Phaedrus Audio GROOVE SLEUTH MK.II EC8020 User manual

User Manual for
GROOVE SLEUTH MK.II / LOCKDOWN /
EC8020 versions
NON-EQUALISING
PHONO PREAMPLIFIER
(for needle-drop* recordings with Stereo Lab Software)
* A needle-drop is a term which means a version of a music album that has been transferred from a vinyl
record to a digital audio medium. Needle-drops are also sometimes called vinyl rips.
Version 6.1 (May 2021) –new universal Groove Sleuth Mk.II
includes LOCKDOWN and EC8020 appendix

Chapter 1 - Introduction
Phædrus Audio's Groove
Sleuth Mk.II preamplifier is
designed to be used in
conjunction with Pspatial
Audio’s Stereo Lab
(Phonograph or
Audiophile) app which runs
under OS X on the Apple
Mac. Stereo Lab has a wide
feature set but it devotes a large part of its
functionality to software equalisation and decoding
of analogue records.
This isn't just technology for technology's sake.
There are real, audible reasons for doing this:
phase-linear warp and rumble filtering is only
possible in the digital domain and reveals a bottom
octave with unprecedented clarity and realism. The
accuracy of RIAA equalisation and perfect channel
balance ensures an uncoloured sound with superb
stereo sound staging. And the flexibility in recording
characteristics will bring to life LPs you thought
mediocre. Moreover, Stereo Lab also includes
software decoders for QS and SQ quadraphonic and
Ambisonic LPs; thereby bringing life to forgotten,
analogue, multichannel gems.
For Stereo Lab to process needle-drop captures and
equalise them, it needs recorded files of the "raw"
signal, direct from the groove, unfettered by
analogue equalisation. And that is where the
Groove Sleuth Mk.II preamplifier comes in. It is a
phono preamplifier of the very highest quality but
without equalisation, so that the signal fed to the
computer is the closest version of the signal direct
from the groove, but at a suitable amplitude for
digitisation. The Groove Sleuth Mk.II preamplifier
has various options to augment this basic task to aid
with monitoring and to ease integrating these units
into a high-quality audio system. These are
described in the pages that follow.
Chapter 2 - Safety
General
Before using any piece of equipment manufactured
by Phædrus Audio, be sure carefully to read the
applicable items of these operating instructions and
the safety suggestions. Keep them for future
reference. Follow the warnings indicated on the
unit, as well as in these operating instructions.
THE USER SHOULD NOT ATTEMPT TO SERVICE THE
UNIT. ALL SERVICING SHOULD BE REFERRED TO
QUALIFIED SERVICE PERSONNEL OR FACTORY
ONLY.
Phædrus Audio products should NEVER be
connected to the external power supply or in any
other way energised when the case is opened
and/or the circuit boards are accessible.
General Safety Instructions
Do not operate this equipment near any
source of water or in excessively moist
environments.
Keep this equipment away from babies,
children and pets.
Do not let objects do not fall, or liquids be
spilled, onto the enclosure.
Situate this equipment away from heat
sources or other equipment that produce
heat.
Ensure this equipment has adequate
ventilation. Improper ventilation will
cause overheating, and can damage the
equipment.
When cleaning this equipment, remove all
connections to the unit; including power
and gently wipe with a clean lint-free
cloth; if necessary, gently moistened with
lukewarm or distilled water. Use a dry lint-
free cloth to remove any remaining
moisture. NEVER use aerosol sprays,
solvents, or abrasives on this equipment.
This equipment should be serviced by
qualified service personnel or returned to
Phædrus Audio when: an object (or
objects) have fallen into the enclosure; or
liquid has fallen into, or been spilled into
the unit; or the unit has been exposed to
rain or high humidity; or the unit does not
operate normally or exhibits a marked
change in performance; or the unit has
been dropped, or the enclosure has been
damaged.
Chapter 3 - Gramophone record
equalisation in software
The signal recovered from a gramophone
(phonograph) record via an electrodynamic pickup
(moving-coil or moving-magnet type) has the bass
drastically attenuated and the treble boosted.

