Selecting a Valve Audio Output Transformer

8/17/2019 Selecting a Valve Audio Output Transformer

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Selecting a Vave Audio Output TransformebyN •If, like me yo have a good seection of vave oup rasfoes a you've picke p oraybe a po or wo eac a raio raies or BVWS eeings or exace ro o raioswe hey wee beyod pacica epai yo ay be wodeg whe exacy yo ca maese o e. We he ie comes o se oe ehe o epace a aie oe in a rado yoryg o brig back o ie, o we bidg a ew vave-based pojec i ca be fic o

kow wic oe o seec e 'o days yo wod have smpy orere a repaceeansforer by pos (see Figre 1 for a Sepeber 955 aver for op rasforers) boay s no ha easy Tis arce descbes sipe mehos of esig he rasorersyo have ad assessg he suiabiy o se w a paicar vave opu sage

Ou TA "OR 8 1 ro

364 e. . .S . 3o .. SnCaPn :0 t3Q .. . 4 9 ' Q . S1

, o o .. m 1 -S : l

: . 9 1 CBs

tul

... PPG1 � 6V6 0 o

50 sUy wnd . Uu JGl2 & b 8V8

3r5o ... -· . 19- w y

wnd 6, K .• 3 or 5 47/9wun ty ex .• M·

ig 1: od Ad tt sfom S 195

g 2

What does e Oup Transome Do?e mai eao wy e sfoeis ee s t peom e impdaasaio om e g impeda(a is, ig volage d low ce) valve

ode c o e ow mpeace a islow volge ad ig ce ospeake

coi o ow mpedace eapoes Tspocess esls i a macg o e vale'sop imdce o e speaes ipimpedac opelly ove a wie eqecyage wc esls i e mos eiciepowe sfe a bes qaly so ome speake. Noe a e e impeaceepeses e combiaio of e eacaceo y icace ad/o acace wiay pe sce i e cici I geae mpece o ay cci cages w

feecy as e idcive ad capacivecopoes become moe ad ess oi

I e ol days' speakes wee pcew ig impeace coils, o lisesse ig impdae eadpoes eeo wic edd asome ad wic

g

4

wee coecd ecy o e aoe ccos saly i sees w a C-bocgcapaco Sie maybe e mi1930s owimpeda spe coils e bmealmos ivl ee e exsive

se o some is applcaoAoe sel co o e op

asome is o isoae e speae oeadpoes fom e HT voage o eop vlves aoe mig i e o plgi headpos o exeso spaes.

ome se oes o vave adio opsages ad wa ca go wog wi emca be o i Reeeces 1 ad 2.

Mease e essaces alwys dy o c a m-meediga o oewise we yoe oe look o fo asome ad cokeso a yo ca ceck e coiy o ewiigs of ay compoe yo ae igo byig epable salole wil alwaysagee o e es ad may ave a meavailable mlve cse yove ogo

20

L F : p o a t

'c f t st r nto "'tht c the ea as sb .L: g 3: gap ypal s a prc p te i


2/8

Rp

P1M•NAt

Lp

Cs

U ELT, S f (t -

�G S( a C1Rur I A" -'

Rp L l%i vo�-

] .

,N1,A.

l 6�. &1MPUf �VlET ricT

w 1 ;l

Fige6: Te GR tpe T.8 BW output transfme,----I 65 1

v :.Ho�a

1 4J 1. ! I " P

. -

\ I7K :

n icto of he wiig to of hetrasormer otewise lfe woud e veysmle. his s ecuse he wo wdngs wltypicly e me wit deet guge wreYou c oe see ta e seconday s wouwh mc tce wie ha te piay wichs what yo' exec snce or give oweflow g e nsome te secondas to car mo cure h te pima

Sommes te w compisng hesecond comes srigt o o te wndngand coects dey to te speker

who gog trogh sodered termnaI spose this ws a way of cig tecos of e tasfome sigty and asoas te beefcia effect of elmiig cope o solee jons eey reducgthe cnces of y joits i te p o teseker See Fgure 2 fo a eampe of atrormer wh hese flyig eads. someraios te out nsoe s outeo a bcket o te speake itself atetan on he ios casss ad te nwac send a ew uzzed momens lokngfor te ransoer above nd eow techssis You my come acoss a seaewh oput trasformer already aace

nd yo ca negoate a ce o a couleof qi or so, its geerly wort spngtese o eep fo future roects.

d e Gap e of e deeces ewee n outptsfome choe or t matter) ad amis tsfomer s hat te pay wndngof he ome neds o pass some amon oDC cure wle opeatg as a imedacetsto Tis s not true o aistsfome whee te prma is excey pe AC. a ypical ado he oputvve may ae a aode cret o aygbewee mA (say n vve e poes)

5mA o moe wich has to ass hrougte rnsormers rma widig, whoustutg he tasfomer wch woud ave

e et of rducig te icce o te

S/M : 1'Al

L_ -• -.

h€ SJl\'QN MD e V >1 'JfV E � /jC F

rma wdng e gp eeds to be largeeough o peven is hapeig uo so large ht te AC lux s a rolewit cossng he g wich woud lsote o rduce te pimy duace ece e efcecy of e as oe

A sl ai gap ical y of e oder o afo o mm i te mgnetc ccuitsolves he C stuto pbem witoutsgcaty woseng he AC peomce.

gure 3 wee Ive poogpedte gap on smal vve oput tsformer

he ga is aiclary esy o see on stasfome soeimes its o so esyto spo because it den by te gcm or wax ccmled ir.

