Acoustat Monitor Brochure

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Acoustat Monitor Brochure

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Page 4


In the beginning. there were. lube amplifiers.
tubes are basically high inpedance nevioes Magnetic
eoeairere are low impedance lcads. Hence. STEP-
DOWN transformers were almost always p-‘ceont.

A ur'g cattle power transistors. which could
directly drive magnetic speakers. Tne first generation
of electrostatic designers then inverted the past
and put in STEP-UP translcrmers :3 get back to the
"ugh impnamcc Cl lhOSO speakers.

Wl'y wasn't it obvious that vacuum. tubes were a
much more natural and e’ficient match 1m
ernrt'ostancs’l Actually, this was obvious to :i few
dillerent individuals involved in such research.

lr‘ the early 1960s. we burll our ‘rrst amplifier
using the tour quadrant uutput hr dge. which was to
become the mainstay of all Acoustat amplifiers.

Its immediate a-omisc was so obviwu that we have
never dev ated f'om this basic outth drive

Fva pusaible JU'litlllLKIU is utiiricu by tailor us;
the amplifier to the electrcstatic panels anc not the
other way around:

I OWN VOW-90$ can UC generated by this design
which are appropriate to the speaker: thus
cmnnlmely eirmmatinn the need lor audio
step-up trans’ormers and crossounrs

2, Low generator impedance. compared to the triad

impedance. can be assured at all lrequencies:

providing excellent panel control n'id damping.

Higher e‘li-ziency is attained. 'educi'ig am: i‘rer


-1 Any desirable analiurion required to the "attest
UVG'EI" 'esponsu can hr: oca'iouuctillv



Aii iiitarestir'g ’ uriansweranle quesriot in tn 3
case. Unanswerable because a full-range electrostatic
is essentially a very large capacitor. arc oower
carrot be measured into a capacitive lead. in the
laboratory. using a. dJ'hrny resistive load. the Servo-
Charge emolltler memurcs in the 1C0 wall "angel.

Because of high coupling etilclericv ol our high
impedance am: first to the high impedance capacitive
load which the panels icpruscr‘t a hundred watts
becomes marvelously effective in Dioducrng
srratterrngw large amounts 01 sound pressure level
and is able to Ur) lliis slay-rig well williiii llic pluli:
dissipation parameters of the output tubes. In an
average listening room on music material head at
[yo-cal listening distancus. a pair at Monitors will
produce over l to an betore amniitier clipping or
over 1% {rural limrnuui; disturlivn oi the total
system occurs.


These units are contained in the pedestals ol the
Mcniter speakers and are of hybrid aeslgn employing
solid state circuitry for all low level functions and
tl‘i‘, about: described direct drive output from high-
voltage tube elements. coupling directly to the
speaker panels.

The output drive tubes are high vonagc ponloues
which are used in a conservatively rater: application.
Even on the rrosl cemanding muarcal r'tater til it
is extremely Gilt-Cult to roach the maximum
dissipet on level or the tunes. oven momentarily.
TJba l to in an average application ha; [generally
exceeded our: year and the replacement cost is
mocest as. matched sets a": not ruqui'cd.

The Servo-Charge amplitier incarnoralcs the
‘ol owing leatures:

"Instant-On" Relay Circuitry

This feature. which eliminates the need for any
ncwer umh Ilccls trnm the preamplifier source.
canalsts at a unique aunio triggered automatic
turn-0n circuit. The ampl tier is lett ccrrecten in
Is wall Outlet at all times. A very I'Jw power is
let: on the four vacuum tube tllamonis when tt-u
arrplifiar lfi not l'l use This f8Cilllfllfi3 he. instant
lurn»un when an audio signal is supplied provides a
dti'iiu-cl'nscr cl‘ccl and because switcn'ng power
Surges artL eliminated greatly cxlcnus tub: I to. Two
cast 01 this stand-by operation is es: than 14‘ nor
day per speaker. After the audio Signal has been
runruveu [or a period 0" approximately five minutes.
the automatic ci‘cuitry w ll shut down tne amplifier
to the low power start: by mace

Low frequency equalization

Active equaliealioi‘ is user: let me ollf‘l ratlcn 0‘
low lruuucncv icspurisu uburraliuns causal; in
interaction of the reflecting wall sir-face WI'..'l the
dipole raciaticn pattern.

During extensive 1.53 octave frequency analySis n
testing the response at the system. it was veriliud
that a vliuriu'iicnori cl quarter wavelength
reinforcement and half wave—length cancellation
:aikes place in "‘5 luwer liequeiiuiee. Tlus is lruu
I3: nil Lunch} radiators in the :irnxrmity or a reflecting]
wal. Witl' typica speaker to rear wall cistances the
net effect cf this roinlorcci'nont canccllatiur'
phenomenon is to pruduuu: il “liurrip ' in tin: response
a: 90-' 00 he due lo quarter w an) lurch rcmtarcnmenl
il'ld ti ' dip" at tall-:JIKI H7 matinee. nt hall
wave-lergt'i cancellation. The so'utiu’t to this
problem which i‘ left uncsrmctnd causus it "vuvrriy"
50". at JPPU' tiltiti Cf‘itldl'cernulll and own mizlmi‘nn
"<1 mp-cut". was to prov de specific active ecualizatic'i
t: currecl llie rcspurisc.