Toroid Output Transformer from Plitron - diyAudio
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Old 25th November 2011, 10:54 AM   #1
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Default Toroid Output Transformer from Plitron

Any one ever build an amplifier with Plitron toroid output transformer? I download their specification sheet and found their high frequency is quite poor.
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Old 25th November 2011, 11:13 AM   #2
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Where have you looked? At their site there is a list of transformers and specs, and with the exception of one unit, they all have HF well over 100kHz. There is one that reaches almost half Mhz.

Looks quite good to me!
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Old 25th November 2011, 03:59 PM   #3
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This one seems pretty limit on the high frequency.

150W Special Design Output Transformer

Maybe this is a high power with 211 in push pull circuit. My friend sent me, so I wonder. Toroid should be pretty wide bandwidth.
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Old 25th November 2011, 04:28 PM   #4
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Location: Alps:Tube amp designs over 150W, SMPS guru.
Designing a tube amp with an o/p tranny of 100Khz b/w requires some thought on the layout and type of tubes used; generally the response gets "stopped down" in the circuit well before that, otherwise with ex video b/w tubes it can become a perfect oscillator and will zap-up tweeters without hearing it.

I've come across many mistakes of UL amp builders simply swapping o/p trannies for wider b/w types with horrendous results. It isn't quite that simple as one/another o/p transformers have their own phase relationships with the circuit used. Hence if in doubt stay with a design that has been proven to work with a particular transformer, til one gathers more experience. Standard Push pull is certainly easier.

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Old 7th December 2011, 11:51 PM   #5
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I would not recommend using toroids with uncut cores (like plitron) unless they can be ac-feed.
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Old 8th December 2011, 07:23 AM   #6
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Quote:
Originally Posted by gorgon53 View Post
I would not recommend using toroids with uncut cores (like plitron) unless they can be ac-feed.
This is common disbelief that toroids without fixed or distributed air gap can't tolerate small DC typical for any PP amplifier. Properly constructed PP toroid can handle small DC without any problem whatsoever. Cutting toroid core to make air gap basically kills almost all
of its advantages.
A pair of 60W PP toroids I designed can sustain 7mA of DC imbalance for each output vacuum tube.
Toroid SE transformers or DC chokes should have fixed or distributed air gap, however.
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Old 8th December 2011, 07:28 AM   #7
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Quote:
Originally Posted by Tubenstein View Post
Any one ever build an amplifier with Plitron toroid output transformer? I download their specification sheet and found their high frequency is quite poor.
Plitrons have excellent top HF limit. However, top frequency is usually limited not by leakage inductance, but buy resonant frequency caused by leakage inductance and stray capacitance. Toroids usually have much higher stray capacitance compared to EI or double C core with comparable technical characteristics.
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Old 8th December 2011, 10:27 AM   #8
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Why not use grid stopper resistors and add a 70-80k pole between the 1st and 2nd stage to keep the beast from singing on its own?
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Old 13th December 2011, 02:25 AM   #9
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common disbelief is that common, uncut toroid cores have a uniform airgap. They dont.
They consist of a coiled strip wich has a oxidlayer and windingdependend small but fluctating gaps. The manufacturer of the core has no way to controll this gaptolerances
in a way that would even come close to what is possible with a cut cut core.
Draw your own conclusions, and dont let you influence by statements like "7ma" wich is meaningless as such.
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