VTL ST-15 User manual

Makinqmbes
vLserjrienb[y
HANOCRAFTEO IN THE USA
\TTL
ST-150StereoPower
Amplifuer

f:able of Gontents
CHAPTER I
Water
and
fufoisture...
Location
and Venti
lati
ort
I
I
I
Sen,icing
Operarionot
wonni:ng;. ...... . ...
CHAPTER
2
Gprrnc Srnnrrp ...........3
Unpacking
theST-150
from its
box. ......
3
The
S'f-150
Front
Panel ....--.---4
Check
for tube
placement ....'..........-.-.4
ST-150Back
Panel.... .....-.....
J
Connecting
YourAmplif
erto
yoursvstem... .........-.-.
5
VoltageSetting ..-...6
Power
Source
for -your
Atnplrfier .........-
6
CHAPTER 3
OpsnnrrNc
rr-rEAvpltptpR
Powering
your s.ystenr
on....
GroundLoop
Hutrr..
Powering
the
system
off......... .-.....8
Bias
Checking
andSetting.... .......8
Top
viewand
Bias
Measurenent
points
oftheST-150
Amplifier.. ...-.....
.l0
2
3
7
-
7
7
Cnnp AND
MAINTENANCE
ot'-YouR
WL AupLIFIER.....
Bnrex INPpntoo
Power-on
Period.
TubeType.t......
TubeLife
Ohanging
Tubes..
Changing
theAC andB+ Iiuses
Cleaning.
il
u
il
t1
I1
n
t2
t3
I3
I4
15
t5
ST-{50 Owney's Manual
VTL

CHAPTER 6......... .-...
16
WannaNrY...... ......
16
APPENDD(.......... ...-..l7
WarrantyRegistratiot't
....... ...17
Sen,iceltlotes. ......
I7
ST-150 Owney's Manual
VTL tl

CHAPTER 1
lntroduction
Corryratuhtions
onlourpurchase
of
the
VTL ST-150
Stereo
Power.4nrplifer.
wrth the
he ST-150 StereoAmplifier, a 150 watts per charurel
amplifier, is designedto deliver a-n
involving and
tnre-to-live listerringexperienceto yoLr. Prope
r care and maintenance of the ST-7
50 u,'ill assureits
la-sti1g
value zurd
.na-*i*um perforrnance. Plea-setake a moment to read through dris owrlels manr'ral
arrdplease take time to get familiar with the features of tlls producg so that you can become fanitar
opeiatilg a1d maint.,',rl.. procedures needed for the ST-150. After yotr have ftiished reading dus
Ulltrerand Moisfuirc
T5e amplifier
should
not betrsed
close
to any
water
or rnoishrresources.
If liquidenters
theamplifier
it must
be immediately
urpluggedand retumedto your dealer
for servicing.
If this occursyou shouldturderno
circtrmstalces
trytopo*.. the
turit
onbefore
the
tuit has
beenpropedy
serviced
by atrained
repair
technicia-n
- tlrere
arcltaz.a1dotrs
voltages
preserlt
in thisurit that
czurcause
se
dotrsuriury
if they come
in corltact
with you.
ST-150 Owner's Manual
VTL
mantralplcase
keep
it in asafeplace
for ftrhrre
referetrce'
T6e VTL team
isprotrdthat
youhave
selected
theST-150
poweramphfienasarlewmemberof your home
atrdioa'd horle il-rcater
system. We sincerely
hope drat tl're
VTL ST-150will contribr,rte
torvards
yotrr
enjoy'r-nent
oFmtrsic
md give
yoLl
mally
hotrnoflisteningpleasure.
SlrmbolGornrentions
used inthis guide
Certan $.'rnbols
are
trsed
For yotrrowrr safety
and
s).'rntlols.
The'Van*tg - Paypartictrlar
Attentiotr"
synbolused
is
and
the'lWanring
- Observe
T'hese
Precautions
For YottrSafety''
is
Elec{rbal SaffiVNotbe
Electrical voltage Frompower cables
is hazardotn. We recolrunelld drat
be usedwrth apropedy groturded
otrdet.
To prevent electdcal
shock do
arnplifier, especially
v4rilethe turit ispowcred on.
urtlusowler's manualto drawyour attenrion
to intportant
pourts
beurg
discussed.
thatof your equipment
you should
noteandheed
drewanrings
drat Followdlese
CAUTION
RISKOFELECTRIC
SHOCK
drepower cord comected to dris uiit
not remove ally oF dre covers of th,rs
CAUTION
RISKOF ELECMC SHOCK
CALJTION
RISKOF ETECMIC SHOCK

