Not just an replacement, but an improvement!

The XLS Series tubes are based on an extra large size (XLS)  plate system.  This sytem is taken from earlier 520B tubes, and has proven to be ideal for high power applications. 

The 320B-XLS  tube is a stronger version of the 300B.  The difference between the 300B  and the 320B-XLS is  the higher filament current of the 320B and the higher power handling capability. 

The 320B-XLS will bias  like a normal 300B tube,  when used in any 300B amplifier,  but it needs to be checked if the higher  filament current can be supplied by the amplifier.   When used like this, due to the stronger electron emission, this tube  will develop the output signal with  more ease. 

When biased higher than a standard 300B,   the 320B-XLS will show more of  it's superior quality. It will now show a better dynamic behaviour, and lower distortion at all power levels. 

All critical parts, like filaments, grids and plates are constructed of hard metal for higher reliability and reproducable quality. 

• Hard metal filaments and Plates, Wolfram Grids (Note1)
• 6 circular cooling plates 
• Wolfram Grids (Note1)
• Two extra large getters, flashing the complete tube bottem. 
• Hand blown ST Glass bulb
• Anti-microphonic plate- and grid  suspension
• These tubes are shipped in a high quality dual box
• Tube pinting with real gold (metal),  red color is burned into the glass 
• Machined, solid tube base pins for highest contact precision. Ideal for the YAMAMOTO tube sockets. 
• Gold plated pins,  black ceramic socket.  (White bottem)

• Note 1)  Hard-metal filaments prevent filament breakage with DHT Tubes.  This material has a higher melting point than the classical nickel wires. Hard metal plates have a more precise plate distance, and do not change shape when heated.  This ensures  reproducable tube parameters, and long term stability. Wolfram grids  allow the most precise grid wire distance, because wolfram is an extreme hard metal.   This ensures better uniformity and linearity at the low end of the tube curves.
• Note 2)  Individual Test data, such as:  Matching Data, Grid Current, Vacuum, Filament Current, etc,  are on the Certificate that comes with each individual Tube.  Each tube is numbered, inside the bulb  with a metal Tag
• Note 3)  Plate Curves:  Made with the Sofia Digital Curve tracer.  Plate curves with courtesy of AMR
• Note 4)  Plate Curves:  Check the plate curves of this tube, and note that at higher dissipation, the curves get more linear.  The result of this is very positive for the sound of the tube.    First, more linearity means, the not good sounding  3rd. + 5th. harmonic will reduce.   Second,  the  tube plate resistance will be lower at higher dissipation.  (plate resistance is measured as the angle of the curves).  A lower plate resistance  will give a better damping factor of the bass spaeaker.  The result of this is a more exact transformation of the electrical signal into the correct speaker movements, goving a more natural sound, also at  low power level. 
• Note 5)  Higher filament current:  The function of any tube is based on emission.  The more emission, the less distrotion at peak power signals. This is true for any electron tube, regardless the application or the brand.  More Emission can only come from a cathode which is using more power.  This is why the 320B uses so much filament current.