Welcome! Need support, you got it. Or share your ideas and experiences.
In Reply to: need help with the ella posted by mikey115 on November 28, 2002 at 09:31:10:
I've never built one of these kits (yet) but the safety ground and the signal ground(the one off of the main PCB) and a chassis ground should all connect together with individual wires at the negative side of the last capacitor on the power supply PCB. This is called a star ground. If they are not recommending that you use this configuration in the instructions then shame on them. This is the best way to ground any audio circuit SS or tube. It almost gaurantees that you will not get a ground loop induced hum coming out of your speakers. Also remember to twist the leads on the primary of the power transformer together when routing them for wiring and the same goes for the secondary leads as well as the primary and secondary leads for the output transformers. I hope this helps.
Take a look at how the wiring looks in this amp:http://www.idealinnovations.ca/gallery/s30internal.jpg
Follow Ups:
These amps do essentially have a star grounding scheme. Thats why the RCA jack ground must be returned to the star ground instead of being arbitrarily grounded to some point on the chassis. Often the chassis safety ground is NOT connected to the star ground point if this induces hum because of its interaction with the power transformer. But that sacrifices the safety effects, of course. So a solution is to connect the safety ground to another point on the chassis far from the star ground point.Long story short.. no ground loop problems or coupled 60hz hum and a safety ground in place. No worries.
I've heard of people on the BottleHead forum talking about isolating the RCA jacks from the chassis and running the nagative pin of the jack straight to signal ground and then also taking a .1uF ceramic disk cap and tying it from the negative RCA jack pin to the chassis. This might work well for the Ella and Joplin. But this is just speculation. I wonder if the problem with the hum on the Ella is due to the use of an aluminum chassis instead of a steel one. If they are steel chassis and steel covers on the transformers there shouldn't be any magnetic coupling of the transformers. If there is no magnetic coupling going on then there should be no reason for star grounding not to work everytime. Not just sometimes.G
To clarify, there is no problem with hum on the ella. The small amount of hum reaching the speakers could be reduced even further with more power supply filtering. I don't even have a filter choke and the hum is only audible when putting your ear up to the speaker. Both the chassis and the tranformer covers are steel.I didn't mean to imply there was a problem. It was more just information for what you can do in general IF you encountered something like this.
(yay me...I finally registered after a year and half or something)
I see. I guess I'm just a little miffed at being informed that if I want a choke in the power supply of my Ella(if I order one) then I will have to modify the PCB board and shoehorn a choke in. On the DIYCable site it says that the Ella comes with a choke supply designed into it, not that you will have to modify the kit to use one. Then I misunderstand about the severity of the hum problem that is being discussed. I thought that I had wasted all of the time drooling over the Joplin and the Ella only to find out that they are not such good deals after all. I'm releived to find out that this is not the case. One other trick that I have seen done is to twist together the chassis ground and the safety ground wires and then solder a 10 ohm resistor bypassed by a .1uF cap on to the ends of the twisted wires and attach the resistor and the cap to the star ground point. This is supposed to work well at breaking up ground loops. Thanks for setting me straight Zarniwoop.
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