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". ,. \ - ..... '. Research.Department

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WOl~kcarr:Led ,out:by H.Da:\riet3 ".,. '. ]1'~ .'H~2B~ Cuilen •.. H~'Hiiic:J:iriffe

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REPORT No. '0.045 .\. . .' ,' .. ~ . 10th January~1944

.;', ... -- Fig { No. C.Q45 ~'1'

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:'INTERiMREPQ~TON': THE 'TYPE:D RE00lIDING.EQ,UrPMENT.

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,,~··,',·Thei~TY:pe'<DRecorq.~ilgEquipm&ritishowbeing designed a;nd manufactlired<~to proV,idethe ':'Oorpo:pati9'~w:i;th high grade appai'a tus whicli' Cf.j.ri, be made, in; ~his c.oun:trY~; ; . .'The apPa.:ratlis is urgently requir,ed, and ,it has th:erefore been necess'aryto. stabtlisethe'designat a point where we' hliy~:qot . Cluite reached the hi@h:sta-nda·:rd ;'of .speed.constancywhich.:was·<!8sired;putthe: equipment wtll\bsvan:improvemEn{ton,anythirigin service so. far~ . i

, 'The. Type'D ~eqord.ing ECluipment lS being designEi.d 'to meet, the need for l1igb. grade recording m:l.'Chintls, whichhavenotcso far b~en' JI¥luufacturedin :Grea-tBri tain.'th~·C.9'rporati6n :hasbeen obliged to obt!'l.i~' equipment on .Lease';;'Lehd'fr.om::A.!ilerica to enable 'it to ca:i:'i-yout the n~qessary expansion '01' 'i'tsrecQrding servicef?,and altho~gli ·this equipment, ha,s enl3.bJ.edus to main-tain .a·servicei t is Iicitwelldesigne'd mech8.nicallY or electrically, a:Q,dcan only :be ,considered' an expedient Untll it can be replaced by something better~

, ". w~~n:,ihe}le~ign Of~h~~:·iik~·:·~ Re66rcler;wasc~~enced,it wasdecid~.d after'IlU,1cl;i'dlscu'ssion -that~it.: would pe· advisable t<;>. make apparatus suitable f'orpeace~ti:m,e servicesand':uoit'only,:forJ u:s,e duringthEl :war, and with this en<?:lD:y'iey/, 'oe.rtainfacili ties rio~ titbsOJ.1.:l.telYessentlal but "highly des~rab:Le, hdV$·.h.e'.eh'iii.c6rporated~ '" Particula:'r attention' has been giyen.' to robustness, of,.Q:es:i.gn,J,',ongwearing properties .andeEl,se.of operation and maintenance'~

,. . >, '.~ .• '. :,', :~...> . '.: . '" ::'. '.' .' ':.' '. , ... ., . "I~viewof the-lack of desigJJ.data many experiments have been ?arr~ed .

out wi:th af~,r~,t mod,el,macp.i:p,e; .. ?-p.~:.a.,nu:m,'P.e,:j? .of.di:t'f.icu.lties ,requiring sOJ.uti'onp.as .. been: encounte·red.:-,::::::····'· , .

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·,.~;»~efirst major'difficultY was in isolatfng motor vibrati.on ffoffi,the.· beqp~ei;t,El.: .', :~e machine' iri:;tl~e . i,S. :a1500r.:.R~m~ • s:ynchronous3-PllasE?\IIl9~or ': • " .. *liA,?h~wa;~ ch8~e:n,b,e.eatlseof' :i~s(:1mooth rUnning prbpe,rties, ·but. ,ev€lI:l,::Wi,th.· this Iria$l.h~rl.e: . ftVras 'foun:d' tha tvi~r.ationwas beingprodupedon thepeAp.late~ ....... , COri,s~d.~1'eJ~.leinvystigation Vllth.:t'UbberIll9uil~iIigs and, 'f:ie;x:i ble.co~p1.ing~Y~8;s n~c8 si:ia.:tY bef:d;fe thearrangemen t whicli ls'·.n97N ~ ir,t 'llse was produced~' ,Th~ ... riio'to~:jj~' hu.Iigon"rilb?er 'm6untirigs'rpadfi'bY~"Ru'bber Bonders", and the 'drive sh.8.ftlSd:d -ien.through a:douplingc~ns:fsi:i.rig pf two sheet~ of polyvinyl chloride -. nn arrarigem~nt·g;j:vii1g·ve.ry· good results •. '

