I think I need DC for my 5687 heaters on my Aikido pre-amp due to some slight humming and was wondering how much filtering is needed. I'm planning on using a bridge rectifier to just one 4700uF cap for smoothing out some of the ripple. Is this enough or do I need to add somekind of regulator ie. 7506? Is there a rule of thumb on how much filtering a DC heater circuit needs?
On a side note, I using four 5687 tubes and these guys get pretty toasty! I know they are power hungry just to fire up the heaters but are these tubes designed to last a long time running this hot?
On a side note, I using four 5687 tubes and these guys get pretty toasty! I know they are power hungry just to fire up the heaters but are these tubes designed to last a long time running this hot?
You might have an earthing problem. Try running the heaters off a 6VDC supply or battery, if the hum goes then start building a regulator.
Otherwise you should use multiple star grounds to connect the cathodes at one point, signal grounds at another, then heater grounds at another, then join them all together at the chassis at one point.
You could try connecting the heaters to ground with a 100 ohm resistor instead of directly. (I havent seen the schematic, so if they are raised above ground ignore this advice!)
Otherwise you should use multiple star grounds to connect the cathodes at one point, signal grounds at another, then heater grounds at another, then join them all together at the chassis at one point.
You could try connecting the heaters to ground with a 100 ohm resistor instead of directly. (I havent seen the schematic, so if they are raised above ground ignore this advice!)
Good thread on the subject:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=49312&highlight=hum
http://www.diyaudio.com/forums/showthread.php?s=&threadid=49312&highlight=hum
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