Beare of ais raorers..You mg come acoss some liely caiatesfo op tasfoes b tey coudsiy b sal mais tasfoes. If eyook new te hey roaby e 6V or Vmns asoes (wc n temselvescn be use but some od miso63Vilamen trasformers oo sspciousy leopt tasfoes. Fgure 4 sows such a

sfoe d beg out te rgh size

weight and hvig fou termnals codeasiy be ise or an out asoe.Hopefly y such ansorer you coecross wil stil ave s akgs ita uc 6.3V laen' ransormer wl have a tunsio of bo 3:1 wch gn s i teigh bal-ark o a otut rasformer

ae goo oo fo he ai gap: you c't see i o te sele does'tkow e rovence of e trsfomer

he s pobly not woh byig.

.• t Look out for Chsow quecy coes e slly esy oiey hey have oy two es or wo

eials, sice tere s oy oe wi dig,but gai yo can look or an r gap which hey soul hve tog i t cn es behie ue pit nd te guge t uis

2

up ove e yeas May choes you comeacoss ae ex-MD compoents a heyare oten coveed i a lack tr-ie elwc makes spoig ay ai g imossbe

Agan s woh alyng he DM o mke se teres esistce o afew ndred oms wc s cl foa mas-diven power supy coe osay 41O, across te teias yorekeen on vave roects, ese cokes ofsevea Heres cace are ve useflfor smooig n owe supes so its

stil wor byig suc a comoen.

mpedance ransfrmai A fuamenal popey o a rasoe is o efe y mpece cnned acosste soy wdng bck to wteveis drvig te piay wnig. Lets sy trasforer as urs on its pimand Ns rs on s secondar ten it sa rs raio eqal o Np/s wic or noutut ransorer is usualy mc biggetan nity e imedace ato is equato te square o Ns heeore tetasfomer s a tus rio o 30 tete ipeace io s 9. and so 1Q

oad o te scoday wl be see s2 imes = ,00Q a he m.

Was he eect of vig o o hts an op crcit crss te scoay?is is defely bd news eseciay if hevolume s ted u lod wich woudroy e te irs eacto notng coulde erd i no od o te seodaryte pima crci sees a hig mpecea ts ca cause he A voge levelsto ise o hig eves at te aode of heoput valve eve to he on of damagngte valve he tsfoe ad e capacioote sraped acoss he rma widigto se te hig freqecy resose of

te ame. Tis capacito is ypicly 1 µF or smale} componet, s ofete t 1000V C to coe wit he igvoltge siens see ts cc an


3/8

Ta l : a ( soe es alle d Zou) and ou tput powr valu s for so pop lar aud io ou valves.

alelose

o

ientical

Bsequivts

6V6 A S CV510, 1 t

S

V

6

AYS

50, 7

t

6

C 286 5

O

66 2, 5

t

L

6 A8C746L15 BA

E

2 M8 ,

PL C

67

B9A

UCL82

1 SA

E

C8 6GW8, CV87 A

EL

CV89

A

U41

V

7

Lotal

6B, 65 CV069, N709 B9A

8 65 65 CV69, N709 9A

4

455

B9A

X

CV 68

4

5

V4

0 R

4

0

B

O35 5·GT C c

O2

34 CV

O 34 C93

O

30

B

DL96

P3C BG

8 1

B

19

1

B

8

CV371

B7G

8 7

BG

N7

65 65, C89, EL

9A

K6 CV 8

tal

GT

1A5 C755L1 2

P 3C4.

L B

3 DL92,V230C4 B7G

5

CV81

O

V

4

OL94 CV6 CV98 BG

6BW6

1 CV216, C4043 CV8 B A

S

6P1N14 B7G

CV233 T5 UX4

6 C55, 553 V20 Oa

GD

3

4

G D5

A

G

3B

7G

6

561 CV2

a

0A5

?

B

ot

SBS

7

sc C19

7

SL GT

SOL V53 C5 a

s a oo pit of fail i od radiosn ho at lest th mpdace rato of

te rasforer is ndpden o h aualmbr of trns o th pria and scndywidigs its jus t rao hat maers In

y his 't uit ase wether htfoer acualy ws r ot depnds ono oher transfor fdaes. I don'titnd to c trasfor thy in geat

dtil bu is woh long ito tis in somo del Hopfully his will expin why if

you nd a 1 trns rio tsfome to give you a 00:1 impedace ratio) yo ca' siplypu 10 urs o t pia and a singlet o scoda, wich s a qti ohat z os asfom vigns.

efo I aswe tis qton es takea oo a saker and vav mpdce.

