Hi Glen,
I get the feeling that T1 is fairly tolerant. I've done 4, 4, 4, 31 windings instead of 3, 3, 3, 30 -- in a guestimate attempt to make the RX work on both 20m and 30m (but I cannot check this as yet until there is a firmware update as something else prevents 20m being received when 30m band has been selected).
I find the audio range from min to maximum is quite good and the RX is very sensitive, on a par with big rigs. What you have done may have helped reduce the volume a bit, who knows. Great she is working well, and that the number of turns on T1 is not too critical it would seem, looking at the charts near the end of the manual you can see the BPF is quite broad.
