Audio Valve CORDA EARTUBE-1 User manual

EARTUBE
USER MANUAL

Dear music-lover,
The CORDA EARTUBE-1 is a small-power amplifier, specially desig ed to drive headpho es. It offers
a sou d quality a d drivi g capabilities far beyo d that of a ordi ary headpho e socket fou d o a
CD-player or amplifier a d thus allows you to exploit the full so ic pote tial of your pho es.
Due to the close co tact to your ears, headpho es provide a extreme cha el separatio whilst
liste i g to stereo recordi gs. U like loudspeakers, o e of the so ic i formatio i the left cha el is
acoustically tra sferred to the right ear a d vice versa. Although this adds to the extreme high level of
detail that ca be achieved with headpho es, it subco sciously also i troduces me tal stress. The
atural correlatio of stereo sou d i terpreted by the brai is lost.
The CORDA EARTUBE-1 ot o ly offers ormal stereo reproductio of your music, but it also has a
facility to add some of the left cha el i formatio to that of the right cha el a d vice versa. Thus
me tal stress is reduced a d music ca be e joyed with more ease.
By desig o ly tubes are fou d i side the sig al path of the amp. Solid state electro ics are o ly used
to create a stable voltage supply.
For safety a d i order to obtai the best possible results with your ew headpho e preamplifier, we
ask you to read these i structio s carefully. The EARTUBE-1 was developed by music-lovers for
music-lovers a d we hope that it will serve you well for a lo g time.
Helmut Becker

Safety precautions
Childre a d mi ors are ot to use the device a d should be kept at a safe dista ce from the device
while it is ru i g.
Do ot ru the device without the top cover i place. Voltages i side the amp ca be lethal a d
temperatures are high.
Please check that the mai s voltage pri ted o the bottom pa el of the amplifier correspo ds with the
mai s voltage i the cou try where you i te d to use the amplifier.
Disco ect the powercord before a y service to the amplifier.
I the u likely eve t of a failure of the device repairs may be performed by authorized tech icia s
o ly.
Use ORIGINAL spare parts o ly!
Please take ote of the fact that we decli e product liability for damages caused by our devices, parts
a d compo e ts as a result of:
U professio al a d/or faulty a d/or i correct repairs that have bee performed i other tha
the approved repair facilities.
Usage of other tha ORIGINAL a d approved spare parts.
All devices must be operated u der moderate climatological circumsta ces, comparable to those
u der which huma bei gs usually live. Whe the surrou di g temperature is too high, the device will
heat up beyo d its optimal parameters. This ca damage the amplifier.
Proper ve tilatio is eeded, a d the amplifier should ot be covered i . Allow approximately 3 cm of
air sidewise a d approximately 4 cm above the amplifier to cool the amplifier.
O ce the amplifier has arrived at its desired desti atio , make sure the amplifier has ample time to
adjust to the climate at its ew locatio . It is likely that the cha ges i temperature a d humidity
betwee the last locatio a d the ew o e, has caused co de satio to build up somewhere i the
amplifier. This ca damage the device. Please allow the amplifier at least two hours to acclimatise.
The amplifier comes fully assembled, ready to go.
The decive MUST be switched OFF while co ecti g it to other compo e ts.
A softstart preve ts high i itial curre ts through the cold, low impeda ce, heati g eleme t. This
preve ts the eleme t to break at its most arrow spot.

Connections
At the rear side of the CORDA EARTUBE-1 two pairs of i puts allow you to co ect two differe t
audio sources that have typical output voltages above 0.1 Volts (CD-player, cassette-player, tu er,
mi idisc-player, ...). The source you wa t to liste to ca be selected by the switch at the left fro t side
of the amp.
If your audio system already co tai s a ce tral preamplifier or i tegrated amplifier you may prefer to
co ect the EARTUBE-1 to the tape-out of your ce tral amplifier. The source ow ca be selected by
the Rec-switch of this ce tral amp.
Your headpho e should be co ected to o e of the headpho e-sockets o the fro t side of the
EARTUBE-1. You ca also use the sockets to co ect two headpho es simulta eously.
The sockets are i te ded for 6.35 mm stereo jacks. If your headpho e o ly has a 3.5 mm jack, the
use a adapter that ca be obtai ed i most electro ics or audio shops.