What is e paks mpednce? To es hat ransorr as a godidanc a you it d o deternwa h ipdac o th saer s. ss saly staighoard ad hoefuly

Ra or t os Va (vl)O r

()5 2

4

.

0 2

4,

3

6

,

3

65

11, 4

3

.

,

50

.

2 .3

7

5

4

.2

3 1

5,0 2

5

2 1

2,5 2 53

3,5 3 45

4

6

9

4

27

10,0 .2

.2

30 2

10,0 02

10, 02

7, 2

4

9,0

0 9

2 2 57

6, 543

2 5

13 8 2

8 902

8

9

2

,

7

5

18 2

6,0

25

4

4,6 3 2

3 200

4.

1

1.

11

.

5

4 200 .

3

0

4.3

2,5 120

.3

0

9

3, 0

1

on of a e of ehods wil slt nthe answer Fs of al look on h sakitself - ay b makd! If not measre

he DC resstace o e seakrs col aft disonneng it he otpt rsfo

of e seful le-of-hub is that yo uliply his ssta masurmby .2, youll get h AC ipa I

me he resistace of a skr i myVd N43 Mruis obl at .6Q mllying by 12 giv m 31 , wicis p le o 3 I susc it is

Anohr way is to cons the akroga sice see, o th rad sh

or he adio ad his sold ll yo hspeaker's medace t shod al tel yo

h DC ssae of the ou ransorsa and coda wds pablyso a seie ma oud hk s in cseof a ssee a b sagey ad

ot annoyngy no he winding ao.See Referene or w yo an

uy a vt rage of ma and Taderseie data fro. I'm no aoated

2

Noe

Css

A sg

lnd

r

, la

A

,

pup

Ca A

i

le

Pe

i

, in

cs AB

l>-

st,

la

A ileeed

e t a A igle

e

O ect

c

a s A e.

et a A

ede.

ss A sgd

Cs A snned

Css A snged

Per par, In cass AB pus-

Css A sngend

Clss A stg·ded.

Cas A ine end.

Clas A ingl-ned yply used i bty I ans potbls.

C lss A singleed ypaly used baty I mins pbls

ss A sie-ened. T ypaly used bate mains bles

ss

A glee Typialy used

n b

te

r

main

b

C A sile-e pal u bate I mais prs.

a

s

A sigle-endd Tcal

y

sd batry I mai e

l

a

ss

A

s

-

e

d

d Tca

y

s

in

bary

I ae

las A s

Pr pa inss AB1 sh-l

ss A e-ed

ss A

s

i

gl-d

pt.au in mans as

ss A l

n . l

u

t

m

p

ss A sde. l

i

tI a tb

ss A s Ty use i bt a ps

Css A i l· ed. yply e i be y I ans sM r a r

p

nte

O

. C lss A sg-nd

Pot

ut

Aleal bam r afrMr bam wer p .

M

n

ar beam

ode.

Ba we mpl

Bap

ower m

Mia bam p aif.

i

ure b

e

am

pe

n

o

..

Peo �·

bam

wt te suier of his D- asatisfid usom and r f his daa.

What is the Vaves Impedane To make te ieda rsion

clculaion yu ll ned o kow haoe ipe ofe abbvatdto Ra or smemes ou for toupt valve driving he tfoer.

We I' looking for nfoatio on valvthe days I nd to mn on-linsous h fr s e Te Da Shtocaor (DSL see Reerene 4, d thesend s he Natiol Valv u seefeene 5 o whih DS ofn lnks so a a gh qai poogah of h valven uon an b se TDS dsplays aso o daa sh of he vav a i ofqivalns d ve f ul y, otn isto sevea sanned manufacures' oigna

daa sees or hat aiula vve.I abl 1 v ls a fw valves ofen

sd i audio otu sages alog withir a valus You se e range o


4/8

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.R\

r

I c I / DHM ON� \ Il RI =TlfL

- - I

�

PV

Vo

h6l v '&c T : '"70F b T+

F2 9, SGv! f D";J b1N ; S WfA PA U1� PT

l - ,- - - 'I

IZ-3\ ps

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E

& i.


5/8

le : Sumy of e et

Inducance Measurement

Mehod Used Amirlty chk GR Typ e T8 rns rerno. 3

Pk A U a L C R M

t

534H@1kH 7 .43H@1kz .

9H

@1

kz

070L LCR

M

er @0H 8.91H@27Hz 36@27H

Reference 8 M h (Fgure 8) 7.@ @0z 9@

Ra requey e iue 9.@7 8.S@

6

9 @6 @210H 860@57H .7 @854z

•

Trasforer Choke es

rsfoer I Ck TesePry D C eod DC Pma Iuce Prim Idtnce tl Intce

Tr io Wt (gs)ressce m rssce hm) H wh s /c m wt se sc L I

6

d

i

r l c

h

e

N ppb3

4

N

pc

Nt aN

ot i

c

b

7

5

e Typ T.85A 496 0.6 7. 59

46

7 3: 6

Tra no 1 D L9 Bty

5

9

0 93

16

4

7 0: 17

a

fm ·al t?

