2.5khz (although the “resonant peak” looks more like a “dome” with a so low resistive load).
b)No 33nF Orange Drop here. But our tests involved things like a 33nF ceramic cap and it didn’t shape the harmonic spectrum like the 33nF PIO evoked above: no correlation has been found between measured capacitive values and frequency selective behavior.
c)Now, as a matter of fact, a resistive load + cap doesn’t necessarily appear to filter harmonics in the same way than a resistive load alone, and i also see something interesting in this apparent paradox.

More later maybe: it’s late at night here, my bed is calling me. ;-)


...I EDIT this message to complete it quickly, before a working day.

Below is a 5spice sim illustrating my tedious explanation a) above. One can see how 33nF or 22nF caps make a clear difference for the resonant peak of a generic humbucker with a tone pot @0/10 (peaks 1 & 2), no difference at all with a 500k tone pot @ 10/10 (peak 4) and an almost imperceptible difference when the resistive load of the tone control is 120k (=a linear 500k set @ 1/4, peak number 3; the red and black lines reffering to 22 or 33nF caps don't overlay exactly but the difference is minuscule).



The distribution of electrically generated harmonics SHOULD follow these curves at least approximatively and with consistency. A tone pot set @ 120k SHOULD filter the harmonics in the same way whatever is the tone cap used. In experimental reality (ours, at least), it's not the case (regardless of the capacitive value of components and of the related phase shift). That's precisely why i've shared harmonic measurements above.

 

[EmiAba]

IOW, you have tried the PIO caps and now you prefer it to the Orange Drops described as your favorite in the first post ? This is a friendly question: no irony in my words.

I have a couple of Russian Pio caps but I have never tried them or any other PIO cap. But I've tried differ Polypropylene caps and different ceramic caps. The orange drops from Sprague are currently installed on my guitars. They seem better to my ear. Don't know if it's only my impression or it's reality but the guitar seem to have a more open tone. I just wonder if in term of quality and durability the PIO caps are better than the other types and and why they seem to have a certain aura. And why the bumblebee costs three time a Polypropylene cap

 

[beaubrummels]

I have a couple of Russian Pio caps but I have never tried them or any other PIO cap. But I've tried differ Polypropylene caps and different ceramic caps. The orange drops from Sprague are currently installed on my guitars. They seem better to my ear. Don't know if it's only my impression or it's reality but the guitar seem to have a more open tone. I just wonder if in term of quality and durability the PIO caps are better than the other types and and why they seem to have a certain aura. And why the bumblebee costs three time a Polypropylene cap

FYI the current bumblebees are actually polypropylene inside. No reason to pay that money unless you like the color.

https://www.mylespaul.com/threads/historic-gibson-faux-bumblebee-caps.118027/

 

[freefrog]

I have a couple of Russian Pio caps but I have never tried them or any other PIO cap. But I've tried differ Polypropylene caps and different ceramic caps. The orange drops from Sprague are currently installed on my guitars. They seem better to my ear. Don't know if it's only my impression or it's reality but the guitar seem to have a more open tone. I just wonder if in term of quality and durability the PIO caps are better than the other types and and why they seem to have a certain aura. And why the bumblebee costs three time a Polypropylene cap

I had understood that part of your questionment but your post 13 quoted again below seemed to suggest that you had tried PIO's in the meantime and that you prefered them finally. Or am I missing something?

So to summarize, same value same tone regardless the material they are made of. The PIO are less stable and less reliable in terms of durability. Mmmh why they are so pricey? I mean, taking aside the vintage aura, what is the reason I do prefer them over all the others?

Anyway...

Your questions seem to have been answered in previous posts.

Price: probably due to a conjunction between popular demand and more complex product + process (easier to wrap a metalized foil and to encapsulate it in a solid compound than to put it in a tube, before to fill the tube with toxic oil and to seal it hermetically).

Durability: as beaubrummel said, PIO can drift. I'd just modalize this idea by stating that 1)many electronic components can drift (carbon resistors, electrolytic caps, but also other non polarized caps: there's vintage mylar "Black Beauties" in our collection of old components and they have drifted too) and 2)there's is way less reasons for a PIO to dry and drift if it's not exposed to heating / cooling cycles and if it has been properly sealed first.

Quality: generalizations don't appear to me as pertinent here. A cap designed and built on high standards (like a low ESR) will be "better" in its adequation with theoretical value and absence of parasitic properties... but if you don't hear the difference, it won't be "better" musically.

Reason why I wonder why you don't simply try them. It's not even necessary to open or (de)solder anything: alligator clips and components can do wonder once the end of a guitar cable unscrewed and giving access to hot+ ground.

