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Re: another few questions and trany suggestion

0.22 uF is the closest common cap value - I would suspect that's the only reason that Naim went with two 0.1 uF in parallel to get 0.2uF. While all of these supplies don't use cheap caps, they don't use anything exotic either. We are just dealing with wall current here.

I think Naim uses a 3 Watt resistor. I would think 1 Watt would be suffiencent but I used a 5 Watt which was easier to get.

I'm sure the transfomer you are looking at will be more than adequate. I just use a cheap old RCA ISTOP as per the link at the end. As longs as you get the voltage and power requirements you need and I think there is a benefit to eletronstatic shielding as well. I would think that 100 VA would be more than suffiencet but Naim uses a 300-400VA model and I've heard people use 500 or 1000 and claim better results.

Using better quality parts may get you slightly better results but I doubt much. It was so much better even with the cheap parts I used that I can hardly imagine any more improvement. I think it's more a result of design and simplicity. My advice - stop over thinking it and just try it with what's easily available. You will be impressed.

I think it makes sense that the cap and resistor go on the live feed from the mains. As far as which winding of the motor will only determine direction.

Check out the schematics in the two links for more details

http://www.neilmcbride.co.uk/ttpsu.html
http://www.multimania.com/jadai/Geddon.html

Ot the two from the Linn FAQ:

DIY "Gedon"
-----------
"The transformer in the Naim Armagedon is a 340VA to 110V type. Then
comes the little phase shifter after which the output is 79V. The phase shifter
consists of a serial resistor to drop the voltage to 79V and two parallel caps
in one leg.
31V
---/\/\/\-----+------------- motor 1
|
| | +---| |---+--- motor 2
110V 79V | |
| | +---| |---+
---------------------------- motor common
The resistor is orange, orange, ? i.e. 33x? Ohm. I measured the current of my
Mantra motor (same as in LP12) that was 10mA. So I'd guess the dark third ring
is red. => 3.3KOhm (31V / 3.3k = 10mA).

The caps are Siemens types MKT. (Siemens MKH) These rectangular green types,
where the connecting legs are soldered onto the outside case. Dimensions are
7.5mm leg distance and about 4 mm thick.

So lets guess a little bit. My Mantra had a similar circuit (130V to 75V through
serial resistor) and then a 220nF cap in series to one motor leg. There are
several capacitors that would match from the dimensions side. There is a 220nF
100V type cap with just the right dimensions, But in the Armageddon has two in
parallel. There is also a 100nF 250V type which is the same size so that could
be the solution."

Do It Yourself Power Supply
---------------------------
There has been some discussion on the list about power supplys for turntables.
Most turntables have an synchronous motor which has two windings (4 wires). An
alternating current supply is applied to the windings which forms a rotating
magnetic field. The motor's rotor follows the field produced by the stator at
the frequency of the supply i.e. the rotor turns at a speed synchronous with the
alternating current supply. Most motors require a supply with a voltage less
than the voltage available from the mains. The windings also must have supplys
of different phase ideally with a 90 degree phase shift. The most basic supply
uses combinations of resistors to drop the voltage to acceptable levels and a
capacitor to achieve the phase shift.

"Suggested values are (given a motor resistance of 8k8 ohms and inductance of
10H).
For 240V, 50Hz
C1
--------+----||---------------- Blue
| R1
+--/\/\/\---+---------- Red
240VAC |
= C2
|
--------------------+--+------- Grey
|
+------- Grey
R1 = 20k ohms C1 = 0.1uF, C2= 0.1uF, Vout is about 75V

For 120V, 60Hz
C1
--------+----||---------------- Blue
| R1
+--/\/\/\---+---------- Red
120VAC |
= C2
|
--------------------+--+------- Grey
|
+------- Grey
R1=3k3 ohms, C1=0.2uF, C2=.47uF, Vout is about 85V"





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  • Re: another few questions and trany suggestion - ar guy 12/15/0111:25:18 12/15/01 (1)


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