Updates to the Pleiades DL94 single electron tube battery powered audio power amplifier operating in class A1

 

At your risk. Lethal voltage present.

Five rectangular holes have been created by a jewelers saw for housing five 2 x 9V batteries for a Vb of 90 volts. 

All 5 Bulgin battery holders will be at the back of the diecast aluminum box. Then the output transformers then each DL94 for each channel and then the step up input transformer for each electron tube.

In the front will be a Bulgin holder for 2 AA batteries for the direct heated cathode voltahe Va, and a battery holder of AA size for the -6V Vc bias.

This amplifier is using no resistors or capacitors, like the original Harold Arnold 20's patent of the use of thermionic currents...

Please visit older posts for more details.

 

Other single transistor amplifier circuits

 

At your risk. Please take all safety precautions. A suitable fuse always in series with a battery to prevent burn injury or fire hazard. in this case a suitable fuse (200mA?) will prevent your speaker from blowing in case of thermal runaway etc. 

These amplifiers are similar to the Pleiades 2N3055. Now usually an air gaped output transformer is used but the second schematic is what was simplified from the book Amplifiers by Jones. There is also a very interesting book Transistor Amplifiers for the home constructor by SIr Clive Sinclair who is also behind the famous ZX Spectrum home computer.  

One of  first listening experience with such an amplifier was with just a 2N3055 fed by the song Is it a Crime - SADE from CD, the amp feeding a SONY APM speaker with just a low cut capacitor from the paper cone tweeter. Jaw drop mode. When Vicky first heard this amplifier on Constant Craving - K.D. Lang she could not believe this fabulous sound was coming from this small mess of wires on the floor and one transistor cooled by a French wrench. She still calls this amp the French wrench amplifier.

With just one amplifying stage here is only one set of distortion products and you may be in the league of the Neumann U47 with its amplifier of one VF14 electron tube. 

Marios from the photocopy shop told me that this great sounding PC USB powered Fujitsu Siemens speakers from the 90's may have just one transistor inside for each speaker.

By doing a search on google for "90's usb powered pc speakers one transistor amplifier schematic"...

https://forum.allaboutcircuits.com/threads/simple-pc-audio-amplifier-circuit.109732/

Life is good!

Why does pitch change with change of intensity?

 At your risk.

For example playing a 440Hz louder gives the perception of a lower pitch.

Why?

Not clear to me.

A piano can convert frequency to distance. For example by pressing the right pedal we leave all strings undamped. Then then if we whistle for example, the higher the frequency the more to the right strings are vibrated by resonance.

The basilar membrane converts frequency to length. 

Is it a nature's way of protecting the ear? Pitch change by stimulus intensity preventing the same hair cells being fired  along the length of the basilar membrane?

Is the change of position at the basilar membrane due to some non linearity in amplitude response. creating a DC offset?

Similar to demodulation of AM signals by the rectification effect of a diode?

(Side chain signal of a compressor created by diode rectification? Does the movement of the 3 tiny bones in the middle ear play a nonlinearity part too?)

Similar to DC bias change of single ended amplifiers with cathode current bias, RC (cathode resistor).

Similar to expansion in solids by temperature increase, there is nonlinearity in the vibration of molecules, the displacement to the right is higher that the displacement to the left.

Handbook for Acoustic Ecology

 At your risk.

https://www.sfu.ca/sonic-studio-webdav/cmns/Handbook/

Pitch

 At your risk.

https://www.sfu.ca/sonic-studio-webdav/cmns/Handbook/Pitch.html

Pitch Change of tone of 440Hz by changing the intensity

 At your risk. Please keep volume down to protect your ears especially if using headphones.

By comparing soft volume to higher volume, the higher volume sounds to me lower in pitch.

As loudness tends to zero pitch becomes maximum.

How about you?

The fact that i hear a lower pitch makes me sing along a note of lower pitch. 

This (even if it is a small difference) is important because it makes a singing note sound really bad and out of context with the music or backing track. For example annoying beats could be created.

Listening carefully to good singers, the very good world class ones, it can be heard that they too begin almost any note flat (below correct pitch) but then raise the pitch while the note sustains until it sounds correct. I tried this trick and my singing is so much better and enjoyable. I try to correct almost every note.

Psychoacoustics - Pitch Perception

 At your risk.