Safe Sound Audio P1 User manual

P1 Audio Processor User Manual Safe Sound Audio
Model P1 Audio Processor : User Manual
Safe Sound Audio, UK
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Page 2 User Manual P1 Audio Processor
P1 Audio Processor Features
Advanced audio compressor wit peakride w ic utilises multiple side-c ains
allowing t e compressor to ‘ride’ t e crests of t e audio so t at control of fast audio
peaks, especially vocals, may be as fast as desired w ilst release from
compression compliments t e natural decay of t e audio waveform. Exceptionally
low levels of ripple distortion.
Limiter featuring multi-stage dynamic threshold control w ic provides a very ig
degree of overload protection wit out t e undesirable side effects of traditional
‘brick wall’ limiters.
The limiter has three side-chains each utilising zero delay ‘look ahead’ dynamic
control of limiter threshold. This allows the ‘natural’ limiter threshold to be
dynamically adjusted to match the dynamics of the incoming audio signal and
provides for very safe control of maximum audio level without the need for ultra fast
attack times all accomplished with 100% analogue processing.
Single knob expander wit ‘follow-audio’ release time w ic tracks t e natural
decay of t e audio; useful for post recording noise reduction and adding punc to
drum sounds.
Hig quality balanced microp one input using t e latest Burr-Brown INA217 c ip.
Balanced line input.
Hig impedance (1 MΩ) instrument input.
Balanced line output offering +21dBu drive capability.
Balanced and unbalanced stereo monitor inputs wit separate source level control
providing zero latency eadp one monitoring of t e source/replay mix.
100% linear internal mains power supply (t row away t ose wall warts for good!)
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P1 Audio Processor User Manual Page 3
Contents Page
P1 Audio Processor Features ………………………………….. 2
Safety Information; READ THIS FIRST ………………………. 4
Quick Start Guide ……………………………………………….. 5
Audio Connector wiring information …………………………… 8
Detailed Operational Guide …………………………………….. 12
Power on …………………………………………………. 12
Typical audio connections ……………………………… 13
+48V P antom Power for microp ones ………………. 14
Setting t e input gain ……………………………………. 14
Overload warning ………………………………………... 15
Setting up t e output gain ………………………………. 16
Hig pass filter …………………………………………… 19
Expander operation ……………………………………... 19
peakride compressor operation ……………………….. 22
peakride compressor t eory …………………………… 24
Limiter wit dynamic threshold control operation ……. 26
How t e P1 limiter manages dynamic range …………. 27
Answers to some common questions …………………. 29
Monitoring facilities ………………………………………. 31
Tec nical Specification ………………………………………….. 33
Fault finding ……………………………………………………… 35
Customer Care …………………………………………………... 37
Warranty conditions ……………………………………………... 37
How to contact us ……………………………………………… 38
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Page 4 User Manual P1 Audio Processor
Important Safety Information : Read this first!
There are dangerous vo tages present within the unit. Do not open the unit
and refer a servicing to qua ified service personne .
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T e lig tning flas wit arrow ead symbol, wit in an equilateral
triangle, is intended to alert t e user to dangerous voltages
wit in t e unit.
T e exclamation point wit in an equilateral triangle is intended to
alert t e user to important operating and safety instructions in
t is user andbook.
T is unit s ould only be connected to a mains supply of t e type
marked on t e rear of t e appliance. Take special note of t e required
mains voltage.
T is unit must be eart ed.
T e IEC mains connecting lead originally supplied wit t is unit as
been fitted wit a 3A mains fuse. Always replace wit a fuse of t e
same rating.
T is unit is fitted wit an externally accessible fuse. Always replace
wit a fuse of t e same type and rating. T e fuse type and rating are
s own on t e rear of t e appliance just below t e fuse receptacle.
Always disconnect t e unit from t e mains supply before replacing t is
fuse.

