Pleiades long tailed pair tube only microphone pre preamplifier with No resistors or capacitors

This started at about 1999.


The microphone drives the primary of the input transformer. The secondary is connected to the grids of a balanced configuration of UCC85.


The anodes are connected to the primary of the output transformer. The secondary is the balanced output of the very quiet pre preamplifier.


The cathodes are connected together with one side of a 270 ohms resistor , the other side to ground.


This was a stereo 2 channel amp so two UCC85 were used. Heaters in series were driven by 4x12V lead acid batteries in a separate sealed cast aluminum box.


So 48V were also connected to the center tap of the output transformers.


48V is also convenient since if connected to the center tap of the primary of the input transformer, phantom power is ready.


The amplifier was built in a cast aluminum box from Canford. Tubes on top as well as as the 4 Sowter transformers. 1:7 was used for input and 1:1 for output either 10K:10K or 600 to 600.


The amp was used with AKG 12A Nuvistor microphones as Blumlein Pair.


The mics were near the drums. The mics were on cardiod looking at the organ past one step so that some direct sound could be picked up from the drums. All instruments including drums, self amplified guitar, bass guitar and PCL86 amplified organ with Pleiades Leslie hung from the ceiling so that the open back speaker could freely revolve sounded very nice. Out out of the amp was connected directly to the input of Philips CDR870. Some more gain could have been useful as the amp could not fully modulate the recorder. This was useful as there was no clipping involved in the jam no matter what, or was this the compression effect of tubes with grid bias self adjusted when peaks were trying to charge grids negatively  due to diode rectification effect?


The interesting thing about this amp that there is no return circuit for grids.. By listening and watching now at VU meters it seems the amplifier was self compressing at loud signals since the grids were free to keep the potential convenient for them.


There was also an 1K resistor in series with battery plate supply inside the amp,


Now the amp has been changed to 2 ECC82 parallel heaters and O ohms cathode resistor, and 12V battery supply. Interesting is that the intensity of light in the room adjusts gain of the amp possibly due to photoelectric effect of grids?


The amp may be reconverted  to UCC85.

Learn how to compose music in a few minutes

Step 1
Choose a scale:
We will choose the simplest one but the same will apply with any scale.
Let's choose A minor scale.
That's is A B C D E F G A.

Step 2
Using the simple 1 3 5 rule, this defines 7 chords that can be used.


ACE
BDF
CEG
DFA
EGB
FAC
GBD


Note some are minor and some major. This is selected automatically by nature so you do not have to remember anything.

Step 3
Start playing

Apart from rhythm music consists of Bass, Harmony, Melody.


We can begin by Bass A and harmony ACE, then bass C, right hand CEG.


Note ACE, CEG can be anywhere in the keyboard. So inversions apply.


Melody can be any note of the scale in any imaginative way.


A key element of music is repetition.


Experiment having your ear brain as judge.


Avoid consecutive 5ths which sound bad.


For example ACE to GBD sounds much better, as ACE to GBE to FACE.


This introduces us to new chords having other code than 135.


For example GBE is written as G6.


With a 6th a third is taken so G6 is played GBE.


With a 7th or a 9th the 3rd and 5th is taken too and the 7ths and 9ths sound better when they are prepared or

How to wind a toroidal core by hand

The trick is to use a thin and long peace of wood with some material removed with a knife or thin file on top a bottom.


The long wire is wound on this peace of wood several turns.


Every turn on the toroid is made by passing this peace of wood through the toroid to make great Pleiades microphone filters or input or mixing transformers.

Amorphous Transformer Cores for microphones and MC cartridges

Amorphous is similar word to nano crystalline or met glass, metal glass signal transformer core.


Pleiades microphone transformers use nanoperm tape would toroidal cores made by Magnetec which have an extreme magnetic permeability. This reduces number of turns for given inductance, increasing bandwidth and decreasing noise as wire resistance is very low.

Ribbon microphone random corrugated.

A ribbon microphone can be corrugated in an asymmetrical random sort of way to avoid standing modes of vibration.


This is done by folding many times by hand the sandwich paper that protects the ribbon before or after cutting the ribbon strip.

Microphones in series or parallel

Connected an MD421HL in series with 515SB. The resultant 400ohms was connected to Pleiades V5. Great sound, MD on vocals, 515 on acoustic guitar. Proximity effect is further compensated as effective mic Zout is increased. In fact many mics could be connected in series, in a Christmass tree lamp way and the proximity effect be automatically compensated. A live band could be recorded this way indoors or outdoors with a great sound with no reflection components as the mics would be really close to the instruments and a great signal to noise ratio for the same reason.


