Rememering all the good things only creates much hapiness

Pleiades Crossover finetuning with a variable inductor

At your risl. As on previous posts, an inductor in parallel with a capacitor is in series between amplifier and woofer-fullrange drive unit which is hung on air without baffle. The inductaor takes away the mid heaviness leaving the bass and the capacitor supplies the high frequency music content. Music source is Careless Whisper - Wham from Wham's last CD. The Sony Walkman has two outputs one for headphones where Sennheiser HD580 are connected for reference and direct comparison. Second output is line output where Pleiades 2N3053 single transistor class A power amplifier with output transformer and no negative feedback is connected feeding the Pleiades crossover. The air core inductor is 1.07mH. Capacistor from yesterday's listening tests directly comparing with HD580 changed to 1 microfarad. and results were impressive, sound closer to HD580 than other cabinet speakers in Pleiades lab as they sounded more bass and treble heavy than HD580. That there was still a bit mid heaviness. Remembering Mr. Yiannis from Elina, his crossover with iron screw inside by accident, it was decided to gradualy insert a screwdriver inside the air core inductor in order to make it a variable inductor , increasing inductance to cut more mids, while listening in real time! It worked remarkable well. George Michael's voice sounds as natural, very close to HD580. Inductance measured by the bridge is 1.7 Henries. Actually it just happened that the air core hole is facing the ceiling and the screw driver is inserted until the floor were the air core stands, so the screwdriver stands supported by the air core.

The magical power of the Universe

Quoted by Natalie.

TubeTrap patents by Arthur M. Noxon

At your risk. Please take all safety precautions as on all euroelectron posts. There are many patents, i think this is the one I had read, US4,548,292. Limp mass membrane absorber is also used, see also: https://www.acousticsciences.com/artblog/limp-mass-membrane-bass-traps/ i may be wrong but i get the impression that what Sean Davies had told me on using betumin roofing felt or linoleum panels are mentioned on Gilford's BBC Acoustics book may be different. Linoleum or roofing felt dissipates low frequency energy by bending itself thereby converting vibration to heat by the hysteriis loop of the material. But porous absorbers are added to these for extra damping. Art Norton discusses on his blog (above link) that the resistive (disipative) part is the porous material. But if i am not wrong the vinyl sheet on the TubeTrap may be doing heat dissipation by deflection too. How would TubeTraps absorb using linoleum, perforated linoleum? Or perhaps could Pleiades absorbers be made by twisting linoleum so that it becomes a cylinder and then let it stand on floor or hung from ceiling, linoleum wouild absorb bass by deflection, and would provide dispersion by sound waves of other frequency hit its cylindrical surface. Would porous absorber be needed inside? Hiting this material gives a well damped sound.

Reading agian after many years that Michael Jackson was recording vocals surrounded by Acoustic Sciences Corporation TubeTraps...

placed by Bruce Swedien, invented by Art Noton. This is a page of articles by Art Noton: https://www.tubetrap.com/tubetrap-art-noxon.htm i remember the patent document had also been found on espacenet.

Shure SM58 connected to Pleiades (175mH:175mH) or EMI RS106A part 2

At your risk. The Pleiades high pass filter, transformer in this case, has a slope of 6db per octave as it is 1st order (only inductance). The EMI RS106A should have a slope of 12dB per octave as it is 2nd order, C in series, L shunt, C in series, ie a T network. This explains why it sounds less dense at 150Hz cutoff setting. It sounded also very nice at 300Hz setting when mic was at 12in or 9in distance from nose. There is some buzz maybe because the filter in unbalanced or because the ground terminals at the back barrier strip are not properly set. There is no buzz or hum on the Pleiades filter as it is balanced, in fact a bifilar input transformer. A low inducatnce Pleiades filter, just an inductor of say 150mH may be tried for a less dense vocal. It may also be a good idea to create a Pleiades filter of 2nd order T network or O network for balanced. Equations for constant k filters (constant image impedance) may be used, is this what the EMI engineers or Rupert Neve did for his eqs? If memory is corrent there are also some filters called m derived. Details for all those could be found in the book Cinema Engineering, or the book Elements of sound Recording - Frayne, Wolfe. There is also a nomograph by Seito Yamasita in Radio and Television News - Aug - 1952. The equations given if R is the image impedance and fo the cutoff frequency: L=R/4PIfo (we take R, devide by 4, devide by 3.14, devide by fo), C=1/4PIfoR. where PI approximation is 3.14, Pythagoras constant. Then the T network is C/2 in series, L shunt, C/2 in series or i guess the H balanced version should have C, C on the left side, C,C on the right side. The PI version given on the article has L/2 on the left side shunt, C in series, L/2 shunt on the right side, the O balanced version i guess should be similar for inductors but 2C on top and 2C on the bottom. According to the book:Elements of Sound Recording - Frayne, Wolfe the T network should be 2C capacitor on left side, inductor L to ground, capacitor 2C on the right side. Network Pi should be on left side inductor L/2 to ground, Capacitor C on top sending music signal to the right inductor L/2 whose bottom side is connected to ground.