P1 Audio Processor User Manual Page 5
Quick Start Guide
After reading t e important safety information, you may wis to ‘plug and go’. If, at
any time, you are in doubt as to t e correct operation of t e unit, all operational
points are covered in detail later in t is manual, but as a quick start;
Basic functions
T e P1 is a mono audio pat processor wit separate stereo monitoring facility, as
s own below;
T e t ree audio inputs ave separate connectors but only one of t ese inputs is
connected to t e main processing c ain at any one time. T is is controlled by a
simple priority system t roug t e actual plugging of t e connectors.
T e balanced LINE input (3 pole ¼” jack plug) will always ave t e ig est priority.
T e unbalanced INSTRUMENT input (2 pole ¼” jack plug) as priority over t e
MICROPHONE input.
T e balanced MICROPHONE input (3 pole XLR plug) as t e lowest priority.
T e connector wiring follows normal audio convention. Details are given later in t is
manual.
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Page 6 User Manual P1 Audio Processor
Alt oug t e t ree inputs s are a common input gain control, t e gain range
available to eac input is different and appropriate to t at input;
MICROPHONE GAIN 0dB to +70dB
INSTRUMENT GAIN 0dB to +30dB
LINE INPUT GAIN -10dB to +20dB
Phantom Power
T e microp one input as switc able +48V p antom power suitable for powering
most types of studio condenser microp ones.
ALWAYS CONNECT THE MICROPHONE FIRST BEFORE
SWITCHING ON THE +48V ot erwise damage to t e microp one amplifier is a
possibility. In a similar way, always switc off t e +48V and wait for 10 seconds
before disconnecting t e microp one. If you are unsure w et er a microp one
requires +48V p antom powering always c eck wit t e microp one manufacturer
first. DON’T GUESS!
Most professional BALANCED dynamic microp ones will not be damaged t roug
t e accidental application of p antom power.
HI Pass Filter
T e switc able ig pass filter as a -3dB point at 80Hz and a slope of 18dB per
octave.
Peak indicator
Lig ts w en t e main signal pat (before t e limiter) comes wit in 3dB of clipping.
Expander
Variable t res old expander wit a fixed expansion ratio of 1:3, fixed attack time of
around 3ms and variable ‘follow-audio’ release time.
Compressor with peakride
A sop isticated multi side-c ain compressor wit variable t res old, attack and ratio.
‘Follow-audio’ release time. LED bargrap s ows gain reduction in dB’s.
Limiter with dynamic threshold control and output level control
T e most sop isticated part of t e processing c ain but it as no user controls! Full
explanation later in t e manual, but for now a brief set-up procedure;
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P1 Audio Processor User Manual Page 7
T e limiter is actually t e last signal processing element and sits just before t e
preset output gain control. T e limiter t res old is fixed, so for quick set-up;
•Ensure t e expander and compressor are switc ed OUT of circuit
•Apply a fixed level test signal (s ould be a 50% duty square wave) to t e line
input and adjust t e input gain control until t e red LIM LED just lig ts (a
suitable test signal is available to download from our web site,
www.safesoundaudio.com)
•Adjust t e preset output gain control (screwdriver adjustment) until t e desired
recording level is s own on your recording device metering; best to allow 1dB
below 0dBFS.
Main Output
T e balanced main output is fed via t e preset level control described above to a
3 pole balanced ¼” jack labelled ‘LINE OUT (BAL)’.
An LED bargrap s ows t e output level prior to t e output gain control.
he Monitoring Chain
Stereo input designed to be fed from t e replay c ain of your recording device. Can
accept eit er a single 3 pole ¼” jack for unbalanced stereo connection OR two 3 pole
¼” jacks for balanced stereo connection. Plug as s own on t e unit’s rear panel.
T e monitoring c ain feeds t e front panel ¼” stereo jack socket best connected to
eadp ones wit an impedance of 600 o ms or above. It is safe to connect low
impedance eadp ones but monitor audio quality will degrade.
For track laying and overdubbing, it is also possible to mix in a feed of t e unit’s main
processor pat w ic as it’s own ‘source monitor’ level control. T is level control
does not affect t e processor’s main audio pat level.
