Odd or not......

[cressy]

So...... Having quietened down the phono to bugger all hum by recasing it and adding a diy hifi supply heater module cadged off mi old man, WHY does it not do it for me as it did before when it was noisy and a pain in the arse with its constant popping and farting?
It does what it did before, i.e amplifying and correcting, but its not the same. Other than the dc supply its identical.

Bemused, confused and spurred on to write my incoherent ramblings on what passes for paper these days, in wondering if my ears are having their own subconscious rebellion against having silicon in something.

Or am i talking bollocks and am missing some colouration and or harmonics added by noisy ac heaters???.

Probably none of these things. Hmmmmm

[Paul Barker]

The dc heater supply on an indirectly heated valve shouldn't make it sound worse.

What can happen is the now rectified low voltage winding transmits noise which is induced in the HT winding and through mechanism of the B+ polutes the amplifier.

There are 3 fixes.

1/ screen between HT and LT windings

or

2/ seperate heater transformer

or

3/ use only the best diodes and bypass them with small cap.

I always use seperate heater transformer except for HT rectifiers.

I think it was Crowhurst who said this phenomenon can cause a "ticky hum which is very hard to get rid of."

If you use AC heating there is no reason at all to use a spereate heater transformer, it is diodes that create the noise.

[cressy]

The heaters of all the nuvistors are all in series off a separate 2.5 0 2.5 0 transforme. The windings are in series to give the module 5v to play with. The transformer is lukewarm after an hour but the heatsink on the module is too hot to touch. Tbh im not too happy wuth the temp the module gets to as it is. And it sounds different perhaps the module is being stressed too highly

[Paul Barker]

If it is seperate transformer it shouldn't be a problem.