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The nextd~fficulty was ~ith 'speed variations, eventually traced to the rubber i'd2.et wheels. When this machine was first cQiii3fdered it was decided that idlenwheels show'ed the best promise of producing asatisfa:ctor,y-drive', as most moderIl recording equipment uses this type of drive" 'and,we were at' 'Ghat time not awo.re ,of any seriotlsobjection to it. There'sults of our experiments have been to, show, however, that due to the stretching ,of the

, ~~~~~b~~ti:;d V!~tig~~~~:0~Qb~i:~'~~~:!~~~h:;'~~~~~;~,'~!~!'~ .'dis~~~e;:~!o;;n~~. lS ,one~~fl:\~~~~: .. ,causesof,'wow' inthePrest9;}~Q~,~:tff~s, and ~lthough it lS ' POssibf~:\t!l5yjtmprove upon the arrangement' of~(rf~U::iF~~~as carrled out by Presto, we have Qeen unable "to produce 'a drive "using. rubber idlers which' .is entirely

,free of ',Vv~ow',~ "It has b'een establlshedthati.f,a ·thiri.flexibiebu~ 'inextensible skin can ,be placedround,the rubber idler"the ,stretching of the 'wheel is eliminated and very good results are obtained,but it has not been possible to do ,this in practice~ although a number of manufaoturers has tr~eQ.. ,d number of experiments has shown that the most effective way of reduc~ng 'wow' when using rubber wheels is to use a turntable with very high inertia., ,and this is being done in the final design.

unfortunately in view of the urgency of manufacturing equipment we are , , ';·U:b.able t6 coritempla te -3xperimentswi th other types ofdri ve for i:nclusion in

"" ,the'fl;r'st model of 'the 'J.iype D recorder, but experiments will of course continue,and .if a better drive is produced it can be fitted to SUbsequent 0':luipments.,

", ' The, performance of the equipment will therefore be comparable with a . good Presto machine ,fro,II).thepointof view or 'wOw'and; rumbl(jl, but will bee more· easy. to operate and will be more r~liable. . -

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. The amplifiers are placed in the pedestal's under the ma.chine~,. to sa,ve s:pace and for cOIlvenience of operation, and some difficulties· with hum were

'- . encountered, but -these have been overcome' by screening; The auxiliary equipment is accommodated in a separa,te control desk, and here again special precautions have been taken to prevent:b,um.··· ,We are~n6w in a position to lfinalise th,e ::(j,e,si'gn as fo~lows:

".l

The pedestal of each recording machine houses a recording amplifier and i t8 mains unt t, and Oil a sloping control panel, is mowited the. starting knO.b-, indicator lamp, and a f\inglemeter which normallY1n:dicat~s that programme is: reaching the cutterheads~ . When a red push' button :is presse'd the- meter reads cutter, head voits (for lining up) and the needle.'shou.ldbe on a red sector on the 'sQa,le;when agre'eIl push:.button i~, pre'f?sedthe~ter reads the various amplifier feeds and: '.the needle reads on a green sector. ': .' A swi toh on' .the amplifier i tself,'selectsthe feed being mea.'Sured. ' There is also a push button far 8crolli~1g,the amp11fierprotectfon ihdicator, and a large 'dial indicating, \ihe number of minutes of 'recording time remaining.

The remainder of the amplifier equipment is contained in a control desk

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~,laced ,between ',the • two ';reCO~d.il1gfuachines 'and,havfng', on, i,ta, s~o;Ping Panel the! the,,:f.Ollow}ng,l'teIns'. ' programme meter ;cohtrol pot.entiomet'er, recording ',:

'cha,Iige7:pyer ~E:JY; comprellensi.vecheck key" 'gainccnitrolon linE3 POSl don of ~6In.p.reiierisive qheck,key,. 'lou.dspea~er amplifier gain control ,J;oudspeaker , anrpl1fiermutil1g switchand'cllanileilirikingkey.The gain ,control of the liheaJUplifiers,' the variable pick-up attenuators and the BI1 controls, which are u~~d>oIUY:"f9.r ,lining-up; arEH3.ccessible inside the def.jk.i,' '

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I "'Eleelectricalcircuits arc shown in sChemattc form in Fig! 1. ",' , . . " "

