EL34 in place of a 6AS7G (used in the supply circuit as a pass tube). how? - diyAudio
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Old 7th June 2006, 03:08 PM   #1
jarthel is offline jarthel  Australia
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Default EL34 in place of a 6AS7G (used in the supply circuit as a pass tube). how?

This is the circuit (http://headwize.com/images/barbour3.gif). It's the supply for Barbour's "brute force in a line stage" as originally published in glass audio?

anyway in the headwize article (http://headwize.com/projects/showfil...arbour_prj.htm), there was addendum of using an EL34 instead of an 6AS7. Here's the text:

10/7/98: Changes to power supply schematic (figure 2): R1 restored. Also an EL34 with a 100 ohm resistor connecting the plate to the screen can substitute for the 6AS7.

looking at the datasheet, the EL34 is a pentode while the 6AS7 is a dual triode.

I already have an EL34 and my 6.3 secondary is limited to 2A so it would be nice to use the EL34.

Can someone help in figuring out which pin goes to which? Also what is the wattage for this 100ohm resistor?

Thanks for the help
============================

Here's what I came up:

1. after R3, it goes to pin 3 which is the plate.
2. 100ohm resister from plate to pin4 grid2 (can't see any screen on any EL34 datasheet)
3. Vout is from pin 8 which is the cathode
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Old 7th June 2006, 06:39 PM   #2
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Hi Jarthel.

With the 100R resistor you are making the EL34 operate as a triode. So, "V in" goes to the plate of the EL34, 'signal' in goes to grid number 1 and V out comes from the "cathode" of the EL34. It's pretty easy - I just don't know the EL34 pinout out of my heat.

Be sure you wired it right, if in doubt, repost here and we can give more advice.

Erik
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Old 7th June 2006, 09:25 PM   #3
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Don't forget the suppressor must be connected to something too, usually the cathode.
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Old 7th June 2006, 10:18 PM   #4
jarthel is offline jarthel  Australia
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Quote:
Originally posted by ErikdeBest
Hi Jarthel.

With the 100R resistor you are making the EL34 operate as a triode. So, "V in" goes to the plate of the EL34, 'signal' in goes to grid number 1 and V out comes from the "cathode" of the EL34. It's pretty easy - I just don't know the EL34 pinout out of my heat.

Be sure you wired it right, if in doubt, repost here and we can give more advice.

Erik
when you said "signal", I assume you mean the string of zener diodes?

also what happened to the 100 resistor? where is it connected?


Quote:
Originally posted by ray_moth
Don't forget the suppressor must be connected to something too, usually the cathode.
could you please explain what is the suppresor?
=============

can someone suggest what wattage would be enough for the 100ohm?

thank you for the help
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Old 7th June 2006, 11:26 PM   #5
jarthel is offline jarthel  Australia
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as a guide, here's EL34's pin config:

pin1: grid3
pin2 and 7: heater
pin3: plate
pin4: grid2
pin5: grid1
pin6: NC
pin8: cathode
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Old 8th June 2006, 12:32 AM   #6
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I'm sure someone can correct me if I'm wrong, but this is what I'm thinking:
Attached Images
File Type: gif el34.gif (2.3 KB, 287 views)
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Old 8th June 2006, 12:38 AM   #7
SY is offline SY  United States
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Perfect.
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You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
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Old 8th June 2006, 12:48 AM   #8
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@jarthel

Quote:
could you please explain what is the suppresor?
What would we do with out google?

http://en.wikipedia.org/wiki/Suppressor_grid

www.answers.com/topic/suppressor-grid


Quote:
can someone suggest what wattage would be enough for the 100ohm?
1 watt will do fine. 1/2 watt should be okay.

Cheers
Wayne
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Old 8th June 2006, 12:59 AM   #9
jarthel is offline jarthel  Australia
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Quote:
Originally posted by cogsncogs
@jarthel



What would we do with out google?

http://en.wikipedia.org/wiki/Suppressor_grid

www.answers.com/topic/suppressor-grid




1 watt will do fine. 1/2 watt should be okay.

Cheers
Wayne
suppressor is almost a generic word. I wouldn't know I need to use it in combination with "grid" if you didn't tell me
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Old 8th June 2006, 12:59 AM   #10
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Quote:
when you said "signal", I assume you mean the string of zener diodes?
Yes. I wouldn't call it signal but reference (V).

Also be sure to connect pin 1 to pin 8, the suppressor grid to the cathode as in the EL34 these are brought out to seperate pins unlike a 6L6 etc.

Wayne
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