Connected MD421 in parallel with Shure 515SB. Great sound, more bass, less treble. This can be explained by the lower total Zout, this time 100Ohms. Cutoff proximity compensating frequency due to Zout and the 47uH input inductance of V5 is now halved, ie one octave lower.

Adding (Mixing) many Microphone signals

Can many microphone signals be added together by series parallel connection of the microphones themselves to keep resultant mic impedance at 200 Ohms.


It would nice doing away completely with mixing console or even hybrid adding transformers.


It would be nice recording a live band this way.

Electro-Voice Microphones

it can be found on the web that Dolly Parton and Elvis were using the Electro Voice RE15 moving coil microphone in the studio.


There is also an excellent demo on harmonica using the RE15 on YouTube. Amazing sound, fabulous midrange.

Pleiades V5 prototype finished? with circuit discription

2 stage EF183 electron tube microphone battery field pre preamplifier with proximity compensating input transformer




It took 40 years and a few days.


Balanced input
Microphone proximity compensated input
Unbalanced low Z output or balanced with an output transformer
Uses 2 3.7V Li Ion batteries


Circuit description:


Energy feed first:
 The 2 Li Ion batteries and the fuse are in series and the 7.4V are connected to the series heaters. Each EF183 tube feeds from 3.7V instead of 6.3V. This keeps electron emission congestion low so that the tiniest signal from the microphone can be amplified with least noise.


Advantages, portability, no transformers, no diodes, no chokes, no electrolytic capacitors, and above all no countless sources of hum when we want to extract the subtlest nuances of voice.


The negative battery supply is connected to the XLR shield connector and everything negative is star connected there including of course pin 1 (see excellent Jensen transformer papers).


When microphone is connected electrons move back and forth in a balanced way in twisted cables 2 and 3, feeding through the XLR the primary (orange winding) of the microphone input transformer. Common mode signals ie not moving back and forth but in the same direction such as RF and line hum travel along the orange wires and collide with themselves so there are extinguished.


The input transformer is completely symmetric electrical and physically allowing a fully balanced operation with no shield needed. The toroidal core is a Magnetec nanoperm noncrystalline core of extremely high magnetic permeability.


As each electron moves back and forth at the microphone music signal it repels the next electron on the orange twisted cable and so forth so all electrons get to dance!.


Inside the orange transformer coil currents move clockwise anticlockwise dancing to the music.


The core is Magnetec 060, Primary winding is 35 turns and secondary 350 turns.


Jealous electrons see all this spinning in the primary winding and they cant help but spin too inside the noncrystalline tape wound core. Jealous electrons at the secondary winding dance too spinning in a waltz sort of way but since there are 350 turns the corresponding voltage is 10 times.


One side of the secondary is connected to star ground the other to the coupling capacitor to eliminate direct currents to and from tube grid on the other side. It is the dance back and forth component that matters.


When we connect the batteries we have a closed circuit of electrons  moving fast through the heaters. Fast electrons collide with atoms and heater atoms move back and forth at greater speeds ie the temperature is greater. Collisions with surrounding cathode inside the evacuated EF183 tube make electrons move faster. Some of them as temperature ie speed is increasing can escape into empty space nearby inside glass.Because of them surrounding space near grid becomes negative repelling further electrons or cathode is positive wrt grid due to lack of them. This is one reason why we do not heat up with 6.3V as there is no point in having billions of electrons move in all sorts of directions when the tiny music signal arriving at the grid has relatively few romantically dancing electrons.


A 4.7Megohm resistor is connected to grid and its other side to positive anode. Its purpose is neutralising the negative potential that as explained exists at the grid so that we can have anode current influenced by the dancing electrons at the grid ie amplification.


To be continued. 

A great way to mic up drums...

Is with 2 mics, one above drum set, the other as close or inside the bass drum.


Electro voice RE microphones do the trick.


See an amazing clip on YouTube with sm57 and RE11. How did he mic up the drums?


Also one showing Bob Clearmiuntain.


Photos of Beatles showing a ribbon mic, Coles 4038. Also on various books how the technicians at Abbey Road managed to persuade management to allow the, to close mic the bass drum.


Saw a veteran drummer once micing g a whole drum set live with just one Electro Voice mic.


Amazing.

Shure Unidyne iii

Barack Obama and all US Presidents since 1965 use the Shure Unidyne iii or SM57 microphone  for speech.


It is also used by Brian Wilson on Pet Sounds as well as Sinatra, Bono U2 (SM58), David Bowie for recording vocals in the studio.

Pleiades V5 prototype under construction

Prototype under construction Pleiades V5 microphone pre pre amplifier with 2 EF183 electron types positive biased for freeing electrons at 7.5V 

Schematic of Pleiades V5, 2 stage EF183 electron tube with positive bias, microphone pre preamplifier with proximity compensating transformer and instantaneous clipping rounding waveform capacitor