0

9

5

8

.

:

27

T

rsr 8 V

C

N

D

08

0.

686

77

8.

8

7:

1

8

Tf

o

6

CL82

8

5 3

9

1 5

7

38:1

280

se ·sm nt' 7 0

2

8

70

4

5

2 31 80

s

6 V sfo

r

20 08 6

6

1

26

5.

�s

Table 3: Vms als fr a series speakr idancs a t pwers. Ne:hs s t RMS vlage arss h sday wndg. h vlag arss t

ay wil gra y e a f wig ri

(h p (W) R (h p W R (h) p (W) Vr

25

.

7

8 05

1.1

1

25

14

3 5

1.22 8

5 20 15 50 7

7 1.5 8 05 245 15 7 33

1

0

1

.

7

8

2

.

1

1

0 8

7

1

22 8

5

15

1

50

7

200 25 8 2.0 40 5 20 548

0 30

8

3.0 49 5

30 71

0 8 5 .2 1 5 0 8 66

70 4

5

8

8 .0 7 .4 1 70 0 25

3 10.0 5 8 0 94 1 00 5

A, : e V idr CN431 poale DL t r. er otu fo ths set is y 7mW ads rfr v mpac and light.

he maler te uing efec i ha o Mea te a Paaeer Now we an btitte ee vale to he igna paig togh e tanfer So e ook at hw we eaur w w ad e equivale ircu gvg e icA te frqe get hge, eve a ali L. In fat wh e g re ee ow gure . wel a owg edae a a ig eatane ad a be meared ve eail b two iple raorer del th dagam ao hwteref L a te geaet efet n e meurement f he pa windg ne a C divg ore V w eow eqe epoe of e traorer made wih he enda pen it ad reitae, and a teratg reit Noetypal wha goe o beow a 00Hz te ter with he enda o itd tha e deal raoer a bee oved

ia Lw i ers wh e pa I ave a eak la CR4 mpnet ad te eminating eor vale f 365Qo te idea tanfme and we wa meter w I bgt a ew ear ag wh repee a Q load aored b e

te vale f Lw o b a mal a psible i a ve uefu ad mpat re. I quae of the tun raio o te raforero at ontibues as al an reaae easred te pia paaeers f aGR fa abt 3:1 e late or hw i

a pbe t ee patgain a Trafe pe .85 (e gre 6) whih wa deemied and at I have ade

equen ge iger eve a allh I piked p at a BVWS eetig a whe ago te dvg impedae eqa to hi aeindutane a a gh reaae ad wh e eoda op iruit ad te vaue. I ilated t uing pe eefore Lw a te geat efet n the iuited uing te CR Te eults wee: IV avaiabe f f arge b ohig en epne f e tafoe Liea Tenlg eeee 7 ad

Even a al ople eqvae it ra Iduae Reitae Seodary e del dated -3dB poin f te(ad I laf he toe model i 7.29H 96Q Open iit aoer o be a abot 4 and 2k,atego) a itelf be a iplai o 159mH 96Q S iit wh date a good al aorer.

he al word o expe te raorer s a e m abe 1, 3675Q lokeqvale make te aupio e C auoaiall dede' a itte te low ide f a tpial pentode a e iuit elee ad terfe he e bet frqe at w t make otpu age ahg a 6V6 (at k a anfme e behave inea ve a large mearee, ad or h 66 (a kQ) aen o far awa. Settg teange f vage apitde ad ha te ompnet it oe' 1k. dvg mpedane to tat f a EL1 kQ eee vaue d no hage ove ad kpig te emiaing eo vale eeqe ee o tee apio i Fr hee eaurement we an ae at 365Q) gave 3dB oint a abt

ike o be tre in real le b e del a at o th tafe: 52 and1

k wh il a anabei le eog t gve e auae epoe depite e ipedae ath.enough or mot pata prpe w = 96Q o pefl hat expla wh raforer

w = 59mH ave have ot f urn te par

= 729 windg general, te e r o e

24


6/8

pia ten e ge he rry nductceand e bee he ow f r eqency esoseOf course hvg ore tns akes eransformer bigge ad more eensiveso tere's defiitey a compomise htas to be rece wch te rnsforerdesger at GEC, ye, Ekco Plps,etc knew vey wel always workng to atigh oveal cost budge for tei set

Ote LCR Meteve recely cqre dgital CR mee,tye 4070L, bogh fom Ca va eBay tw hik s e ve reasoabe rce o£5. Maln soc DMM w cact anceand ndcnce rges bu i yo w hesealong wt voltage esistce and ctten the ee ca cost in te regon o f £50It sees to be muc ore cost eecve tobuy e C mee as a seae e.

e 4070L C eter aso auomaicalydecids' o he test ruecy: fondcance it akes te easurett 1OOHz. hee are ohe pofessoalLC mees avalabe w rces i te

0- ge bt Im not s teye go vae for money for aters.

