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Old 2nd August 2006, 04:56 AM   #1
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Default OPT Project for EL84 SE

Hello World!

I have a request for all of the people that built amps with EL84. Could you recomend a good project of OPT for SE operation? And maybe you could sugest a good "sounding" schematic....
I thought at this

Thank you!
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Old 2nd August 2006, 05:45 AM   #2
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I check the design.
Looks like a guitar amp. volume pot after the tube is a big no-no
Some how the sound will sound compressed when done like this.

For el84 there are many around
check for the stc (jap style) or even popular ones like the AN parallel style
There is a website with all the links for most tubes. Can't seem to recall it.
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Old 2nd August 2006, 12:24 PM   #3
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I haven't found those schematics you have suggested, but I have something here and here
What do you think about them?

Anyway, does anybody wants to share a OPT project with me? Please.....I already have the lamination (grain oriented, EI 28 mm tongue), it's only missing the project.

Thank you!
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Old 3rd August 2006, 02:33 AM   #4
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I heard the ef86 yesterday, sounding really good.
Go for the ef86 project. Should be all well
http://www.jogis-roehrenbude.de/Verstaerker/EL84-6W.htm

used some funny feedback but looking at it i should work well.
Also with ef86 you have to put some rubber grommet aroudn the tube and the socket. It is a microphonic tube
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Old 3rd August 2006, 03:12 AM   #5
mach1 is offline mach1  Australia
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This is the best EL84 I have heard so far.

http://www.tubeaudio.8m.com/RH84/rh84.html
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Old 3rd August 2006, 09:55 AM   #6
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Default RH84

Yes, RH84 is one of excellent sounding EL84 SE amp. I built one and modified to SY's technique by using led at cathode and controlling the cathode current by controlling Screen Grid Voltage. with this way, i noticed the sound is tighter specially in the bass (which is usually the weakness of small power SE amp).

rgds

Penk
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Old 3rd August 2006, 10:32 AM   #7
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All right! I will adopt the RH84 project, and in the future i will try a version with EF86, wich i heard is a high performance pentode, anyway, i already have this kind of tube.
Thank you!
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Old 3rd August 2006, 02:32 PM   #8
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this is also a nice project;

http://www.jogis-roehrenbude.de/Lese...E/Goecking.htm
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Old 3rd August 2006, 03:22 PM   #9
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Mas Penk, would you tell me in detail youre modding? Thanks
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Old 4th August 2006, 04:27 AM   #10
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My modding is simple, i just removed the 270R and cap on cathode and replaced it with series and parallel led (5 in series and 4 series in parallel).
To control the current through cathode I used SY's technique by using Maida's Regulator.
So I removed screen resistor 2k2 and plugged the regulator. I adjusted the curent on cathode by increasing/decreasing voltage on screen. Please read SY's article Red Light District Amp on Bas' DIY MAgazine for Regulator Detail.

On article, SY mentioned that we can push more current on Cathode by increasing current on screen grid and that is what i tried, and it sounds better than before (my opinion of course).

The measurement result is not much different than original version but it sounds better.

rgds

Penk
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File Type: jpg xperiment el84-se - 12at7 se - rh84 sy modified.jpg (32.8 KB, 974 views)
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