Electro voice a 30 owners manual

Page 1

r

Model A30 Amplifier

l
' l all-watt Circlnimn

; i High-Fidelity Power amplifier
i,;...i
mului mumnou - m EquoVain Model A30 lawman i. . high quasi,

30mm! pawn unplifier. Hw brushed-hm: and rich brown bikini «:1sz finish
preset: In mam uppunnce which will bind with mntmwnry room damn.

Infill 7 The Modal. A30 ample»?! the M!!! Wiggins Circlmmn Circuit. DC
output run-rem is removed {mm :11: output manicure-z: through (h: we at
a bridg: circuit. All Wlwlllllg umaiems gr: elimimied (brough unity coupling
blmeen 01:th tuba. "nu griuury impedance of [he oulprul mnsfnmicr is on:
winner 0! flu: found in mvemiaml mplificr output circuit}. ullwiug In
but! in power MIMI I: ma 0f the inqumq xpeumm.

A. dumping (um: (Mimi pun-lit: perk coupling buwetn {he Implifitr tad
lowing-kn mum aliminuing are null Inn of bl {mm overdnmping or
Inasmu- due In uodudunping. For the flat time, Waugh Ill: use of this con-
uol, optimum apuntiou of my Imkll syucm i: mud.

SPECIFICATIONS

Specifications and W.»
l Instructions WWW

i

Pm: Output: 30 won; rand, 60 won: can pull:
Sue Fig. 2 Maximum Undiunriod Pow VI.
Frequa ncy"

frequency Ruponuz 20.5 din 20 m 75,009 cpl

543 Fig. 3 "quuuncy Rnpunu"

mmanic Ubtorliom has; lhun 0.396 m mud oulpm
Inhrmodulmion Distortion: Lou than 0.5% ul rah-d ampm
. 5n Fig. 4 "Pawn vs. ininrmdulafion
Hz. 1 - Mud-I A30 amplifier Dill-anion
Hum and Nniflu 55 db balm» rand ampu:
Speaker Outpuh , 4 chm, 8 ohm, 16 ohms; 70 win balanced
m Redbflk. l-WP iaedbock: 13 db neqmiva
Drive plate: 2 db pmifiw
Ouipui circuit: 17 db negative
Tomi: :15 db negative
Damping lemon Adimmhla human OJ and 15. Sea tabla
fur critical dumping foams of all E-V
when.
Input lmpcdum: 250.000 chm;
Scnmwim 1.25V RMS in: Iami ompm
Cnmroln a. Gain 1
b. Damping Facior
c. Power Oil-OH
van-m- - "I Tubfll Total of 6 uITollowu
m m m. -. m i 12 AX?
1 IZBHVA
2 1614
2 5Y1?!
$- 2 '* Maximum Undistamd fin: Pmr Consumption: 117V 60 cycle AC 0! 1.3 am?! max.
t FHQUIMY 5km 33* in. wide I 9 In. deep x 7 in. high

Wfllahh 21 lb not, 24 lb shipping

Page 2

um.-
la.ai

.. - «.- w- ma
m t- u-

Flg. 3 -Ftattua1tt:y Resume at1u~mtt Laval

we um

Fla. t - Patter vs. intermadulaflntt
nhtortlnn

Hz. 5 - Simplified Diagram
Girctotrnn Circuit

Fig. 6 - Mllllng Momma: Brackets

THEORY 0F BPERATIDN

ml 001")! YIANSIOIMII ml} ctucntt - One tequitement of n nullity
hifivfideflw amplifier ii that it has In output transformer with negligihle lexhge
renctmce. 'fltit lnkzge reactant: must be low to timid the mmimt distum'un
ordinuily resulting from collapsing cut-mum in dm AB at B opemtian. when
either output tube it driven pin tut-off. The tt-nsitnt dillarllofl will App! :5
t pituitic owilhtiw in the my: form II the instant of cut-0K. A high value of
leakage wartime Illa will flu the guru! transform: of 1 conventional Impli-
fttt to lose eificienty ll high frequenting. The diatributed upncity oi the output
translntmet- :hnuld be very low in axder m minimize high-(sequency lflmuflion
Ind phi" mill. The Citclatrun circuit emu'zgumtiun avoid; mnny ol the limit:-
tiom imputed by the output tundormr and twertumu the inherent (lit:
tdvmtaget of muventinml push-pull nutput circuits.