vig a mete ike te Peak AtasC40 cooen meter mde he c osurng he ndctace and resistceof iducor vey easy yo js coec

up te iductor pess te Tes buo,wat for abou fve secods ad hee bovaues. Te C4 has te advaageht toatcaly compesaes for eccice ad iductce o ts eads,whch is seul whe esg ve smalvles Usng a moe mode C etersc s te 400L is even esier ad eidcace aswe pers editely

Old asie' ethod ofesing IductaneUe resance nd voge iductce s quty most o us don easre vey ofe,d n fac os metes igitl or alogedon ve coveet ndcce rngeswe cn switc o d yo may not possessan C meter ike te Ats C4 or te400 A od o wen ivesigtng a few ehods easrng iducce iturs ot to be a rae elsve quty tevalue of wich ss to deend o howyo mease it. In the cotext of opurnsforers t e eac vale of te pia

ndance st too mpoan as long asts easoaby igh as expan ee.

togt d t a coupe of old fsoedbck to basics, ods for measgndcace sitble for ose wo do otossess C meters. sing tese et ods,yo eed a lle mts to ge e fnlaswer bu its not too feaoe assicalLCR mees consist o bdges were tecooe beng mesed s comparedwit a own stndrd, weter ts s esistor cctor or ndco. Sice Idd't ave kow dad dco(less beiev te vaue m my woC eter, I eted tis eod

Fig 8 sows my set for a bc tobscs mesemet of dcace orte AC sore I sed te noaly 1Vwidig on a ms ransforer so Vs ws

bot 1 AC he essor Rw serwit te iductor represens is wndgsDC essace R complees te cicitcross wc te otu voge o seasured o can see ha te reactanceof te idcor i sers wit Rw fors aotet dvide i ssociion wit . he maths of hw te vaue of e iductnces cacate can be see n efeence 8bt e vaue of L i Hens s give by

q [()2 - w + ) ]L=

2 r

were: x= Vo s

he I ve be of calctos tomake I ted to mke a tae Mcosofce of he reslts nd eter te eaton ia cel tt ccl e aswes I nd hissaves ots of ie Of corse yo cn simpyuse a cacult o f yo dn ve ae xe ee T able 2 fo he ess obtned

'

"

0

°

.

«•o

�

D

.

.

.

•"

�

V

·

°

•

•

F 13: eagmet d by GEC sB445aio lo mbn t u pu sfe

nd he per upy smootg chok.

for his ehod Te reslts dot see tocorrespond wit tose obt i ed m he LCRmeters ee ater f o why his gt be so.

eauring Inuctne by esne Aoter wy to mease he prmay andte secoday for a matter) dcanceof a tasfome is o deterne s resontqeny when coec pae wita ccor Fgr e 9 sows my se up orng ts esue n adio source

od Heathkit SeSqae Wave Geeraorn my case} dives he aalleconnectedcaaco ad iducor (repeseted by aducto ad a sees essor Rw, repeseigs C essace ad he AC voltagedeveloped across he s moored by aDMM switced to ts AC votage range. Aste feecy is vaed a ot s found whhe voage acoss te paalel ed cicit st a mi. he ve o e dve essorR, sn oo crical d found wit it se o33Q he pea i voge ws quite sarp andeasy to spo on e MM. nce e onof resoance ad be fod I coneced adigital rency eter acoss he MM toesur te exac fency. Bause we adeang wit rlaively ow rences d gvaues of aale caacitance and ndcacete ipt caacy and ead dcance o

25

te DMM ad eency coe ke vele dfeence to t he resona rquecy

Tese days soe MMs are capabe ofmesg recy drcty wic woldsmpy need you o change rage o tesrmen You may ot eed to ae hisqency easureet i yore coideof te cabrao of yor ado geeraor

e vale of te idco s found

smpy fo te fora:

1 = ....

Yo ay hve otcd ht te equio abovees o enio of w te idctos Cresstance cared ot a few saos tosee how coparaivey sma vale of wafected te esonat reecy of he paeued cct and te efect w neggbehence why it is goed i he om omy recogise Rw as beng measur of the of te iducor and te mao o a

rcio n 'Q s a aeng i he ampitdepe ond te onn qcy.

he roblem of easrng iducace snow edced to easurng fequecy (wc smeasred sng a reqecy oune or w a'oden DM M) ad capcitace. Ag ylow cos modern DMMs ve cacceranges bu f yo do ot posse a DMM wtsch ages yo ca probaby smpy st emang on e caacos you se. measeda cope of new mtaised polystyrene fi capcos obtn fm he VS)nd .0 µF and 0.1 µF cpacito clymesd 06n nd 0n rectvelyso sng the rk vle sn goig to spol

e dcace easee by too mucAgn I pogrammed' is orla o

xcel b a calclto is peecly acceptbleOne eat fere of ts aproch s tt

you c coose te ency at wcyou ae measrng e iductce byseig ccor ve ta esoaest a qecy. In pctce its bt tocose several cpaco vu easree ke he resoance tests ad pot ga of iductce versus eecyto mae sre yo cover te feqecypoits o age ta yo ae neesed n.