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,,~l;lc0lill.ng prog~amme is fed via a' ,cohtrolp()telitiom~ter &nd' the nOrmal :t:e,90rd:jl'ng.;Change-:-o,ver:switch to ei therorbo'~h of the :pecgrding amplifiers,' eacih:ofwhich:feeq.,(:\ one:cutter,head.~diuscompensa~iop. ~sprovide,d in:' ,thes~amplifiers,'a4d j;tJ.e:re is an a:utowltic protection 60~ti'oJ,.'which~ , if the "q~tput': stage is 9yerlOaded'or ift-he' level on the disc i~r~oo :high,reduces

,t,h~ ,g~iri.:·qfthe~·an).p.lif~ers sufficiently, to.' ay-oid, disto;r~~Or;t; ,,' "As:~th~ " :pr9teq~ibn,60n:t:rol/ OPElratesfrointheoutputstage it "\iake~" aCCOu.l);~ pf the amouirfiof'radius ?,pm,pensation being used at any momen~~'" 'Pie protective·

. deV'i,ce shquld only op~:iJe.1ie, on overload, and not during .p,.9rinal: recording, and I, ::,i,; ;itsoperatibn,will p~'indicatedbya'signal lampoIi, the'con1ircilpanel., ,This

lamp',may~itherSf+~;{l~;orprefei'abiy", remain lit until: ce,:p.qel1ed by a'push 'b1,i-tjion~ " rr.liear ::i.sconP.ected, to: the output side of,thEl go:qtrol potentiome.ter and 'the C9rltr.e pos~~io:o. of the compre,hen:~ive c,heck key: ~~. fed from ~he input side. " " , ', ' ,

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, .-,:.. "EaGli"pi~k":'upiS: connected toa transf9rmer" mounted on the recording, .. ' machine,. which, is conne'ctedvia.'an.attEimuator'toa pre-amplifier in tb,e desk. The attenuator lsvar~able ·over<~a·r8.nge of 12 db. forcompensati~ differences insEms.itivities,' of .. p1ck~up$~: '" Tl;t:l.sarrangementprQvides a high input.levE:l~", ',., :-. ,,", '" _! I \ " .,', ~ . , '.' ,: ' _ ;'" . " . ~ : ' , '. .' ",., • : '".' ". ~ ' ..

tP tl,1e~ preTampli:t±ei' 'wh~ch lia;s'suffic'ientgain to ,ac,commoda t,e p~ck-uPs20. 'db. , , ,,'f~.s~··;~e~~~t.i,~e,t¥Il'~~eE~,'M~:(.~iPe"12. ":"Thep-Vnit:i'c,11oVis'the pre-~n,1p+itier

, . -vr~ic~)~~:,,~'Uf;t'~Ciet+t,gain t~ ,:E;tllpw:to:e36:db ~ . att~I+ut;j;~9n,; so ,that "no~lly .t:hEri;~V:t:l:~~.nEile~'Ln.9t'be.a .. cQnsta:nt ~in~eda~o~~.ircuit., .', .. '. . . i.

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~\:TA~s~rran~~~~nt f~' dtlpii9~ t~d .f9.r:'E:JEich,:pick~Up, atidcb:arige~over' i3Wi t ~hitig' is> provided ':011 t1l.eoutput ~ of the'" ~uni t s. : Thi s. ;Swi tching cqnneotEl' eachptck-u.:p ,phf:tinto one o:r. othsr"of ,2 line amplifiers which, 'will feed' +4 db. 'to ~. 6 00':' ohm l}':ne. , ., . . ,

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; .,.A."~I>ecif:tl·high gain.l.oudspeaker ~mpl,ifier wi th'.,a 12 watt,O,utput.· stage j, 13 90nne9~Eld,viathecoml?,rEltiep,sive cJ:i~.clc:k,ey, ~9f~xed, a ttenue:iior"s,,9Il~ thE? ,.,.:. Qtlt:pU.t:sbf.~he line amplifier~,a,hd 'ioa~aria1?le atteriuator,q9:p,heq~ec1, to. thEl::ip,comiilgiiI+G., .•. lXi: serif?s· With' ,the1.oudspeaJrerl?:~plifie+.'· .. ,is ... ~'20 .. ,db.,