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Page 8 User Manual P1 Audio Processor
Audio Connector wiring information
Note : All connector wiring information refers to t e cable end connecting to t e P1
audio processor unless ot erwise stated.
Balanced Microphone input
Any standard balanced XLR-3 to XLR-3 microp one cable s ould be suitable.
At t e P1 end, use a cable type XLR-3 pin plug wired as follows;
You s ould not use t is input to connect unbalanced ig impedance microp ones
w ic in any case are normally supplied terminated in a 2-pole ¼” jack plug.
Balanced Line input
Any standard ‘off t e s elf’ balanced line level cable s ould be suitable. T ese will
be typically eit er jack to jack or jack to XLR depending on t e type of equipment you
are connecting to t e line input. If wiring your own, at t e P1 end use a standard ¼”
3-pole jack plug wired as follows;
It is also possible to feed t is input from an unbalanced source w ic may be t e
case w en feeding t e P1’s line input from some keyboard instruments or
unbalanced sound card outputs.
If you want to use an ‘off t e s elf’ cable t en use a standard unbalanced line level
cable (guitar cable) wit standard ¼” 2-pole jacks at eit er end. If wiring your own
unbalanced cable we suggest t e following wiring arrangement w ic will give better
noise and um rejection. (Note t at t e sleeve of t e 3-pole jack is intentionally left
unconnected.)
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Pin 1 = screen
Pin 2 = signal +ve (also called ‘in p ase’ or ‘ ot’)
Pin 3 = signal -ve (also called ‘anti-p ase’ or ‘cold’)

P1 Audio Processor User Manual Page 9
T e balanced line input s ould not be used to directly connect to electric guitars and
basses. Use t e INSTRUMENT input instead.
Unbalanced Instrument input
Any standard unbalanced ¼” to ¼” 2-pole instrument (guitar) cable s ould be
suitable. If wiring your own use standard ¼” 2-pole jack plugs for bot ends wired as
follows;
Insert Point
A ‘Y’ type cable is necessary to access t e processor’s insert point. T e ideal cable
type is a twin ‘figure 8’ unbalanced cable. T ese are available ‘off t e s elf’ but if
wiring your own, a typical wiring sc eme is s own below.
Balanced Line output
Any standard ‘off t e s elf’ balanced line level cable s ould be suitable. If wiring
your own, at t e P1 end use a standard ¼” 3-pole jack plug wired as follows;
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Page 10 User Manual P1 Audio Processor
It is also possible to feed t is output to an unbalanced destination w ic may be t e
case w en feeding t e P1’s line output to some unbalanced PC sound card inputs.
In t is case use a standard ‘off t e s elf’ unbalanced line level cable. If wiring your
own, at t e P1 end use a standard ¼” 2-pole jack plug wired as follows;
It is possible t at t e input jack on some unbalanced sound cards will be for a stereo
input typically via a 3.5mm stereo jacket socket. Assuming you are feeding only one
P1 unit into t is soundcard’s stereo input t en it is important to ground t e unused
input of t e soundcard to prevent crosstalk. A typical wiring sc eme is s own below.
Monitor inputs
T e P1 as t e option to accept eit er unbalanced or balanced monitor inputs w ic
allows standard cables to be used in bot cases. T e monitor inputs will most
commonly be fed from a stereo output of t e recording device or PC sound card.
Unbalanced connection : plugs into t e jack labelled ‘MONITOR INPUT L/R
(UNBAL)’.
If you want to use a standard ‘off t e s elf’ cable t en use a standard stereo twin
‘figure 8’ unbalanced cable wit a single 3-pole jack plug at eit er end. If wiring your
own, at t e P1 end use a standard ¼” 3-pole jack plug wired as follows;
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P1 Audio Processor User Manual Page 11
Quasi balanced connection : plugs into t e two jacks labelled ‘MONITOR INPUT
LEFT (BAL)’ and ‘MONITOR INPUT RIGHT (BAL)’. If feeding from an unbalanced
monitor output and wiring your own cable, we suggest t e following wiring
arrangement w ic will give better noise and um rejection. (Note t at t e sleeves of
t e two 3-pole jacks at t e P1 end are intentionally left unconnected.)
