Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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Re: Jon, questions about resistor and transformers

Posted by Jon Risch (B) on November 29, 2004 at 20:46:13

In Reply to: Jon, questions about resistor and transformers posted by mark maloof on November 29, 2004 at 13:18:56:

RE#1 See:
http://www.AudioAsylum.com/audio/tweaks/messages/47160.html

Instead of 220- to 270 ohms, use 390 to 470 ohms, so as to draw less current from the transformers. Do not use a cap larger than 1 to 2 uF, as the cap can actually draw some current to charge and discharge it.

RE#2
If your CDP draws too much current, then the transformers will run hot and the output voltage may sag some, providing les than the original 115VAC to the CDP. Neither is fatal, as long as you oprovide enough ventilation, and the CDP works OK with a slightly low AC line. As long as the output voltage does not drop below about 107 to 105 VAC, most players wil not have any problems.

RE#3
The RS transformers was a quick and dirty solutioon to finding an isolation transformer, as quick as your nearest RS. They were never considered the ultimate solution, just an option.

As noted in the second post, if you install the resistor, you lose about 3W of total capacity, and I mentioned that the capacity was ABOUT 50W.

There have been a lot of posts on this filter, and the idea of using othr transformers has been discussed I believe, as has the wattage overhead.

At 38W, your CDP is on the edge of being a potential problem unit, and as I said, I have been conservative in my statements regarding wattage ratings.

It is very likely that it will work just fine, but I can not possibly "guarantee it" for you. Just be sure to provide ventilation holes in the metal box, and to fuse it appropriately. BTW, a 1 amp fast blow may not be enough, either use a 1 1/2 amp fast blow, or a 1 amp to 3/4 amp slo blow, so as to allow for the turn on surge current.

If you have a cheap voltmeter, or can borrow one, check the AC voltage on the output of the digital iso filter when the CDP is hooked up and running, and see where it is at.

Jon Risch

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