Locatbn and Ventilation
llstall this amphfier in a locadon wluch is stable and rvell vendiated. if dre amplifier is placed in a
built-i1 ilstallation, erlsure that there is adeqtrate room for a strpply of air to flow drrotrgh the
ventilation operrings. Allow at least 9 inches clearanceon dre top atd arolurd dle sides of the
amplifie
r. Besure thearnplifier
isatleast
10urchesaway
From
yourpreamplifier
topreverlt
possible
noiseintroductior-r
Lrto yorlr system. Tiptoesor other isolation
accessodes
may prove trsefi.rl
in reducing
mechaical vibrations. Do not place amplifiers directly on high pile carpets as this will block the
ventilation vents.Do notplacethe
amplifier
nexttoheat
sources
such
as
radiators,stoves
or otherappliances.
Do not placeampllfier
on thefloor u,4rere
small
children
cantamper
wrdrtheequipment.If it isnot possible
toplace
amplifierout oFthereach
of srnall
children
it isrecommended
dratyouremovepower
cableswhendre
equipmentisnot in use.
Selbltg
Do not attempt
to servicetheamplifier
beyond
the
procedtrres
described
urdris manual.For allotherservice
andquestions,
plea-se
contactyotrr
atrthorized
VTL dealer
or thefactory.
Operational VUamtEF
- Do not touch ttre tubes afterthe arnplifieris turned on. Tubescanget
ve
ryhotwhiletheampLfiers
are
operating.
Tunr offthe amplifier and
allowdre
tubes
tocooldowr before
attempdtg
toworku,iththetubes.
- Do not attempt to disassemble the amplifisl ghassisor rernove any covers from fttg amplifier.
Always constrltwith y'our VTL authorizeddealer
or the VTL factory support departmentbeFore
attempting
artyservice
workortatly
VTL ruilt.
t Always corurectyotrr lotrdspeakerto the amplifier beforeporvedng dreurilt on. Operahng ary VTL power
amplifiers u,ithout a speakerload cornected can damagedre ouptrt transfonner, artdu,'ill
not be covered
turder the warranty. Also, ensrlredrat no spealier
cablescar becomeloosedumrguse artd that there are tlo
interrnittent farrlts wrth the cables.
- Tube amph6erscanbeheavy
andarvlsvard
to tift,widr dre
rveighturevenly
drstnbuted,andyou should
rlot attemptto move theurit widrouthelp.
Eachuit of theST-150Stereo
weighsapproximately
58 lbs
(%.4Ks)
Do notattempttomakeor breakarly
corxlections
to dreamphfier
w4rile
theturit
isporvered or1asdris
can
damagetheamplifier utdfor therestof the
system,anddls damage
isnot cove red
bywarranty.
If dris tuiltl'ra-stetrode/triode
su,itcl-r,
donot flrpdretriode
tetrodesu'itches
whiledreturitispowered
on,
a-sthis
candamagedreswitch
and
isnot covered turder
warraltty.
- Do not exceed
frrseratings
or attemptto bypa-ss
arly6lses,
a^sthisctutcaLrsearl extrentely
hazardotrs
conditiona-nd
will void anywarrantees.Llse
only dresanlet)?e and rating
of frrsesasspecified
ur thc
owrersmantralzurd
marked
on theturit.
CAUTION
R6( O. Et€Cm(]y<fci
CAUTION
R6KOFELECU?|C
SUCC(
A
A
ffi#,H.Lt?Si
ST-1 50 Ownsy's Manual
VTL

GHAPTER 2
GetfngStatted
Unpacklrg fte ST-150
from its bot(
The ST-150 Stereos
are
shipped
in cartons
andwrapped
in thickplastic.The plastic
is not strong
erroughto
sgpport the turit,and may tearif you try to lift the turit out o[the box with it. Also thereareprotnrding
swiiches
which could breakif the tuilt is not propedy handled,and in addition to the awkward,turbalanced
hear,ry
load theurit hasacleaning
polishon it which makes
it slippery andhard to grasp.
We havefound that
thebest
wayto rernovetheamplifierfrom thebox isas
Follows:
1. Wth theboxon athickcarpeted
floor,foldbackalltheflaps
of thetopof thecarton,
leaving
all
the
packing
foam
inplace.
Rollthe
carton
orltoone
longside on topofdre flap.
2. Roll thebox once
moreonto theopentop artd,
makiltgsurethatnotre
of the flaps
is trapped
underthe
carton.
hftthe
carton
off the
tuilt.
3. UFt the top foam awayfrom tl're
trpside
dowrrurit and careftrlly
ctrt awaythe plasticfrom
aroturd
dreampl-i6er.
4. Uft theamplifier
up a:rd
away
from thepackagurg
eidrerby holdingonto themetal
ha.ndleson
thefrontof the
ruritor by rolling
the
turitonto ashortside
anddren
againsodrat
it landson it.s
Fotrrnrbberfeet.
ThenIift av,tay
thepackaging
andsetalldrepackaging
in drecarton.
5. Whenliftingthe
turitbesure
to onlyhft it from drebotom turderthetransfonners.
Be careful
not to break
any
suritches.
Besuretoonlysettheamplifier
dor.rnr
on itsbottom side
on the four
nrbber
feetona
stable
strrface.
Setturg
it onanyother side
maydamage
protnrdirlg
components.
If theturitis too hear,ryor too awkward
to hft then
do not attempt
to do tlnsby younelF,
but radrer
furd someotre
to help you. Save
the carton zurdall packagurg
for any fi.rtureshipmentof the
arnpli6en.
ST-150 Owney's Manual
VTL