Balanced connection : plugs into t e two jacks labelled ‘MONITOR INPUT LEFT
(BAL)’ and ‘MONITOR INPUT RIGHT (BAL)’.
Use two standard ‘off t e s elf’ balanced line level cables, or if wiring your own,
at t e P1 end use standard ¼” 3-pole jack plugs, wiring for eit er left or rig t inputs is
identical as follows;
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Page 12 User Manual P1 Audio Processor
Detai ed operationa guide
Power on
If t e PWR LED does not lig t t en go to t e fault finding section of t is user manual.
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Wit t e IEC mains cord securely fitted to t e
rear of t e unit, plug t e P1 into a suitable
mains power source taking special care to
ensure t e mains voltage is as indicated on
t e rear panel. Note t at a UK 240V AC
supply is suitable for powering a unit marked
‘230 VAC’
C eck t at t e front panel green PWR LED is lit.

P1 Audio Processor User Manual Page 13
ypical audio connections
T e diagram below s ows a typical application of t e P1 audio processor in a
recording set-up.
T ree audio input types are provided for, t ese are;
Balanced microphone input, for use wit eit er dynamic or p antom powered
condenser microp ones.
Balanced line level input, for use wit any line level source suc as keyboards and
t e outputs of certain guitar and bass effects units w ic offer a LOW IMPEDANCE
line level output.
Unbalanced instrument input, for direct connection of most electric guitars, basses
and ot er electric instruments. T is is sometimes called a DI-INPUT (direct
injection).
Alt oug it is possible to connect sources to all t e P1 inputs simultaneously, only
one will function at any one time;
T e balanced LINE input (3 pole ¼” jack plug) will always ave t e ig est priority.
T e unbalanced INSTRUMENT input (2 pole ¼” jack plug) as priority over t e
MICROPHONE input.
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Page 14 User Manual P1 Audio Processor
T e balanced MICROPHONE input (3 pole XLR plug) as t e lowest priority.
So, for example, if you are using a microp one wit t e P1 make sure t e ot er two
inputs are disconnected!
+48V Phantom Power for microphones
As a general rule, if you are not sure w et er your microp one requires
p antom power t en don’t press t e +48 button. If in doubt c eck wit t e
microp one manufacturer. For t ose familiar wit t is powering met od t ere are
only two golden rules;
Connecting t e microp one wit t e +48V already switc ed on usually causes an
almig ty ‘audio t ump’ t roug t e unit and is not user friendly to your monitor
loudspeakers, your eadp ones or your ears if you are unlucky to be on t e receiving
end. T e P1 as circuitry to elp protect t e microp one amplifier from damage in
t is case but it’s impossible to protect in all circumstances so you ave been warned!
Most professional balanced dynamic microp ones will not be damaged t roug t e
accidental application of p antom power.
Setting the input gain
T is is done independently of any output level setting and independently of any
record level setting in your recording device or PC sound card.
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ALWAYS CONNECT THE MICROPHONE TO
THE P1 BEFORE SWITCHING ON THE +48V
SUPPLY
ALWAYS SWITCH OFF THE +48V SUPPLY
AND WAIT FOR 10 SECONDS BEFORE
DISCONNECTING THE MICROPHONE FROM
THE P1
T e red +48V LED lig ts w en p antom power
is active.
Alt oug t e INPUT GAIN control is calibrated
from 1 to 10, t e actual gain available depends
upon t e input connector in use, as follows;
Microp one : 0dB to 70dB
Line input : -10dB to +20dB
Instrument input : 0dB to 30dB

P1 Audio Processor User Manual Page 15
Overload warning
If the PEAK LED f ashes and you cannot prevent it by lowering t e input gain
control t en you ave to deal wit t e very ig signal level at source in one of t e
following ways;
If you are using a microphone source (now we’re guessing, but maybe mik’ing up
a 4 x 12 stack running really ot!) t en eit er move t e microp one away from t e
loudspeaker, or turn down t e loudspeaker amp. If it’s a vocalist, t en t ey’ve got a
great career a ead of t em! Try switc ing in t e PAD on t e microp one if provided.
