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DIY Valhalla improvements

Straight from the Linn FAQ

-------------------------
WARNING: Those considering DIY improvements on Linns Valhalla power supply
should be aware that the output of the unit is not isolated from the mains and
that all the supply lines to the motor are a number of hundreds of volts above
earth.

"The Valhalla does not have a well regulated DC supply rail. I got an apparent
improvement in sound with an extra RC filter between the rectifier and the
on-board caps. A regulated DC supply would probably help it some more. However
this doesn't address what is probably the main deficiency of the Valhalla which
is the use of a single phase shifting cap on one winding giving much less than a
90 degree shift."

"After extensive trials this week with a new motor, it looks like the following
mod is effective in reducing motor vibration. NOTE: don't do any measurements
with respect to ground, the grey 'zero volt' connection is actually at around
130 volts. BE VERY CAREFUL with the Valhalla circuitry if you do any mods or
measuring - it is live all the time the unit is plugged in and carries voltages
in excess of 300V!

For 60Hz, a 0.20uF cap in series with one winding seems to give the least motor
vibration. The measured phase difference is almost exactly 90 degrees. For 50
Hz, 0.22uF appears best. Note that the winding with the cap on shows a higher
voltage than the other winding. Adding any dropping resistors, either before the
cap to reduce both winding voltages, or after the cap to even voltages on both
windings, gives an increase in motor vibration.

In addition my Valhalla had the 'Zener Mod' that had been added by my Linn
dealer. This consists of two diodes and a resistor added between the grey and
blue outputs:
------Z1-----R------Z2------
| |
| |
Connect to Connect to
Grey Wire Blue Wire
Terminal Terminal

Where R=12K - Looks like a 0.25W Carbon film 0.5W might be safer. Z1 and Z2 are
Zener diodes type 1N5266B"



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  • DIY Valhalla improvements - ar guy 01/22/0222:37:14 01/22/02 (0)


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