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Old 3rd December 2003, 02:32 PM   #1
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Default EL-84 Integrated amp Project

Having "re-entered the tube building hobby with a push-pull EL34 amp, I would now like to build a single ended unit. Having researched this forum I came upon the article in the 9/99 tubecad Journal which showed a 5 Stage single ended EL-84 amp without an input stage. I would like to build this unit and integrate a liestage (driver stage) and volume control, however I have neither the software or the skill to create this stage. I would ask therefore, for help in this area from some of you learned tube guys. Please help!

Pete
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Old 3rd December 2003, 07:00 PM   #2
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Well done. Did you build the EL34 push-pull design from a kit without problems ?

You don't need software to build a tube amp! We are in a true analogue arena.

There are several other questions.

As you have built an EL34 push-pull i.r.o 25 Watts pout why suddenly a meagre EL84 SE . Why not go for the cherry on the icing with a more beefy design ?

1. What Output power are you contemplating ? 5W @10% THD (without feedback) from an EL84 is bit skinny with low efficency LS.

2. Or did you really mean SE EL34 ? On the back of my hand the EL34 SE would give you double the Pout of an EL84. That's not the end. You can design with parallel or triple output tubes to lower the effective anode resistance for better bandwidth.

3. This article in the tubecad. 5 stages.... somethings' amiss ?

4. Have you thought of other designs ? triodes in lieu pentodes ?

tell us more !
rich
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Old 3rd December 2003, 08:57 PM   #3
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Rich;
The EL-34 amp is a Dyna front end, (Magnequest OT) driven by a point to point wired version of Triode Electric's driver stage. Good circuit, terrible PCB! The EF-86 front end and the EL-34's are all triode connected, no feedback, probably put out about 7-9 watts. (Just a guess) All Solen cps in PS and DC heaters on the driver stages. Sounds very nice to these old ears.

The 5 Parallel EL-84's in the article should be good for 10 Watts and that will be enough for the full range speakers that I am planning.

I have a love for small tube amps, built a dyna ST-35 in "62 and loved it, also have heard the SV-83 unit from Decware and it was a very clean 1-2 Watts that made a Klipshorn realy sing!

Money is also an issue and I believe that the prices in the SET world are obsene. I can't comprehend spending $900 plus for tubes that my father threw away when they became noisy!

So I am back to this little pentode which I like, the opportunity to go single ended without a winning lottery ticket, and a need for a driver stage. There looks to be some very interesting triodes around for this purpose, so I need some help with a circuit for one.

Pete
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