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#151 |
diyAudio Member
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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? |
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#152 |
diyAudio Moderator
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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.
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#153 |
diyAudio Moderator Emeritus
Join Date: Sep 2002
Location: Germany
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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 ![]()
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It's only audio. Member of the non modular PCB design committee Last edited by jean-paul; 1st August 2020 at 09:14 AM. |
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#154 |
diyAudio Member
Join Date: Jul 2016
Location: Johannesburg, South Africa
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@jean-paul by PE you mean protective earth? I'm taking it you mean the earth in the mains L-N-E.
Last edited by AllenB; 28th August 2020 at 02:19 AM. Reason: Remove excess quoting |
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#155 |
diyAudio Moderator Emeritus
Join Date: Sep 2002
Location: Germany
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Yes, Protective Earth.
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It's only audio. Member of the non modular PCB design committee |
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#156 |
diyAudio Member
Join Date: Sep 2003
Location: London
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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. |
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#157 |
diyAudio Member
Join Date: Nov 2020
Location: Israel
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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?
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#158 |
diyAudio Member
Join Date: Jun 2011
Location: SCOTLAND
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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. |
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#159 |
diyAudio Member
Join Date: May 2014
Location: UK
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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. |
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#160 |
diyAudio Moderator Emeritus
Join Date: May 2003
Location: Maybunga, Pasig City
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no element inside the tube should be left hanging not connecting to anything, i think this is the basic rule...
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https://www.facebook.com/tony.tecson |
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