· 'atteH~ator:wb.ich cal+ be,i,p,s~*t~,d'1>Y>tl1e .. 9P~reti9~,pf· anori-lockiilg)tey on, ;'" ti1e,C?l1t:r:olJ)aIle~t9~iv~,1l1Utiftg~,. ~~s.k;~Y·.9anl3-~SOnaye a~ .',Q·tf'pof?~~ion

· if deElired. .A gaili .control for the 'loud~peaker amplifier,willbe moun,~ed, on. the conttoI,i:>!meh.E;ln9"Ttl.th€l· inio., :posp~~oti. wil+giye~thefu11output of. the; :Lqud~pE.>ake;r amplifier .wlit;in;z~;t'o.l,e.vel: ,1 s P:f+'tll/3' incorirl,.ngand · oli tgo ing. l:t;r;les~.~Tl:ieeo,ntrolcan;ho~v;e;r,;"be, lisscft9 increasethe,.gain of the "

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19Udl3pea'keramplJ.:eier another 15 db. for listening to backgroUnd noise •

. The loudspeaker amplifier and the line ,amplifiers areoia new design, bu.t thE; n6W microphone I:imp;LifierA~/2 can be used for the pri:l..;ampiifier pq$it.io:p.~~ .' ,

. On top ef the &esk' i~ a. jackfield, I in. which line distribution '~s ' .- __ obtain!Fp.:]l'1:i;~b,cordless plugs.. _ Jacks are- prov,ided for plugging the PM to a. outgOi~J\~~,p¥or to 'WL,' and there, isa, lou~~~~~er amplifier input; j,ack •.

. ', For tesjlil~:Puiiloses" access to the pre-ainpnff~r~;;':~ick:-:up attenuators, G-Units ' . and lin!3,amplifiers is given by jacks mounted ,alongside ,or" (m . the amplifiers inside-the deek. No spare ampLifiers are providedinsid,e th~ qesk, but all

.amplif~er.s are inrnediately removable after disconnecting a plug" .' The' .' alternative, is to have a much larger desk with s:par~ alnplifiersalways 'running in readiness. fora breakdown' -a wasteful procedure. If' the .

, -',:ampli;t:iers ar~ .notswi tcJ:ied 'o~ an lnterrtiption for warming 'up 'is inevitable, . ':'~nd little ,IjtB~:~ time-viil1. be required tp change a faulty, unit. . .'

'irli,e :t'()l:tbwiilg facil:!,:Cie.s will be provided on each r,ecording machine!' .. '

The-mechanism of the machine- will betotallye-nclosed, the ,traversing, geil,r being mounted 'along the- left;..hahd side Vii th the -cutt.er head . a.rrange-dto cut along the remote side of the disc, so giving 'a layout· with the pick-up at the front of the disc for easy operation'. '

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(2) .' ~e trave~~8e h~ad. rotates upwarcls when release.d py pr~ssizl.g a button to' . ' .. Cleat the table for changing diSCS, and to bring the cutter Jnto a • I

.. Visible pasi tionfor inspection and r:eplacement. . '. ." . . .

'.(3) J • • ' , .

Scrol~ing is provided by a separate motor<li'ive.'l'o.star~ scralling a. ;. push bu'i;tob. is pressed. ,To stop scr~llip.g and: 1nake a' concentric gr6dvetraver~e is disengaged in the'ordiriai'y Way which automatically stops the .scralling .motor. The cutte'J:. head is riot cannected to the scrolling mec'hanism and has. to' be lifteci. by hand in the. ordinary way.

-A,. separate ~li~in,g" push button is provided to' rilake short s~ralls linking up two bands aria disc •. ScrOlliD.gl$tarts when this button is pressed arid stops when this button is. r~leased. . .

The direction of scrall reverses with the direction ot traverse. .",

The~$C'rdiling' pitCh, will.increase or decrease propqrtionatelY.to the cutt~ng pitch,i~e.,.about +2e%. An a.djustmen.tt.:or scrolling pitch c~n b~,provid~d ifrequired:- .

