09-09-2020, 06:33 PM
Curiouser and curiouser.
I assumed other uses for the valve in current products at Murphy at the time, otherwise it makes the choice quite odd.
I thought that this would make a good subject for a project, and one of the reasons I wanted to read the Murphy News article on it is because there may be some clue to some of the design choices.
Kalee 20 mentioned the NFB already and explained to me that it was described as a bass boost system and how it is most effective at low signal levels by the way it is feed into the bottom of the volume control, of course it may have been the design intention from the outset.
The tone control position is definitely a strange choice...
One thing that I find odd is that the heater winding on the transformer is centre tapped. So, given that they could have used a 12 v bulb for an indicator why didn't they? Then the centre tap could be returned to ground to help cancel heater hum, after all, they fitted that him canceling output transformer?
Second sourced valves....
I'd read that the British government encouraged manufacturers to make each others product designs?
Mr McBoyne....if this player needs a lot of work on the amplifier I may do some mods along the lines of the Mullard amplifier. Though it may be unnecessary, I'll do the capacitors first and get it working as is and go from there.
I have been warned that the output transformer is a weak point though especially as the grid capacitor on the pentode is a known bogey.
Amie
I assumed other uses for the valve in current products at Murphy at the time, otherwise it makes the choice quite odd.
I thought that this would make a good subject for a project, and one of the reasons I wanted to read the Murphy News article on it is because there may be some clue to some of the design choices.
Kalee 20 mentioned the NFB already and explained to me that it was described as a bass boost system and how it is most effective at low signal levels by the way it is feed into the bottom of the volume control, of course it may have been the design intention from the outset.
The tone control position is definitely a strange choice...
One thing that I find odd is that the heater winding on the transformer is centre tapped. So, given that they could have used a 12 v bulb for an indicator why didn't they? Then the centre tap could be returned to ground to help cancel heater hum, after all, they fitted that him canceling output transformer?
Second sourced valves....
I'd read that the British government encouraged manufacturers to make each others product designs?
Mr McBoyne....if this player needs a lot of work on the amplifier I may do some mods along the lines of the Mullard amplifier. Though it may be unnecessary, I'll do the capacitors first and get it working as is and go from there.
I have been warned that the output transformer is a weak point though especially as the grid capacitor on the pentode is a known bogey.
Amie
