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Old 8th November 2006, 06:05 AM   #1
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Default Please help out a Noobie...

Hello Everyone,

I am in the process of designing my first tube amp(Yea, I am new to all this stuff). I have decided that it has to be a simple SE design. However I need to drive a pair of Bass Reflex cabs with hempacoustics full range driver with a 94dB sensitivity. I like to listen to music at approximately 84dBSPL @ 1m. How much power do you think I will need from the amplifier to achieve my listening levels? As you can see power is a concern and I am not very familiar with Push-Pull designs so I cannot consider them.

I was thinking about using a 6SN7 driver stage with a EL34 power stage (triode mode), since they can put out a decent amount of power.
My second question is do I need to strap both g2 and g3 to the anode?If so are they connected in parallel to the anode? In the Phillips data sheet it says that g2 has to be connected to anode but it doesn't say anything about g3. Also, which plate curves should I be looking at if I want to use this tube in Triode? The curve sheet I have are for Vg2=250V Vg3=0V. Is there any links where I could find the required plate curve sheets? I am confused about the g2 and g3 and am not too sure about how to go about triode strapping them and what data I need to look at to operate the EL34 in Triode mode.

I know these are a lot of questions and I would greatly appreciate it if someone could help me out. Being where I am, there is practically nobody who I could turn to for help and guidance which is why I think DIYAUDIO is the coolest thing ever!
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Old 8th November 2006, 06:42 AM   #2
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I cannot answer your questions but maybe you can find some help reading these articles by Claus Byrith?

http://www.lundahl.se/claus_b_se.html
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Old 8th November 2006, 12:14 PM   #3
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Here you will find a list of tubes including EL34 (just scroll down). The data sheets are pdf files you can download. I think the Mullard data sheet will have the info you want but there are several sheets listed for EL34 from different makers.

The normally recommended way to strap EL34 as a triode is to connecr g2 to the plate using a resistor of about 150 ohm, 3 watt rated, with the lead to the g2 pin cut very short, so it can be effective in suppressing parasitic oscillations. Most manufacturers tell you to connect g3 directly to the cathode.
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Old 8th November 2006, 12:51 PM   #4
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Hello!

About a year ago I was in the exact same place you are. I decieded on an EL34 SE design that is triode strapped. It has a great sound, and I have not stopped tweaking it sense. I think an EL34 in triode more is more than enough power your speakers are rated at 94dB for sensitivity, then an EL34 triode strapped design is going to work out just fine.

Don't rule out Push-Pull. It is simpler to get sucsess with in a first amplifier. The output transformers are going to be cheaper, making the design lighter on your wallet. A good Push-Pull El84 design is a good first time amplifier. a good design for a El84 pp design can be found onDiy Paradise . But this is all about Doing it Yourself, so do what you want, your the boss!


-Moose
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Old 8th November 2006, 09:41 PM   #5
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Thanks for the info andRookie and ray_moth this was what I was looking for! Also alexmoose I would really like to build a PP amp but I really don't know how one works. could you please send me any links you know outlining PP amplifiers in detail?
I would really like to understand how an amplifier topology works before I build one!
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Old 8th November 2006, 10:18 PM   #6
2wo is offline 2wo  United States
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Check this one out. There is a part kit and great help from members of this and other forums...John

http://www.decware.com/cgi-bin/yabb/...num=1126228937
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Old 8th November 2006, 11:44 PM   #7
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hey, here is a good example that explains the difference between Class A, and Class A/B, and Class B (Class A/B, and Class B can only be achived in a push pull design).



The examples use transistors, but the amplification fundementals transfer almost flawlessly


http://en.wikipedia.org/wiki/Class_AB_amplifier#Class_A
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Old 9th November 2006, 02:09 AM   #8
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Hi audio_moksha,

I found this site created by Max Robinson to contain some helpful stuff. Browse around his site and you'll find that he covers many aspects of audio (and other areas of electronics). After reading what he has to say, I expect you'll be much clearer about push-pull. It's usually an easier path to success for most people, as alexmoose says, despite being apparently more complex than SE.
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Old 9th November 2006, 10:27 PM   #9
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Wow all this information! Thank you everyone. I'm going to be doing a lot of reading this weekend. I have already built one of those K-12 PP amp kits so I really have my heart set out on building a SE amp. The Claus Byrith article was very informative and I'm going to use a similar approach: 6SN7 driver with EL34 Triode Mode, around 375V B+, instead of using a hum control I will simply have Schottky rectified heater supplies and a diode B+ supply.
The only thing that i am unsure about is the choke value. Any guideline s, articles, suggestions, links? I'll probably use 370-0-375 centre tapped rectifier. You guys are awesome thanks once again!
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Old 11th November 2006, 01:35 AM   #10
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I really like the EL34 in triode mode. I built a version very close to this http://www.tubes.mynetcologne.de/roe...el34set_e.html

The 10k primary may not deliver enough power for 94db speakers though. I didn't use any feedback, but don't have an acurate way to measure my output. It's plenty for horns though. Good luck and keep us posted, Jay
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