A gai see Tble 2 for he esultsobned or tis eod.

How to Determine the s RtioWe ow t te rs to o aasfoe is key to owig s impdaceansfoo ao so pesee wh afay onyous rnsfoer how do wefnd ot wa he ts raio s? wodseem tat all we eed to do s to py own ry voltge and mease tecody voage d clclte e rtioof tese voltges I togh Id sa bytestng a own qanty i e form ofthe G Trasf orer yp T.85A enioedaove wc epuly sates o ts abel:

8 wa oupt asfoeOvea pr im ay ipance 8Qpeec coi mpance 4 - .5Rato 81


7/8

gre 0 shows he tes setp I used omease e ns ratio o s tasfore1 is a standard as rasforer

I sed a oa seconda voltageof V o y tess t someweeetwee 12V ad 30V sod OK.Do o even hnk abou onting teot tasfore diecly across teains Ts wold e vey dageous

O coe tis est set-u reslts ite asfore being tesed a 0Hwhc s poaby beow he reasonaeoeratg frequecy or hese mostlynoni-Fi trasormers ! houg Id esta cople of tasfore a 400H ws te stadad equency a wic ayseakers ipedaces ae speciied, ands aso wel witin he ad o quecesat wich te rasfoe wod eexected o wok we o see ifhere wasc diference fom te 50H vale.

Wt sale asfores he fectvetrs aio at 0 was abo 0% hgheran a 00 indicatg a drop o inpeomace of he asfore at te lowe

eency s s ecase a 0H heseoda voltage was ower fo a gvenpriay voage a at 400H, and so teste dow ratio ad heefore te eecvetrs aio loos ighe. t is heeforerecomended at i he 0H value iseasred {whh is probaby muc orecovenet a akig he easremetat 00z) yo siy add o 10 totis value to gve te tre rns atio.

he es Ress

esed a nmbe o rasfoes fowiding esistace indace ad nsraio e wee oes I kew he og

o (fo examle one ro a Vdo CN41whh uses a DL9 otp vave; one wDL92' ad aohe wit UC8' wieon tem ad oters of ow orginpced at alies etc. aso eased hedctace of a ex-Adray coke wic

was coveniety marked 'Ad Pa W66A6H 0 140Q so was a good indcaor

o wehe e dctance measeeswere givig eaonabe ress See Fge1 fo a amiy ora' of te asfoesI ested, ad a few oters he eltsof tese ests are sow able 2.

The Idctane Measemet secto of

he tae sows he esus or he Admiay

coke he G Type 8A raomerad a aoyos smal eode outpttransomer wic I had abeled o 3Ayo ca see te rests corespod retywel, exce o wa ca e Referene 8Metod so I sspect heres eiher a eroi he forula, o ore iey Ive measedo aaed soetig incorectly Tisshows e vae of akig easreentsby vaios mehods rater ta lindyaepg a sigle se o reslt hevaraon of he ndcance measreents foreah ompoe is ieresig: you cetainly

wodn epec ta spead for examlewe akig a easureen of sisace.

les remember ta tese ducaceeasmets are made a dfeencefreqenies and voage amlitdes oh

of wic ae lely o afec te resus

Te ao o tual iducace (ta s,e piay indcace eased wte seoda oe cicu o e leakageiducace (ta s e imay indcacemeased wh he secoday shotciuited) wors o retty consisetlybeween abou 35 ad :1 across alhe oupt ransoes tesed. e GRTye 8A ad he hgest vae, at aot4671 , indcag a g ualty rasfoewic I defg as oe wh hg mtualindtace and ow eaage induace bue oers didn ag beid y oo c

he easred ns ratio of 1 oe Vdor CN431 L94 nsore (seegre 2 for a poograp o hs opacransomer) o gve n pedaceransomao of aout 320 (ta s10kQ o 3 ooks core wheeas heL92 rasfore easred s ratio at90 oos n te g sde. aybe ndo e ta reslt aga. t ooks ie Ivego a good seletio o s raio wite oer ransomers Yo can see frome easremets at he as-to-6.3V

transormer oos remaraly like a otprasforer ad woud probaby wo ywel in tis role as ong as e DC curettroug he piay was e at a low vale

Fo rasfoes where I ested te nsao at 0z and 400z te vale gvenn ts ae is e average of te 0z and400 vaes hog ypcaly tey vaedy ony abou 10 i e wost cae

I've aso sow te weg ( gms)for eac ransome so yo ca ge apessio o te size of each o eAfte esting each trasomer I aaceda tie-on tag wh an identit be adte meased detais windg resstace

ndctace ad ns ratio wrtte o itso ta cod acess te omaoqy ex e I eeded a transomer.

