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christophe sas
christophe sas's picture
Last seen: 4 months 2 weeks ago
Joined: Apr 12 2019 - 7:53pm
KT88 tubes durability?


I'm currently using a Cayin A-88T integrated amplifier, with KT88 Genalex Gold Lions tubes, and would like to know what would be the average life span of such tubes, because I haven't found any official ou reliable informations/specs on the web.

Thank you.

JRT's picture
Last seen: 12 hours 21 min ago
Joined: Jul 12 2007 - 12:36pm
I am not familiar with specifics on the Cayin

Much depends on the voltages that Cayin is using in the application.

Many ultralinear applications of the KT88 use an output transformer that operates the tube's screen grid at the same supply voltage as is used on the anode, uses one winding with separate taps rather than using a separate winding. Better output transformers have a separate winding for the screen grids and operate the screen grids at reduced supply voltage for lower distortion and longer tube life. The separate winding adds a little cost to the transformer. The reduced supply voltage on the screen grids adds a little cost in the circuitry. The Cayin is competing in a cost sensitive market segment.

Menno van der Veen's VDV-2100-CFB-SSCR-PPS is an example of a very good output transformer for this family of output tubes.

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