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Old 16th March 2005, 04:14 PM   #1
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Default Another timekiller project

Hello! As i finished the other project i have started a new one. This time it uses EL38 for output, here are some pics: http://hififorum.knaak.dk/Tekko/EL38%20experiment/
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Old 16th March 2005, 07:05 PM   #2
SY is offline SY  United States
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The EL38 appears to be a really good tube. And still reasonably priced! I think I've still got some NOS Mullards laying about...
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Old 16th March 2005, 10:21 PM   #3
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Today i finished the chassis for it except for the OPT mounting holes as i dont have the OPT yet. Heres some pics: http://hififorum.knaak.dk/Tekko/EL38...assis/mounted/
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Old 17th March 2005, 06:58 PM   #4
316a is offline 316a  England
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Default EL38

Hello ,
The EL38 anode is rated at 25 watts . I ran these as triodes a while ago at approx 22 watts dissipation and with the lights out the anodes could be seen glowing a dull cherry red . In my opinion these valves do not make a good triode (Ra at my op point was about 2k!) and even in UL , it is best to run them at much lower dissipation that the specified 25 watts . Out the amp they came . It should also be noted that these are more suited to cathode bias rather than fixed bias unless these are run with >400V HT . However if using these in UL AB1 , quite high power output can be obtained and they're very easy to drive

cheers

316a
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Old 17th March 2005, 08:20 PM   #5
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Im going to run them in pentode for about 50 watts.
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Old 19th March 2005, 01:54 PM   #6
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Heres the schematic im going to use for this project:

Click the image to open in full size.
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Old 19th March 2005, 02:05 PM   #7
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Regulation is going to be an issue with that power supply. And no matter which PS design you go with, you want to have tight, separate regulation for the EL38 screens.
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And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
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Old 19th March 2005, 10:20 PM   #8
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A steady 383 volts! The amp is now put together and playing and what can i say ? Well it sounds beautiful even tho i only have a test OPT from a small 14 watt amp thats not the right impedance. My other amp with 6L6GC that has a way bigger OPT is not even near this new in bass output, turned it full volume and **** it was like someone turned a sub on, i looked like Whoever said tubeamps is bad for bass must have been drunk or something.

Here are some pics:

Glow in the dark:
Click the image to open in full size.

Click the image to open in full size.

Notice the small test OPT:
Click the image to open in full size.
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Old 19th March 2005, 10:44 PM   #9
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The big gold unit, that's your power transformer? Lordy, it's a big one! What's it from?
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Old 19th March 2005, 10:47 PM   #10
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Yah its the PT, its from a Nikko NA2000 amplifier, about 500VA. Backplate said the amp drawed 625Watts so the transformer gonna be in the 500VA area. And its not gold, its boring steel gray :P
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