If you are using an e ectric guitar or bass plugged into t e instrument input, t en
it’s more t an likely being played t roug an effects unit wit lots of gain. Eit er back
off t e gain on t e guitar or t e effects unit, or if using a pro-audio effects unit, try
connecting it to t e balanced line input of t e P1 w ic as more eadroom.
If you are using a source connected to the balanced line input, t en back off t e
output level of t e source device.
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Adjust t e input gain control so t at during t e
loudest parts of t e performance t e level
bargrap is peaking to –2 or 0dB (lig ting one
or bot of t e yellow LEDs). Normally you are
not trying to lig t t e RED ‘LIM’ LED but don’t
worry if it flas es occasionally; t e really
excellent ‘dtc’ limiter in t e P1 will protect your
recording device from overload in a very
friendly manner!
Alt oug not usual, it is possible for a very ig
level audio source to overload t e P1’s input
stage. T e red PEAK LED will lig t w en t e
input level is 3dB below t e maximum signal
level w ic t e P1 can andle.

Page 16 User Manual P1 Audio Processor
Setting up the output gain
T e P1 limiter takes care t at t e maximum audio level t roug t e processing c ain
is carefully monitoring and controlled wit out aving to adjust any settings.
However you do ave to adjust t e output gain control so t at t e maximum level
from t e P1 (after t e limiter) matc es t e desired maximum recording level.
T ere are two ways to do t is; by using a test signal, or by trial and error using any
dynamic audio source.
By test signal
If you ave access to t e internet, and your ave access to a PC w ic can replay
sound files, t en go to our web site www.safesoundaudio.com and download t e
recommended set-up test signal w ic is available as a .wav file.
Set-up your normal recording c ain as s own below, so t at t is test signal can be
replayed from your PC ard drive from one c annel of your sound card, t roug t e
P1’s line input and t en entered back into one c annel of your recording device.
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P1 Audio Processor User Manual Page 17
Adjust t e P1’s input gain until t e red LIM LED just lig ts.
Now set your recording device to monitor t e incoming test audio signal level on its
record meter. If your recording device as a recommended input level setting for
best audio performance, t en set t is first according to t eir recommendation. If
t ere is no recommendation t en we suggest you set it to its maximum setting.
As long as you are using t is recording set-up t ere s ould be no furt er need to
adjust eit er t e record device input gain or t e P1’s output gain setting.
W y use suc a strange test signal during set-up?
T e 1kHz square wave signal was c osen to ensure t at t e recording device
metering gives an accurate indication of t e PEAK level being fed to its recording
input. Many ‘peak’ reading meters still ave a finite ‘integration’ time so t ey will
display correctly t e peak level of t e more usual tone based test signals but under
represent t e actual peak voltage value of very dynamic audio. T e use of a 50%
cycle square wave test signal ensures correct peak level indication.
Setting the output gain using ‘real audio’
W ilst setting t e recording c ain levels using t e test signal is recommended, it is
possible to do it using any source of dynamic audio material eit er ‘live’ or pre-
recorded.
Set-up your normal recording c ain as s own below, so t at t e audio source is
being fed into t e P1 (use t e input socket to suit t e type of source material) and
from t e P1’s LINE OUT into one c annel of your recording device.
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Now adjust t e output gain on t e
P1 using a flat blade screwdriver
until t e desired maximum
recording level is viewed on t e
record meter of your recording
device. We suggest you set a
maximum level of 1dB below
0dBFS.

Page 18 User Manual P1 Audio Processor
Adjust t e P1’s input gain until t e red LIM LED just lig ts during t e loudest part of
t e source material.
