May 31, 2012

• Tung-Sol 6550 Three-Hole Grey Plates

  Tung-Sol Electric Inc. made the three-hole version of the 6550 output tube from 1963 to the 1970’s and it is the final iteration of this type manufactured by them.  The quad of tubes under review all bear a “322RM-3” manufacturer and date code.  I have never been able to decipher their alphabetic dating scheme and so I’m not sure exactly when the review set was manufactured.  The “322” portion of the code indicates that they were made by Tung-Sol.

  This is a three getter output tube with one top getter and two on opposite sides near the top of the plate structure.  Tung-Sol utilizes four clear mica spacers around the tube’s top portion and the splatter shield is also transparent.  The tube has the classic Tung-Sol ST shape, a chrome-colored collar, and brown base.

  Tung-Sol 6550 three-hole grey plate                                                          Top view with original box
        

  Review set                                                                                               Close-up
       

  The review set was originally purchased as two pairs c. 2004, most likely from E-bay.  They have seen hundreds of hours of play time since purchase and are therefore well broken-in.  As a result, there was no change in their sound other than what occurs during normal system warm-up.

  An ergonomic aside:  the tubes snapped into place as if the sockets had been made specifically for them.  Too often the output tubes fit more loosely than I’d prefer or feel as if they’re being forced into place.

  A Little History:
  The 6550 output tube type was first developed by Tung-Sol and was introduced in 1955.  The first three iterations had black plates and were in order of development:  top getter only, top plus one side getter, and finally, top plus two side getters.  Next to be introduced were the solid grey plate version and lastly, the three-hole type under review.  The consensus is that the best were produced first and that as time went on and the plate structure changed, each succeeding generation was not quite as satisfying as its predecessor. 

  Personally, I think they all have their unique charms but that’s for another discussion.   

   

  Listening Impressions:

  • Bass is solid and well articulated with no overhang or bloat.  GE 6550A’s have a reputation for their bass reproduction but I’m not sure what, if anything, they have over these T-S 6550’s.
  • Dynamic range is excellent.
  • Midrange is clear and neutral with dialogue easy to understand and vocals sounding natural.
  • The treble range is delicate, refined and extended without being tipped-up and exaggerated.  Harpsichords are delicate without being threadbare and you can hear the strings resonating within a wooden body.
  • Silences are black – the music just stops.
  • Sound stage is wide and deep.

   

  Vintage Tung-Sol 6550’s, the three-hole grey plates included, are not my reference output tubes, in both the c-j Premier 11A and the Premier 140, because they possess a handful of reference-level sonic attributes.  Rather, it’s the fact that they are consistently excellent across the panoply of characteristics a reference-level tube should have:  evenness of frequency response, low level detail due to vanishingly low noise, excellent transient attack, decay, inner detail and truth of timbre, a dynamic presentation, a fully-fledged sound stage populated by realistically scaled images, and an unassuming quality that allows the music to flow and connect with the listener without drawing undue attention to itself.

  Other output tubes best the Tung-Sol in some of these attributes but none, in my opinion, have all of them to the degree that the Tung-Sol 6550’s enjoy. 

  
  

  • 8:19 am
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