Effectrode LA-1A User manual

Specifications
• Input impedance:Greater than 1M
• Outputimpedance: Less than 1K
• Controls: Peak Reduction,Gain, Boost, Attack and
Knee
• Features: Dynamic tube equaliser, active tube
boost and tube buffered output circuitry
• All tube: Super low-noise parallel tube input stage
(four tube sections) operating in class-A
• Photo-optical: Ultra-linear, low distortion photo-
resistive attenuator (fast attack time < 1ms)
• True bypass: With ‘anti-pop’ foot-switching circuitry
• Power requirements: 12VDC@ 1Acentre positive
• Dimensions: width 7.5" depth 4.8" height 1.3"
• Weight: 2lb (on Earth);¼lb (on Callisto)
• Construction:Solid die-castaluminum box
• Finish: Tough light-grey powder coat
Serial #
Copyright © 2017 Effectrode®Thermionic
Owner’s Manual
12 Broughton Crescent, Barlaston,
Staffs,England. ST129DB
www.effectrode.com
LA-1A

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Introduction
The Effectrode LA-1ALeveling Amplifier was
designedwith onepurpose in mind:toenable artists
and engineersextract everylast nuancefrom a
musical performance… without compromise.Tubes
are renowned for beingunparalleledtone
enhancers, adding warmth,depthandclarity to
recorded andlive instruments and Effectrode wanted
to pushtheirperformancebeyondcurrent limits. To
that end we based ourLA-1Aon a parallel tube plate
design –the type of tube circuitry only ever found in
high-endtube phono preampstagesfor turntables
(remember those?).
Parallel tubedesignminimisesthenoise floor and
maximisesthesignal tonoiseratio of your
instrument. It'sanexpensive wayof achieving noise
reduction,as fouridentical input tubestagesare
required,however it yields stellar tonequality without
the compromise ofnoise gates or 'cutting'certain
frequencies with equalisation.The parallel tube
design hasnever been built into astompboxor even
aprofessional studio leveling amplifier/compressor
before, makingtheLA-1Asomething truely special.
Thankyoufor supporting Effectrode pedals. We
wish youmanyyears of musical enjoymentfrom this
veryspecial hand-built, all-tube pedal.
Phil Taylor –Designer
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Tubes
The 12AU7 and 12AT7 tubesintheLA-1Acan be
swapped withequivalent miniature 9-pindouble
triode tubesfrom other manufacturers –Mil-Spec
N.O.S.tube types, such as the long-plate Philips
JAN6189Wor JAN 5814Aarehighly recommended
in the 12AU7 position and JAN12AT7WCin the
12AT7 position.Although vintage long-platetubes
are generally more microphonic than short-plate
designsthey are highly soughtafter byengineers
and musiciansseekingsweeter and richer tones.
Pots
This pedal is fitted withcustomBritish manufactured
Omeg sealed-for-life potentiometers. Thesesealed
potsprevent dustanddirt from gettinginsidethem
so they never require cleaning or lubrication.

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The releasetime oftheLA-1A
is determinedbythephotocell
in the gain attenuator.The cell
hasadesirable two-stage
decaycharacteristicwhere it
releases within 40to 80msto
approximately half its off
resistance whenlight is
absent.The remainder of the
releasethen takes place over
several seconds. Additionally,
the recoverytime of thephotocelldependson light
durationandintensity.Inuse thisresultsin afaster
releasetime for short signal burstsand aslower
releasewhen the signal remainscontinuously above
the compressionthreshold.Thisis analogous tohow
the human ear recovers from highsound pressure
levels andis whyphoto-optical compressionsounds
so incredibly natural and transparent.
Side-Chain Circuit the LA-1Aisbased on‘feed-
back’ control circuitry wherethesignal usedto drive
the side-chain isaffected by the gain-reduced signal.
This type of control circuitry ispreferredover ‘feed-
forward’ for its more musical characteristics.
There’s also some pre-emphasis on the side-chain
similar to an “A”weightedfilter curve.Thiscurve
characteristic mimics the wayhumanear works
whenexposed tohighsound pressure levels. Here it
worksto minimise the ‘pumping’ that occurs when
the LA-1Ais processing low-frequency material.
ce
Controls
Peak Reduction knobsets boththethreshold and
the amount of signal compression.Whenadjusting
the compressionor sustain agoodstarting point is
the 9o’clockposition wheresubtle leveling
enhancesnote detail,creatingafuller,warmer tone.
As the knob isrotated clockwise the volume level of
loud notesis reducedrelativeto quieter ones,
squashingplaying dynamics –thisis thedefinitive
sound of manycountry and funk-style guitar riffs.
Gain knob adjuststhe‘make-upgain’ and isusedto
match the relativelevels of bypassed and effected
signal.It can also provide+15dBu oftube boost
whenthe‘Peak Reduction’ knobfully counter-
clockwise (zero compresson).
Boost knob givesan additional +6dBof gain (ontop
of themakeup gain)–this isusefulwhensoloing
on guitar or bassand canpushtheinput stage ofa
tube ampinto overdrive verynicely too.The ‘Boost’
footswitchengages(red LEDlit) and bypasses
(green LEDlit) the boost.
Attack and Knee knobsallow the compression
character to be tailored perfectlyto suit instruments
that are challenging toamplify or record.For
example,active 5-string bass guitars, nylonand
steel string acoustic guitars fitted with piezo pickups
and even especially ‘difficult’ stringed instruments
such as hammered dulcimer,harpsichord or tar.

Rotatingthe‘Attack’ knobclockwiseincreaseshow
fast the side-chain reacts, i.e.the speed at which
compressionkicksin.The ‘Knee’ knob alters the
input/output curve, i.e.how the LA-1Atransitions into
compression–rotate clockwise andtheLA-1A
becomes alimiter andcounter-clockwise for
compression.
When the Dynamic EQ toggle switch isin the‘down’
position theLA-1Adynamically boostshigh
frequency material.With the'PeakReduction'knob
fully counter-clockwise (zero compression)dynamic
eq is inactive,however astheknobis rotated
clockwise,and the pedal beginscompressing,the
effect becomes increasingly pronounced.Fabulous
for jangly 12-string Rickenbacker guitar sounds.
BypassFootswitch utilisesquiet true bypass
switching tominimse ‘pops’ or ‘thump’ when
engagingthepedal and ensure there isnolossof
guitar tone when the pedal is bypassed.
Balanced Direct Out ¼” TRS(stereo)jack socket
allows connectionof the LA-1Atomixingdesk,
computer soundcard or external audio capture
device.This output is fully balancedandtransformer
isolated, eliminating earth loops and reducing hum to
an absolute minimumandfeaturesagainpad
(+6dB,+12dBand +18dB)to facilitate matching with
anyline or instrument level gear.The Triad
Magnetics audio transformer alsoimpartsit’s own
character to enhance and sweeten the direct sound.
External Select ¼” TRS(stereo)jacksocket.This
enables an external footswitch,such as the Fender®
‘Twin Reverb’ Amptremolo/reverb dual latching
footswitch), to be utilised for remotebypass
switching andactivating the tube boost.
TheoryofOperation
The graph below compares theinput/output
characteristicsof acompressor,perfect amplifier
and expander.It can be seenthat an amplifier
provides afixed gain independentof the signal level,
whereas acompressor adjustsgainin responseto
changesin input level.
The larger the input signal,the lower thegain,
resulting in areduction of dynamic rangeor
compressionof the signal.Conversely,anexpander
increases the dynamic range of a signal.