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Old 7th March 2008, 03:12 PM   #1
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Default Combine EF80 with El84

This is the first time i'll build a tube amplifier.

I have two EF80 tubes and will get two EL84 tubes from a friend. I have also ordered to output transformes. I need help with combining these tubes and the transformers to an amplifier.

thank you
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Old 7th March 2008, 04:49 PM   #2
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Hi and welcome to the DIY valve world!

I assume you will build a stereo SE amplifier? Have you seen thiswebsite ? It is one of the websites that offer a walkthrough for the design of a SE valve amplifier. You can follow the same steps with the data from the EL84 and the EF80 (I would probably triode connect the EF80, curves in triode mode can be found here

The above does help, but do not expect to have it ready on the back of a napkin. Better to sit with lots of paper and a pen, a calculator comes in handy as well!

Good luck, Erik
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Old 7th March 2008, 08:42 PM   #3
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Yes stereo! Im not sure though what SE means? Is it Single ended, in that case yes it's this config i'm aiming for.

I will read the instructions carefully.
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Old 11th March 2008, 04:04 PM   #4
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I have about 170V dc supply. I gues that is not enough for the el84 tube?
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Old 11th March 2008, 04:04 PM   #5
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I've checked out the boozhound link. The power stage is pretty easy to understand i think. But when they calculate the pre-stage they use som alreday finished example from the datasheet for the tube. The EF80 tubes i have does'nt have this ready example with suggested component values ....!?
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Old 11th March 2008, 04:13 PM   #6
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Quote:
Originally posted by newbadboy
I've checked out the boozhound link. The power stage is pretty easy to understand i think. But when they calculate the pre-stage they use som alreday finished example from the datasheet for the tube. The EF80 tubes i have does'nt have this ready example with suggested component values ....!?



Download and read this . You could then use the triode curves that Eric linked to to determine your operating points.

Best of luck.
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Old 12th March 2008, 01:53 AM   #7
SHiFTY is offline SHiFTY  New Zealand
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http://www.bonavolta.ch/hobby/en/audio/el84_3.htm

The original 1950s Mullard schematic...
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Old 12th March 2008, 09:59 PM   #8
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Nice.

I'm not using the Mullard though, i use. a chinese one. Is there big diffrence?
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Old 12th March 2008, 10:40 PM   #9
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Quote:
Originally posted by newbadboy
Nice.

I'm not using the Mullard though, i use. a chinese one. Is there big diffrence?
The Mullard he's referring to was an amplifier circuit designed by Mullard to promote the use of their tubes back in the forties and fifties..
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Old 19th March 2008, 10:17 AM   #10
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Quote:
Originally posted by pedroskova





Download and read this . You could then use the triode curves that Eric linked to to determine your operating points.

Best of luck.

Ive read thru the manual. It only describes as i understood the preamp stage (in my case ef80). I will also use the el84 to the power stage and this is not described?!

I would also like to power the whole amplifier with 155VDC only. What do i loose/gain by having this low supply voltage??
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