MlTappg

adiospares (and ohes sod replaceeot asfores wih ltiaigson he rmary ad seonda windings os 3/8/ speaes and varous imayiedaces between about ad 15Q.Tese ae ve seul ad so if yo see oeits wo sappng . I probay wotmac te style and apeaace of teoigal b s qe possbe you couldide it beeah te assis and leave e

aied oigal rasfore uconectdi lace for cosetic pposes

Ps-ull Amplifes

ige ower ad ige quality apiersoen ave a par of outpt valves ausl aragee drvng he priay ofa sgle otp asfore. n ae I havesow uspl (as we as snge ended)vaes of Ra o Zou) o valves whc arecomonly used ps- ode togey no vey oe econteed in doesicadios I spose te losest you wodge o hs domestic sage wold e a good uality radogram I is tis value

o a at he otp asfoe eedsto atc o he speaer ipedace.

Pusull transomes are sually wondso ha e agnetc fx from e

cret copoents eeding te aodes ote wo vave cacel ot and tereforetey do ot oaly ave an ai gap.

ransoers fo ps-pl amlifersare si avalabe new and secod andon te intere (eBay and oher ses)dont e surpised by e igh picestey comad eseially oes whulra near tappgs o e pimay.

Power Ratng of te Tanso

Tae sows he seondary voage(exessed as an RS value or varosvaues of power delivered to te load fordiferent load imedances Cearly hsower passes ogh e transomerand so has o be apae of adlghs oe at hs sn te sae assayg tat he tasforer dssipates sower cleay doest oewise nosoud wold come o o te speaker

Tee are aayica ways of assessighe powe handig capacy o n otprasfoe wic ae ino accont

he coss seona aea of te oe tecoe maerias ec wel ae esmle agmaic aproac ta yoshoud use a elacemet rasoea leas as big as te oigial. I yoeonsruig a vave rado ew teuse te bigges tasfore you an itin cosiste wih s avng te orwdg ratio of course ness yo onlywant o drve eadphoes wc casea sal rasfoe shoud do te jo

Combned Outu ransoer

ad Smoong Choke

ne cleve way rado mafactrers saved

cos was o cobe te audio outptransfoe ad te powe spy smootingoke Fgure 3 sows he arangeenused by GEC in its C545 adio and yowll fnd tis arageme fo ay ohermafactrers I yo ca nagle herater ady drawn dagam yo an seehat he spply o he a on e imarwindg (whc epeses he op o hermay widing ro te pon of vew ofe adio ot vave) is soohed onyby C 1 a 16µF electoytic. he T reno e es o he adio asses hogh tereag of he prma winding {whchis acg as a coe) hen R15 and s

en soohed by C6. he res ofherado heefore ges a sooher HDC sppy ta te adio ot sage

e BC545 I have has a h dee soudypa o hese wooden ased adios andtees no sig of any ains hm on heado otu so he aragemet seemso wo wel The daa st o s adiosows he ressane for he whole imaywiding (a 460Q) ad does ot sow areakdow (maye he wrong word to use)for te asfore and choe secions

ookg a a me o GC table odels,tis aragemet was prety commo (ty o meas ivera as here ae may

odes whih have seaae smoogcokes ad he aings of tis asforeseems to e dfeent m mode to odeeve e same otu vave he N78


8/8

w ypil or evel ye w uedSie tee dio e ot gretly oletedd heeore not higly prced, t mghbe wort g o p up ople o to kee i e you ave amoe ued moe go wrog You tles o-exact epacemet o seeow we i woks. o plit e niosino erte p mybe idg enew omponet bene te

Conclusions

A I'm e nyoe wo bee ivoled ra� o me deig or etig wod ave o ld me ey re rer moe ompexaimas at o igilly ged ad Ive to d to g oig rathe e hI i i we rtig ti ile.Because te bevour o rasoreepens on e teaco of eerca ageti feld wit io d a across wde quey rge ere' l o mo egoig o (d potenay more o go wrog)a te nwa (ke e wou fst expec

Ee ppretly le oep u

e turn o o the wnding ed ot o be tcer o mease ta I expeceSprsngly I fon at ths rato whc had expete o be a ot mbeaes epeng o ow yo eet Obosy he actua umer o ts ofwre o the pmar a secoay stcagng bu cleary go difere reltdeedg o ow meed t rtillyo te eqeny a wch I made the est

Uig iple tes e -u, it fry eyo measure e ecve us r a5 a fo bete qlit rnfore tiw od o be ae o witi fewpece of e same measee mde t

4. Al o ug 4H loer o e te operag coons o te rasome is a moe cu eeen to mkebee yo eed a oe of AC 400Hz.Wt le rasores t he eecie turnrati a 5 was bot 10% ige t

H dting op o i peorme

o e asore a te lowe freqey

theefore ecomene tha f he 0Hlue s easure y o u mply dd o 10%to ts ae o ge the te ns rato

Wen t e o meuring the ucaceof e piy wdng of a rasomeahough ode d o o moden)ethos were eltiely ey o use or

diferen methods gae or feeanswes Ths ca be expine pal y by eac tha the measeens were ae atifee freqee, wi i uaodabebee te two LCR erig stescoose the equecy t whc teeuremet i mae osie e coto ote use d te oter two measemeswer mae at e Hz o e esonaqecy of e dtor conecte npaae wth tor Fo the nesteo £15 you now by goodqay dgial LR mete wi wl be ue oio to yor tdd DM.

