October 23, 2012
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Power Tube Update
As regular readers of these ramblings will know, I had my conrad-johnson Premier 140 repaired and upgraded with CJD Teflon capacitors by the manufacturer (see Part 1 and Part 2). For almost a year, while the Premier 140 languished, I was using my trusty Premier 11A amplifier and many of the reviews that appear in these pages and this update, were written during that time period.
What I have found is that a good deal of my impressions regarding the tubes used in my system, including both the Premier 140 and to a lesser degree, the Premier 16LS2 preamplifier, have changed since the 140 went back into service on July 18th.
I thought it was time, therefore, to revisit some of my power tube evaluations in light of the Premier 140’s return. During this three month period, I have auditioned the following baker’s dozen of output tubes. NB: Many of the review links are from when the tubes were used in the 11A, and while my general impressions may remain the same, there has been a distinct shift in my preferences based on how the tubes performed in the 140.
Ei KT90 Type 3
General Electric 6550A
New Sensor: Genalex Gold Lion KT88, Tung-Sol 6550 , Tung-Sol KT120
Penta Labs KT88SC
Philips ECG 6550
SED =C= 6550C
Sovtek KT88
Tung-Sol 6550: black plate, solid grey plate, three-hole grey plate
Valve Art KT88It is difficult for me to state unequivocally that this or that particular tube is my favorite because so much of what goes into that decision process is dependent on ancillary equipment, source material, and quite honestly, my mood. That having been said, what can be done is to break out these various output tubes into a general system of tiers. These tiers represent, at this point in time, my overall preferences. Within each tier, the output tubes are cited alphabetically and are not necessarily an indication of actual preference in that tier.
For comparison purposes, I’ve indicated in parentheses how I informally ranked these same tubes when evaluating them in the Premier 11A.
Tier 1:
SED =C= 6550C (#6)
Tung-Sol 6550 three-hole grey plate (#3)
Tier 2:
New Sensor Genalex Gold Lion KT88 (#4)
Tung-Sol 6550 solid grey plate (#2)
Valve Art KT88 (#13)
Tier 3:
GE 6550A (#8)
New Sensor Tung-Sol 6550 (#9)
Tung-Sol 6550 black plate (#1)
Tier 4:
New Sensor Tung-Sol KT120 (#10)
Penta Labs KT88SC (#14)
Philips ECG 6550 (#7)
Tier 5:
Ei KT90 Type3 (#11)
Sovtek KT88 (#19)
There are a good many tubes that were reviewed in the Premier 11A that I haven’t tried as yet in the Premier 140. And so there may be some additions and changes over time, but at this point, these are the standings.
