Mullard Radio - Model MAS-24 Research page..
a.k.a - Philips Radio - Model 660
I am delighted to have a Mullard MAS-24 in my collection and understand that this is essentially a Philips design. The way for Philips to have a presence in the U.K. market and many other countries was to buy into an existing business or to build native factories to assemble or make products for that market...
The feature I find most amazing to my 'American eyes' is the ‘direct tune’ 3-gang tuning condenser. Its unique construction employs three sets of two incredibly precise brass foil helix that mesh with clearances that seem to be less than 0.010”.
The RF coils are a unique design for Philips in that they were tuned by placing on a semi automatic machine that rolled grooves of the necessary depth into the aluminum can at three points prior to installation on the chassis. After this tuning operation, it is impossible to take the coil out to make repairs.
The cabinet employs extremely dense 9 ply - hardwood plywood used to insure that the cabinet would not resonate (boom)..
There is a feedback winding on the audio output transformer for control of volume thru positive or negative phase coupling.... The feedback also seems to have factored in the mechanical loading of the speaker cone giving more precise control of audio response.
References: The Philips 660A by Peter Nash – BVWS Bulletin – date unknown
Direct Action Tuning by Geoffrey Dixon-Nuttall – Summer 1997 issue of the BVWS Bulletin