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Binson Echorec Memory System

  1. HomeKnowledge BaseBinson Echorec Memory System

Binson Echorec Memory System

by Phil Taylor

The Binson ‘Echorec’ delay-echo unit was first introduced in the late 1950′s. At that time effects technology was limited to studio effects such as tube equalisers and compressors, tube driven plate and room reverbs (a tiled room with a speaker and microphone inside) and tube tape delays. Binson developed the Echorec to iron out the shortcomings of tape delay machines, more specifically they wanted to improve the sound quality and reliability. To this end the founder of Binson, Dr Bonfiglio Bini set his sights on developing a new type of signal delay storage medium; something far superior to iron oxide coated plastic tape. His idea was a unique invention utilising a mild steel drum carrying a durable flat aluminium band wound with steel recording wire. Bini registered several patents for the device and the patent numbers (PAT. AND REG. 35142-105678-585955) can clearly be seen printed on the ‘Plexiglas’ front panel and on top of the magnetic drum of many Echorec models.

The Echorec is undoubtedly an impressive feat of engineering. The frequency response is wide and flat and the machine possesses an excellent signal-to-noise ratio too. Further, the Echorec exhibits exceptionally low ‘wow’ and ‘flutter’ and is super-reliable; there are no tape loops to snap or wear out. Bini’s outstanding machine earned world-wide acclaim. Musicians and sound engineers appreciated the quality of Binson products then, and they still do today. The Echorec is considered by many to be the top-of-the-line, the Ferrari 166 Barchetta of echo machines. However, like the Ferrari, this hi-fidelity did not come cheaply, especially when one considers the price of a ‘Baby’ Binson in 1962 was around £140-00 (compare that with a Vox AC30 at £119-00, or a Strat for £160-00). The value, and increasing age, of these wonderful old machines means servicing the Echorec something not to be neglected. This article contains everything you need to know about the workings, care and maintenance of the “memory system”, the pulsing iron heart of the Echorec.

The Drum

Close up of the Binson Echorec drum.
Close up of the Binson Echorec drum. Note the fine wire wrapped around the drum face – Photograph taken by Luigi Amaglio 2014.

The Binson magnetic drum was constructed from three separate parts, the steel axle, balanced wheel and aluminium thread ring. Approximately one hundred turns of very fine 0.1mm (0.004″) diameter recording-grade stainless steel wire were wound around the circumference of an aluminium thread ring—a very tricky operation. The wire was wound on to the drum using a modified coil winding machine which Binson built specially to do the job. The wire had to be kept tight against the drum face with no overlaps and no kinks and the beginning and the end the wire was secured by a small pin (the external pin is visible on the edge of drum).

Even more challenging was the following operation of using a lathe and very fine (280 grade) tungsten carbide grinding wheel to accurately mill the rounded edge off the wire so that it was almost, but not quite, semi-circular, creating a very smooth, flat wire surface that could be properly magnetised by the heads. This was a delicate and crucial operation and the milling had to be performed very slowly as the wire would all too easily break. A new worker on the job would break a lot of wire before finally getting the knack—this was among one the most difficult operations at the Binson factory.

Magnetic drums are no longer manufactured and it’s rare to see used, let alone new old stock ones for sale. Consequently, even an old or damaged drum with worn surfaces is still a valuable commodity—it’s irreplaceable—and it’s perfectly feasible to rework it. The drum can be rethreaded with new wire and resurfaced to restore it back to factory-new condition. The milling and finishing work is vital if the hi-fidelity performance of a brand new machine straight out of the Binson factory is to be achieved. If the wire is left round the head will only be able to make direct contact at one small point on the wires’ circumference as shown in the cross-sectional drawing (a) below. It can be seen that just about all the head to wire contact is lost to air gaps (coloured in blue), which results in a weak signal being ‘printed’ on to the drum. In practice this means there’s no possibility of attaining those lingering, crystal clear repeats as heard on Pink Floyd’s 1973 track ‘Time’ from ‘The Dark Side of the Moon’ and the signal to noise ratio of the Echorec will be lousy too. Drawing (b) shows how milling off the wire rounds maximises surface area of the wire (coloured in orange) creating a wider recording track for the head to magnetise.

Head and six turns of recording wire in the Binson Echorec
Head and six turns of recording wire in cross-section magnified approx. 100X (a) Unmilled recording wire causes poor contact with the record/playback heads; (b) Milled recording wire yields much improved head contact.

