Heater Wiring - the Good the Bad and the Ugly

[pong Tsui]

Hi ,AC for heater sound is better,dynamic ,bass,etc....but have some digital device,streaming device,router,switch in home,AC it will absort some EMI noise,
Are you agree?

[AllenB]

AC can be very good. Have you considered filtering your AC supply using chokes? Although this could be used to trim the available Voltage, it can also remove higher frequency problems.

[jean-paul]

Maybe it has been discussed before in this thread but I am too lazy to read everything. Anyway, in my limited experience I have seen and still see sometimes quite expensive tube equipment with hum problems.

Often the build quality is questionable but what I do see often is audio GND connected to the metal casing and not even use the PE connection (even when a PE IEC Socket is used!). It completely beats me why anyone would do such a thing but it is more common than one would think. I classify such equipment as unsafe despite the price tag. It also leads to dubious experiments with "ground wires" to get the stuff quiet. Why people /companies do not adhere to decade old safety regulations and why do these devices pass any quality check? In general tube DIY is one of the worst areas in DIY audio with regards to build quality and safety probably because stuff is large and accessible to many.

Especially tube stuff that carries high voltages should have the metal casing ALWAYS connected to PE for safety. One may connect audio GND lifted to PE. When done like this hum is not an issue. When I get the reply that homes in area X don't have PE well PE is out there for a lifetime Even if this would be true one can have PE applied by a certified electrician or one better buys low voltage stuff.

[El Sid]

@jean-paul by PE you mean protective earth? I'm taking it you mean the earth in the mains L-N-E.

[jean-paul]

Yes, Protective Earth.

[andyjevans]

What's the best way to supply heaters for a 19v, 300mA tube like the PL33?

- DC floating
- DC with the negative side grounded, if so where and how?
- AC with a centre tap connected to ground (again, where and how?)

Bias voltage is only around 4v. a-k around 160v, 15-30mA current.

[OferB]

Hello guys - I am new here - building a KT88 SE amp. Re heaters - why not shield them like a coaxial cable - ground on one end - and avoid most of the induction noise? - Also - anybody knows what I should do with pin 9 's' on the ecc85?

[batteryman]

See post no. 150.
Its the way I'll be doing the heater wiring in my parallel SE KT77 amp.
You can tightly twist wires using an electric drill.

[Diabolical Artificer]

andyjevans AFAIK heaters should never be floating, they should always be referenced to ground. Just connect your DC supply to ground. The best way to stopAC heater hum is with a humbucker, EG a 250r - 500r WW pot, wiper to gnd or elevated.

OferB, see - The Valve Wizard

Andy.

[TonyTecson]

no element inside the tube should be left hanging not connecting to anything, i think this is the basic rule...