• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Please help out a Noobie...

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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!
 
Ex-Moderator
Joined 2004
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.
 
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
 
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!
 
Ex-Moderator
Joined 2004
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.
 
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!:)
 
Hello jaymanaa, I have visited you website any times before and I found your EL34 SET project very informative. Anyway, i was planning to use a 5k primary audio transformer. I will be using a single 6SN7 drive stage amd I'm looking for about 5-10W power do you think using 2 drive stages in series would up the output power? . Also didn't you use global feed back at the drive stage in your EL34?

And hey alexmoose what kind of design did you use building your EL34SET? Did you use one drive stage or two? How much power were you looking for? Any help would be very much appreciated considering you were in my place last year:) Thx!
 
audio_moksha said:

And hey alexmoose what kind of design did you use building your EL34SET? Did you use one drive stage or two? How much power were you looking for? Any help would be very much appreciated considering you were in my place last year:) Thx!

My design was an adapted el84 design that I uprgaded to the EL34 triode strapped, it produces about 5wpc, In reality, an EL34 SET can be run in UL mode if you buy a transformer for it (I don't have one) and in UL mode which "has the sound of triode with the power of pentode" which gets you about 12wpc.

The design I used has a very similar "cousin" amplifier that can be found on Tubelab This amp can be built on a pretty modest budget. Tubelab doesn't adversite this much (i'm sorry if you do know, I haven't been on the forums, or your website in a long time), but the power transformer he uses is extreemly affordable, Allied 6K56VG I have never used it, but If I were buidling the same amp again, I would.I used the Hammond 272HX Whic is 20 dollars more than the Allied, but has a little more punch both voltage, and current wise.

Read Tubelab for hours, you'll learn alot
 
audio_moksha said:


Hello jaymanaa, I have visited you website any times before and I found your EL34 SET project very informative. Anyway, i was planning to use a 5k primary audio transformer. I will be using a single 6SN7 drive stage amd I'm looking for about 5-10W power do you think using 2 drive stages in series would up the output power? . Also didn't you use global feed back at the drive stage in your EL34?

And hey alexmoose what kind of design did you use building your EL34SET? Did you use one drive stage or two? How much power were you looking for? Any help would be very much appreciated considering you were in my place last year:) Thx!


Hi, That web page isn't mine, I just used it for a starting point as I'm not a designer (yet). 5K would be great for OPT primary, and easily put you in the 5-10 watt range. I would build it as Tom has it drawn with the 6SL7 (more gain than the SN7). I also used some custom wound outputs to insure good stability at lower frequencys. My B+ is a little over 450 too
:eek: I just didn't need the feedback, so it was omitted.
 
alexmoose said:


My design was an adapted el84 design that I uprgaded to the EL34 triode strapped, it produces about 5wpc, In reality, an EL34 SET can be run in UL mode if you buy a transformer for it (I don't have one) and in UL mode which "has the sound of triode with the power of pentode" which gets you about 12wpc.

\ Allied 6K56VG Hammond


Hey alex moose could you tell me more about this Ultralinear mode for a EL34 SET. How much power can I get using this mode? sounds interesting..thanks for all the help once again, alexmoose
:)
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.