On an historical note, wire recording machines used to zip along at a rapid rate of 2 feet per second (24ips). However, even though the wire was passing the heads at speeds higher than a modern professional studio tape machine, the audio performance was still poor. By increasing the effective surface area of the wire Dr Bini improved the audio fidelity of the Echorec in comparison to the old wire recorders.

The drum is a superlative example of vintage high precision engineering, being accurately milled to exceptionally fine tolerances. Although the drums were manufactured in the Binson factory, the high level of precision machining required between the drum axle shaft and axle housing meant that the lapping and calibration work had to be undertaken by an external company that specialised in building injectors for diesel motors. The drum and housing were manufactured as a pair, matched one-to-one with the same serial number so it’s important to note that if purchasing a spare drum that the axle housing is included as well. Never buy a spare drum without the axle housing: it will never work properly.

Early Binson machines were fitted with drums manufactured from solid cast iron. These were very heavy, weighing in at almost 3lbs. This bit of over engineering was almost certainly intended to reduce ‘wow’ and ‘flutter’, that is, slow and fast pitch variations due to changes in the rotational speed of the drum, to an absolute minimum. All that mass meant that once that metal drum had attained speed it would be incredibly stable—the angular momentum of that spinning chunk of iron acted like a mechanical low-pass filter effectively filtering out any transient fluctuations in mains voltage or unpredictable dynamic frictional changes, reducing wow and flutter to vanishing point.

The same approach was taken to minimise wow and flutter in idler wheel driven turntables, such as the Garrard 401, where the mass is an alloy platter rather than an iron drum. The wow and flutter of a 401 is measured at 0.05%—right at the limits of what test gear could measure at the time. Technically there’s no reason why a properly serviced Echorec should not approach this figure or, to put it another way, wow and flutter should be inaudible in a properly serviced Echorec.

Later on Binson began fabricating their drums from 3mm thick pressed mild steel. The result was significant reduction in weight—the new drums weighed just under 1lb. The reasoning behind this may be that Bini realised all this mass was overkill, that is the rotational stability was not significantly impaired by reducing the mass of the drum, and consequently he decided Binson could ease off on the specs and save money on international shipping costs of their new model Echorecs.

A steel boss was attached to the center of the drum using a process known as rotary friction welding to which the hardened steel shaft was then joined by an interference fit. At the time friction welding was new development. Bini was utilising the latest cutting edge technology to achieve the highest possible concentricity and ensure wow and flutter was kept as low as it could possibly be.

The Heads

The picture on the right shows a Photovox tape head. These heads were manufactured to much higher levels of precision and possessed a narrower gap than earlier designs. This improved the high frequency response of Binson’s machine significantly. Additionally, note the chamfered edges of the head—the head profile is not the same as a standard ¼″ reel-to-reel tape machine head. This modified head geometry was intended to improve head contact with the hard convex surface of magnetic drum and so make it easier for Binson technicians to align the heads properly.

The drum must be kept lightly oiled at all times to reduce frictional wear where the heads contact the drum. This ensures a long service life. Any light lubricating oil such as sewing machine oil will do, however care must be taken that none of the oil finds its way onto the rubber idler wheel.

Photovox Playback head for the tube Binson Echorec
Photovox Playback head for the tube Binson Echorec B2 – Photograph taken by Luigi Amaglio 2014.

Even the slightest drop will cause the idler to slip badly against the drum resulting excessive ‘wow’.  In the worst case all traction is completely lost and the motor shaft just spins uselessly against the idler wheel (and drum), which remains stationary. Any oil contamination should be removed as quickly as possible with isopropyl alcohol.

The record and playback heads are positioned around the circumference of the drum, the first of these is the record head and the others are the playback heads giving four possible different delay taps. There is a delay of approximately 75ms before the first playback head to reads the recorded signal from the drum, 150ms for the second head, 225ms for the third head and the longest delay is 300ms for the fourth head. Heads are selected with the knob on the front panel which gives 12 separate echo selections from one head alone to complex multi-tap effects. The impedance of a tube Echorec (‘Baby’ or B2 model) playback head is typically in the region of 600Ω—700Ω and a record head is 400Ω—500Ω. The record head has a wider gap (10μm) than the playback head (5μm) and fewer turns of wire, hence lower resistance. A wider gap ensures that the magnetic flux permeates deep into the magnetic recording medium (the recording wire), resulting in strong magnetisation, that is a high-fidelity signal is recorded on the drum. A wider gap also means poorer frequency response particularly on trebles if the record head is used as a playback head.