The ST-{5O Frcrrt Panel
The ST-{5O Front Panel showing the Power on switch and the power on LED indicator.
Gheckbrtube placement
Usethe followilg procedures
to check
rvhether
thenrbes
standing
on dredeckof yotrrarnplifier
areplaced
6ontyurtheirsockets,
as
thenrbes
can
become
dislodged
a-r'rd
loosendtrnng
shipping
o[ dre
amplifier.
Vsuallyinspectthrough
theventholesto ensurethatall
nrbes
are
fullyscated
before
porveringdre
urit ou for
the 6rsttime.If thereareanynrbes
not ftrllyseated
then
youshould
refer
to your VTL dealer,andtakedris
procedtrre
widrdreamplifier.
Notes for the serwicing technician:
1. Removetheprotective
urire
cageon thetop deckof theamplifier. The cage
ismourted wrth
three
screws
on eachside
of thearnplifier.hosen thescrervs
ald hft dre
u,'irecage
slowly
and
carefully.
Do not let thecage
touch
or hit any
of drenrbes
nsidedreampl-i6er.
K..p drecage
zurdthescrews
in aseparate place
u,4lleyou're
working
on theamplifier.
2. Make
surethat
the
an-rplifier
isnotcorurected
to the
powerotrdet
zutd
not tr.tntedotr. Use
your
fttgersto hold onto theupper
portionof theftrbe
towards
itstrp. Gendyrockdresideof the
hrbeto see
if tl'rere
isalty movement
Lrthetube. If drere
iszuty
movemellg dtat
meatrs
die tube
ha^scome
loose.Pressthetube
6nnlyinto itssockeg
trsing
agentle
forceandaslght "rocking"
motion.
3. Repeat theabove
testfor tl're
restof thenrbes.
Thereare atotalof eightotlptrt hrbes
andfotrr
inptrt
tubes
in each amplifier.
ST-{50 Owncr's Manual
VTL 4
POWER
ON LED POWER
SWITCH_

4. After yotr've
examined
all
thenrbes
to make
sttre
drat
d"reyare
6"tly placed
in theirsockets,yott
canput the
protecdve
cage
back
onto dre
ampiifier
turit. Tighten
thescrews
to makesuredrat
thecage
issecurely
fasterled
to dleturit.
ST-{5O Back Panel
The ST-150
Back
PanelSilkscreen
Connec*ittg YorrrAnplifier b pur system
The ST-150 .amplifier
is a selfl-conurined
unit with the amplifier and power supply sectrons
or1one
compact chassis.
Follow the instructions
below to coffrect dre amplifier to your audio or home theater
system:
1. Gonnect atl source components (e.g. GD, Tuner, Tape, DAT, Turntable etc.) to the preamplilier.
Follow the instnrctions on yorlr preampliEer and source component mantrals to connect drese
components togedrer.
2. Connect the power amplifier to the output channel of the preamptifier. The htercolxlect cable
behveen the amplifier and dre preamplifie
r lhks dre inprrt chamrelof dre power ampliEer to dre otrtptrt
ST-150 Owney'g Manual
VTL
oo lu
a) $/ffrxc B+ FUSE
Io effid Frbk rwftr ( l
d.B & nd .b9.600 \ ,i
rhbftti.r b rcdd- 1A
S{O &O
8:!g:€ wrRuc r@
/ \ To p.d 9..rlbL lrF.lo.u a\
\ i d.$l..d.iw do ol pr \-/
\e' qb.lmffita{@|tdloil. [rc
rA sfo-alo
tt
xe FUSE
sffa
RIGHT
CHANNEL
rPUT
OEA
t115
vAC)q nl) cl StO 6LO
0)
fo pdad dedc shoc* do trol ndova covca.
l|o c.r sMc.abL parti Insld.. Rafar a.rvlclng
to qualifpd pedonnel. Fd cdtinucd Pobction
tgtict fire h!4rd .ephce only with fr&6 of sm€
lyp€ lnd rtti.g. fo prevent lire or 6h€k do noi
arposc thi5 .pplimcc to.aln d moallul.'
r---]
ol lo
[) ooo
8"f(ER
LEFTCHANNEL
XPUI UanuLctwed btr
V*M Tub. Loglc A
ata ltirictta Srr6t. U,
Sult 10,
Chlno, Cl
91710,
usA (g{re)
62?-s941

