One thought on “Tung-Sol 6550 Holes in Plate – USA”

1. A Piece of Vacuum Tube History

   This is a legendary tube that effectively birthed the entire 6550/KT88 lineage in February 1955. It is a notable piece of engineering history, as it was one of the few iconic designs developed by Tung-Sol independently, rather than by industry giants like RCA or GE. (As a side note for history buffs: Tung-Sol was also the innovator behind the flashing turn signals used in automobiles!)

   Variations and Build

   The Tung-Sol 6550 typically appears in three distinct flavors:

   • Black Carbonized Plates (The most expensive due to rarity)
   • Gray Solid Plates
   • Three Holes in Plate (The later version reviewed here)

   While the black plate versions command a premium price on the market, my testing across all three types suggests that there are no significant sonic differences between them. You are largely paying for rarity rather than a different sound signature.

   Sonic Performance

   In terms of audio quality, these tubes are incredibly musical and detailed with a remarkably even tonal balance. When comparing them to other heavyweights in the category:

   • Low End: The bass is well-defined, though not quite as authoritative or strong as the Genalex UK or Svetlana Winged C.
   • High End: The treble is nicely extended. While it doesn’t reach the absolute crystalline clarity of the Genalex UK, it is significantly better and more nuanced than the Genalex Russia reissues.

   These are exceptionally reliable and sonically pleasing tubes. They successfully avoid the “dryness” or “mushiness” that often plagues modern production 6550s.

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   Final Verdict: A historic, reliable performer that offers a balanced and detailed sound. It is a fantastic alternative to new production tubes, especially if you value musicality over raw bass power.

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