A Word On Head “Relapping”

If the Echorec drum does happen to be in need of rethreading and resurfacing then this is certainly an indicator that the machine hasn’t been properly maintained and serviced, for instance the drum face hasn’t been kept lightly oiled or the machine has been operated with misaligned heads. Over time the precision contoured shape of the tape heads is worn away by friction against the drum ultimately resulting in poor contact between the head and drum face. Recording and/or playback quality gradually degrades—in practice this means, a loss of high frequency response of the delay repeats, a higher incidence of dropouts and excessive background noise/hiss.

“Relapping” can restore adversely worn heads to their original performance. The process essentially involves fine grade sanding or polishing to remove material and recontour the shape of the head. This is highly skilled work that should only be undertaken by an experienced technician such as Terry Summers (Summertone). As long as the head isn’t too badly worn it’s possible to rework it to “as new” condition. Generally heads can only be relapped once—after that too much material has been lost to restore the correct head profile without altering the length of gap and curtailing it’s high-frequency response. If the heads are beyond repair then replacements can be obtained from Photovox company in Italy—the original supplier of heads to Binson back in their heyday in the 1950s.

The Motor

Shaded-pole motor
The shaded-pole induction motor utilised in the model 'T7E' Binson Echorec - Photograph taken by Samantha Taylor 2019.

The earlier model ‘T5E’ and prototype Ecorecs were fitted with a German made Lorenz (type EMKG 302-10b) single phase A.C. induction motor, which required a capacitor to get it to start spinning. Incidentally, Lorenz also developed Hitler’s “unbreakable” cipher machine, the Lorenz SZ42, enabling German High Command to communicate with their forces via radio in complete secrecy during WW2. The Lorenz capacitor start motor in the old model T5E really does like something you’d find in a vintage typewriter, wire recorder or cipher machine and is an exemplary instance of 1940s of German engineering, being reliable and trouble-free. However Binson, always on the quest for something better, and more cost effective, eventually replaced it with an ingenious ‘shaded-pole’ induction motor.  All the model ‘T7E’ (and ‘B2’) Echorecs are fitted with shaded-pole motors.

The shaded-pole motor does not require a motor start capacitor nor does it require brushes—brushes are carbon contacts that supply current to the rotor (the bit that spins)—to conduct current into the rotor winding. Instead, and this is the clever part, currents are induced in the ‘rotor’ by induction and manipulating the shape of the magnetic field with thick copper wires (the shaded poles) embedded in the iron laminates of the ‘stator’ (the bit that stays still). The magnetic field in the stator laminates is generated by the A.C. current flowing in the primary winding, just like a transformer (there’s an excellent explanation of how shaded-pole motors work about 7 minutes into this YouTube video). Because there are no brushes to wear out, rotor windings or start capacitor, the shaded-pole motor is exceptionally reliable and requires little maintenance. It’s also a relatively low power device consuming in the order of 40W.

The rotor spins at fixed speed. Its synchronous speed is determined by the A.C. mains frequency and number of poles in the motor winding (not voltage!). This is 50Hz in UK, Europe, Australia and most of the world, except America where it is 60Hz.

The speed of the motor can be calculated:

ω = 2 × 60 × f / n

where

ω = pump shaft rotational speed (rev/min, RPM)

f = frequency (Hz, cycles/sec) = 50Hz

n = number of poles = 2

ω = 2 × 60 × 50 / 2 = 3000RPM

The voltage selector switch on the side panel of the ‘T7E’ selects various tap points on the primary winding of the power supply transformer allowing the machine to operate from European 220V, British 240V or U.S.A. 120V A.C. mains power. The transformer primary winding also doubles as an ‘autotransformer‘ ensuring the shaded-pole motor always sees the specified 220VAC it requires to operate correctly. This is essential as although the motor is synchronous, that is under no load conditions it spins at the same speed regardless of applied voltage, at low voltage it may not have enough torque to start up under load. This is because at reduced voltage the torque of a synchronous motor is reduced by the square of the voltage ratio. What this means in real terms is that if the voltage falls from 220V to 110V the torque decreases by a factor of four and the motor may stall, overheat and burnout.