Activation of the device
Before co ectio of the CORDA EARTUBE-1 to the mai s, please check the voltage required. The
proper value ca be fou d o the bottom-side of your device.
After co ectio the EARTUBE-1 ca be switched ON/OFF by the power switch. While switched ON
the LED o the fro t side will be lit. It takes arou d 10 seco ds before the amp is fully activated.
We recomme d to power the amplifier ON approximately 15 mi utes before use. If the device is ot
used for a lo ger period of time it should be switched OFF. Not o ly does this reduce e ergy
co sumptio but it also i creases life-time of the tubes.
Volume control
The volume of the CORDA EARTUBE-1 is co trolled by the large dial o the left side of the fro t pa el
a d is i creased by clock-wise rotatio .
The drivi g capabilities of the CORDA EARTUBE-1 by far exceed that of a regular CD-player. This ot
o ly guara tees less distortio , but also has the da ger of severe heari g damage.
While liste i g to headpho es we lack several feedback mecha isms o volume level that are prese t
whe we liste to loudspeakers. Much less distortio , o feeli g of the lower freque cies by our body
a d o psychological restrai ts ot to a oy our fellow-me easily seduces us to liste at volume
levels that are detrime tal to our heari g.
Heari g damage from regular exposure to high sou d levels progresses slowly but is irreversible a d
ca result i perma e t heari g loss.
!! Please choose your volume-setting with caution !!

Directional listening
I ormal daily life people use various mecha isms to locate sources of sou d.
Firstly, the sou d of a source to the right side of the liste er (e.g. the right loudspeaker) ot o ly
reaches the right ear but, atte uated a d delayed, is also heard by the left ear. The level of atte uatio
a d the delay time of this crossfeed sig al provide importa t directio al i formatio .
Seco dly, the sou dwaves are partly absorbed a d partly reflected by the tissues of the head.
Reflectio s at the oracles (pi ae) i terfere with the sou dwaves that directly e ter the ear-cha el
a d amplify or atte uate specific freque cy compo e ts. Si ce these reflectio s depe d o the
directio of the sou dwave the “color” of the sou d cha ges with the directio of the source.
Thirdly, reflectio s of the sou dwaves from the walls, ceili g a d floor of our liste i g room produce
reverberatio that co veys a extra feeli g of space.
The i formatio obtai ed by these mecha isms is further refi ed by moveme ts of the head. Cha ges
i sou d levels, delay times a d sou d color refi e the se se of directio . For a demo stratio ,
bli dfold a frie d a d ask him to locate a ticki g clock that you have hidde i the room. He will start
tur i g his head although he ca ’t see a ythi g. With his head i a fixed positio a exact localizatio
is much more difficult.
Listening by headphones
All these mecha isms are missi g whe we liste to music by headpho es. The sou d at the right ear
will o lo ger reach the left ear a d pi ae-reflectio s o lo ger i terfere with the origi al sou dwave.
Moreover, the headpho es are directly attached to our head, a d so head moveme ts o lo ger add
i formatio . Reverberatio is also ot prese t.
As a result, the sou d heard by headpho es seems to stick to the i side of our head a d to our ears
a d a u atural sou dfield is created. The brai misses logical clues for directio a d this
subco sciously results i me tal stress. Some people ca ot tolerate this stress a d are u able to use
headpho es.