 

[EmiAba]

FYI the current bumblebees are actually polypropylene inside. No reason to pay that money unless you like the color.

https://www.mylespaul.com/threads/historic-gibson-faux-bumblebee-caps.118027/

:bigeyes2:

 

[beaubrummels]

Not easy to dig deeper when life is busy but I’ll try to share the beginning of an answer the most clearly possible…

a)About frequencies: with a typical P.A.F. style humbucker like the pickup involved in my previous posts, pickup inductance + capacitance of the tone cap (without resistance in between) sets the resonant peak around 500hz for a 22nF cap and 400hz for a 33nF one. 3.5khz to 3.75khz is the resonant frequency of the pickup as set only by its inductance + cable capacitance (when the tone control is @ 10/10 and meant to keep the tone cap out of the circuit). With a resistance of 120k, the tone network drags the maximum output of the pickup between the frequencies mentioned and more precisely, around 2.5khz (although the “resonant peak” looks more like a “dome” with a so low resistive load).
b)No 33nF Orange Drop here. But our tests involved things like a 33nF ceramic cap and it didn’t shape the harmonic spectrum like the 33nF PIO evoked above: no correlation has been found between measured capacitive values and frequency selective behavior.
c)Now, as a matter of fact, a resistive load + cap doesn’t necessarily appear to filter harmonics in the same way than a resistive load alone, and i also see something interesting in this apparent paradox.

More later maybe: it’s late at night here, my bed is calling me. ;-)


...I EDIT this message to complete it quickly, before a working day.

Below is a 5spice sim illustrating my tedious explanation a) above. One can see how 33nF or 22nF caps make a clear difference for the resonant peak of a generic humbucker with a tone pot @0/10 (peaks 1 & 2), no difference at all with a 500k tone pot @ 10/10 (peak 4) and an almost imperceptible difference when the resistive load of the tone control is 120k (=a linear 500k set @ 1/4, peak number 3; the red and black lines reffering to 22 or 33nF caps don't overlay exactly but the difference is minuscule).



The distribution of electrically generated harmonics SHOULD follow these curves at least approximatively and with consistency. A tone pot set @ 120k SHOULD filter the harmonics in the same way whatever is the tone cap used. In experimental reality (ours, at least), it's not the case (regardless of the capacitive value of components and of the related phase shift). That's precisely why i've shared harmonic measurements above.

This is interesting information, though some things look funny to me with the graph. It's saying that from 10 all the way down to 2.5, regardless of cap value, all that happens is the peak at 4khz softens to flat 0db, and from 2.5 to 0, all the frequencies above 500hz are suddenly rolled off, almost irrespective of cap value. That doesn't seem linear to start with, and doesn't match my real-world experience with tone controls. Is there some other consideration not stated about the graph?

FWIW I might have expected a curve progression more like this one below (this one uses log pots and accounts for the volume pot also, however. Interesting that the log pot results in what seems like a more linear progression to me). The resonant peak disappearing and coming back is interesting - not sure that's how I've heard it in real life, but I'm open to be convinced and maybe that is how it really sounds and I just didn't perceive it that way; or if there is an audio demonstration that would be helpful.

https://guitarnuts2.proboards.com/thread/7166/effect-tone-capacitors

 

[freefrog]

This is interesting information, though some things look funny to me with the graph. It's saying that from 10 all the way down to 2.5, regardless of cap value, all that happens is the peak at 4khz softens to flat 0db, and from 2.5 to 0, all the frequencies above 500hz are suddenly rolled off, almost irrespective of cap value. That doesn't seem linear to start with, and doesn't match my real-world experience with tone controls. Is there some other consideration not stated about the graph?

FWIW I might have expected a curve progression more like this one below (this one uses log pots and accounts for the volume pot also, however. Interesting that the log pot results in what seems like a more linear progression to me). The resonant peak disappearing and coming back is interesting - not sure that's how I've heard it in real life, but I'm open to be convinced and maybe that is how it really sounds and I just didn't perceive it that way; or if there is an audio demonstration that would be helpful.

Monday morning here, 6:20 AM, answer wrote before a working day. To take accordingly. ;-)

To reply to your two paragraphs in reverse order:

2) my 5spice sim would have looked more like the curves on guitarnutz if I had used more than 3 steps in my simulation (pot full up, @ 120k and zeroed) [EDIT of the next day: and if my 5spice sims didn't involve LINEAR pots, BTW. Necessarily not the same than with log pots in the guitarnutz pic.]

1)yes my simplified graphs simulating the action of linear pots suggest practically identical curves for tone pots fitted with different cap values until the settings are very low (unless the taper of the pot itself changes, of course)... and for many players real life experience with tone caps seems more complex than this.

The guys on guitarnutz or similar forums tend to attribute that to psychoacoustic.

During the 10+ years of tests devoted to tone controls here, another strategy has been adopted, leading to different results.
To sum it up simplistically, the conclusion was that the curves shown above are absolutely realistic and reliable for a swept sine wave or a polyphonic signal... If someone plays a neck PU with tone pot @ 0/10 in chords direct to the board, records it and visualizes the EQing curve obtained on a frequency analyzer, it will look like the curves 1 or 2 in my spice sim, rolling off any frequency above 400hz with a 33nF or beyond 500hz with a 22nF [EDIT - as long as pickup inductance, cable capacitance and input impedance are the same, of course.]

There's a few exceptions to this, leading to measurable differences in resonant frequency / Q factor but generally due to parasitic properties like a very high ESR.

Things change when harmonics are took in account: seems that differences perceived by players with tone caps mainly come down to how tone controls filter harmonics.

It's not a question of capacitive value. It's not simplistically due to cap materials. It's not something that I can explain here (lack of time, questions of intellectual property)... but it can be checked by anyone with an ultra low impedance air coil able to excite pickups, a calibrated soundcard and a software designed to do harmonic tests.

More later maybe. Must go or I'll be late at work. ;-)