The Infamous Paper In Oil Tone Capacitor

Written by
Logan Tabor
Published on
January 21, 2021 at 3:58:31 PM PST January 21, 2021 at 3:58:31 PM PSTst, January 21, 2021 at 3:58:31 PM PST
As any true vintage guitar enthusiast knows, there are a number of topics which, on internet forums, consistently trigger long and arduous debates.  The topic of paper in oil (PIO) capacitors vs. capacitors of any other construction method is certainly no exception; if you dare, try a few relevant Google searches, grab some popcorn, and get ready for a long night.  
Here at Mojotone, while we do pay attention to these debates, we really only do so in an effort to provide DIYers with the components they need and want.  With that said, today we are going to talk briefly about PIO capacitors, their historical significance, and why Mojotone has decided to introduce a few products from ‘Luxe’ into their product line: Bumble Bee and Black Beauty caps.
Historically speaking, the original Bumble Bee and Black Beauty caps were designed and manufactured by Sprague, although we’re fairly certain Sprague never officially referred to them as either “Bumble Bee” or “Black Beauty.”  If you’ve ever scoured the forums, talked to serious techs, or even A/B tested guitar tone caps yourself, you’re probably well aware that the Bumble Bee caps are and were highly sought after; and perhaps much of this hype came about because of the use of Bumble Bee caps in many of Gibson’s electric guitars from the 1950s.  These caps were filled with paper in a special oil inside of Bakelite bodies with the original NEMA color codes printed on them (this is how many resistors are still printed). The Bumble Bee caps were later replaced by the Black Beauties, which contained a winding of aluminum foil and paper film, along with oil, and were printed with the specs on their shell rather than the NEMA color code lines.  
Some engineers say the construction of these caps make them a perfect fit for high voltage applications.  Some say they make for the suppression of arcing, or they improve the cooling of heat spots. Many in the community agree that there is no valid scientific explanation as to why PIO caps should or would sound any better or worse than any other type of capacitor when used in an amplifier or guitar application.  But one thing a great deal of players and techs have agreed on over the years is that, regardless of whether or not a scientific explanation is available, the PIO caps seems to offer warmth and smoothness of sound where other types of caps come up short.  
Just as with anything else, we at Mojotone are not here to speculate on tonal characteristics of this or that capacitor, nor are we here to tell customers they HAVE to buy ‘x’ speaker or ‘y’ pickup.  The simple truth is that, over the years, our customers have expressed a desire to have a source for quality, vintage-correct paper in oil tone capacitors. And being that our primary mission is, and always has been, to provide our customers with vintage-correct parts, we set out to find the best possible resource for these caps.  
It is true that one could still search Ebay for new old stock Bumble Bee and Black Beauty capacitors that were, in fact, manufactured by Sprague and are still in working order.  However, not everyone is looking to sell their first born son just so they can afford a pair of caps. But the need is still there. Nevermind one’s personal quest for tone or the unending need to tweak and modify every piece of their rig, the important thing here is to achieve historical accuracy.  If one were to be restoring or repairing a Gibson guitar from the 50s, it can be assumed that a responsible tech would seek to replace any electronic components with the most historically accurate parts available. The same principle applies to amplifier parts, and Mojotone does their best to cater to this need with things like our hand-wound vintage-correct transformers from Heyboer.  We are striving to pay homage to the forefathers of great gear here! This is why we have decided to include Luxe capacitors in our offerings.  
Luxe is a company with whom we are proud to align ourselves.  Their dedication to the craft is unparalleled and the amount of love that goes into each and every capacitor is truly something to be marveled.  Luxe’s Bumble Bee and Black Beauty clones are not only constructed in a vintage-corrected manner, but are finished and hand-painted/hand-marked to visually resemble the originals down to the last detail.  Read the description of their Bumble Bee clones below:
Each cap is hand wound on an original Vintage Winding Machine using exact vintage spec aluminum foil and paper film. They're hand soldered, hand cast in oven-proof thermoplastic, hot vacuum impregnated with pure castor oil and hand-painted.
Everything is handmade here.  They even use the actual vintage winding machine that would have been responsible for winding these caps back in the 50s and 60s.  The designers at Luxe have really crystallized the look, feel, sound, and essence of the original Sprague caps. Whether one agrees with or can even hear the difference in sound between vintage-style PIO caps and any other type of cap, at least now the option to accurately compare is available; and more importantly, the option to restore vintage relics in a reverent and faithful fashion is totally possible without breaking the bank.
Check out our new line of Premium Historic wiring harnesses featuring these Luxe Capacitors.  This is an offering we have been waiting to roll out for quite some time, we just needed to find the right manufacturer.  We are proud to offer these harnesses and capacitors to our customers who, by the way, have been patiently waiting for quite some time while we got all the right pieces together.  A big thanks to all our techs who have requested these over the years! Now go have as much vintage-correct fun as you can possibly stand, and be on the lookout for more Premium Historic wiring harnesses from Mojotone featuring Luxe’s Fender-style Phone Book caps.