Simplest possible EL84 push pull amplifier

[cooloox]

I was looking for the most simple EL84 circuit to get started and found something like this:
http://www.diyparadise.com/simpleel84.html

Am I missing something or is that website missing something or is it really possible to build a working PP amp with one OPT, two resistors and a pair of EL84? Has anyone tried it? What's going on here?

The schematic:

 

[tikiroo]

You are missing something 🙂. Full circuit is like this but without the CCS (which he adds later as an improvement).

 

[basreflex]

are you depicting 2 output transformers ? a single balanced one has the dc current cancelled in the core.

 

[tikiroo]

Would just be a drafting convenience to show the ultralinear taps, he probably didn't have the right symbol available. I just copied it from the diyparadise website, not my circuit....

 

[waltube]

I have this project one by me
Avoid all diagrams without any lab test.

 

[huggygood]

you can't say that so radically.
you have to take into account the fun side to start with, but also the learning side.
I agree with you that it's safer and smarter to assemble amps whose diagrams have been validated by analysis results but that does not mean that these amps sound good or are pleasant to listen to. to listen .
with the little experience I have, I think the basics are to find two or three pairs of good opts to start with, and then to try several diagrams "to see what happens"

 

[jcalvarez]

I would go for a version of Tubelabs' SPP using a couple of ECL86s. Just two cheap bottles and a proven circuit.

 

[Steve Morley]

A large percentage of the budget will go power and output transformers and a chassis, so why build a stripped-down circuit when with a few more parts a known decent design can be built? As jcalverez says an ECL86 or my preference an ELC82 based on the long-gone Wave 8. If you are in the USA you have inexpensive transformer options from Antek.

 

[waltube]

you can't say that so radically.
you have to take into account the fun side to start with, but also the learning side.
I agree with you that it's safer and smarter to assemble amps whose diagrams have been validated by analysis results but that does not mean that these amps sound good or are pleasant to listen to. to listen .
with the little experience I have, I think the basics are to find two or three pairs of good opts to start with, and then to try several diagrams "to see what happens"

I am radically for one simply reason, the project with test lab that are published are a warranty ( maybe is a strong definition) that this paritcular project can work as designed.
I have seen thousands ( maybe millions) of schematic and simulations without any subsequently realization even as proto.
If someone want to have a reasonable stuff that can run this is the only way.
Of course, the arguments to write are millions but this is another story
I have wrote more than 30 articles on AUdioreview magazine in Italy with ptojects ( maybe not the diamonds of hifi) but every one is certified by measurement.

Walter

 

[huggygood]

I am radically for one simply reason, the project with test lab that are published are a warranty ( maybe is a strong definition) that this paritcular project can work as designed.
I have seen thousands ( maybe millions) of schematic and simulations without any subsequently realization even as proto.
If someone want to have a reasonable stuff that can run this is the only way.
Of course, the arguments to write are millions but this is another story
I have wrote more than 30 articles on AUdioreview magazine in Italy with ptojects ( maybe not the diamonds of hifi) but every one is certified by measurement.

Walter

I can only agree.
I just like to keep the fun side of "what if I do this?"
but you are fundamentally right.

 

[waltube]

tempus fugit,memento mori

my compliments for latin!!!!!!!!

 

[wiseoldtech]

.....with the little experience I have, I think the basics are to find two or three pairs of good opts to start with, and then to try several diagrams "to see what happens"

It doesn't take much to build a good EL84 amp with some proven tweaks.
The amp I built in 2006 justifies that quite well.
Of course, being a long-time experienced professional in audio, I had an edge on knowing what I was doing.
And the results were actually beyond my expectations.

 

[Bas Horneman]

Am I missing something or is that website missing something or is it really possible to build a working PP amp with one OPT, two resistors and a pair of EL84? Has anyone tried it? What's going on here?

You are not missing anything. You can build a working PP amp like that. (though that is just one channel in the schematic). It is self inverting. It would need a preamp though...or a driver stage as shown in post 2.

 

[waltube]

Even also that if you need a perfect Ibias similar to both 84 you must select them at the best, this to avoid a risk of saturation of nucleus due to unbalanced current.
Then without bypass on cathode the Z of the output stage will be higher ( also with lower gain)
Much better a fixed bias for each 84

 

[Francois G]

I have this project one by me
Avoid all diagrams without any lab test.

Why did you post this? Did you perhaps post the wrong picture?

This is a topology, not a schematic useful to anybody, certainly not one you could build and test without the part values.

 

[huggygood]

tempus fugit,memento mori

my compliments for latin!!!!!!!!

This is my next tatoo 😉
I don't know if you know the story of "memento mori" but for me it's really very important and a philosophy of life

 

[waltube]

Why did you post this? Did you perhaps post the wrong picture?

This is a topology, not a schematic useful to anybody, certainly not one you could build and test without the part values.