It should also be kept in mind that the motor speed in a European Echorec will be about 20% faster when operated in America resulting in the overall delay time being 20% shorter. Altering the diameter of the rubber drive wheel or changing the voltage WILL NOT alter the speed of the disc. Echorecs manufactured for the American market under the ‘Guild’ brand name were fitted with motors that had smaller diameter spindles to correct the gearing ratio so the idler wheel was driven at the same speed as European models.

Incidentally, it is possible to roughly deduce the age of a particular model ‘T7E’ by examining the side of the motor where there’s normally a date of manufacture stamped in black ink. This isn’t a completely accurate estimate as the motor may have been sitting in stores for awhile, however the Echorec will certainly be no older than this date.

A few vital statistics taken from a real Echorec model ‘T7E’:

Measured drum diameter (d) = 4.7″
Drum circumference = π × d = π × 4.7 = 15″

Measured rotational speed of drum = 71RPM, so every minute, 71 × 15″ = 1065″ of the magnetic band on the drum surface passes across the heads. Converting this to inches per second:

1065 / 60 = 18ips, which is very respectable tape speed for hifi reproduction

The motor spindle circumference can be calculated from:

Drum ω = 71RPM
Drum circumference = 15″
Motor spindle ω = 3000RPM

Spindle circumference = 71 × 15″ / 3000 = 0.36″

The measured the spindle diameter was just over one tenth of an inch, which gives a circumference of about 0.31″

The delay time can be calculated from the measured distance between heads which is 1.3″ (34mm). If the drum speed is 18ips = 457mm/s then delay time for the first playback head is:

First tap = 34 / 457 = 0.074s = 74ms

and the Second tap = 2 × 74 = 148ms

and the Third tap = 3 × 74 = 222ms

and the Fourth tap = 4 × 74 = 296ms

Bini put a great deal of thought into the positioning of the record and four playback heads around the circumference of the Echorec’s drum. Their relative distances are not entirely arbitrary and were chosen so that the delay times are musically related to one another. If the fourth tap is considered as representing a quarter note then the third tap is a dotted eighth note. This particularly inspiring repeat pattern and has been put to good use by guitarists such as David Gilmour (Pink Floyd) and ‘The Edge’ (U2) to build some compelling riffs and grooves. Continuing on, the second tap represents an eighth note and the first tap a sixteenth note. These shorter delays can be heard in slap-back and rockabilly music from the 1950s and, again by Gilmour to good effect on tracks such as ‘Time’ (The Dark Side of the Moon).

Just a one more thing. The ‘T7E’ motor is fitted with self-lubricating sintered bronze bushings (not to be confused with brushes mentioned earlier). These bushings hold the rotor in position and allow it to spin freely. Over long periods of time the bushings do dry out, which degrades the speed stability of the motor eventually giving rise to increased motor noise, ultimately destroying the bushings and ruining the motor (replacement bushings for these old motors are essentially unobtainium). So be warned, even self-lubricating bushings don’t last forever, and because the motor is hidden within the Echorec chassis, and difficult to access, the task of oiling them is more often than not never even considered, let alone undertaken.

The Idler Wheel

Binson Echorec rubber idler wheel
Binson Echorec rubber idler wheel – Photograph taken by Luigi Amaglio 2014.

The drum is driven via a rubber idler wheel (similar to a Garrard 401 turntable) which transfers the rotational velocity of rotor (motor shaft) to the drum. The idler wheel isn’t directly coupled to the motor shaft, it is mounted on a metal base-plate that is free to slide towards the motor shaft and the circumference of the magnetic drum. Pressure of the idler wheel against the motor shaft and drum is maintained by a spring-loaded mechanism. Binson’s use of a powerful, high torque A.C. motor and idler wheel in the design implies they were aiming to ensure accurate and consistent drum speed in the Echorec.

A useful tip to keep the idler wheel in tip-top condition: If the machine is going to be stored or is unused for any period of time then it’s a good idea to make sure that that idler wheel is not left in contact with the motor spindle. If the metal spindle is left pressing against the rubber it will deform it, leaving an impression or dint in it. To prevent this from happening, make sure that the rubber wheel is pushed clear of the spindle by removing the tensioning spring. Deformed or hardened idler wheels can be sometimes reworked by soaking them in hot water as this softens the rubber, but it’s better to prevent this happening in the first place. The idler wheel is another one of those irreplaceable Binson manufactured parts, N.O.S. ones rarely come up for sale and if even when they do, they’re expensive.

