Hi,
i am french and excuse my poor english,
i have build a tw express, it work very well,great sound ,power is good.
but i have a problem ,it is not a buz, there is a noise like a oscillation ,
i see this noise on the scope and with no signal input there is a oscillation at 400 hz about.
when the volume is at 10 or 12 there is a microphonic phenomen.
tube is news ,bias is good (-30v) and when i touch the chassis with my hand the problem
is down more 50%.
Any wire is good ,and wire shield on first tube.
wire heating is not problem.
please help me i you have a idea on my problem
Many thanks
Gé from south france