eiclone hum fixes?

a DIY, modified Mullard 5-20 monoblock design

eiclone hum fixes?

Postby bootsie » Sat Nov 12, 2016 5:15 am

I've had some background hum in my eiclones since I built them but have never quite got around to fixing it. It finally got to the point that I had to do something about it, so had a read through this thread for ideas:
viewtopic.php?f=2&t=521&p=5315&hilit=hum#p5305
Specifically:
Shannon Parks wrote:We should be able to get your Ikes pretty quiet. I'll throw one of my Ikes on the test bench this afternoon.

The important mod is step #1 here:
viewtopic.php?t=836

The mods here aren't as important. They just lower the gain to a more 'standard' gain level. So the noise floor isn't amplified as much.
viewtopic.php?t=891


But the "step #1 here" doesn't seem to link anywhere other than the build manual.
I tried the mod referred to in the post above:
Shannon Parks wrote:You can simply remove your input ground from J4-3 and swing it over to the ground of R7. You can solder at the unused R52. For reference, the ground side of those resistor spots is towards the center of the PCB.

but didn't really make a difference - in fact it might be worse.

Is there a definitive fix to reduce the background hum?

Thanks, Steve.
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Re: eiclone hum fixes?

Postby hilldweller » Sat Nov 12, 2016 5:00 pm

I used a central "star" grounding technique on mine and have no hum at all. I also used shielded wire from the input jacks to the PCB. Inputs are on the opposite side of the chassis from the transformers. Transformers are mounted to the chassis with nylon washers between the transformers and the chassis. I hope these suggestions help you.
Bricks too tall will fall!
It takes mud to keep it all together.
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