frame grid construction was first produced by Siemens 1952. The most popular frame grid tubes are the Telefunken ECC803S but also the US made 6922 (E88CC).

The benefits of frame grid construction are:

– allows much higher gain; higher transconductance (Gm)
– lower input capacity, allowing higher limiting frequency
– almost no microphonics (stiff frame, resonant frequency of grid wire >20 kHz, beyond hearing limits)
– significantly lower hissing noise level