The same result was achieved historically by the pentagrid converter.

An example would be the 6A7 pentagrid converter.

The 1L6 is a 7 pin miniature vacuum tube of the pentagrid converter type.

For example the pentagrid converter has two.

One of their popular pentagrid converter designs was the MX40, initially marketed in 1934.

Similar to a pentagrid converter, the cathode and the first two grids could be made into an oscillator.

This was rapidly followed by the introduction of tubes specifically designed for superheterodyne operation, most notably the pentagrid converter.

The frequency mixer was of the pentagrid converter design to save the cost of a separate oscillator tube.

The pentagrid converter tube would oscillate and also provide signal amplification as well as frequency shifting.

The All American Five was to use a pentagrid converter from when it first appeared in 1934, right up until valves became obsolete when transistors took over.

The pentagrid converter such as the 12BE6 thus became widely used in AM receivers including the miniature tube version of the "All American Five".

The pentagrid converter is a type of radio receiving valve (vacuum tube) with five grids used as the frequency mixer stage of a superheterodyne radio receiver.

The pentagrid converter in either guise operated extremely well, but it suffered from the limitation that a strong signal was able to 'pull' the oscillator frequency away from a weaker signal.

With the development of the pentagrid converter, these functions were combined inside a single tube which applied the RF signal to the control grid, but also implemented the local oscillator using additional grids.

Some small-signal types, such as sharp and remote cut-off R.F. and A.F. pentodes and some pentagrid converters have a shield fitted around all the electrodes enclosing the anode.