3.
4.
charurel
of thepreamplifier.
Comrect
theI-eft Chamrel
RCA Jackfrom the Stereoamplifier
to dreleft
otrput charureloFthe
preamphfier.
Tl-resarne
applies
todre
nghtcharurelamplifier.
Select the input connector type.The ampliEer
supports
onlyotletypeof input colxlector
- theRCA
inpgt.Place
theinterconnectcable
6or.ly
into dre
inputjack w4rich
matches
dre
rype
youhave,and6nnly
insert
the
intercotuectcable
intodte
inputiack
marked"INPUT".
Gonnectthe loudspeaker
cableto youramplifier. There
isapairof spealier
butding
Postsin theback
of youramplifier
Forcomecting
your
loudspeaker
cables
to d-re
amplifier.
These
bindngpostsare
marked
"*" artd
"-" above
theposts
and"SPEAI(ER" in between
dre
pos$. For example,
if youareconnecting
theStereo
ampliEerto theleft charurel
speaker,
youshouldtake
theqpeaker
cablecomected
to theleft
speakerand coruect it to dreamplifieCs
"I-EFT CFIANNEL SPEAKER" bindingposts. Fint, loosetr
thebinding
postson theamplifier.Taketheredcorurector
from theqpeakercableandcomect it to the
"SPEAKER" bindingpostmarked
"*". Takedre
blackcorxtector
from the
speaker
cableand
cotmect
it
to the "SPEAKER" bindirg post marked"-". Tightenthe bindrng
postsby hand usinga nut-driver
Q/B') Be carefi.rl
not to over-tighten
the
posts,a-s
youmaybrealithecotlrection
inside
theamplifier
if
yotrexerttoomuch force
on the
posts.
Voltage SettfE
Yotrrpoweramphfier
has
been
set
bydre
factory
to dre
correct
voltage
foryotrr cotntry whe
re
youmadeyotrr
purchase.The voltagesetting
shotrldbemarkedon dreSerial
Number Badgelocated on drebackpanelof
your amplifier. Checkto makestrrethatthiscompLes
widryourlocalvoltage
rating
before
pluggurg
in and
tunil-ng
on yorlr
amplifier.
Your amplifier is shippedwith zr.power cord which matchesdre requiremetrts
of your coultry. IFyou
needa replacementalrd you arenot sure
what the appropriate
cord should be,coruult your audrorized
VTL dealeror the VTL factory customer suPpottdepartment.
PourerSource fur pur Amplifier
Your ST-/
50Stereo power amplifier
is ahigh-perfonnarce,
llgh poweramplfier capableo[ouptrtting up to
150
wats percharlrel. To assure
thatyoucan
operateyoLrr
powerampLfierturderthebest
conditions
for the
optimalresults, yotr
shouldpltrgdreturitdirecdy
into awall
AC oudet,preferably oneseparate
outletfor each
urit. Do not pltrgyotrramplifier
into al.ight extension
cordor into dreback
of artothercomponent.This wrll
starve
theamphfieroFcurrent
andsigrificantly
impacttheperfonna:rce
of yours)6tem.
See
thecl'rapteron Speciftcationsfor drepower
corlstuttptrorl
reqLuremetrts
of yotrr amplifier.
ST-150 Owncy'g Manual
VTL

CHAPTER 3
Ofrating tfreAmPlifier
Povrcring ltqrr system on
After you have properly corurected your loudlpealiers to your power amplifiers and all your source
componelts and thepower amphfiers to the preamplifier you ate rcadyto power your system otl'
l. If you haven'r al,ready
done so, vrsually @y looking through the cagevent holes) ensure that all dre tubes
i'side the VTL ^.,-,p-li6.r
are properly seatedall the way i-nto their sockets. Make sure that the power
ampli6er is lot powered on atthis stage
by either discomecting it from the AC source or tuol the power
o1 sw,itch
on the front panel of the ampliEer to dre"of?' or "0" position.
Z. Porver on the sorlrcecompoltent(s) you ilrtcnd to tlsefor yotrr llstening sessiotr
3. porver op yorlr preamplifier. Make strre that your prealrlplifier is either in the mute state or ttrnr its
voltrme knob to the zero position-
4. Uslrg the power cord w,hichcomes with yotrr amplifier, coruect the one end oF the power cord to dle
..AC PC)WER" corurectoron the bottom argle oF
the back of the ampL6er. C-onnect
the odler end of dre
power cord to an electrical
or.rtlet
directlyLrto awall socket.
5. T..nr o1 the power a-rnplifier
in yotrr system.
The power-on su'itch is located on the right hand comer of
the amph6eris front panel. When the turit is powered off, the su'itch poutts ur the "0" position. Clickng
t6e su,itcho,r.. n,o6 on the turit and the su,,itch
is i-n the "L". 'l'he
re is apower-otl LED to the left of dre
Frolt pa1el. The LED hght should be on when the systemispropedy powered on.
-Gaution: when you turn on your amplifier for the firct time, watch the tubes while they warm up and
observe if any of them goes into an exceptionally bright red glow on the plate of any of the tubes' Turn
the system off immediately and refer to your authorized VTL dealer or the VTL factory service dept. if
this happens. This glow may indicate a defective tube which needs to be replaced.
-Gaution: lf powering on the system using the above steps results in tripping a circuit breaker in your
house, or blowing a fuse on the amplilter, then turn oft the power amplifier and the rest of the system
immediately. Find the fuse box and turn the circuit on again to restore power to your house. Gontact
your VTL authorized dealer or the VTL factory customer support department immediately so that they
can help you resolve this Problem.
Grotrnd Loop Hum
If yo' getagrorurd
loopl'nrm
from yourstereo
system
after
insvrllation
ald tLrnt
otl you shotrld
immedrately
n,nr ofi thealrplifiers
andconsr.rlt
yourVTL dealer
or theVTL factory.Unde
r trocirctrmstallces
shotrld
yotr
attempt to lift or defeat
arlygrorurds
on electrical
eqtripment
pltrged into dre AC, as tl-rese
groturdsare
ilstalled for your and the equipment's
safety,
ald an turgtoturded
componellt call presentan extremely
ST-l 50 Owney's Manual
WL 7

