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Old 11th February 2008, 07:58 PM   #1
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Default Choke Input Filter.

I did some research and some calculations and came up with the design below for a 6CK4 amplifier. I was going to use a 12B4A but I can get a whopping 1/2 watt more out of a 6CK4 so I'm going in that direction. The design may be overkill but that is what I like. I only plan on building it once so why not? Anyway I am hoping for some thoughts and constructive criticism from our more learned members here.
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Old 11th February 2008, 08:04 PM   #2
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Two identical LC sections can ring. Have you checked the stability in PSUD2? A current step should tell all.

edit: Just noticed the power transformer wiring. Ummmm... explosive.
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Old 11th February 2008, 08:04 PM   #3
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Seems like your power trafo is not connected correctly. Besides I recommend you give a look at pages 315 until 318 of Valve Amplifiers, 3rd edition, to see Morgan's recommendation on choke snubber networks!

Good luck, Erik
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Old 11th February 2008, 08:13 PM   #4
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Id drop a choke and use an LCRC or LCRCRC with much more capacitance. Much less ringing, cheaper.

Doubt Id use a resonant choke. I absolutely would not use 2 resonant chokes, resonant chokes trade off more 100 or 120hz filtering for almost no filtering at other frequencies.
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Old 11th February 2008, 08:23 PM   #5
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Quote:
Originally posted by SY
Two identical LC sections can ring. Have you checked the stability in PSUD2? A current step should tell all.

edit: Just noticed the power transformer wiring. Ummmm... explosive.
I just showed the transformer sections wired in parallel. I am using a Hammond 300 series power tranformer. I wanted to avoid confusion.
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Old 11th February 2008, 08:26 PM   #6
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Quote:
Originally posted by Tweeker
Id drop a choke and use an LCRC or LCRCRC with much more capacitance. Much less ringing, cheaper.

Doubt Id use a resonant choke. I absolutely would not use 2 resonant chokes, resonant chokes trade off more 100 or 120hz filtering for almost no filtering at other frequencies.
Thanks for telling me. I designed it, crudely, from a PDF of a old tube electronics manual that I have on the 'puter. I will drop the tuning caps.
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Old 11th February 2008, 08:27 PM   #7
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Quote:
Originally posted by Tweeker
Id drop a choke and use an LCRC or LCRCRC with much more capacitance. Much less ringing, cheaper.

Doubt Id use a resonant choke. I absolutely would not use 2 resonant chokes, resonant chokes trade off more 100 or 120hz filtering for almost no filtering at other frequencies.

Also the filter caps are ASC motor run caps. I can get bigger ones but I already have these at hand.
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Old 11th February 2008, 08:30 PM   #8
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Quote:
Originally posted by SY
Two identical LC sections can ring. Have you checked the stability in PSUD2? A current step should tell all.

edit: Just noticed the power transformer wiring. Ummmm... explosive.
What do I need to check? The current through the load or the current through each choke?
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Old 11th February 2008, 09:57 PM   #9
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Reaction to changing current is what needs checked. This can be checked using a current step in PSUDII (use current load, edit the step, be sure to check event timings), or one can calculate the chokes damping.

Id say your better to buy more capacitance than a second choke, given the choice. While not as tough, elcos are fine sections other than the final, the R and L filter elements swamp any differences.

Be careful any chokes dont get noise coupled into them from other magnetic sources such as power supply iron.
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