How to create or fine tune an air gap output transformer?

 At your risk. Take all safety precautions. Potentially lethal voltage present.

See previous post on Pleiades 2N3055 single ended class A power amplifier.

How would a bifilar wound 1 to1 air gaped output transformer sound with a single 2N3055?

 At your risk.

Or even a Darlington transistor with an inverse ratio output transformer, for example 1ohm to 8 ohms in order to get very high power even with 12V power supply?

Pleiades 2N3055 single ended power amplifier revisited

 At your risk.

This is on one transistor only single ended audio power amplifiers with no negative feedback.

Using Italian Transeria Ligure E,I laminations a new lower ratio output transformer was made that the used for the Pleiades 2N3053 operated at 24V, 10mA.

This transformer was made by winding 64 turns of 0.55mm wire, then 270 turns of 0.25mm wire, then 64 turns of 0.55mm, then again 270 turns of 0.25mm,  then 60 turns of 0.55mm.

Inductance ratio with no air gap is 340mH to 47mH.

This sounded very nice with Pleiades BD139 at Vb=6V, Ic=25mA.

Signal path: Flashdance soundtrack on CD - Sony CD Walkman line out - Pleiades power amplifier - Marantz Imperial speakers

Then air gap was introduced by attaching a layer of 3M scotch invisible tape across the open end of stacked Es. Inductance ratio became 227mH to 33mH.

Sound is still very nice with amazing bass, mid, treble.

.

Then Vb was changed to 12V and Ic to 60mA for louder sound but 2N3055 sounded better at 12V and Ic=80mA.

Then transformer was opened up again and airgap was increased by putting all Is in a small transparent plastic bag and placing them by hand on top of the Es while music is playing.

Now inductance ratio is 173mH to 26mH.

Sound is very nice and loud .

 

A quote of Elia Kazan for talent or genius

 

Yesterday at 3rd (classical) Hellenic radio were noticed 2 quotes of film director Elia Kazan from his autobiography book. Here they are roughly translated back to english.

Talent: maniac of working

Ταλέντα, μανιακοί της εργασίας

Genius: shines happiness (they do what they like)

Ιδιοφυίες, ακτινοβολούν ευτυχία (κάνουν αυτό που τους αρέσει)

It's a concert in Vienna and is this microphone an AKG C12?

Juan Diego Florez

 

Creating a boundary microphone out of a mobile phone

At your risk.

First time I saw it was when Zhanna placed the mobile phone on top of the right side of the piano keyboard.

Apparently by placing the mobile phone this way, the mic capsule comes so close to the boundary (the wood of the piano) that it picks up mainly the main reflection of sound from wood (boundary mic principle), plus the vibration of wood itself.

Here are 2 recording of the same piano same day, different solo pianist (the person at the right side), different mobile phones, but one phone is held by hand, the other recording is by placing the phone (Galaxy A13) as described above.

 

Some more information on boundary microphones:

The Wikipedia article:

https://en.wikipedia.org/wiki/Boundary_microphone