hazardous condition and is ill.gul turder most electdcal safety codes. For yotrr own safety please refer all
qtrestionsof this tlahlre to apropedy traired service
tecllrician.
Pourefttg fie sysbm oilf
1. When you'redonelisteningto your system
always
tunr dreamphEer
off 6rst.Iocate the "Power On"
switch
on the
lowerrighthzutdsideof the
frontpanelof the
ampliEer.
Ttrm d-re su,itchto the"0" positiou.
Theamplifier should
nowbe
inpowered-off state,
and
dre
"Power-otr
LED" clnthe
leftoFthefront parel
should
beextingtrished.
2. Wait at least20 secondsaftertheampliEer
ispowered down before
youproceed
to tunr off the other
components
in yoursystem
3. Tunr thepreamplifier
and
sourcecomponents
off,if yotr
prefertokeep dreseoFf
whetl
lrotinuse.
BiasCnec*lg andSettiq
Tlre idle (or qtriescent)draw for theoutput nrbes
has
been
factorypreset
for approxrmately
27 mA For each
ttrbe,
andshorrld
bere-set uponLntiali-nstalladon
into yotrr system.
Thisserdngshotrld onlybeperfonnedby
someorle
trained
in thisprocedure,
as
it reqtrires
removalof oneof dle covers
wllch u,illexposepotentially
hazardousvoltagesrvhichare
present
in theturit.
Do not attempt
to turdertake
dls procedure
yourself
asyotl
cotrldbeinjtrred.The idlecurrent
of dre
nrbes
rvillflr,rctuateslighdy
overtime^t ^ rate
whichisdependent
orr
tl-retrsageo[ the
rurit. We recorrunenddrat
dre
biassetting
shotrldbechecked
on allthetubes
after
every1000 hotrrs of listening
(or onceper year) Using your amplilter with incorect bias
seftings will result in poorperformance
andashortenedlife time for the tubes.
There
isafi,rse
on thebackpanelofdre amplifier
w*uch
u,illprotect
dre
rest
of dre
circtritry
in dre eventdrat
a
nrbe
drawsexcessive
ctlrrerlt.
If dre
fi.rse
blorvs
dren
youshould
immediately
nrnt theamplifier
off and
contact
yotrratrthorized
VTL dealeror theVTL factorycustomer
support
departrnerrt
beforeattempting
to hrnr the
amplifierbackon again.
The synptom for dris
fuseblowing
iseitheraconditionwhere
alldrenrbes
appear
to
belit bgt u,ith
no sorurdcoming out of theampliEer,
or atearing
sotutdcoming
from yourspeaker
if drefi.rse
blowsn'hiletheamplifier
isplayurg
music.This sourd will not damage
yotrr
lotrdspeakersasthe amphfier
is
losing
power while the fi.rse
is blou.i-ng andits levelis not changedby drevoltrmecontrolpositionof d're
preamplifier.
-Gaution: Bias checking and setting on all tubes must be performed every time a tube is
replaced in an amplifier.
For checkirg dre bias you should take the urit and dris procedure to your authonzed VTL
dealerard askd-remto checkthebias
for you.
Notes for the service technician:
Bias measrlremerlts are preferably talien with a digtnl multimeter eqtripped with the atrto-ranging feature. If
you don't have such a meter you carr
purchaseone at alocal electrcnicssupply store strchasRadio Shack. The
Radio Shackcatalog
ntrmbersfor trsable
n'rultimetcrsare:
22-166,22-1,67,22-163,22-174or evetl
22-179.
ST-150 Owney's Manual
VTL