Now set your recording device to monitor t e incoming audio signal level on its
record meter. If your recording device as a recommended input level setting for
best audio performance, t en set t is first according to t eir recommendation. If
t ere is no recommendation t en we suggest you set it to its maximum setting.
As t is is a bit of a trial and error met od, try a few different types of source material
ensure t at t e loudest parts are not pus ing t e recording device into overload.
Once set correctly, t ere s ould be no need to furt er adjust eit er t e record device
input gain or t e P1’s output gain setting.
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Now adjust t e output gain on t e
P1 using a flat blade screwdriver
until t e desired maximum
recording level is viewed on t e
record meter. We suggest you set
a maximum level of 1dB below
0dBFS.

P1 Audio Processor User Manual Page 19
High pass filter
T e HI pass filter is in circuit w en t e yellow led is lit and as two main uses;
To filter out mains um w ic gets into t e recording c ain, sometimes caused by t e
use of unbalanced audio connections in t e recording c ain, or because t e eart ing
sc eme is poor.
To reduce t e effect of very low frequency noise pick up t roug microp ones and
microp one stands (could be rumble from traffic noise) or microp one andling noise
for t ose vocalists w o just ave to old on!
he expander
Expanders reduce audio gain w en t e audio level falls below t e expander
t res old setting as s own in t e diagram below;
T e P1 expander is a simple to use wit a single knob to set t e t res old.
As t e audio input falls below t e t res old, its gain is reduced progressively from
0dB (no gain c ange) up to a maximum gain reduction of 20dB (called t e expander
depth). So loud sounds are unaffected but quiet sounds get quieter. T is is
expansion of t e audio’s dynamic range below t e expander threshold. T e red
ACTIVE LED lig ts w enever any expansion of t e audio signal is taking place.
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T e ig pass filter (sometimes called a low
cut filter) affects only low frequency sounds
below w at’s called t e turnover frequency
w ic in t e P1’s filter is set to 80Hz. W en
switc ed into circuit, it will reduce t e level of
all audio components below 80Hz
progressively at a rate of 18dB per octave, so
for example a 30Hz tone would be reduced in
level by 18dB compared to t e 60Hz tone level.

Page 20 User Manual P1 Audio Processor
T e expansion ratio is ow muc t e audio gain is reduced as it falls below t e
t res old point. T e P1 uses a fixed ratio of around 1:3 (wit a soft knee at t e
t res old point) so t at (below t e t res old) for every 1dB t at t e input level drops,
t e output level will drop by 3dB.
T e P1’s attack time is around 3ms. T is is t e time it takes for t e expander to go
from t e full 20dB gain reduction to no gain reduction as t e input audio level rises
towards t e t res old point. It’s fast enoug so t at t e front end of a vocal p rase
or note is not lost but slow enoug so as not to cause distortion in slowly rising audio.
Hold time is ow long t e expander waits before operating w en t e input level falls
below t e t res old setting. T e P1’s old time is programmed to follow t e natural
dynamics of t e audio signal. S ort duration audio p rases ave a s ort old time
w ereas long audio p rases ave a longer old time.
Release time is t e time it takes t e expander to reduce t e audio gain as t e input
level falls below t e t res old setting. T e P1’s release time is programmed to follow
t e dynamics of t e falling audio signal. So a fast falling input signal, suc as t e tail
of a drum beat will set a fast release time and a slow falling signal, suc as t e
decaying note of a sustain guitar note will set a slow release time. In t is way t e P1
release is able to track t e natural decay of t e audio signal. T e release time in t e
P1 as a programmed range from 90ms (fast) to 900ms (slow).
Expanders are often compared to noise gates, but in general use expanders are
more natural sounding because t eir control of audio gain is directly related to t e
audio signal c aracteristic w ic is not t e case in a noise gate.
Expanders ave a wide variety of uses in music recording but we recommend t ey
are normally used on audio material w ic as already been recorded rat er t an
w en recording ‘live’. To do t is connect your P1 as an effects device in your track
mix down c ain as s own below.
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