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(4)Tte~'pe B Cutte;Head is us,ed' 'but;' is~malinted i~ 'a sliffer,en~ case, elecd;ric ,cb;nnectic)l1s. being, .mad.e ,by . plug and. SOCk:et . when the. head is

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(5) ,~;}'jet of push-buttons g~ves.i:r;t.stantaneous setting of th~ sta,rting. radius for normal d~sc sizes~, PtJ,sh-buttori.s lOck in posi tio:il, andt"lre, rilachinE;} tb,erofore remains set' for 'thepa:rticular condition desired until

, r~-~etby pressing 8,nother button.-If a non:"stanaa~d. set,:"up is deaired .a:~canc<fl.lation button is 'available. The foilowingposi tions are ~vailable:

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OUt to in E:X:~~EiJm.e travel for. cutting 17!ndia. tb4\,d~ll. (the trips operate on traVe1.El 6u.tside these limits)

In

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. , ,:L~}tl·d~a.' for .11i dis'cs p:rocessing or . " . ,'16 ~l.1l ~non':proce s sing

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,10" It "processing or "non~ proc e s,sing

Starting diameter 7"·

!l " ~~%:;·p~tt9n~·.~~~ .. ··' iIi~p~r~t:ii~:·VYh~n; £,~e., ~r:~V'~~~~-'i.S; eJ1gag~~~j·· L'

(6): ~9t~ctive deviges ~~efit:tedtofivoid ;dfilTJl,lgeif'~heniach.i~~isleft ·iii.,·trayer~e and 'tne:carri!ige'rea6liels~the end of its tr~-ifel~ C These <l~:Ir~6~~ operate.:outside the ,normaldutting range, and therefore cannot

': ps; QPe:t;Ei,ted acc~den:~a:LlYWhensett~ngthe ca:rriage by hand. ' ,,' I " \, ,': ~.: ",~, ': ': '., . ~, '0 ." ~. .,' '.. . . " ,

(7) Radius compens~timfisprovidEid by,a'MU:i.rh~adswitch ,mounted so as to 'be: accessible. for'Gleanil1g~~, ',The ra.diuScoffipensation cirpui ts

", ~a.U:t9me,tically chang\3 with the turntable speed; , , : .~ i,' ., .", •• ' : .,' , . -' '. . " .' .' '. ' . , .

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(8)Jll~omati.c switch~ngforthe mqtorstaJ;'Ii~ngi~ combin~d, w~t:p. the turn-table stop-start kJ;l6b. ;,

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The following controls areprovid~d:

. Traverse !t!€;a.g~~ A lever on the front face operates tl::reclutch' and lifts th~ nuttrom, thE> lead screw.

'. Cutter ~dL9!Verg,:S.. :I.ower the cutter h8ado '

A knob on 'the front face, rotating:900"'clockwise to

~ke .A.djustm~i" . A' knob on the top making sevel'13.:L 't~~~ . to' c~ver i" rake . ·tt adjustm~n:~:'"i.~ ... th a scal.e to .. ~how the pOsi tion an:~i';'eiri.;,;i;n..dicat9r to show when the ~djUErtme.nt is co~rect.

GrOOVE; "Pi tch. Adjusted by a knob under a cover on top of the machine. This knob rotatE;18 when them<"l.chin,e is operating. ' Pitch can b~ adjusted .contin­uously frOm 90 to 150 grooves per inch, in to out or out to in, and the :r..umber·of grooveEiper inch is shown on a. transparElnt scale.

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Startin~.2-meter Adj~stment. By push-buttons ~n the' top Of the uni t~

.Qut.ttIllLPJ&J]1~ter Indicato'r. Shows' diameter and cutting time. available.

12££..iill:. of 9'!!:LQ2!!tl'01. This' is mounted on the rotating traverse head and· has a scale sp that:1t can be re-set accurately.

!9-E~~l~Spee<!.The operating knob is mounted at the back of the machine, .but can be reached from the front, and changes the speed from 78 r.p.m. to 33 1/3rdr~p.m. ~

Suction Sv;arf Removal. Will be provided.

CONCLUSIONS, --The design of the Type D Recording Equi·pment is now 'progressing well,

and. production is in hand. Experiments with a first model have, ~isclosed c~rtain fundamental difficult~Eis with the type of drive which .is . in' use, but due to the urgency to commence manufacture it will not"be, possible to carry out more experiments to evolve an improv8d:.system <ro:r. uSe ~n the first production Jnodels. E:X:pe:ri!l),ents will contin:ue, and 14ter models will have

, all improveIl'lents incorporated. The first model however has adv~ntages· in ease of opera tionand has. been· designed to providethe;~·:maJd.mum· possible J;'elia..~i1i ty with the roir..imwn of maintenance. . . .

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