LJse
tl-re
followingprocedures
tomeasure
andadiust
thebiassetting
MaliesurethattheampliEer
ispoweredoff. Removedleprotective
metalcageof dreamplifier,
and maliesurethat there
is sufficient
room aroutd dre amplifierfor you to accessthe bias
mea^suremelrt
poLltsgoingacross
dre front oI dreamplifier.
Setdremtrltimeterfor resistal'Ice
measurement
(ohms). (C.orrsultdreounrer's
manualof dre
multjmeterto makestrredratyou
have
trsed
thecorrect
settings.)
Comtect
the
negadve
@laclq
"-') probefromdre
mtrltimeterto dregrourd poir-rt
on thedeck.
Consultthefollowurg
figtrre
for dre
locations
r>f
drebias
measuremelltpoinrson dreamplifier's
top deck.Insertthepositive
(red,
"*') probeof dremuldmeter
irtto each
biasmeasurement
poirrt. The resistance
readingon eachpoint shouldbe 10ohms,wifiin a l}oh range. If dre
resistance
reading
is outsidethe acceptable
range,
please
consultthe VTL factorycustomer
service
deparunent
immediately.
Repeatdre
measurementprocedtrre
for all4 bias
meastlrement
points.
Removethe mtrltimeter
probes
from dreampL6er.Cl-reck
to makesuredrat dre amplifieris
corurected
to aloudspeaker
or aloadresistor.Eidrershortdre
input or put thepreamplifier
irr
the mtrte state(or .tunr dre voltrme down) to make sure dtat no sigral is corning from the
preamplifier. Poweron dreamplifier
andlet it wann up for about10-15
mintttesso that dre
tubesbecome
stabilized.
Change
themetersetung
to measure
DC voltage. Itrsertdrenegativeprobe (black)
from the
multimeter
into thenegativespeaker
bindirtg
postof theamplifie
r fittingit into d're
postwhere
thespeaker
cable
is comrected.
Insertdrepositive probeinto drebias
measurementpornt of
eaclrttrbe
goiugfrom dre#1 pourtto #4. The reading
or1dre
mtrltjmetershouldstabilize
a:ftera
secorrd
or two and
indicatea reading
between
275to 300milhvols DC (0.275to 0.300
Vols.)
Tlris readutg
mayfluctuatealitdedtreto variations
in dreAC hres.It is not turusttalfor a 12OY
rated
AC line
tovarvbetween
115Vmd 122Y
.
.- Gaution: lf the voltage reading is 50 millivolts or more below or above the acceptable
range then adjust the trimpot in the direction required and ensure that the reading ls
changing.lf the reading
doesnot respondor continuesto climb rapidlyr
or fluctuates with
large swings back and forth then you should turn off the amplifter immediately and
contact the VTLfactory service department for assistance.
Irr gerreral a 70 - 15o/ovanation arourd
measrlrement. \Mren dte measttrement is
sening by using the followingprocedtrres:
$e 275-300 mrlhvolts rzurge is an acceptable bia-s
otrtside dris range, you urill need to aditrst the bia-s
1.
2.
3.
4.
5.
6.
7.
1. Ift.p thepositive
probe
found dre out of range
corresponds
to the bias
r1-reasrlrement
poin
Ls.
from drernillimeterin the saITIe
measuremerltpoint whereyotr
bias readurg.l-ocatethe biasadjusbnent
polrt whosenumber
mea-srlrementpoint. See
Figtrrebelow Forthe localionsof the
2. Insert aIf B" flat
upped
screwddver
(wifi aplashcshaftor apropedy
insulated
handle)
urto
the bia-sadiustrnent
trinrpot which correspondsto the out of rartge
measurelneltt
point.
Rotate
thescrervdriver
slowlyto seedrecha-ngeson dtemtrldmeter
reading.Try rotating
ST-1 50 Owney's Manual
VTL

the screw ur both directions to see
the effect of the change. Adiust dre settirg of dre bia-sto
tlre
proper rarlge,
i.e.275 to 300milLvoltsDC.
3. After you've cornpleted the bia-s
adjustment cha-nges,
it is agpod idea to go back and check
the bias measuremens for all the other tubes sincechanges
made to one nrbe will slightly
affect dre settingof dreothers.
4. Place the amplifiels protective cage fi"tly back onto the amphfier after yotr are satisfied
that dre measrlrementsarestable.
-Gaution: lf your obsenrations do not conform to the above instructionsr or if you do not feel confident
about performing the bias procedures yourcelf, please consult with the VTL factory service
department. lmproper sefting of the bias will affect the curent draw of the output tubes and affect
the performance and lifetime of the tubes.
Top view and Bias Measurement p<lints of the ST'{5O Amdifier
A44
I Meosuremenll I Meostrremenll lMeosulemonll
I toint *Z I I Polnl
#3 | I Poinl
,d I
44^
I MeosuremenllI
Meosuremenll I Meosuremenll
I poinr rs I I Polnr #6 | | Polnt t7 |
10
ST-150 Owney'g Manual
VTL

