No hum / noise on your tube Hi-Fi amplifier ! (Lesson 2)

This is the second video, the last tutorial from this series, which is dedicated to a very important aspect for all who deal with Hi-Fi: how to avoid noise and hum. In this second video, I’ll provide very practical advices on how to build perfectly noise free tube preamplifiers or amplifiers: star grounding, elevated heaters, DC heaters for low level signals, shielding. Enjoy !
By Matteo Bonino, M.Sc.Eng.
#tubeamplifier #hum #noise #goundloop #hifi #tutorial #elevatedheaters #starground

[@kubockferre5532]

Hi you mention in your vidéo that the ground of the electric cable the one going to the wall must go to the star ground ,and star ground to the chassis .Is it exact ! But i saw many tube amp with electric cable ground at one point to the chassis and star ground put on another point to the chassis .Audio ground and electric ground should be separated ,what do you think of that

[@restoreaudioandnewprojects8299]

@@kubockferre5532 indeed, I typically connect the chassis to the ground point. And the safety power ground (earth) to the same grounding point. The solution you saw on other amps (both star ground and earth connected to the chassis) is safe as well. Just, I personally don’t like creating further ‘ground concentration’ point, other than the main one (in your example, the chassis would act as secondary grounding point). I should look at the other ground connections in this amp, in order to be able to comment further, sure it’s working properly. Thanks for your comment !

[@kubockferre5532]

hi very interesting vidéo ,i made a tube preamp with 2 x12au7 and 6x4 like rectifier ,i put a circuit regulation 12v on the tube but floating ,and i put 6.3 v on the rectifier but with a virtual ground ,is it a correct way to do ,thanks

[@restoreaudioandnewprojects8299]

Hi, thanks for your comment ! So, if I understand correctly, you elevated the heaters to 6.3 Volt, applying that 6.3 DC reference voltage to the ‘ground’ tap of the heater rectifier, right ? Indeed, this works. Nevertheless, if you’ve 12V regulated for the heaters there’s less need to elevate them, as they’ll inherently be hum-free. It’s good anyway to have them referenced to a voltage to ground anyway, as you did. The reason to elevate heaters in those cases is for respecting the max cathode to heater requirement of the tubes. As you’ve two 12AU7, I guess one of them if laid as cathode follower, so this is where there’s the major risk to exceed the max cathode to heater voltage rating. Available for further talks on this, please let me know if I understood your setup 😀 and thanks again for your interest !

[@kubockferre5532]

hi my set up is made like this ,i got a power transformer for high voltage and 6.3v for the rectifier referenced to ground and another power transformer 16v ac for supply 12v filament with a regulated circuit lm 317 which is not referenced to star ground.i think its ok like this ,what do you think. @@restoreaudioandnewprojects8299

[@kubockferre5532]

hi do you put rca output to a star ground thanks

[@restoreaudioandnewprojects8299]

Hi, thanks for your comment ! I usually deploy isolated RCA plugs at the output. I mean, the ground side of those RCA plugs don’t touch the metal chassis. The ground side of the RCAs are directly connected to star ground point. This is how I always implemented, and it always resulted in noise-free preamplifier. Thanks !

[@kubockferre5532]

thanks a lot@@restoreaudioandnewprojects8299