20_Kellog

Kellog Switchboard and Supply Co. started around 1925 manufacturing very early vacuum tubes with AC heaters for Frederick S. McCullough, owner of the patent. At the beginning tubes were advertised under the McCullogh brand. Around 1929 Kellog put on the market the same tubes with its own name, as the Kellog 401.

The Canadian Rogers had bought the patent rights to produce these tubes and had started its own production since August 1925. Rogers redesigned the cathode for improved performances and reduced hum.

Kellog completed its AC tube line adding the output power triode Type 20 in the picture aside, actually bought from Rogers and rebranded.

	Just Qvigstad

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