CHAPTER 4
Garc and Maintenatrce of yottr VTL
Amplifier
Bleak ln Period
Your VTL amplifier
isaptrre nrbeprodtrct
desigred
togiveyoudrecontintred
optimtrmperfonnallce
overa
longtimeperiod. Even drotrgh
dreamplifier
has
wrdergone
abunr-inrycle
in theVTL factor|,dretubesand
circuits
will reqtrire
fi.rrther
usage
andbunr-into reachmaxirnr.rmperforrna,nce.
Dudng dre6nt L00horrrs
of
usagedreamplifieluvill
undergo
noticeable
in-rprovementsin soturd.
Fovrrercn Period
We recommendthatyour amplifier
shotrldbepowered-off
whenyou aredonewith yotrr listeni-rtg
session.
l-eaving
yotrramplifiers
nulrirg idlewl'ren youare
not listening
to nrusic
u'ill beawa^steoF
electdcitya^s
wellas
ruxrecessary
usageof dretube
life.
Tube Tlpes
Tlre\TL ST-150 Stereo'amplifier
usesa totaleight6550Crubes
for dreoutput stapp
andtwo I2Nn
a-nd
nvo6350ubesforthe
urput
anddriver
stages.
Tube Lib
Yotrr VTL amplifier
l-ras
been
desigredto ensure
longnrbe
life. Ttrbereplacement
neednot be considered
turtilafterapproximately
3000
houn of trse
(rouglily
3 to 4 years
dependingon your listening
reqtrirements.)
As tl'retubes agebeyond
theirpeakperfonrrance
dreybeginto lose theirabrlity
to provide frrllpower.This
usually
re
sults
in some
loss
of control
in drebass andageneralsofteningoFthe
sourd in theupper
frequencies.
W'e
recornmend
a cornplete
replacementof all hrbes
in your amplifier
at drattime,which will restore
it to a
'1ike
nev/'sourd qtuliry. Your VTL deale
ror VTL factory
service
deparunentwillbehappy
to a-ssistyotr
with
dre
re-nrblrgpnrcess.
Note: use only tube tyrpes
and tube brands that are re{commendedby VTL. VTL specifted 7\
replacementtube-sare availabte
fromyourauthorizedVTLdeater
or the VTLfactory service ,/ f \
department. Any damageincurredto units which use non-VTL
approvedtubes will not be Z-S.
ST-150 Ownertg Manual
VTL 11

covered under the warrantyt.
GhangingTub
Do not attemptto changenrbesyounelf.C,ontactyour authonzed
VTL dealeror dreVTL factory
service
deparunent
sothat thisservicecanbeperfouned by atrainedtecllrician.
You will need
to take
theurit and
this procedureto yotrr dealer
Forthen'rto perFonn drisprocedurea-ndthe correspondingbiasprocedtrre
propedy.
Notes to the Seryice technician:
Besure
toonlytotrchthenrbesthemselves,and
donotallowuty partof yourbodyor hangurg
jewelry
to come
into contactwidr any
partoFdre circuit
inside
theurit.
1. Diagnosethe tubes: If youare
not urdergoingacomplete
renrbefor theentireamplifier,dren
you mtrst 6rst decide
horv many tubesand rvhichnrbesshotrld
be chalged. Use the bias
checking
procedureasdoctrmented
in dteCettirtg StanedsectionoFdls ma,nual to ftrd out horv
to mea-strre
thebia-ssetdngofdrenrbes
andto detennine
u,'hedrer
d'reyarewitirindreacceptable
range. For example if yotr find olrt from the bias
measurernens
that nrbe#1 utd #3 are
fltrctuating
freqtrently
anddrey
areaboveor below
dre
acceptaLrle
range
this
mayindicate
that a
replacement
of dresetwo tubes
isnecessary.A fi.ilIpov/ertest
of the amplifier
mayneed
to be
turdertalien
to ensrlrethatall
power
nrbesare
condtrctingequally.
2. Poweroff the amplilien To cl"rangenrbes
urdrisamplifieryoushould
6rst
powerdrerurit
dorvn,
unplug dreturit from drewall oudetanddiscorurecttheamplifier
from therest
of yoursystem.
kt theamplifierstaypower-offfor atleast15minutesbefore youstartworkirg with it. Malie
strre
thenrbesarecoolbefore
1'ou
touchthem. Usinga Philips
#2 point screw driverremove
dreprotectivecage
Frorn
theuut by looserilng
dretwo screws
from thesideof drearnplifier.
Carefrrlly
remove
drc
cover
a-nd
thescrewsandstoredrem
in asafe
place.
3. Removing Tubes:l-ocate
drenrbeyouneed
to remove ard holdonto dreupperpordon of the
tr.rbetowards
is tip.
Gentlyrotate
and
rockd'rettrbeu,ith
yourfurgers toloosenit from itssocket
urtil its pinsarecompletelydisengaged frorndresocket.
Ta],e
thetube
outof dre
tuit.
ST-1 50 Owney's Manual
VTL 12

