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Old 21st June 2010, 02:15 PM   #511
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Hi Coolzero,


Just wondering about the 1st choke in an LCL supply, is it better to use 1 coil in each leg + & - (ala common mode) or use them in series just on the + leg? Can anyone share some knowledge on this?

Rich
like Cmc I hope is better as I will use in my new phono , just try is fast

Thomas use LCL not CLC To have higth impedence?
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Old 21st June 2010, 03:30 PM   #512
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Hi Sheldon,

As regards resistor temperatures, I bought an IR thermometer to measure this. Thorough, eh! What we do for science.....

Well, after about 15 minutes the temperature in the centre of a 10 ohm 30W vitreous enamel resistor is 150 degrees centigrade. Temperature at either end is 90 degrees. This will probably go up a bit more. Ambient temperature is 24 degrees.

Amusing little things, these IR thermometers!

Andy
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Old 21st June 2010, 04:31 PM   #513
Sheldon is offline Sheldon  United States
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Makes sense. Will burn your finger, but the resistor is just coasting.

Sheldon
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Old 21st June 2010, 04:36 PM   #514
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Amusing little things, these IR thermometers!
Hi Andy;

IR camera is a stunning thing. You may see all your amp in colors depending on temperatures. Change layout and test again. Change heatsink and see again. Until it is near perfectly optimal!
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Old 21st June 2010, 04:47 PM   #515
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Sheldon/ Andy,

I have 15R/50W resister in hand. If I use this with 12V supply, guess the filament will be little starved at 0.8A. Is this OK? Is it a must to have exact 1A current from the 12V supply? Which I got now is 12V-3A supply. Any other issues you could see with this setup? Appreciate your advice.
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Old 21st June 2010, 07:38 PM   #516
Sheldon is offline Sheldon  United States
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Sheldon/ Andy,

I have 15R/50W resister in hand. If I use this with 12V supply, guess the filament will be little starved at 0.8A. Is this OK? Is it a must to have exact 1A current from the 12V supply? Which I got now is 12V-3A supply. Any other issues you could see with this setup? Appreciate your advice.
You are running the 26 well below its maximum current, so starving the filament by 20 percent should not be a problem. Though, I think with coated filaments, you wouldn't go much lower.

Sheldon
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Old 21st June 2010, 09:42 PM   #517
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Coolzero,

You could put a 47 ohm resistor in parallel with the 15 ohm. At 1 amp, wattage would be 2.5W through the 47R and 8W through the 15R, so I guess rate the 47R at 12W. That would give you 11.4R. A bit nearer.

Andy
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Old 22nd June 2010, 06:25 AM   #518
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Thanks Sheldon, Andy. I will try this and post the results soon.
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Old 22nd June 2010, 03:04 PM   #519
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Is filament PSU's ampearage a concern here? Mine 12V/3A.
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Old 22nd June 2010, 04:17 PM   #520
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You need two filament supplies - one for each 26. If you mean 12V secondary that should be fine - once rectified (Schottky diodes) should give you 17v or so. Then a big cap like 15,000uF rated 25v. Three amps per supply should be OK. For testing I used a LM1085 as voltage reg. I used a 120 ohm resistor from adjust to out and a 950 ohm sense resistor from adjust to ground. Actually this was a 1.1K bypassed with a 10K pot. See data sheet for how to use the LM1085 if you do so. There are better options like chokes and better ss devices, which is my next step.

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