Variacs.

[NickG]

I found the DC blocker improved things for me, until the 211 turn on surge blew it up, but I suspect for sane use it would be fine.

[Global]

The 'Swampy' filter does not remove DC offset from the mains supply. IIRC, it is a common-mode choke + Cap filter. I think the choke must have done something to the mains impedance. Very good for removing spikes though!

The effect of DC offset on the mains is to push the mains TX towards saturation resulting in extra heat and buzz.

A DC blocker helped my mains transformers to stay quiet and, I think, cooler. Some people have found, however, that it has little effect. These latter cases will probable be down to excessive mains AC volts rather than a DC offset.

Sonic effects? Hmm.. I can hear no difference except for the absence of mechanical transformer noise BUT I would not claim to be 'golden-eared'.

For the cost of a couple of caps and diodes it's worth a try and very easy to remove if you don't like the results.

Mark

[Global]

Originally Posted by NickG

I found the DC blocker improved things for me, until the 211 turn on surge blew it up, but I suspect for sane use it would be fine.

You need a NTC thermistor in there!

Mark

[Tony Moore]

Just measured my mains; 241vac 0.03v dc.

However, at this very moment everything sounds ok. I will have to remember to measure when things are sounding rubbish!

Cheers,
Tony

[NickG]

You need a NTC thermistor in there!

May not help, the 211 and 866 fillaments start first (about 0.5 amp), which would warm the thermistor up, then 42 seconds later the HT kicks in with about 5A while the caps are charging up. Once its up to voltage it drops back to about 1(ish)A total.

I have a 1kva isolator on order that I hope will help with the **** mains and DC.

I have a load of 350v clamping diodes free if they are any use.
ST 1.5KE 350 bidirectional. max voltage 500. pre-driver supply.
http://www.ortodoxism.ro/datasheets/...onics/2913.pdf