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Printed Circuit Boards by Emissionlabs.

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EE51 Fault finding hints

This MC unit designed to work right away. If there is hum however, there is a problem in your set up, and the root cause must be found somewhere outside the EE51. The combination of record player, MC Box, phono pre amplifier, and power amplifier, with all it's cables, is complex. So any random set up, we can not tell you here, what causes hum in a particular case. This needs some local testing, for which the EE51 board has some options. It can not give a final answer to everything, but a good hint may well result from it. So if one of the tests in positive, read in the comment box, what MAY be the cause.

Music will not play with these settings. This only for testing, in case there is some hum, which is not caused by EE51 board.

  • >> First, write down the regular settings you had now, for A, B, C, D, H1, L, H2, GND!
  • Keep all equipment and cables connected.
  • The settings below here, must be done for both channels together.
For Test only
A, B, C, D
H1, L, H2
GND
Comment
1
 If hum with this test setting, the problem is more likely in the PHONO amplifier itself.
All Jumpers In
None
None
This disconnects the transformer inputs at the primary side, both signal and ground. So the primary side can absolutely not transfer signal to the secondary. Also effects from a ground loop are stopped this way, when the ground link is opened. In addition, the phono pre-amp inputs are shorted to ground. Remaining hum, if any, it can be said almost for sure, this is generated by the pre amp itself.

A very small chance remains it is caused by a ground loop in the cables connecting pre amp to the power amplifier, but because ground is also cut off (Ground Jumper is open), this is unlikely.

2
 If inserting and removing the GND link will make hum come and go, there is probably a ground loop somewhere in the external cabling.
A, B, C.
None
In and out
 Primary transformer side is also fully disconnected here, but now the pre amp is connected, with damping added. Adding and removing the Gnd Jumper, will connect or disconnect the record player ground. If this test is positive, there may be a ground loop in the record player cabling.
3
 If hum with this test setting, there may be external field radiation into the MC Transformers.
None
H1, H2
None

Though the Lundahl transformers are probably the most hum insensitive on the market, low cost mains transformers of other equipment are sometimes terrible sources of magnetic field.

However such fields have always a source, and you can find it easily. If this test is positive, try placing the MC box further away from the equipment which radiates the hum, or rotate the MC box 90 degrees. This is not intended as solution, it only proves, if so, where the problem is coming from.
4
When done:
Do not forget to restore the original settings of the jumpers :)

 

When the MC box is finished: Burn-in is NEEDED!

There is so much stupid voodoo in the internet, even about burning in DVDs, and gold plated mains fuses. Feel free to believe it, if it doesn't harm you. However all magnetics devices need burn in. This is strange, no burn-in guru talks about it. So we do it here :) This is not Lundahl specific! All magnetic materials adapt to the orientation of the earth magnetic field if they are tapped on. You can try it with a large iron nail. Like 7cm length. Place it in front of you, and point it to the Earth's North Pole direction. Firmly tap on it with some a metal object, repeatedly, in the axis direction. After this, you will see it is slightly magnetized, and it is able to pick up small iron particles. This is how easy materials can become magnetized.

The tone transformers during shipment, are rattled in the truck, the package is dropped and kicked, and perhaps you dropped one on your desk, unaware of this effect. This small magnetism will automatically go away, if the transformer sees electrical signal for some time. The signal shakes up the magnetism, and any remaining magnetism gets removed by that, slowly. The transformers are literally burned in during production, as heat removes the magnetism too. So they are shipped free of magnetism, but the journey may (sometimes) add some small magnetism.

It is not possible to express the burn in time in hours, but it is in the range of a few weeks of normal use. Did you hears sometimes people say, their transformers improved sound during burn in? Well this was no voodoo, it was real, and this was the reason.