Crazy newbie tube driver question

john65b · 13th July 2008, 07:22 PM

OK all, I have seen a few driver circuits to a PP Output (long tailed phase inverter, Cathodyne phase inverter)...but as I was looking at a Audionote M7 circuit with (I believe it to be a parafeed??), I was wondering if this was an option or possible... to feed a 6L6GC PP output section with 6sn7... disregard the values for the time being, just overall

Please forgive me if the if the question is totally ridiculous...

jerluwoo · 13th July 2008, 07:50 PM

There will be no output for the cathode end because of the led bias. A led has very low on resistance, basically a short so no signal will appear across it. The led should be replaced with a resistor the same value as in the plate side. As for paralleling tubes, it should be fine as your are basically doubling drive current. Are you sure the circuit you saw is not a paraphase splitter instead?

john65b · 13th July 2008, 08:07 PM

OK. I can see that. So like this would be doable? Is there caveats to this type versus Cathodyne Phase splitter? Is bypass cap needed?

SY · 13th July 2008, 09:06 PM

The bypass cap will prevent this from working at all.

Before proceeding any further, I'd strongly recommend reviewing the section on phase splitters in Morgan Jones's "Valve Amplifiers." You can try all sorts of random things without really "getting" it, but if you understand the theory behind how a split load or long tail pair actually works, you're vastly more likely to come up with a successful scheme.

kevinkr · 13th July 2008, 11:44 PM

Quote:

Originally posted by john65b
OK. I can see that. So like this would be doable? Is there caveats to this type versus Cathodyne Phase splitter? Is bypass cap needed?

Sy's dead right on his comments, and what you have is a broken cathodyne phase inverter.. (The bypass cap amongst other things breaks it.)

I'd add Jones's "Building Valve Amplifiers" to the list of recommended reading in addition to Sy's suggestion of "Valve Amplifiers." I strongly recommend a cover to cover read of both titles for all newbies, and many veterans of the tube wars as well.

You do know that you need appreciable voltage gain ahead of the splitter to drive your output tubes?

Read first, ask questions next, build last...

mashaffer · 14th July 2008, 01:07 AM

See phase inverter sections here

john65b · 14th July 2008, 02:42 AM

I will do so. I appreciate your comments.

Thanks

13th July 2008, 09:06 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Austin, TX Blog Entries: 1	The bypass cap will prevent this from working at all. Before proceeding any further, I'd strongly recommend reviewing the section on phase splitters in Morgan Jones's "Valve Amplifiers." You can try all sorts of random things without really "getting" it, but if you understand the theory behind how a split load or long tail pair actually works, you're vastly more likely to come up with a successful scheme. __________________ “Listening to records is like ****ing a picture of Brigitte Bardot.” - Sergiu Celibidache

14th July 2008, 01:07 AM	#6
mashaffer diyAudio Member Join Date: Jun 2004 Location: Indiana	See phase inverter sections here __________________ mike - www.keepingsundayspecial.org

14th July 2008, 02:42 AM	#7
john65b diyAudio Member Join Date: Jan 2005 Location: Chicago	I will do so. I appreciate your comments. Thanks __________________ "I speak Spanish to God, Italian to Women, French to Men, and German to my Horse" - Charles V

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13th July 2008, 07:50 PM	#2
jerluwoo diyAudio Member Join Date: Feb 2006 Location: Ashland,Ky U.S	There will be no output for the cathode end because of the led bias. A led has very low on resistance, basically a short so no signal will appear across it. The led should be replaced with a resistor the same value as in the plate side. As for paralleling tubes, it should be fine as your are basically doubling drive current. Are you sure the circuit you saw is not a paraphase splitter instead?

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