2n2222 PUSH PUL AMP

Hi Vaclav,
exactly as the model shows. Both the input secondary and output primary are a single center tapped coil, with no direction change. The polarity of the input primary and output secondary does not matter.

VBR from Ivan OK1SIP

The start points should be in opposite of each other. The transistors are acting in push-pull mode, with the output transformer combining the power from two transistors and delivering to the load or antenna.

That is exactly why a started this discussion .

The base statesmen is  - they conduct in in opposite  half wave  - so how does that work if they are both NPN type ?

I have  build spice model and BOTH input secondary and output primary are wound in SAME direction - otherwise the model did
not produce same frequency full wave , but either double frequency or  pure garbage.

The relations between primary and secondary , in both input and output transformers , as far as winding direction  does not mater.
In other words - the phase change or not , between primary and secondary winding , does not matter.

Harry uses beads and his winding , both primary and secondary , have COMMON core , hence there in no magnetic core direction change between primary and secondary, so if there is a phase change it is because the primary and secondary are wound in OPPOSITE direction . But that phase change does not matter as I explained above.

Now if one uses real toroid and DOES NOT wind primary and secondary on top of each other - then there is different magnetic flow in each , hence phase of 180 change , if wound in same direction.  Which again does not matter.


In other words - the split winding (center tap ) has to be in same direction, at least  that what spice analysis indicate.

That is a mouthful, but it does makes sense.
73  Vaclav

Ivan wrote:Now I have met a Czech guy here, so let me write a personal greeting in our mother tongue.

Absolutely no problems Ivan. The forum and the hobby is all about communication. I have absolutely no problem with you communicating in your own language.
If people want to know what you write then there is always translate.google.com, which seems to have improved a LOT during the past decade.

S pozdravem od Harry - SM0VPO

vaclav_sal@yahoo.com wrote:...
So what is your favorite Swedish beer ? 

I am partial to Fosters'  (little too strong ) - but after learning that Aussies really do not make it national beer...

Hello Vaclav, Interesting question.
As regards beer I rather like Norrlands Guld. It has a nice strong flavour and tastes like beer. I do not like lager beers as they tend to remind me of water.


Fosters is nice, but if I go to the Swedish government-controlled liquour store (Systembolaget) the I usually take Abbot (English) ale.



Having said that I am more a whisky man. I love Speyside whiskys, such as Abberfeldy (12 years, single-malt), or even the Lidl "Ben Bracken". It is a single malt and it is really respectable, IMHO, on-par with many of the more expensive drinks. Unfortunately I cannot get it here in Sweden. I have only one bottle remaining from when I last visited Spain.


Having said that, I do not drink much. Maj-Lis bought me a bottle of Lagavulin for me 50th birthday and I had the last drop for my 60th birthday. If I am to drive a car or work tomorrow then I have a strict no-alcohol rule.

Very best regards from Harry - SM0VPO [hic!!]

vaclav_sal@yahoo.com wrote:Hi all,

I have always preferred using English only on this forum. English is still the main language of internet. But now I have met a Czech guy here, so let me write a personal greeting in our mother tongue.

Nazdar Vašku,
jaká náhoda, taky jsem vyrostl na Žižkově, jen o stanici tramvaje výš, blízko sv. Prokopa. A o trochu později, jsem ročník 59.
Tvoje čeština je výborná na to, že ji asi moc nepoužíváš. Na psaní "bez hacku a carek" jsem zvyklý z dob DOSu.

73 Ivan OK1SIP

Tak nazdar Ivane.
Moje chyba , ja to necet do konce

To nevadi ze nepijes pivo, kazdej ma nejakou vadu. Ja jsem "dicinky  ze Zizkova", bydleiy jsem naproti Penzikanu (?) , pozdeji "URO".
Co je tam ted, to nevim ale je tam fura  anten...
Me cestina dela potize a ceskou klavesnici jsem nekde "zaloziL" asi na pude.
Ja jsem rocnink 43 - valecny dite. A ty jsi okdud? Muj nejlepsi kamos je Ivan, ma chalupu v Bedrichove. Mel by mu napsat...
Tak ahoj
ex OK1 1902 a OK 1 KDG
73 Vasek AA7EJ

vaclav_sal@yahoo.com wrote:No , I do not have any Czech relatives - I is a lone Czech , born in Praha ( Prague) and raised on fine Czech beer. 

When I was younger I always enjoyed hockey - and matches between Czechs and Swedes ( heya heya Swerige ...) or Finland were always fun to listen to . Yes, we "watched " hockey on radio ! Sometime the commentator could not keep not with the game....

So what is your favorite Swedish beer ? 

I am partial to Fosters'  (little too strong ) - but after learning that Aussies really do not make it national beer...

