VAC Vintage Mk III User manual

ValveAmplification Company
1731 NorthgateBoulevard, Sarasota, FL34234 USA
Telephone[phone] /Fax[phone]
www.vac-amps.com
VAC VINTAGEPREAMPLIFIERMk III
Operating Instructions
DO NOT OPEN THISUNIT- THERE ARE NO USER SERVICEABLE PARTS INSIDE.
DO NOT TOUCH TUBES UNTILUNITHAS BEEN SWITCHED OFF FOR 5
MINUTES. TUBES BECOMEHOT INUSE. DO NOT EXPOSE THISUNITTO
MOISTURE. DO NOT PLUG INTO AN AC SOURCE UNTILALL CONNECTIONS
ARE COMPLETED.
Introduction
The Vintage Preamplifier features a zero-global-feedback, Class A, triode line amplifier &
controller, and a Class Atriode phono amplifier employing bothpassive and active RIAA
equalization techniques. It is tobe operatedfromthe voltage labeledon the backpanel, 50-
60 Hz. The fuse is a slowblowtype ofthe size labeledon the backofthe unit.
Connection
1.Complete all connections before connecting the AC cordtothe wall outlet.
2.At turnon, the volume control shouldbe full counter-clockwise and the mode switch
shouldbe set toMUTE. Also, always MUTE the preampbefore switching power off,
toprevent damage toamplifiers or speakers.
3.Allow30 seconds for warmup before leaving MUTE.
4.The Vintage Preamplifier inverts phase fromall inputs tothe mainoutputs. To correct
for this reverse the speaker connections inbothchannels. Output tothe tape jacks
does not invert.
5.Innormal operation no signal is present at the tape output jacks. This is done to
ensure that no degradation ofsound occurs due toinput non-linearities or loading

effects ofthe tape recorder. To record, select the recordenable position ("TAPE ON")
ofthe TAPE MONITOR switch. Ifyou wishtomonitor the output fromthe recorder's
monitor head(ifsoequipped) select the monitor position ("MON"). It is
recommendedthat this switchnot be cycledduring important recordings.
6.Tube compliment is:
V112AX7A/E83CCphono input amplifying triode - LOWNOISE
V212AX7A/E83CCphono input amplifying triode - LOWNOISE
V312AX7A/E83CCphono amplifying triode
V412AX7A/E83CCphono impedance translator triode
V512AX7A/E83CCphono impedance translator triode
V612AU7A/E82CCline amplifying triode
V712AX7A/E83CCline impedance translator triode
7.XLR balancedoutputs (optional) followthe EIAstandardconvention, where the
positive phase signal is carriedon pin2and the invertedphase is carriedon pin3.
Manymanufacturers fail tofollowthe standard.
8.Some systems will sound different depending on the polarityofthe AC line cords.
Manyaudiophiles experiment withthe relative cordpolarityoftheir components. In
general, incorrect relative power polaritywill result ina somewhat thinand wispy
sound. We recommend that you consult your dealer for suggestions.
Tube Types
GoldenDragon tubes are generallyrecommendedand have beenusedextensivelyduring the
development ofthis amplifier. Please feel free tocontact VAC ifyou require additional
information or advice.
About Microphony
Everyamplifying device, be it tube or transistor, produces some output withmechanical
stimulation (microphony). Infact, evencables possess microphony. Inthe Vintage
Preamplifier, V1, V2, V3, and V6will emit a sound through the speakers ifdirectlystruck.
This is a normal situation. The exact amount ofsound depends on the tube type, its location
inthe circuit, and slight randomvariations intube manufacture. Whenthe chassis itselfis
strucksharplythere maybe either no sound or a slight sound emittedfromthe speaker, but it
shoulddie awayrapidly. Again, this is normal and not representative ofthe type of

mechanical or acoustic stimulation encounteredwhenthe unit is properlyinstalledand
playing music. Replace the offending tube ifexcessive mechanical sensitivityor ringing
occurs.
It is best not tosubject the tubes totapping or the chassis torepeatedmechanical jars, as this
maydamage the precision ofthe tubes and cause themtobecome more microphonic.
About Noise
Everyamplifying device produces some amount ofnoise. Infact, evena resistor produces
noise inthe presence ofcurrent flow. Acceptabilityis not a question ofwhether this
characteristic is present but rather the degree towhichit is present.
The most likelysource ofphono stage noise are tubes V1&V2. The audibilityofnoise
producedinthe phono stage is influencedbythe output level ofyour phono cartridge.
Pickups withoutput levels lower thanapproximately.4mVmaybe problematic. Witha
pickup ratedat .4mVoutput and lownoise 12AX7s (V1, V2), the subjective level of
electronic noise will be approximately1/3ofthe groove noise on a good direct todisc
recording.
The most likelysource ofline stage noise is V6. The audibilityofnoise producedinthe line
stage is not affectedbythe volume control setting, and is determinedbythe sensitivityofthe
power amplifier and the efficiencyofthe speakers. Witha speaker ofextremelyhigh
efficiency(for example, a Klipschorn) the preamplifier itselfmaybe modifiedbyVAC for
more appropriate noise and output levels. Noise shouldbe insignificant withspeakers inthe
typical efficiencyrange.
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