Butler Audio TDB 3150 User Manual

 

8 

Within reasonable limits, it has been our experience that you get 

what you pay for in cables.  A good set of shielded input connection 

cables coupled with large gauge, high quality low-loss speaker wire is 

well worth the investment.  Do not degrade the remarkable 
performance of your amplifier with inferior connecting cables. 

 

The Marvelous Vacuum Tube: 

Triode Vacuum Tubes were the first method of practical audio 

amplification patented in 1907 by Lee De Forest.  At first, he used 
an open flame to produce thermionic emissions, but later found an 

electrically heated filament was much more practical.  

 

The first triodes were inefficient and often very mismatched in 

performance.  Thankfully we now have reliable sources of precision 

manufactured triode tubes, which are very consistent in quality and 
performance. 

 

Over the years, BK Butler has experimented with virtually every type 

of audio vacuum tube.  In 1992 he obtained a large Vacuum Tube 

Analyzer formerly used by the FAA to test and analyze radar tubes 

for aviation control towers.  This old but very high-quality apparatus 
enabled him almost unlimited control to adjust and experiment with 

virtually every conceivable parameter of any tube.  For example, 

input and output pins could be reassigned.  B+ voltages and bias 

currents switched to any desired value or configuration.  During 

these test, it was noted that a Phantom voltage was being 

generated. 
 

It turned out to be nothing less than the original thermionic effect 

that one of Edison's assistant technicians (a Mr. Hammer) 

discovered in the late 1800's while testing early light bulbs.  He 

noted a blue glow around the positive pole in a vacuum bulb and a 

blackening of the wire and the bulb at the negative pole.   At first, 
this was referred to as "Hammers Phantom Shadow", but later 

Edison took credit for the discovery himself (as was his practice) 

and re dubbed it as "Thermionic Emission".  More tests followed and 

soon the first vacuum tube diode was invented.   Limited at first to 

rectifying AC into DC, Edison failed to make the one essential step 
needed for tubes to achieve useful amplification. 

 

However, around 1906, Lee De Forest vastly improved the  

2-electrode vacuum tube diode by adding the crucial element: a 

third electrode, or control grid.  The rest is history.  The successful 

invention of the amplifying vacuum tube triode, which could regulate 
the thermionic emissions of electrons from heated cathode, 

became the foundation for our modern electronics industry.  

Without De Forest's great insight and marvelous discovery, you 

would probably not be enjoying your new Butler Audio amplifier!