ECF801 Triode/Pentode any useful application ? - diyAudio
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Old 2nd March 2013, 09:41 PM   #1
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Default ECF801 Triode/Pentode any useful application ?

There are some Triode/Pentode combinations like ECF801 / 6GJ7 in which the two tube systems share a common cathode.
Are there any known applications where both systems can be used in a circuit ?
audio, power supply or whatever ?
I mean aside from their original purpose as oscillator/mixer in a frequency changer or using just the triode or the pentode separately ...
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Old 2nd March 2013, 11:39 PM   #2
AJT is offline AJT  Philippines
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how about a Radford phase spliiter?....Radford pentode-triode LTP splitter
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Old 3rd March 2013, 01:37 AM   #3
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Paraphase/See-Saw is a good possibility. Since one system has 100% feedback, its parameters don't matter.
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Old 3rd March 2013, 08:15 AM   #4
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Quote:
Originally Posted by Tony View Post
how about a Radford phase spliiter?....Radford pentode-triode LTP splitter
Yes, that may fit. Found this, think it's the same: New Phase Splitter
In this article the emphasis is more on phase stability.
I gave it a try but although I used ECF82 spice models I could not get symmetric output signals ... played varying plate resistors but could not get it right, yet.
Don't have model for ecf801 either.
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Old 3rd March 2013, 08:44 AM   #5
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Quote:
Originally Posted by the_manta View Post
Paraphase/See-Saw is a good possibility. Since one system has 100% feedback, its parameters don't matter.
so the 2nd (unity-gain) triode could be the pentode, right ?
The Valve Wizard
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Old 3rd March 2013, 08:55 AM   #6
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Quote:
Originally Posted by payloadde View Post
so the 2nd (unity-gain) triode could be the pentode, right ?
The Valve Wizard
It's up to you ! If you want high gain, use the pentode for the amplifying first stage and the triode as second tube (slave). Otherwise, vice versa
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Old 3rd March 2013, 04:11 PM   #7
Ketje is offline Ketje  Belgium
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The fact that you can't get the Redford symetric doesn't surprise me.
I don't like that circuit.
To use the ECL801 as a paraphase splitter try it like this.Didn't build it but looks promessing.
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Old 3rd March 2013, 08:03 PM   #8
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Yes, floating paraphase, I guess.
I like the split cathode resistor, makes it easy to match non-equal tubes.
Modifyed it a little, hooked up the pentode in triode mode. All I had to do is to change the upper cathode R to 220 and the lower R to 470 ohms. Et voilą - symmetric outputs.
Not that I need a phase splitter right now, but good to know ... maybe some day ...
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Last edited by payloadde; 3rd March 2013 at 08:05 PM. Reason: typo
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