Hi Vaclav,
you probably got confused a bit.
Harry SM0VPO is the owner of this forum and author of all those amazing electronic constructions. He is an Englishman, living and working in Sweden.
Me Ivan OK1SIP is a helping moderator. I live in Prague, therefore my question.
Do not mind it.

I enjoyed ice hockey matches on an AM radio as well. I remember the Czech and Slovak commentators interchanging in the time of Czechoslovakia. But, strangely, I do not drink beer at all.  

VBR from Ivan

Sorry Harry, it helps to read "fine print" - found this.



8-turns primary winding and 1+1 turns secondary. This means 2-turns with a centre-tap. Use a little thicker wire for the lower impedance windings.


I finally found those ferrite beads , had them for many years(1), but do not have a wire skinny enough to fit - perhaps I need to visot  my junk box and find some  relay to cannibalize ....



No , I do not have any Czech relatives - I is a lone Czech , born in Praha ( Prague) and raised on fine Czech beer. 

When I was younger I always enjoyed hockey - and matches between Czechs and Swedes ( heya heya Swerige ...) or Finland were always fun to listen to . Yes, we "watched " hockey on radio ! Sometime the commentator could not keep not with the game....

So what is your favorite Swedish beer ? 

I am partial to Fosters'  (little too strong ) - but after learning that Aussies really do not make it national beer...



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Hi Vaclav,
YES. To make things simple, let me consider a pure B class amplifier. There are two identical secondaries, but only one of them leads current at any moment. The other one is disconnected at one end by the closed transistor. So the turns ratio is 8:4 via one secondary and half of period later it is 8:4 via the other one. (Turns ratio 8:4 means impedance transformation 4:1 as you know.)

BTW, your first name sounds Czech. Did your relatives come from Czechia?

VBR from Ivan OK1SIP

I do not  know where is the problem, but I am having one heck of time finding
and replying to this forum.

I have  managed  to build the model of the 2N2222 amp - using LTSpice.
That did answer the question which way to wind the coils / transformers.

Now for a tough one.
The transformers are primarily used to match source impedance to load impedance.
For example  - source is x , load is y

So the primary has 8 turns and secondary has 4  - again as an example.
The question is
primary has x turns which matches the source impedance , but there are TWO secondary loads / winding
so does  it means 

8  turns of  primary and TWO winding secondary  = center taped in our case

hence 8 primary and 8 center taped secondary ?  (  8 + 4 +4 ) ?

The # of turns is not the question - the question is
is is correct to say

the  ratio is  8 to 4  - to TR1  and 8 to 4  to TR2 - primary winding is "shared" and there are two independent secondary windings.

vaclav_sal@yahoo.com wrote:Harry,
could  you tell the directions of both T1 and T2 windings?
Adding start "dots" would be nice.

Or does it matter ?




I am also trying  to understand how the amp actually works with  ONLY NPN transistors, not with pair of NPN and PNP.

73 Vaclav AA7EJ  Texas

Hello Vaclav. I think I can understand your concern.

Very simply, TR1 and TR2 are operating at (almost) cut-off so that each transistor will only amplify the +ve 1/2 cycle of any input waveform.

T1 is a high-low impedance converter and the secondary is centre-tapped. This means that the centre is grounded and the other two ends have output in anti-phase. This means that all +ve input 1/2 cycles are fed into TR1 and all negative input 1/2 cycles are inverted to +ve and amplified by TR2. (To complicate things a bit, all transformers have an output waveform at 90º to the input waveform, but don't worry about that ).


T2 transformer works in exactly the same way, combining the 1/2-cycles from TR1 and TR2 to re-assemble the original (but amplified) signal using another centre-tapped transformer.

T1 turns-ratio is usually something like 4 : 1 + 1 and T2 turns ratio is usually something like 3 + 3 : 1 to feed the speaker. The output transformer turns ratio can vary HUGELY, depending on the amplifier power level, the supply voltage and the speaker impedance.

The winding directions of T1 and T2 is of no importance. It will only change whether TR1 or TR2 amplifies the positive 1/2-cycles. But since they are re-combined in T2 it will not have any practical effect. The winding directions (indicated by dots) are only relevant in applications where the phase of different windings is important, such as radio frequency phasing transformers, baluns and POTS telephone hybrids, etc.

Have I answered your question? Is anything unclear?

Very best regards from Harry - SM0VPO

The start points should be in opposite of each other. The transistors are acting in push-pull mode, with the output transformer combining the power from two transistors and delivering to the load or antenna.

Harry,
could  you tell the directions of both T1 and T2 windings?
Adding start "dots" would be nice.

Or does it matter ?




I am also trying  to understand how the amp actually works with  ONLY NPN transistors, not with pair of NPN and PNP.

73 Vaclav AA7EJ  Texas