Re: 6DJ8 substitute idea - reverse engineering

Michael Perkins

They were actually a cascode, not a cascade.

On Tue, Jun 22, 2021 at 2:58 PM Michael Perkins via <terman08=> wrote:

Western Electric made solid state replacements for tubes, calling them
fetrons. They were a cascade of two fets, one a high gm fet and one high
voltage fet. It might be harder to do with Jfets in decline, but they would
last longer than NOS Russian tubes or trying to find working 6DJ8s. Tek
wrote a paper on creating the 6DJ8. If I can find it , I'll send it to you.

On Tue, Jun 22, 2021 at 2:32 PM Michael W. Lynch via <mlynch003=> wrote:

On Tue, Jun 22, 2021 at 03:04 PM, David Holland wrote:

When the definition of perfection is the shape of a plate, or its
the color of the pins, or even the factory of manufacture, it's not
all that hard to find perfection in old 6DJ8's.

Exactly my point, more importantly, the tubes in question need to solidly
meet the basic spec for the TEK gear in which it is to be used. However,
the tube certainly does not need to be the "pinnacle" of physical
characteristics,electrical "perfection" or identical performance. When
more than one tube of a type is used, a "Perfect" match between all tubes
is also not generally needed, unless the schematic calls for a close
of some certain specification. I do not have a dog in the tube "hunt" as
most of what I work on has those three legged bugs and little black
caterpillars or centipedes. I just know that when I see a $5 USD tube
selling for $100 or more for a single tube, based on some mystical
combination of characteristics, even a solid state guy such as myself
begins searching around for the "snake oil salesman"; especially when it
comes to test equipment. It will be interesting to hear the results of
your purchase and how these tubes compare to the 6DJ6.

Michael Lynch
Dardanelle, AR

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