June 20, 2012

• Electro-Harmonix 6922EH

  The subject set of six Electro-Harmonix 6922EH tubes was purchased directly from conrad-johnson design, inc.  The 6922EH has the typical Russian squat, larger bottle shape, “flying saucer” getter ring and steel pins.  Although they  are available in a gold pin version which should show a resistance to getting grungy, I don’t know if there any real sonic advantages to having them.  This set was manufactured in August, 2008.

  6922EH front view                                                                             Flying saucer getter
       
  

  
  According to the c-j web site:  “At conrad-johnson we spend countless hours evaluating various vacuum tubes for each product. The tubes are selected based on sound quality and reliability. We know of no currently available tubes that are reliable and will improve the sound quality of your conrad-johnson component.  All tubes that we supply are then tested in circuit for performance to our specifications. For consistent results, we recommend that you purchase tubes supplied by conrad-johnson.” 

  Elsewhere on their site:  “Many of the newer CJ preamps and power amplifiers come with circular rubber tube dampers as standard. We recommend the use of these on all preamplifier tubes and on amplifier input tubes. Avoid using the very soft Sorbothane tube dampers that have been commercially marketed. These melt from the heat of the tubes and can foul the tube sockets. Do not use any kind of damper on amplifier power output tubes.”

  Review set with rubber O-rings in place
   

  These quotes are cited to explain why, contrary to my usual practice of using older production tubes, the subject tubes are the ones actually supplied by c-j and the stock O-ring tube dampers were used.  It’s recommended that the two O-rings per tube be placed approximately 1/3 of the way from the top and bottom of the tube.  Quite honestly, I think there are better tubes out there and that the O-rings, while of some benefit, change the sound of the component in some ways that I don’t care for.

  That having been said, there is the counter-argument that using the tubes a component was voiced with and in the manner that they were intended to be used (i.e., with the tube dampers), gives the listener the opportunity to hear the component as the manufacturer intended it to sound.  Also, in defense of c-j, the tubes I’m referring to, that I think are superior, are old stock (used, ANOS, and NOS) and therefore in limited supply and sometimes, much more expensive.  An audio manufacturer needs to ensure that their customers are able to purchase a ready supply of replacement tubes.  The 6922EH fit that bill.

  I’m in the process of having my c-j Premier 140 amplifier repaired and while it’s in the shop, the capacitors are being replaced with the newer CJD Teflon jobbies.  According to both reviewers and c-j owners, these Teflon caps take an inordinately long time to break-in.  Estimates range from 300 to over 1,000 hours before they are fully settled-in and their true potential is realized.  With that long time period in mind, I’ve decided to use the 6922EH dual triodes in preparation for, and during the break-in period.  Although not exactly cheap when purchased from conrad-johnson, I figure I’d rather burn these than NOS Bugle Boy 6DJ8’s which are going for $110 to $130 each nowadays.  Plus, using them while I still have the 11A on line gives me a basis for comparison when the Premier 140 finally does come home.  

  The Listening Impressions portion of the review is based on using the following output tubes in conjunction with the 6922EH:  New Sensor Gold Lion KT88, Ei KT90 Type II and New Sensor Tung-Sol KT120.  The small signal tubes in the Premier 11A continue to be my currently preferred configuration:  all General Electric of the older white label type.  They are the GE JG 5751 black plate, triple mica with a D-getter and the GE 6CG7 grey plate, double mica with an O-getter.  Years of manufacture are unknown.      

  Listening Impressions:

  • The sound of wooden blocks and percussion is excellent.
  • Rock music through the Ei KT90’s is forceful and detailed.
  • Female voice varies in quality depending on the output tube, suggesting these are very accurate in that range.
  • More extended in the upper frequency range.
  • The sound stage is not as consistently deep as the Bugle Boys.
  • Not as grain-free as the Amperex tubes.  Although that is a hallmark of the Amperex brand in this tube family.
  • A little less of the emotional content and musicality in comparison to the Amperex Bugle Boy 6DJ8s and 7308s are conveyed.
  • The match with the NS KT88 is better than the Amperex Bugle Boys in terms of overall clarity and macro-dynamics.

  Although the 6922EH may not be among my favorite dual triodes for the Premier 16LS2, they did allow for clear differentiation among the output tubes.  I’ve previously referred to the chameleon-like quality of the Premier 16LS2 and in this respect, the 6922EH are able to show that characteristic of the preamp about as well as any tubes I’ve used. 

  I haven’t used any currently produced tubes in the 16LS2 other than these so I cannot draw any comparisons to either the New Sensor Gold Lion 6922 or the JJ brand.  I can say, however, that the 6922EH “speak” with a clear and neutral voice.

   

  • 9:12 am
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