DIY Record Player

  1. MADNESS – the short story of a long trip to heaven and hell

diy record player general view

As a  youngster I started to build my own gear,  no matter the field of activity! After building bows and toy guns from wood, model airplanes or vessels, I started to focus on popular electronics. I can remember my first radios, first walkie-talkie and a bit later, my first audio amplifier.  Living under the communist regime at the time, having your own quality audio reproduction chain was not for everybody: every audio equipment piece of decent quality was expensive, and hard to get cause was not made inside the country, and all imports were controlled or very expensive. So, for the most of audio enthusiasts building your own gear was the only way to achieve a good audio chain (except those  made by the local industry, which quality was almost bearable, but they were not available for everyone). Do It Yourself  was not just a way those times, it was THE ONLY WAY for most of the passionate people. Hoping I did not  bored you with strange stories, back in the days everybody was building  hand made audio amplifiers, preamplifiers, loudspeakers plus some various TV and satellite antenna amplifiers and other various stuff. That mean lots of people were using home made audio equipment for their homes or PA purposes, all this phenomenon being actually a small underground business!  I was tackling  two times the project of a cassette deck player, very complex for that period, both of them succeeded and worked for years. But even for my experienced ”home made” builder background, building a high quality RECORD player from scratch it seems crazy!!  Until one day :D

Here there is the general plan for the madness record player:

attitube diy record player drawing

Madness was designed by using separate elements not linked to one chassis, but supported by a 60 Kg stone slab. No elastic supports or buffers were used. Also, it uses belt drive as transmission system, and an AC synchronous 24 poles Pabst Motor.

The Platter – is made by marble, machined in only one catch by a master turner in stone on a calibrated machine. Yes, the marble is ringing! But what is not ringing in this physical world we live… You can kill this in various ways. The platter weight is 15Kg. On top of the platters rests a 5mm CNC machined acrylic mat bought from www.phonophono.de. LPs are fixed onto the platter with a threaded clamp. The clamp was made by aluminum alloy treated black, and it is decoupled from the bearing shaft by using a big threaded solid PTFE  washer, and the contact area clamp-LP disc is made by a plastic crown with low friction properties (to avoid damaging the disc label). The clamp is made from one piece only, is internally damped and weights 216 grams. I tried to make the platter from granite, but the turner said it is quite dangerous to process a 15-20Kg disc, cause the granite he had was not so homogeneous like the marble samples, and if it is broken while turning, the debris could killed someone… The marble win, due to its ease to process qualities, without any danger for the operator. The platter is driven by a silk belt.

The Bearing – is a non inverted type, over sized  steel shaft- sintered bronze massive sleeve.

1 – The bushing – is made from a massive sintered bronze rod. The bronze bushing (which houses the iron shaft) is fixed for good with epoxi by the base plate. The sleeve receives the steel shaft, of which axial forces are taken by a 9mm high polished sapphire ball, resting on a PTFE  (solid teflon) thrust plate. Despite sintered bronze is oil impregnated, the bushing is full of oil .

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diy record player non-inverted bearing system by attitube

 

2  – The shaft – was made on the turning machine from a special iron alloy to exactly match the inside diameter of the bushing hole, with just a small  play to allowed the free  rotation of the shaft. After being turned, the shaft was suffering a thermal treatment to increase its surface hardness, and then was polished. The shaft was provided with an exterior spiral channel which rise the oil from the bottom to up, in order to ensure continuously an oil film between shaft and bushing during the clockwise spinning of the supported platter. Also, the shaft contains all necessary to be attached to the marble platter. The system is simple, by using an upper inverted hat – like nut, made from brass, with a very fine pitch thread. The platter is fixed between the upper shoulder of the shaft and the inverted hat. A washer made by special cylinder-head paper (or ptfe) could be used as a buffer between the platter and the shaft sustaining shoulder, to allow friction reduction and a bit of vibrational isolation .

3 – The base plate – is a huge cheap and heavy iron disc that supports the bearing, painted in black, and fitted with three threaded holes for the three leveling  adjusted spiked legs. The adjustment legs are made by steel. The threaded legs allowed a very precise leveling adjustment of the platter. The base plate ringing was also reduced by various treatments.

The Motor – is an AC synchronous 220 Volt/ 50 Hz, 24 poles, made in Germany by Pabst Motor. The electrical motor was taken from a professional tape recorder, were it was having the role to drive the capstan. The speed of a synchronous motor is determined by the following formula:  V = (120X f)/n where v is the speed of the rotor (in rpm),  f is the frequency of the AC power supply(in Hz) and n is the number of magnetic poles. In our case, V= (120X50hz)/ 24, then we have V=25o rpm. The variation of the AC frequency into my town ranges from 49,950 to 49,999 Hz, while the speed is only depended by the frequency of the AC line f, not by the tension! A brass belt pulley for the motor axle was turned from aluminum. The external diameter of the pulley was left wit 0,1mm bigger than calculated, then adjusted with sand paper until the rotation speed of the platter was exactly33,3 rpm by using a 50 Hz strobe flash and a calibrated disc.

The engine it is very quiet while rotating, but has some vibrations, being quite old and heavily used. In order to cope with the self generated vibrations, the engine was suspended on the multiple layer engine plate, which in turn is supported by three lags terminated with big threaded spikes, allowing the for the engine assembly to be easily leveled. The engine assembly is sustained by three anti-vibrational devices, that are using sand. This way, just a small amount of unwanted vibration generated by the motor reaches the platter via the stone slab support. The vibrations transmitted via the silk belt could not excite a 15 Kg platter easily :)

The Sound – First, I must to say a DIY complete turntable from build from scratch is not a project for sissies ! It is a long term project with many variables, and someone needs lots of time and patience to succeed. A was making various experiences with techniques and materials for each item/step. The refinement of the design and proper tune and fine tune seems endless at the beginning! It took two years to make the Madness sing in a decent manner, then the fine tuning started.

Madness was tested with three arms in time – Magnetico (Schroeder like clone tonearm), Ruby unipivot and three versions of inverted Ladegaard airbearing inspired by Vic’s Terminator tonearm – and  two cartridges were used  – Van den Hull DDT II , Van Den Hull MC1 Special and Lyra DELOS.

To be short, the sound is powerful and clean, very fast and accurate. The treble is unaltered while the lower spectrum is speedy and articulate. This turntable set was able to reveal all the qualities of the MC cartridges I used, without any major drawback.

© attitube 2011

Madness_record_player_04

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