A simple MOSFET power amplifier with just a 12V battery, a potentiometer and resistor for bias, an input coupling capacitor and no output transformer

 

At your risk. It may blow your spekaer if  a protective fuse is not connected in series etc.

Please see previous post on Pleiades K951 amplfier with speaker connected directly to the drain of the MOSFET.

Update on Pleiades K951single MOSFET zero feedback single ended power amplifier

 

At your risk.

Today the bifilar 1:1 output transformer was disconnected from drain and connected to the source. This was done fairly quickly as all connections are done with Wago snap terminal connectors.

Source follwer configuration worked with change with readjustment of bias from the 50K potentiometer in series with 47K  but sensitivity was low as there is no voltage gain.

Signal path:

CD - SONY CD Walkman - Pleiades K951 as source follwer - Marantz Imperial 5C

So power suppling the speaker was low.

The amplifier was remodified to drain follower.

Then the output transformer was removed and the AKAI SR H-44 speaker connected directly to drain instead of a load resistor. This should not blow the speaker if drain currect (which now passes through the voice coil) is kept by suitable bias to up to say 300mA. It worked and sounded nice, but less loud than when using the output transformer due to loss of efficiency.

Betasilk or Betaplast etc

 

At your risk. This is not a medical or dermatologist advice. Betadine cream is not suitable for persons with thyroid problem.

Combining 2 products together to create a new product. 

Hansaplast with Betadine cream.

Hansaplast moistened with Betadine cream applied on skin spots may vanish the spot if applied overnight(s) or during the day. 

Betadine cream softens the spot until it breaks, it disinfects and the Hansaplast tisue absorbs.

Thsi idea comes from adapting my dermatolosgist Yiannis Peros' advice when I had a serious skin infection.

 

Merino Wool t-shirts

At your risk.

One of the best thing bought this year. Black long sleeved.

They are 3 times more expensive than cotton but they last at least 3 times more.

Minerva brand.

They keep you warm in the winter, dry on both seasons.

When the is heavy air conditioning in the summer, you are saved as you are dry before entering the air conditioned environment and you don't feel cold.

Dryness in the key.

And they feel compatible with one's skin.

Πολυκυκλωματιστής 501-Β, electronic construction game Polykyklomatic 501-B

At your risk.

Educational Electronics Laboratory.

It is made in a box similar to Monopoly.

70's, 80's game. 

Springs are used to secure contact to electronic components.

The amplifier does not have an output transformer.

The germanium transistor is directly coupled to the loudspeaker.

Everything operated on a 9V battery.

C1 100nF

C2 2nF

C3 220uF 10V

C4 1.8nF?

C5 40uF 16V

speaker Sanyo PAN  Q GH 8ohm 0.3W

potentiometer: 8.8KOhm

lamp: 14ohm when cold

3 Germanium Transistors, using the diode setting of a digital multimeter they measure:

T1, 9H: BE 0.13V, BC 0.123V

T2, 9o: BE 0.4V, BC 0.142V

T3 7c: BE 0.125V, BC 0.111V

By examining the schematics and internal connections below the springs, the amplifier output stage seems to be an emitter follower capacitor coupled (C3) to the speaker

I fondly remember this game. It gave the opportunity to make my first amplifier. I did not know whether it worked. I did not know how to test it. All I could hear was a click in the small speaker and I thought I had done something wrong.

It all came to life when the radio AM tuner from the bigger game 1002 (102 constructions) was connected and radio could be heard around the room with good quality.

 

Pleiades K951 single N channel MOSFET zero feedback audio power amplifier in class A1

At your risk. Take all safety precautions. A suitable fuse must be in serries with any battery for injury or fire hazard protection.

Today the 2SK951 MOSFET was placed on the big heatsink.

Vb=12V. Output transformer bifilar 1:1 with air gap.

Signal path:

music on CD - SONY D-EJ758CK CD Walkman line out - Pleiades K951 - Marantz Imperial 5-G

It sounded not loud, and when the 1K pot was near maximum the sound started to fade out.

Fortunately before abandoning, on a quick decisive move the Wago connector was opened and the signal was sent bypassing the volume pot directly to the gate terminal through the 560K Philips orange coupling capacitor.

Sound became big and loud indicating a broken potentiometer.

The amplifier sounds very nice with deep bass and extended treble, smooth midrange. Some overload at peaks as the full signal is feeding the gate without attenuation.

Id is 500mA at Vd 12V. So power dissipation 6W. Possible power output 3 Watts?

It seems a suitable MOSFET can do the trick without the need of a step up input transformer.

But the electron tube Pleiades DL94 seems to sound better.

Thanks to Vasilis encouragement the Pleiades single transistor amplifier experiments were not abandoned

At your risk.

After so many failed experiments today the power is ten times what it was last year. About 3 Watts? 

So according to S.S. Stevens law loudness is double.