Shure SM58 connected to Pleiades (175mH:175mH) or EMIRS106A for hi pass filtering

Male voice singing softly No Surprises - Radiohead 24in from SM58, mic 30 degrees towards nose above head. After filtering connecting to the mic input of Sony TC-D5M. At the 150Hz setting EMI 106A sounded fantastic, less fat than with the Pleiades 175mH:175mH which may be better together with other instruments in a mix? But then listening again to Radiohead there seemed to be some more bass in the voice. Monitoring was with Pleiades 2N3053 class A amplifier connected to Celestion Ditton 150.

The Pleiades Crossover, Inductor value bridge measurment

At your risk. The Pleiades crossover is an inductor in parallel with a capacitor between amplifier and single speaker drive unit. Its purpose is to equalize the single drive unit (a woofer or a woofer fulltange) in order that it sounds correct without the addition of any other drive unit, without a cabinet, without even a baffle, just the drive unit hung on air. See previous posts. The first experiment had an inductor of 0.9mH, Q=0.8 and a 2.2uF capacitor. Since Big in Japan - Alphaville was unsed for the listening tests with the Pleiades 2N3053 single transistor class A power amplifier and there was still some midrange empphasis on the singer voice even after adding the capacitor, L was increased to 2mH with better results resembling listening to the sennheiser Hd580 headphones with a bit less bass of course since there is no baffle or cabinet. Other nice combination is 3mH and 1mF which sounded nice on Careless Whisper - George Michael. other nice combination used today is 1.07mH (Q=3) air inductor (previous experiment was with iron core transformer like inductor) and 1uF MKT Philips orange capacitor as on previous experiments. Obviously measurments should be made on anechoic or open air enivirinment.

DL93 must be replaced by DL94 on previous post

At your risk. It is a typo but the same schematic can be used for all sort of different electron tubes. EL94 is also a possibility as the input transformer can bring the volatge up to the same level (say 4V) as needed by DL type electron tubes. In fact the schematic is very similar to the Pleiades V6 battery powered electron tube low noise mic booster. The only difference is that the power amplifier does not need the high Megohm contact potential compensating resistor from anode to control grid (Pleiades bias) that makes the mic booster amplifier operate at say 4V at the anode only. When the context is electron tubes by contact potential we mean the potential created by the electron cloud boiling electrons that makes it difficult for new electrons to escape cathode (when the anode potential is low). When the anode potential is high there is electric field penetration which reduces the negative potential at grid from the electron cloud. But a power amplifier as opposed to a very low noise pre preamplifier, needs higher powe,r hence the high anode voltage together with negative bias in order to keep the anode current reasonably low in order not to destoy the electron type. (The inventor of what is called here Pleiades bias seems to be the inventor of battery powered electron tube guitar pedals, see older posts). Anyway everything in euroelectron is open source, free to use provided other party rights are not infringed.

eureka!, How to Make a (Speaker) drive unit Sound Good Without a Baffle or Enclosure