Figure 5 i! a simplified version In! the Wiggins Citdmtm circuit. Two power
supplie: we used and are indinled 1; batteries. Etch power supply is connected
(mm the plxt: of one tube to the cathode hf the other. The plate current of each
tube circulate! thtaugh hotl- power supplies without {reverting the winding! til
the output rut-dimmer. Bennie my pair of opposite point! in this configuntion
is equipmmlini. the circuit is I bllmtcd bridge under no-rignzl" conditions.

_ The total primary winding of the output tension-met preterm I load to each of
the two output tubes. One half of this lead is in the cathode (int-tit. the other
half in the plzte circuit: the glue load of one tube is the cathode load of the
other. Beam: each tube looks into the um: land I! the other. the result is unity
caupling between the tubes. Despite the tezidual leakage mutant: in the (tin!-
(owner. no switching trmtienu an occur during the operation of the amplifier.
for both halves at the tnnslormer grit-nary have the same signal current flowing
through them. 'I'luu, thmugh the use of thit circuit. troublesome switching
transients, not-nully found in even high-quality amplifiers. are completely
eliminated.

The impedmee of the primary winding 0! the output tmsfurmer it no: fourth
tint oi the tnntlotmert in usull amplifient. Riel-dun, the Cinlotmn trims»
fut-mgr hat much less distributed capacity and leakage teatunce. so that 1 wide
frequency teypome mtg: is much more :15in nttaincé.

Low quintet-t current in the Cirrlotmn circuit result! in higher elfiriency
and predates more puwet without enteeding the dissipation ruling: of the tubes.

"I! DRIVE! CIItUlI - The gain of III! Cirdotmn output stage is Ilmalt
unity, thus requiring I high drive voltage. This higher IOIIOKE is obtained by
meant of terhnique culled boat stripping". By this method the 3+ iupply (a
the driver stage i: dymmx'ally changed as signal voltage change: nllnwing line-t
operation over : much wider nnga.

UAIIAILI nmvma unto- ~ It ll necessity for the Implifu: tn prelim: the
curt-mt eflcuive impedlnu to the speaker for optimum Itnustic performance I!
luv] luquencin. This value a! critical dumping resistanre vain widely with
different speakers. and is dependent upon flux density. type of enclotuu. length
a! conductor in the air gap. and to tame extent. the positinn of the enclosure in
the mom. The Electra-Mince damping factor control is variable over a. wide muse
so that ill optimum mntth can he made between the amplifier and any speaker at
lament. Varying nmnunts at voltage Ind curtent leedhatit ace combined to match
the ellective impedance while maintaining the total feedback II at centunt value.
The mximum pave! available from (he amplifier is independent of the damp
ing tutor, retraining tonstant at all settings 0! the tunnel.

lflSTRUCTlUHS FOR SET- UP Mil] flPERATlBN

lhtmedintely upon unpacking the umplifiu tin-Fully inrgett it let physical dam-
age. ll dump is evidenced. notify the dealer from whom the unit was puuhnsed.
or the transportation company if the unit was 5hl|1p¢¢l to you. Responsibility lot
thipping deluge lies with the «trier nod claim should be made for recovery.

moummo-Ttu- A30 may be mounted in mutton. The amplifier i5 :upplied
with rubber feet In prevent warring til the surface on which it is plueed. For
mounting in A vertical position or lot fixed upright wanting (See Fig, 6 "Allah
in; Mounting Brackets) remove these feet by extracting the scum located in
the center of each rubber foot. lmtzll one mounting bracket in the desired
locatim on supporting well at tut-lact- with the limits painting up. lmttll the
second mounting bucket on the lower and at the bottom plate with the hacks
twin; dawn Place the amplifier so Ill) the hook: on mounted bracket engage
the three cutout: on the bottom pint: nearm the top and fasten the second
mounting hntket to the supporting well or sutltce. Reasonable ventilation is
uquiretl. Ind the unit should am he operated in small. completely enclosed
spacer. Bucket: may ['50 be used Im- pcmunent horizontal «matting. Under
unuwttl mndition. at very restricted ventilntion. the tube and campumt cover
may be remand to Illlil cooling. ,

.

Wad-Mh w