Armageddon clone VA size vs. regulation - diyAudio
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Old 20th April 2013, 07:22 PM   #1
amt is offline amt  United States
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Default Armageddon clone VA size vs. regulation

Im going to build an Armageddon clone and after looking at all the information out there, Ive been unable to find an adequate answer to way a 500VA transformer is so important.

The larger the VA, the better the regulation but does the difference affect the performance in any meaningful way? Plitron lists 160VA at 8%, 300@ 6%, 400 @ 5% and 500 @ 4%.

So the is a gain of 2% (300 vs 500) worth the extra weight, cash and light dimming?

amt
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Old 20th April 2013, 07:46 PM   #2
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I'm not sure how good the mains is in the US, but here in the UK, the 50hz is rock solid, so the regulation does nothing. How it filters out high frequency crap and allows for more DC before saturation are important, and bigger is better.

Very happy with my Geddon clone, it beat all the Linn PSU's and the Hercules when used with thicker oil to provide some drag and load up than crappy motor to reduce cogging.
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Old 20th April 2013, 08:16 PM   #3
DF96 is online now DF96  England
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Regulation (i.e. how much your transformer drops voltage when you take more current from it) is either enough for your circuit at your minimum mains voltage or not. If enough, then improving it will make no difference. If not enough, then improving it will make a big difference.

There is a separate meaning for regulation for constant voltage transformers - how well the transformer compensates for mains voltage variations. This meaning does not apply to normal mains transformers as used in electronics PSUs.
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Old 21st April 2013, 04:00 AM   #4
amt is offline amt  United States
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Not sure how good the grid is here but after looking more closely at what regulation refers to, I would think that a 5 watt motor is close to an absolute minimal load on a 300VA or bigger transformer. If this is the case, I would think that a small drop in regulation shouldnt decrease performance. As to the filtering of noise Im still unclear.

sq225917, I looked at your nice build on Flickr and it looks exactly like what I would like to do. Im guessing a varistor at half the voltage would work for 115V mains?

amt
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Old 21st April 2013, 03:26 PM   #5
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check out this thread:
Linn Lingo vs. Dr. Fuß or Square-Wave vs. Sine Wave Oscillator for Motor Control
I don't understand the kind of filtering by only a transformer use.
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Old 22nd April 2013, 03:05 AM   #6
Jim W is offline Jim W  United States
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I'm really puzzled by the use of a massive transformer for a few watt motor. I was about to build a geddon clone with a 36va Stancor transformer that I had in a parts box, but got the Valhalla working with some minimal troubleshooting. (Actually, zero troubleshooting since it's hard to troubleshoot something that works.) Any impedance difference between my small 36va transformer and a massive 500kva toroid will be swamped by the 3.3K series resistor.

Can anyone explain why the huge transformers?
thx,
Jim
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Old 22nd April 2013, 10:27 AM   #7
DF96 is online now DF96  England
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I was wondering that too.
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Old 22nd April 2013, 01:56 PM   #8
Jim W is offline Jim W  United States
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500kva would indeed be massive - I meant 500va...
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Old 22nd April 2013, 05:39 PM   #9
amt is offline amt  United States
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From what a Naim rep explained in a Stereophile article, the size has to do with
proper creation of the sinewaves that arent "gutless". (apparently, wimpy sine waves are to had with smaller transformers)

Naim ARO tonearm & Armageddon turntable power supply | Stereophile.com

amt
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Old 22nd April 2013, 06:16 PM   #10
DF96 is online now DF96  England
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They say they use a transformer to filter out high frequencies. These would anyway be filtered out by the mechanical inertia of the motor and platter. I suspect marketing rather than engineering. A big transformer might give higher starting torque so faster spin-up.

My guess (I could be wrong) is that a crystal oscillator will have far less jitter than the mains frequency. Crystal frequency depends on a high Q resonator. Mains frequency depends on the instantaneous balance between load (set by who has switched on what) and supply (set by how high they have turned up the knob at the power stations); it is adjusted so the average is about 50/60Hz and the total number of cycles per day is about right so synchronous clocks remain about right.
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