At your risk. Please take all safety precautions including protecting your precious ears. If a woofer with lightweight paper cone is held by hand and fed by a good quality very low power (protecting our ears) class A amplifier with no negative feedback through an inductor (inductor in series), the sound is surprisingly nice. There is somehow deep bass and the midrange nastyness is missing as the inductor lets the bass in and cuts everything else at a gentle slope of 6dB per octave. But treble is missing. But is the same speaker is disconeected from woofer out of the crossover network just used and connected to tweeter out the treble is very nice without the razor cutting edge of using a tweeter on its own. If said speaker is connected directly to said amplifier only mid nastiness is heard which covers in our perception both bass and treble. So said speaker is connected back to woofer out ie inductor in series. And then.... a capacitor of say 2.2 uF feeds it simultaneously from the amplifier! So we get trable too, the bass we had before and the mid nastiness missing. In fact the balace by chance was almost right the reduced mid blended well with bass and treble. And according to the experiment by Olson of RCA perhaps as many octaves were missing from bass and treble part of the human hearing spectrum creating a balanced sound. Since we have a single speker point source there were no phase errors and since no box there is no colorations. And according to speaking with Costas at Praxis studio hearing mid detail is important in creating or checking a mix, hence the Auratone speaker. But perhaps this is simpler and sounds better. The inductor has not been measured yet. The speaker used is printed at the magnet back: 00 80400/W4, 2422 257 28204, made in Belgium, DD 00 543 5. Signal path Italian 60's songs compack disc club compilation or Careless Wisper - George Michael on CD - Pleiades 2N3053 single transistor power amplifier in class A - said speaker. So the nice little trick is feeding the no baffle air hung drive unit with a parallel combination of inductor and capacitor in order to create a gentle slope low frequency (bass) high frequency (treble) pass filter or a gentle slope mid frequency regect filter. Obviously it cannot be used at high intensity (power) as the cone ir unloaded but it sounds loud if used at smaller distance and the most important is protecting our ears from high intensity.

Stars - Dubstar

It was played at AB supermarket. They were very kind at headquarters to inform the title and artist of this nice song.

Using a MOSFET on these single transistor Pleiades powwer amplifiers?

At your risk. Please take all safety precautions. It looks tricky as by looking at some datasheets the on channel resistance is a fraction for an ohm. Typical current is a few amps. So it seems a step up output transformer is needed with a step up input transformer. Another option since depletion FETS do not need a say +4V at gate to turn on, is to use JFETS such as 2N3819. Many in parallel.

Increasing the power of the single transistor Pleiades BD139 amplifier at 12V only

At your risk. Please take all safety precautions. A multy turn ratio output transformer (it must be air gaped but so far tests have been donbe without introducinbg air gap) was created with secondary 9speaker side) inductance of about 40mH. Various collector volatges were tried including 12v, 24V, 36V, 48V. 24V sounded very nice, see also the Pleiades 2N3053 amplifier. The BD139 due to higher hFE is more sensitive needing less bias current and less music input voltage. Using the 5:1 ratio at Vb=12V requires about 27mA collector current for great class A operation (electrons flowing all time) sound. Rb=71Kohms. It sounds loud and clear. The schematic is just a single transistor with air gaped output transformer in the collector circuit, and just a bias resistor from collector to Base. The 2N3055 (not to be confused with 2N3053) sounded briliant as all the other mentioned transistors but it seems even more sensistive than 2N3053 and even BD139. But it blocked at Vb=48V for no reason known to me. It sung at Vb=24V. Higher Vb was tried with higher transformer ratios eg 7:1, 10:1, 13:1, 17:1. The laminations used were EI grand orient by Tranceria Ligure bought from Stefos in Athens.

How does the Pleiades DL93 single electron tube, 2 transformers and no other component audio power amplifier in class A schematic look like

At your risk. Please take all safety precautions. It looks very much like figures of patent US1349252A, Method of and Means for Utilizing thernionic currents - Harold D Harold.

Recording as many needed parts on the same analog magnetic recording track without generation loss

At your risk. See also a previous post. This is how Mike Oldfield created his Tubullar Bells demo by covering the erase head. Anyway at Pleiades lab the erase head of a Tascam Porta 03 cassette recorder has been disconected. Many singing parts were recorded on top of each other using just an SM58 at 24in above head connected to a Pleiades 175mH high pass filter. It is like painting on the same paper with different crayons. The 2nd pass partially blurs (only the very high frequencies are more affected) the 1st. The 3rd pass partrially blurs the 2nd and 1st. But the 4th, 5th,..., pass does not affect the 1st! For example a male singing voice immitated singing ducks of different age. Then the casstte recording of about 10 ducks in choir concert was played to Vicky's hi-fi system and she thought the recording had been done in a commercial good quality recording studio.

At the most unlikely places extraordinary things can be found

For example the Restaurant Samos by Olga and Fotis on Liosion street.