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Old 27th July 2012, 01:28 PM   #1
limono is offline limono  United States
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Default ac quartz speed controllers (linn , roxan)

Does change of power grid frequency from 50hz to 60 hz require modification of those units? Like for example in old Roksan or linn PSU? I know It's time for me to learn more about motor controllers but for now I look for quick answer.
Thanks, L

Last edited by limono; 27th July 2012 at 03:22 PM.
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Old 27th July 2012, 03:23 PM   #2
limono is offline limono  United States
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Ok, to answer my own question ,no it doesnt require anything but switching the connection on the board (linn) and transformer tap on Roksan.
TIA, L
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Old 27th July 2012, 04:30 PM   #3
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Normally the equipment only need to be switched the input line voltage, except for clocks. By the way, I don't know what are you talking about, but be more careful with the voltage switch (110/220V) if any.
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Old 1st August 2012, 12:28 AM   #4
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Default I know a few things about the Linn ...

I've been gathering info on the Linn TT for a few months; my power control board went down this Spring, and I just installed a replacement Valhalla board (also newer than the one I had, so had a few updates).

The first thing to know is that because the Linn TT uses a "synchronous" AC motor, the speed of rotation is dependent on the line frequency, not voltage. So the motor spindle (also called the pulley) will have a different diameter for a 50Hz motor vs. a 60 Hz motor. If I understand correctly, Linn sold all their LP-12 'tables for use with 50 Hz output, whether in Great Britain or the U.S. The less expensive Basic TT would be different, and would come outfitted with a 60Hz motor. So if you upgrade a Basic to use the Valhalla or Lingo power supplies, you have to replace the motor and spindle as well.

A variation on the Valhalla PSU is manufactured and marketed by a third-party -- this is the Hercules power supply, and its variants. This can be obtained as an "outboard" PSU, or tucked in under the TT sub-chassis. Many speak highly of the Hercules, and many feel that separating the PSU from the TT makes an audible improvement as well. The Hercules comes in both 50-Hz and 60-Hz versions, though I think the 60-Hz may be harder to find.

Probably the second thing to know about these power supplies is that they are transformerless, so can be vastly more dangerous for the diy'er than other projects. I didn't even take any meter readings from my replacement board until I hooked up a proper isolation transformer. (That is, I modified a commercial isolation transformer to remove the ground reference, to create a "tech bench isolation transformer" for this use).

Schematics of the Valhalla board can be found online. Are you thinking of designing your own PSU, or modifying an existing one? What other info are you looking for?


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Old 1st August 2012, 12:39 AM   #5
limono is offline limono  United States
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No, I was thinking of importing EU table to US and a possibility of voltage conversion.
I have early Linn , nirvana (I think it's correct name for one speed controller) which has 60hz pulley so yes, there are 60hz versions of nirvana/ valhalla out there. I think I'll try DIY Geddon supply for this one. Thank You for a nice post!
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Old 1st August 2012, 12:41 AM   #6
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Default Also ...

BTW, if you haven't seen it, there's a lengthy discussion of quartz crystal speed controllers --- options and designs --- in the thread "Linn Lingo vs. Dr. Fuß or Square-Wave vs. Sine Wave Oscillator for Motor Control "

I'll try to post a link here

-Paul
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Old 1st August 2012, 12:48 AM   #7
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Default Converting an EU table

If you end up importing a Linn table from the EU, I would expect it to be easy to switch over to US mains voltage and frequency -- I'm assuming Linn designers have been consistently great in this regard. I only know in detail about the Valhalla board -- for the Valhalla, the changeover would involve opening the unit and moving the location of one fuse and one power cord wire. A simple ten minute project, if that.
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Old 1st August 2012, 12:54 AM   #8
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Default The Armageddon

I'm also looking to build and audition a 'gedden motor control unit. Very intriguing! I may have started out on the wrong foot though -- see my thread here.
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Old 1st August 2012, 01:45 AM   #9
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Quote:
Originally Posted by truepaul View Post
A variation on the Valhalla PSU is manufactured and marketed by a third-party -- this is the Hercules power supply, and its variants. This can be obtained as an "outboard" PSU, or tucked in under the TT sub-chassis. Many speak highly of the Hercules, and many feel that separating the PSU from the TT makes an audible improvement as well.
I'm using an externally mounted Hercules II. It's definitely a sonic upgrade over a later Valhalla, plus you get 45 RPM.

jeff
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Old 1st August 2012, 04:56 AM   #10
Nanook is offline Nanook  Canada
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Default Guess I'll butt right in...

The simplest and quickest way to do a speed conversion (non-electronically) is buy the correct motor pulley from the maker of the turntable, or get a new pulley machined if one is not available. As trupaul points out the frequency of the mains determines the speed of synchronous motors. Those of us in North America have 115VAC@60Hz, and Europe usually has 220VAC@50 Hz. The motors themselves are the same motors, just the voltage being fed to the circuitry prior to the motor and the frequency vary.

If one were to create a 50Hz PS, with the appropriate voltage, then you could run a European table here without any other changes. If creating a 60Hz PS, then a smaller diameter pulley would need to be had or as stated above, a 60Hz pulley from the table manufacturer. The math is just a simple equality:

D₁*S₁=D₂*S₂
where the subsrcipt indicates a specific motor and pulley, D is pulley diameter, S is in RPM. To solve for a new Diameter pulley:
D₂= D₁*S₁/S₂

We know that common synchronous motors used in turntables spin at 300RPM in North America, and 250RPM in the UK (for example). We can measure D₁ and know S₁ and S₂. Just plug n' chug.If an Ariston (or Linn or whatever) uses a 38mm pulley in the UK, we then know that it requires a 31.66mm pulley to operate at the correct speed in North America, or we must generate a 50Hz signal and step up the voltage to the point that there is around 80VAC to 90VAC (the common Airpax/Thomson motors as used in many turntables are quietest around 72 VAC, but that could be just for a specific motor example not all motors of that part number).

Don't hate me: I bought a Roksan Xerxes for $150 (in CAD) that required a minor tweaking to the power supply. Once completed it was speed stable. YMMV. I think the final output was 78 VAC@50Hz.
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