It’s also worth mentioning another new idler wheel design made by Italian engineer Marcello Patruno for his custom ‘Special Binson‘ Echorecs built from N.O.S. Binson parts. His Echorec idler wheel is fabricated from aluminium and has a thin rubber rim, rather then being solid rubber, the exact same principle as a low profile car wheel. The idea is to prevent its shape from distorting, therefore yielding lower ‘wow’ than the original Binson solid rubber idler wheel.

Servicing the Memory System

Binson Echorec Memory System
Binson Echorec Memory System (the magnetic drum and head transport) – refurbished by Binson, U.K.in 2009

Servicing jobs, such as cleaning and oiling the drum or installing new anti-vibration mounts for the motor are relatively straightforward, however there are other tasks, for instance aligning the heads that, well let’s just say, “here be dragons”. It is possible to make an attempt at aligning and calibrating the heads without electronic test equipment, however it should be kept in mind that the high frequency response of a typical guitar amp only extends up to around 6KHz—you won’t be able hear high frequencies let alone tweak the Echorec to reproduce them. And, even if a high fidelity amplifier and speaker system are utilised, the human is ear is subjective and easily deceived. For this reason head alignment is almost certainly best carried out by a qualified electronics technician with access to an oscilloscope and signal generator and experience of aligning heads on reel-to-reel machines.

There was a time when Binson and their international distributors would undertake this kind of Echorec servicing work. For example, the picture above shows a completely refurbished memory system. This work was undertaken by Eric Snowball, Binson UK in 2009. All an Echorec owner need do was remove the memory system from the chassis of their machine, pack it carefully and post it to Eric for him to work on. At the time Binson UK had the capability to reface the drum, relap the heads and clean and electroplate the mounting plate and any corroded metal parts so that the memory system could be restored to “factory new” condition—the original audio performance of the Echorec was restored!

Binson UK could also undertake a modification to install a high-quality D.C. motor (manufactured by Trident Engineering Ltd. Part number: 2-40/1212) and vari-speed control circuitry to adjust or fine-tune the delay time (tempo matching). But such bespoke modifications and super-specialised restoration work did not come cheap. Rebuilding the memory system is labour intensive work costing in the region of £700-00 back in 2009. The take home message: Look after your Echorec. It’s essential to perform basic maintenance and employ sensible practices to preserve the performance of any delicate, precision mechanism, and the Echorec really is the very definition of a delicate, precision mechanism. Make sure the heads are aligned properly, the drum is kept lightly oiled, the idler wheel isn’t left parked and pressing against the motor spindle for long periods when the machine isn’t in use, that the drum bearing gets regreased every few years and the motor bushings are periodically lubricated too and, do use your Echorec… often. These machines love to be used—it keeps all the moving parts, well, moving! If you promise to commit to undertake just these few simple things then I promise your Echorec will continue to operate beautifully for many, many, many years to come.

Special thanks to Luigi Amaglio for supplying excellent close-up photographs of various Echorec components and David Bozzoni and Marcello Patruno for supplying supplemental technical info for this article.

In This Section

  • Binson Buyer’s Guide
  • Binson Echorec Pages
  • Binson Echorec B2 and Export Head Specifications
  • Binson Echorec Head Adjustment
  • Binson Echorec Manual
  • Binson Echorec Memory System
  • Binson Echorec Parts Suppliers
  • Binson Echorec Schematic
  • Echorec B2 Trimpot Adjustment
  • Echorec Export Trimpot Adjustment
  • Echorec Multi-Section Electrolytic Capacitor Rebuild
  • Geloso Sockets And Plugs
  • Geloso to ¼” Jack Socket Mod
  • Got Oil? Properties of Echorec Oil
  • History of the Binson Amplifier HiFi Company
  • Inside The Binson Factory
  • Recording the Echorec
  • Servicing the Motor
  • T7E Echorec Overhaul
  • The ‘Magic Eye’
  • The Bias Oscillator Inductor
  • The Binson Echorec Chassis
  • The Dark Side of Echorec Restoration
  • The Dream Machine: the Echorec 3°
  • The Green Slime: Echorec Wire Rot And How To Cure It
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