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K&K Audio / Lundahl Transformers

About 'jumpering'

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I'm going to go over my step-up to see if I can track down the loud hum it's producing. Yesterday I went over the instructions again and took a look under the hood to see what the possibilities were.
One thing I noticed is, I didn't use the teflon jacket on the jumpers on the board, due to space constraints - the lengths of wire seemed so short I thought I could do without them. So maybe this is the culprit.
This is really dumb, but I remembered I wasn't sure when I was doing the kit either, so I'm going to go ahead and ask. (I have my step up wired for the 14 db gain, btw.) When you have to jumper the wires on the pc board, I ran them so they shaped like an upside-down 'u,' sticking straight out, then straight across, then straight back in again. Is that the right idea? I'm going to slip a piece of teflon over the part that's parallel to the pc board, since the teflon would likely melt during soldering if I get it too close to the pc board pads.
Sorry for a silly question, but while I've done a fair amount of diy soldering, I haven't done much 'jumpering.'
Thanks Kevin.
david

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Re: About 'jumpering' - KevinC 04:50:45 09/12/03 (1)
David,
The usual cause of hum is not connecting all of the grounds together. This means that all of the RCA jack shells should be wired to the case ground, as well as all of the "-" transformer terminals and the transformer shields, too. If any one of these is not connected to case ground there will likely be hum. The other problem that cna be encountered is that of placing the transformers in a strong magnetic field. Although the LL9206s are shielded, their shields will be overwhelmed by close contact to a power transformer. Try repositioning the case to see if this is true.
For jumpers that connect adjacent pads, no insulation is necessary, however if the jumper crosses several pads that it should not touch as with three of your jumpers, they should be insulated. The "U" shaped jumpers should just be inserted directly from above the holes into them and soldered. The instructions show them lying alongside the pads for clarity, but that is no the way they are normally inserted.

Kevin Carter
K&K Audio
www.kandkaudio.com
- Re: About 'jumpering' - Will Shade 08:19:28 09/12/03 (0)
  Thanks Kevin. I'm going to go through the whole thing and track theproblem down, hopefully over the weekend. At first I thought it was RFI causing the hum, since the hum does seem to change a little as I move it around; but I was recently playing around with attenuation on my amp, and have it presently so I have plenty of gain without having to use the step up; and there's no hum. So I'm pretty convinced there's a problem with the way I wired it up (and I actually re-wired and checked the whole thing over once already).
  In spite of an extra I/C and a whole other component in the signal path, it sounds much better with the Lundahl trannies in there.

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