Te tha ado otpt rasomes

wor a work well ot aerados a amplier tbue to theeoreca and pacicl ss o te ugengee wo deiged them l those

ye go Im ure te me wthe RF deige wo wee een teoator a the deign o oeg mple n opt troerw le o e le klled deige.

opelly ths ace w hep in ooinghe gt forme o vve ottge pec that mos oupt sagesre prett tolet o te ext pecificaion o te oupt roer d o if yo

cat mae e tess desce bove jscoose a lemet bot e samee te oigl ad gie t go!

ope e ace w lo ipie youo ietigae the popees o teseecepey simpe oog compoets alitle oe w I ti wll turn ou to bemoe cope ad irigig n expeed

Referece

Refe 1: Prci Hadbook o Vave adoRepair by Chas E Mile. bished by NewTechcal Book in 198 Conais a useful seciono !obe-shong and eparo auio fqenyamplife and outpt sages Alo is a are berof auio otu valves with teir eeical paates.

Refeee 2 Soe uful no o valve aiooupt stages. an what go wong with emcanb od a witageadioomepairo-omatoa_otp-sagesm

Refe 3 Raio seie data D-Rwseaao.

Ree 4:Tbe aa St oatoht//sl.dcaams.co/ubeserchhp

Re 5 Naol le Mu atwr-ypeor/saimusem

Refere 6 Uvsity o ennsvaa

Deamen of leccal and ystems gneerngransore L.w.seas.upenedese2lafosfoeab5pd.

eferee 7 e Tecoogys LTspiceV sofwr downoa sie wwwlinigls/sotwaresiejs

eference A ime cede foasing dcane by ilermo Rioee ht://ehnolgynerface.nsu.ed/fa9/ectoicin unhm

e a some oe fees on vave audioapier sfoe mahig, loudspan mearing nta I yo a themaga o bks menoned ay be

wo diggig em ou ad aking a loo

Raio l ad ransfoer Maa' by 'Raiocian.ulse y Bears bishes) Ld, 1944

Coil Dsg an Conso y aanVaos editios pbise by Bead aaniL Incus chapters o Ou sfoesfo ge Vave; Ar ap etenao s-pltut an Lodspeak ransormes; and otersOverll I fod e boo to be e efl than expec u t' robably stll worh e £6 ors yo sol expc top scond and.

oosing an pt ansoe by iown aio Consrctor eptebe

9 A ef, bt usful, ae eing ebsi ofopt ansfome oation

Fidig ansfomer Connecions by GRaye cta Wir Agst 1956 ov

27

mnly tansfoers, bu aso sggessse ehnqes o op ansomes

·A asorme or a Single-n Oput aey P Fsh. Paccal Wie eay 195.scusses n detail e design an onsrn ofan out trnsfoer an is a useful suce o eules gorng the magnec popert of the oe

A R ndge by J illma. PactWir anar 1 958 Shows te design andnsructon of a valvased CR bidge,ncudng a magic eye bala idiato

'odseaer Macing byKRlat Wi ana 99. Diussesmpedane tansoation and esgtus io an als dig mutpeodspars sei an lel

'An Ica Measug Insmen y D SalIacta Wiess h 90 Desbes a simlemod omsrig iduance wic allows aD bi o be appied o e inuctor ude est

'Adio ansfoe Dsg y D al rcticalWies ly 1960 Coes te dsgno tansfoerfo mainy lass 'P asiso opu staes t

some iomao eevn o valve otp stag.

'elecing up nse by J ayta Wiree oveber 1 960 Disussespedane mahg ad allatig he turns raton singleene an pushpl ot stag

Aou Lodseakes by PJ Gd PractialWie ctobe 1961 oes some of he ingstha go wng wit loudspers an tets ac be peroed o oupt asfoes

ow o Measre danc by S Jacb PcialWieess Dember 196 Show a simple meh ofmesuing e Inductace of AF an RF ndo

'e es y R D Owen. acal WiessAgst 966 sbes a omrehensive analoguemete an LCR bidge aabemeasuingndcae u t o 000H a z o Hz.

'desandg Rad Pae ad PushPulOpu Vlv by W G Moey. Raio Consrcoly 1967 Cotains a sef disuio otanme argaps ad lamnaios

ild Your Ow Audio Vave Amlfies by Rainer rnde. Plshed by Eeo lecocs (lsing199. on many usefl hapes o vleado amlie bt ssingly ite nfoaion othe esig ad oce o e ou tasfoe

le ad so Adio mlfies b y John

Lsley Hoo blis by ewnes of Ofo,1997 Cnas may sefl hates oal andrasisor adio amplifies ldg disssionson te desn and et o overall formco te otut tansfoe i al apier

Ohe socs valve dataRado Va an anso aa A Mall Vaious ediions Pbished by Ilfe.

All a ea' editios o e ARR andboo aa useful ave eerene data scion at e a

ee aemneiions of the Mulad enialandboo un wic cotain seful ve ata

Selecting a Valve Audio Output Transformer

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