4. plugging in a new tube: Hold onto dre upper portion of dre tube towards its tip. l-ower the
ttrbe
onto the sockeg
makhg surethat drepins Fromdre
nrbe
matches
drel-rolesin the socket.
There areeidrer
two
pinson dretubew4richare
qpacedat a u,iderdistancefrom
eachodrer
drandrerest
of drepins(9pin minianrre tubes),
or the
reisalocating
keywayin dre
middle
of thetube(Bpin
octal
tubes).Makesurethatthese
locatorsgo into dreside
of dresocket
w4rich
matches.Pressthe nrbe 6"ttly irtto is
sockeg
usingagende
forceanda slight"rocking" motion.
Whendretubeispropedy
a-ndcompletely
inserted
into the
socket
it shouldbe6nnlyimplantedanddoes
not givein to
arly movementatallwhenyou try to rock it.
5. Replacing the protective cage: Iower dre amplifiels
cover chassisslowly back into the openedamplifierbox,
making
strredratdre
cover
is
ptrton in thecorrect
front and
back
posiuon.l-ocate
thescrews
rfich were
removedfrorn
drecoverand
put themback
urthecorrect
holes.Tighten
all screwsto malic strre
that dre cover is sectrrely
faster-red
to dre turit.
Changing the AGand Br Fuses
The B* fr,rsefor yotrrampliEer
is rated at 1-,{.ceramicSlo
Blo. There is also
onepdmarymainsfuserated
at
8A SloBlo (120VoltAQ, 10A SloBlo (100Volt
AQ or 4A SloBlo (220/240Volt AQ ceramic. The B*
fuses
are
housed
in two holden located
on theback
panel
of theamplifier,anddre
mainsfuse ishousedin a
separate
holderalso
locatedon dre
back
pa-nelof dierur.it.
To changeeither
fr,rsemake
sttre
dreurit ispowe
red
o[f, anddiscomect
the
AC powercordfrom therurit.
Move theamplifier sodrat yottcanwork wrththe
pa-nel
Lrdre
back.
The t'rpeof 6murg
used
for drefi.rscsiscalleda bayonet
6t,whichdescribes
dreactjon
needed
to
rernovetl-re
fusecap.
l-ocatetlieapp.opriate
fuse
holder
andto loosetrit tr.rnrthescrewhead
approximatelyone
quarterof atLlnr
Lracoturter-clockv,ise
direction
u,4rilepressing
Lrrvards.The fusecapshouldspnng
out from
itshotrsing
with drefuse
held
insidedrecap.
Takedrefi.rseout and replaceit with anew otre,andinsert
dre
fusecapbackLrto dreholder,
pushing
it dowrrward wllle hrnringit in the clocku,ise
directionto lock it irr
place.
WARNING: For continued protection against fire hazard only replace the fuse with the same
tlrpe and rating as was originally specified for the amplifier. lf you have problems locating
the correct fuse contact your VTL dealer or the VTL factory service department.
Glemng
Your \IIL an-rplifier
shotrld be dtrstedoccasionally
widr a damp non-abrasive clodr. Yotr should not use arly
solvents for cleaning dre front panel, as dls czurdamage dre lettering and dre ftrish. It is recommended dtat
you use a contact cleanerstrchasPro-Gold on dle input and ouq;trt cornecton regulady to ensure optimtrm
soturd and proper signalcondtrcdng capability.
ST-150 Owney's Manual
VTL 13

Transpottitg ST-{5O
If yotr sl-rotrldever need to ship yotrr ampliEer,pack dre turit widr dre ongural cartort artd foam. Crlltact yoLlr
VTL dealer or the VTL factoryif you need replacemerltpacking matedal.
ST-l 50 Owney's Manual
VTL 14

CHAPTER 5
Specifications;
ST-l50Stuwpuwruttpffn
VacuumTube Complement
Otrtput Power
20Hz - Z}lJlz. into 5 ohm load
S/N Ratio
Porver
Constrmption
T.H.D. 20Hz - 20 kLL @ 150W less
than
3%o
T.H.D. 20Hz - 20 kllz @ eOW
Inptrt
Sensitrvity
@ 150W 100V
= 0.880V
120/240\'
= 1.0\/
Inptrt
Impedance 130IiOhms
Opdmum LoadRa-nge 2-B ohms
8 x 6550C,
2 x 1.2AT7,2 x 6350
Tetrode:
150
wattsperchannel
Tnode: 80 watts
perchannel
-95d8,
1.20112
Idle
= 240
W
FtrllPower
= 800
W
PrimaryMains
Ftrse
Rating 100V= tOA Ceramic
Slo
lllo
120V
= 8A CeramicSlo
Blo
220/ 24OY
- 4A Ceramic
Slo
Blo
B* FtrseRating 1.0A
ceramicSlo
Blo
Dimerrsions W = 19inches
(48cm),D = 1'2inches
(26cm),H =9 inches (23crn)
Weight 55lbs(20.5Kg){total65 lbs(25Kg) packed}
ST-150 Owney's Manual
VTL {5