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-   -   ECF801 Triode/Pentode any useful application ? (http://www.diyaudio.com/forums/tubes-valves/231204-ecf801-triode-pentode-any-useful-application.html)

payloadde 2nd March 2013 10:41 PM

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 ...

AJT 3rd March 2013 12:39 AM

how about a Radford phase spliiter?....http://www.diyaudio.com/forums/tubes...-splitter.html

the_manta 3rd March 2013 02:37 AM

Paraphase/See-Saw is a good possibility. Since one system has 100% feedback, its parameters don't matter.

payloadde 3rd March 2013 09:15 AM

Quote:

Originally Posted by Tony (Post 3393215)
how about a Radford phase spliiter?....http://www.diyaudio.com/forums/tubes...-splitter.html

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.

payloadde 3rd March 2013 09:44 AM

Quote:

Originally Posted by the_manta (Post 3393342)
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

the_manta 3rd March 2013 09:55 AM

Quote:

Originally Posted by payloadde (Post 3393624)
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

Ketje 3rd March 2013 05:11 PM

1 Attachment(s)
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.
Mona

payloadde 3rd March 2013 09:03 PM

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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