May 19, 2012

• Electro-Harmonix 6550EH

  The physical description of the 6550EH is basically the same as the KT88EH:  it is a top getter only, three-hole grey plate tube with a chrome-colored collar and black base.  The 6550EH is less expensive than its fraternal twin, the KT88EH.  You can purchase a single tube for $29.95 at Upscale Audio and a matched pair will cost you $49.95 at the Tube Depot.  I’m sure it is also available at many other tube vendors since it is still in current production.

  6550EH front view                                                                                  6550EH rear view
               

   
  6550EH close-up
   

  
  A Little Background
  
  The New Sensor web site states that the 6550EH dissipates 42 watts in tetrode mode which makes me wonder whether this is really more like a KT88 than a 6550.  (A 6550 output tube is rated at 35 watts dissipation while a KT88 dissipates 42 watts.)  However, they also spell Genalex as “Genelex” in the same ad copy and that makes me wonder, too, how closely I should pay attention to their ad copy.

  And speaking of ad copy, every single description I read about this tube, regardless of the web site, states that the 6550EH has “four-pillar construction” even though I count six.  Four of the support rods clearly run from top to bottom.  Maybe the other two are just additional supports for the getter splash screen but they certainly seem to me to be embedded in the plates and then come out the bottom.  I have two words for you:  Sturgeon’s Revelation.

  All four tubes under review were manufactured in November, 2001 and, therefore, may bear no relationship to current production.  One of them has the tell-tale greenish cast.  Perhaps that has to do with the leaded glass formulation that New Sensor says is used in their construction.

  The tubes continued to change, for the better, during the audition and didn’t fully burn-in until approximately 28 hours total playing time. Because of this relatively long time period, I believe the tubes were unused prior to auditioning them.  The KT88EH, in comparison, took less than half that time (about 12 hours) before they were fully settled-in.

  Two comments before I get to my Listening Impressions.  There seems to be a real dichotomy between how I feel they sound when listening to music on CD and LP versus the sound portion of video on a source such as cable or Netflix streaming through my Oppo BDP-95.  I preferred them with purely musical source material and quite honestly, I’m not sure why there was a difference.  When listening to music, I prefer these to the KT88EH but the case is reversed with video sources.

  Second, although the 6550EH appear to be physically identical to the KT88EH, except for minor differences in bottle shape, and their claimed dissipation is the same as a KT88 type tube, they do not sound identical.  That having been said, they sound more similar than dissimilar.  I don’t think I’m in “how many dancing angels” territory here, but thought you should know.

   

  Listening Impressions:

  • A little bass shy and lacking the articulation heard with very good output tubes in the 6550/KT88 family.  At times, it seemed more thuddy than deep.
  • Violins were pleasant but too soft without any bite at those times when they should’ve had it.
  • The “clacking” which sounded so realistic with the GEC KT88, is much less realistic this time around. 
  • Crowd noises and clapping weren’t as nicely defined as the KT88EH.
  • Their strength is in the midrange.  Listening to Sade’s “Love Deluxe,” there were times she sounded like she was in the room and there was a rich, creamy texture to her voice.
  • Dynamics and detail were better than the KT88EH but still nothing to write home about.
  • Very good sound stage abilities and similar to the KT88EH, there was more to be heard behind the plane of the speakers than typically.
  • Images were compact and, for the most part, occupied their own space with only occasional blending of imagery.

   

  The 6550EH doesn’t have the apparent power and smoothness of a GE JAN 6550A or the clarity of a three-hole Tung-Sol 6550 but at 1/5^th the price of the former and 1/10^th of the latter, the comparison is unfair.  However, when viewed from the context of more cost equal offerings from Russia and China, they still do not shine in my opinion.

  It isn’t that they do anything especially badly.  The bass could go deeper, the treble could be more open but I could say that about a good deal of the output tubes in this family that I’ve reviewed of late.  But ultimately, they just leave me cold.

  Of course, your mileage will most definitely vary.

   

  • 7:48 am
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