UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Mullard 5-20 high DC Voltages

Techman · 6th May 2020, 10:29 pm

Chris - the small valves are in the 'high impedance' and sensitive to these things, part of the circuit and would have full metal valve shields fitted as standard. The output valves are in a low impedance part of the circuit, so are not affected. The high quality transformers, although unlikely to be affected, will all have shrouded windings, so the only thing to ruin this brilliantly designed amplifier is to build it on an un-shielded chassis. Built on a proper chassis as designed originally, with good quality shielded connecting cable feeding the input/s, there would be no problems with this amplifier picking up anything it shouldn't.

The good thing about the OP using a wooden box is that it's sparked off a very interesting debate and I'm sure the OP has learned a lot in the process, so it's not all bad.

6th May 2020, 10:29 pm	#101
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: Mullard 5-20 high DC Voltages Chris - the small valves are in the 'high impedance' and sensitive to these things, part of the circuit and would have full metal valve shields fitted as standard. The output valves are in a low impedance part of the circuit, so are not affected. The high quality transformers, although unlikely to be affected, will all have shrouded windings, so the only thing to ruin this brilliantly designed amplifier is to build it on an un-shielded chassis. Built on a proper chassis as designed originally, with good quality shielded connecting cable feeding the input/s, there would be no problems with this amplifier picking up anything it shouldn't. The good thing about the OP using a wooden box is that it's sparked off a very interesting debate and I'm sure the OP has learned a lot in the process, so it's not all bad.