Hi

the project
It works in class A close to the max power

V1= 6922-ECC88-PCC88

V2-V3 = EL84

Zoccoli noval



R1= 50 kohm ½ watt passo 5 mm

R2-R7= 470 ohm ¼ watt passo 5 mm

R3 = 27kohm 1 w passo 15 mm

R4 = 270 ohm ½ watt passo 5 mm

R5 = 68 ohm ½ watt passo 5 mm

R6 = 2k7 1 watt passo 1 5 mm

Rx = da definire ½ watt passo 4 mm

R8 = 1 Mohm ¼ watt passo 5 mm

R9 =470 ohm ½ watt passo 5 mm

R10-R11 = 18 kohm 1 watt passo 15 mm

R12-R13 = 2k2 1/watt passo 5 mm

R14-R15 = 1 kohm 1 watt passo 15 mm

R16-R17 = 1 ohm 1 watt passo 15 mm

R18-R19 = 220 kohm ½ watt passo 5 mm

R20 = 1 kohm 1 watt passo 15 mm





C1 = 0,1 uF 400 Vdc passo 20 mm

C2 = 0,1 uF 100 Vdc passo 5 mm

C3 = 220 uF 25 Vdc passo 2,5 mm

Cx = da definire passo 5 mm

C4-C5 = 0,22 uF 400 Vdc passo 22

C6-C8 = 0,1 uF 400 Vdc passo 20 mm

C7-C9 = 10 uF 400 Vdc passo 5 mm





Trasformatore di alimentazione =

primario 220-230 volt

1° secondario 230 volt 1 A

2° secondario 30 volt 50 mA

3° secondario 3,15-0-3,15 volt 4 A



T.U. =

Primario 6600 ohm anodo-anodo

secondario 6 ohm

 

[Francois G]

That’s great! Thanks. Now we can build, measure and play too!

 

[rongon]

When you use two EL84 as an LTP phase splitting output stage (with a CCS in the 'tail' cathodes), won't the output power be reduced because the gain is reduced?

The unbalanced signal goes to the grid of V2, while V3 is a sort of grounded-grid amplifier stage, so the output stage sees half the driving voltage it would see if it had balanced inputs. The cathode of V1 drives the cathode of V2 (whose grid is grounded).

No?

 

[waltube]

This is my next tatoo 😉
I don't know if you know the story of "memento mori" but for me it's really very important and a philosophy of life

This involved every one of us!!
And someone plays again with war!!!
There is a beautiful poem by an napoletan Italian actor died many years ago.
"A livella" the title
" The level"

di Antonio de Curtis

Every year on the 2nd of November,
it is usual for the dead care, to go to the Cemetery.
Everyone should do this present;
Everyone should have this thought.
Every year, exactly on this day,
Of this sad and unhappy happening,
I go there too, and with some flowers I garnish
the grave stone of Auntie "Vincenza".
This year an adventure has happened to me ...
After completed the sad homage,
My God! I am still scared (if I think at it)
But then I got braveness.
The fact is the following, listen to me:
We were next to the closing time
When slowly slowly I was going out
Having a look at some graves.
"Here sleeps in peace the nobleman marquis,
lord of Rovigo and Belluno,
brave hero of 1000 enterprises,
dead on 11th of May 1931"
A Logo with a crown at the very top ...
Below a cross made of bulbs;
Three bunch of roses with a mourning list ...
Candles, Big candles and six little candles.
Very Next to the grave of this lord
There was another very little grave,
It was abandoned without any flower;
As a sign only a little cross,
And on the cross it was very difficult to read:
"Esposito Gennaro - Dustman"
I felt pain, looking at him ...
This dead man without any candle.
"That's life" - I thought in my mind. -
"Who has had a lot and who hasn't had anything!"
"Was this poor man aware
that he was beggar at the other world too?"
While I was daydreaming to this situation,
It was nearby midnight,
And I was left closed and prisoner,
Dead and scared in front of the candles.
Suddenly what did I see in the distance?
Two shadows coming to me ...
I thought: "This seems to be very strange ...
Am I awake, sleeping or is it fantasy?"
It was not fantasy ... he was the marquis:
With the walking stick, the monocle and the greatcoat;
Following him, you can see, the ugly badly dressed,
Stinker and with a broom in his hand.
"Yes, he is for sure Mr Gennaro."
"The dead poor man ... the dustman".
"This situation is very unclear: they are dead
and they come back at this time?"
They were about a palm away from me,
When suddenly the marquis stopped,
He turned and slowly slowly quite quite,
Told to Mr Gennaro: "Hey mate ...
I want to know from a so low swine like you
With what such a dare you have allowed
To bury your body, with my shame,
next a such titled like me!"
"Caste is caste and it should be respected!
You lost the sense and moderation;
Ok, your corpse had to be buried but
I think inside the garbage!"
"I cannot suffer
your stinky presence anymore
So it is necessary that you will find another grave
among your dear, among your similar"
" Mister marquis, It's not my fault,
I had never made this wrong to you,
My wife made this foolish think,
What could I do if I was dead?
If I were live I would make you happy,
I'd get my box with my four bones
and now, you know, just in this moment,
I'd go inside another grave."
"So what are you waiting, filthy badly created?
Do you want that my wrath reachs overflow?
If I hadn't been a titled man,
I'd already get angry!"
"OK, I want to see ... let's take this violence...
You know, marquis, I am annoyed to listen to you
And if I lose my patience
I forget that I am dead and I'll beat you!
Who do you think you are? A Lord?
Do you know that in this place we are all the same?
Dead are you and dead I am;
Everyone is equal to the others."
"Bloody pig! How do you allow
to compare yourself with me that
had as my ancestors very revered, very nobles
and perfect to make regal princes envious?"
"But what Christmas, Easter and Epiphany!!!!
Do you want finally understand inside you brain
That you are still sick of fantasy?
Do you know what is dead? It's a spirit level ...
A King, a Magistrate, A great man
that coming through this gate has understood
that he has lost everything, life and the name also:
Hadn't you already considered this?
So, listen to me ... don't be reluctant.
Suffer my presence close to you? Don't you care about it!
This are jokes of alive people: We are more serious...
We belong to the death


It is OT, but fine!
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