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Old 17th June 2005, 05:35 PM   #11
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Default I.E.C. with R.F.I. filter

Sy,
I would like to congatulate you on a great thread. One thing that I have found is the R.F.I. filters that come on some of the I.E.C. connectors are detrimental to the sound of the unit that its on. I remove these type of I.E.C. connectors and replace them with regular I.E.C. connectors on every piece of audio electronics. I think you will find a very noticable improvement in sound. In this pre amp design you are planning proper filtering so there is no need for the R.F.I. filter. Please try this for yourself, compare with the filter to without filter. Find out for yourself.

Andy
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Old 17th June 2005, 05:38 PM   #12
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Do you think the problem is with specific filters or line filtering in general?
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Old 17th June 2005, 06:05 PM   #13
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Sy,
I think this is a problem with this type of filter. In my opinoin this type of filter limlts current to the circiut. With out the filter there is no current limit. In my opinoin.
It will be nice to hear other thoughts on this subject.

Andy
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Old 17th June 2005, 06:27 PM   #14
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Quote:
Originally posted by SY
One more detail that EC8010 nagged me about: in the heater string, if you reverse the position of the heater and the dropping resistor, the heater will be at a more positive potential, a Good Thing as far as potential noise from heater-to-cathode leakage is concerned. I'll change that in my preamp and on the drawing tonight.
I don't know this....is the design goal just to get the heater voltage as close as possible to the cathode voltage, or is it better to be above it?

Quote:
Originally posted by Andy Bartha
I think this is a problem with this type of filter. In my opinoin this type of filter limlts current to the circiut. With out the filter there is no current limit. In my opinoin.
It will be nice to hear other thoughts on this subject.
Well, it makes sense that if you are in the "fancy power cables sound better camp" that sticking one of those cheapie 3A rated filters would largely negate the benefits of the thick power cables. But those RFI filters do come in hefty 10A versions as well. Has anybody tried those?
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Old 17th June 2005, 06:35 PM   #15
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Quote:
Originally posted by Andy Bartha
I think this is a problem with this type of filter. In my opinoin this type of filter limlts current to the circiut. With out the filter there is no current limit. In my opinoin.
It will be nice to hear other thoughts on this subject.
The AC line's not even in the picture the majority of the time. What ultimately provides the current for the circuit is the reservoir caps. The AC line's only in the picture for a very short time every 1/120th of a second as it tops up the caps during the refresh cycle.

Any current limiting on the part of the line filter would basically just result in a very slightly lower average supply voltage.

Now, those filters typically use common-mode caps (i.e. the caps that go from hot and neutral to safety ground) which can increase chassis leakage currents and in certain situations increase noise because of it.

But the current limiting issue is a non-issue in my opinion. But then I'm not a big fan of AC power in the first place.

Click the image to open in full size.

se
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Old 17th June 2005, 06:35 PM   #16
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I tried the 10A version also with the same effect. In this case it was a tube output cd player. It had one of the three amp filters in it and I replaced it with a non-filter I.E.C. and the sound improved. I then installed the 10A version of the R.F.I. filter and the sound went back to the same as with the 3A R.F.I. filter. So the current rating of the filter doesn't seem to make much diffrence. I can't explain why this is but this is my experiance.

Andy
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Old 17th June 2005, 06:38 PM   #17
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Leadbelly: Having the heaters biased positively with respect to the cathode is a plus. Not too high, but high enough that any heater-cathode diode effect is reverse biased.
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Old 17th June 2005, 10:21 PM   #18
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This is a great thread - thanks, y'all!
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Old 18th June 2005, 04:33 PM   #19
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Default Re: I.E.C. with R.F.I. filter

Quote:
Originally posted by Andy Bartha
...some of the I.E.C. connectors are detrimental to the sound....
Hi Andy, what changes do you hear? I've been experimenting with Spice-optimized micro-Henry air chokes in a tube amp power supply and wouldn't mind the sanity check. Thx in advance.
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Old 19th June 2005, 04:13 AM   #20
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Hmm, another Firesign Theater fan .....

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