Hi there,

I've recently bought a second hand SET DHT 300b amplifier, a Fi X3,
around 9w per channel.

I'm using it connected to Lowther Acousta's fitted with EX3 speakers and
I can hear a fairly hum (100hz?) from the speaker, from the amplifier,
at my listening position, around 10' back. The hum drops off only
slightly in the central position of the hum potentiometer.

I believe the Acousta's are 96dB/W/M efficient.

I've tried lifting the earth by inserting a 66ohm resistor (3x22ohm) in
line but with little effect.

I did intend to construct a Hedlund horn but am now worried about it
being of increased efficiency and therefore even louder background hum.

Any suggestions as to hum cures, was 66ohm enough of an earth lift,
should I use more inefficient loudspeakers.

Any advice appreciated.

--
Stoatgobbler