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November 26, 2020, 07:29:34 PM

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Author Topic: learning about "Totem pole and topologies using output transformers"  (Read 3532 times)

juanMotta

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Hi to all, i think this is my first topic here, i started learning electronics and it has taken me many years to understand the basics ( yeah .. I'm slow :-[), now i´m reading the Teemu Kyttälä book and have found  the "Totem pole and topologies using output transformers" section in this book, to my it´s  very interesting because i´m planning to build a hybrid amp, pre amp of a Marshall jmp (the pre amp is done) and transistor power amplifier.  I would like to have a tube sound, that´s why i´m very interested in this type of power amps in my build, but I wonder if there is material to read or circuits to experiment that someone can help me for a beginner. :dbtu:

thanks for your time, and many greetings to Juan Manuel Fahey,i know he is follower of this forum.

Juan Motta


Roly

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Hi juanMotta, welcome.


Quote from: juanMotta
i´m planning to build a hybrid amp

Why?

Quote from: juanMotta
I would like to have a tube sound

...and the most reliable way to get tube/valve sound from an output stage is to use tubes/valves and a mid-fi output transformer ('tho even that is no guarantee).

Generally speaking transformer-coupled s.s. output stages are a thing of the past and you may have an interesting time finding a suitable transformer, particularly if higher power.  Hunt this vital component down first, before you move too far in this direction.  If you can't find one you may have to reconsider.

If you say theory and practice don't agree you haven't applied enough theory.

J M Fahey

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Hola Amigo  :cheesy:

The old totem pole configuration *did* get closer to some aspects of Tube sound, mainly because of its inherent high impedance output, because although it's hard to visualize, speaker load is in series with collectors (because base drive is "floating", since it comes from a floating winding, is not referenced to ground) and power transistors show voltage gain, while most "regular" transistor amps drive speakers from unity gain emitters, which by definition are very low impedance sources.

But modern (transformerless) SS guitar amps can simulate that high output impedance very well by using "mixed feedback" which is the unwritten standard in guitar amps today, and not asking for hard to get driver transformers.

Search the Forum, there's a lot written on mixed feedback amps.
Good luck.

And post a step by step account of what you experiment and build :)

juanMotta

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Thanks for your answer!!!

My  interest is in building an amplifier is because i want an a "hobby" project an love guitar amps!!! I need a an amp that sounds more in the "tube path" and  working because I am a beginner. I was searching in the forum an i found this topic from Teemu "60W Power amplifier" but the circuit is lost... other topic or circuit to recommend?
Yes, i´m going to post the result Juan Manuel.

Thanks!!!

Gracias!!!

phatt

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Thanks for your answer!!!

My  interest is in building an amplifier is because i want an a "hobby" project an love guitar amps!!! I need a an amp that sounds more in the "tube path" and  working because I am a beginner. I was searching in the forum an i found this topic from Teemu "60W Power amplifier" but the circuit is lost... other topic or circuit to recommend?
Yes, i´m going to post the result Juan Manuel.

Thanks!!!

Gracias!!!

There was a similar discussion recently which might be of interest; http://www.ssguitar.com/index.php?topic=3751.0

BTW, Tiss very unlikely you will find one silver bullet circuit that will magically make the tube sound as it's a combination of many factors from guitar pickups to speaker choice and many things in between.
Phil.

juanMotta

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Thanks again for your replay!!! I will continue my learning, but for the moment i´m going to work with the pre amp section, I'll be updating.

Juan Motta