he natural crossfeed filter
I pri ciple, digital sou dprocessors ca simulate all the mecha isms for directio al liste i g but the
results are, thus far, ot very satisfactory. I particular, pi ae-reflectio s are very complex a d
liste er-specific a d impossible to simulate accurately.
Fortu ately, the mai directio al i formatio is provided by the time delay a d level of atte uatio of
the sou ds that reaches the opposite ear. The CORDA EARTUBE-1 ca electro ically simulate this
process a d, with appropriate atte uatio a d delay, add some of the right audiosig al to the left
cha el a d vice -versa. This co siderably reduces the adverse symptoms of headpho e liste i g.
A u ique feature of the crossfeed circuitry of the EARTUBE-1 is that it “recog izes” the virtual
positio s of the i strume ts a d si gers i a recordi g. The sou d of a i strume t i the middle of
the sou dstage will be equally prese t i both audio-cha els a d is ’t give a y crossfeed. A
crossfeed sig al is o ly ge erated for i strume ts that are ot placed at the ce ter. The more off-
ce ter the i strume t is placed, the stro ger the crossfeed a d the lo ger its delay. This feature is
called “ atural crossfeed”.
Activation of crossfeed
The crossfeed filter ca be activated by the seco d left switch at the fro t of the amp.
Lower position STEREO.
I this positio there is o crossfeed o the headpho e outputs. We recomme d this positio for
recordi gs with a arrow sou dstage.
Upper position LOW level crossfeed
This setti g is especially recomme ded for recordi gs with a relatively high level of reverberatio
(orchestra, choir) or extreme spatial positio i g. Although the differe ce to the stereo positio may ot
be discer able to you at first, after lo ger periods of liste i g you will fi d the crossfeed positio much
more relaxi g.
While activati g the crossfeed the liste er may otice a appare t lack of bass. I stereo mode, lower
freque cies seem to be much more prese t. This is a psycho-acoustical effect a d does ot represe t
a limitatio of the crossfeed filter. Lower freque cies heard by o e ear o ly are much more u atural
to our brai tha higher freque cies a d therefore i stereo mode are more oticeable. Crossfeed
i tegrates the lower freque cies i a more atural way i to the sou dstage which makes them less
oticeable.

Replacing tubes
The EARTUBE-1 uses three tubes 6N3P a d two tubes GU17 (or its equivale ts QQE03/12, RS1023,
6360)
If you wa t to excha ge tubes, please disco ect the power cord before removal of the top cover. Also
make sure that all pi s are properly mou ted i to the sockets. It is ot u commo that a pi is be d
a d does 't e ter the socket.
Do ot ru the device without the top cover i place!
echnical data
Measures: 28 x 30 x 11 cm
Weight: 6.0 kg
Power supply: US-Versio : 100/120 Volts, 50/60 Hz
Europea Versio : 200/240 Volts, 50/60 Hz
Maximal amplificatio (1 kHz): 16 dB at 200 Ohm
Maximum output: 35 Volts at 200 Ohm
I put impeda ce: 47 kOhm
Output impeda ce: 20 Ohm

CE – Confirmity
Declaration Of Conformity
Manufacturer: AudioValve,
Germany, 34123 KASSEL, Umbachsweg 70,
[email protected]
Product Name: ASSISTENT 100
Product Type: Audio Amplifier
Complies with Standards:
LVD: 92/31/EEC, 93/68/EEC, & 73/23/EWG
Safety: EN60065
EMC: EN55013, EN55020, EN55022, EN55103, EN61000-3-2,
& EN61000-3-3
The official Declaration of Conformity for this product is kept on file at:
AudioValve, 34123 Kassel,Umbachsweg 70, Tel. [phone]

W A R R A N T Y
AUDIOVALVE warrants its components for a two - year period on all electronics and a 90-
day period on the tubes from the purchase date
In the event of a failure of your amplifier , AUDIOVALVE will repair or readjust this unit or
, should the occasion arise , will replace it provided that all conditions stipulated in this
warranty are met
In order to initiate service of any kind it is necessary to obtain distributor or dealer
authorization prior to shipping the unit for service
Any of the following conditions shall void the warranty:
•Operation not in accordance with this manual
•Abuse , accidental damage or unauthorized modifications , as determined by
AUDIOVALVE or its agents exclusively
•Removal , defacing or falsifying of the serial numbers
•Shipping without the original complete factory crates

WARRANTY REGISTRATION
Please fill out and return this warranty form to the distri utor within 15 days of
the purchase date with this form here, or make it online on our we side.
•MODEL : _______________________________________________
•SERIAL NUMBER : _______________________________________
•PURCHASE DATE : ______________________________________
•AUTHORIZED AUDIOVALVE DEALER:
•PURCHASER`S NAME : ___________________________________
•STREET ADDRESS : ______________________________________
•CITY : __________________________________________________
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