Replay processing is therefore required to present
a complimentary characteristic to restore the
original audio balance. The electronic amplifier
which corrects for the equalisation applied during
recording is today universally called an RIAA
preamplifier. The design of good, accurate RIAA
equalisation has taxed the ingenuity of audio
hardware engineers for sixty years.
Pspatial Audio believe that, after 60 years,
hardware RIAA equalisation has just about reached
the end of the developmental road and that
equalisation is nowadays better performed in
software for the following reasons:
REASON 1: Greatly increased digital
resolution
Stereo Lab has internal processing in software
which uses double-precision floating-point math.
CD audio represents the audio signal with a
dynamic range of 96dB, smaller then than the
capacity of the human hearing system, which has a
dynamic range of about 120dB. The very best
analogue circuits can just about match this dynamic
range. But, by contrast, double precision floating-
point math is a binary format which has a precision
of 53 bits or 320dB. That's a dynamic range which is
ten billion (1010) times greater than the hearing
system.
REASON 2: Filter accuracy and stability and
perfect left-right channel matching
Even the very best electronic components can only
be manufactured with a certain degree of accuracy
which is rarely better than 1%. Physical components
are also subject to ageing such that they go "off
value". Digital processing ensures perfect channel
balance and frequency response for ever, which
guarantees an uncoloured sound with superb
stereo sound staging.
REASON 3: Better warp and rumble handling -
with phase-linear filtering in software
In a perfect world, all gramophone records would
be perfectly flat, there would exist no inevitable
resonance of the arm-mass and the stylus mounting
compliance and the mechanical vibrations from the
driving motor would be eliminated. But LPs do not
exist in a perfect world so, when warp or rumble (as
these imperfections are named) are present, they
are better eliminated. The technique always
employed to remove these effects is high-pass
filtering and that is the approach taken in Stereo
Lab too: a slightly under-damped fourth-order filter
may be employed as a rumble filter so that the
response falls sharply below the audio passband.
However, very differently, the rumble filter is a
phase-linear, non-causal design which means there
is no phase distortion introduced. Phase distortion
is inevitable, real and audible in causal, filters and
can never be eliminated in analogue designs]. But it
is entirely eliminated in software processing. The
result is a bottom octave which will sound like
you've never heard it before.
REASON 4: Flexibility of equalisation
characteristics - to cope with records not
equalised with RIAA curve
Conventional wisdom has it that, by the mid-fifties
in a belle époque of international cooperation, most
American labels and most major European labels
had adopted the new RIAA standard and had
brought to an end a very chaotic situation which
had existed since the dawn of electric recording in
which the record companies all specified different
equalisation for their discs. However, the truth is
that many labels were much slower to adopt the
RIAA curve and disc recording characteristics were
not effectively standardised
until the late 1960s, or possibly even later. It is
therefore a great boon to the vinyl enthusiast to
have flexible equalisation characteristics. But such
flexibility, combined with perfect mathematical
precision is very complicated and expensive to
implement in hardware.
In providing digital equalisation as part of Stereo
Lab, Pspatial Audio wished to offer a
comprehensive range of these non-RIAA
equalisation options for gramophone disc collectors
whilst avoiding a complex and over technical user-
interface. So, Stereo Lab features equalisation
options to cover any disc (or indeed cylinder)
recording from the 1880s to the present day.

Chapter 4 –The Groove Sleuth
Mk.II Preamplifier
The signal from a gramophone pickup is too small to
apply to the line input of most sound-cards or audio
interfaces. What is required is a dedicated phono
preamplifier to bring the small signal from the cartridge
up to a healthy level for input to the computer sound-
card.
Many phono preamplifiers exist at all price levels
from a host of manufacturers. But, the vast majority
of the phono preamplifiers apply RIAA equalisation
in the hardware of the unit and that is not what is
required here. We need a preamplifier which
provides gain and impedance conversion, without
applying the equalisation. These are unfortunately
very rare, especially models which guarantee
extremely low-noise, exemplary headroom,
excellent linearity, and an accurate and extended
frequency-response. It is to fill this need that the
Groove Sleuth preamplifiers were developed.
The Groove Sleuth Mk.II
The Groove Sleuth Mk.II is a second generation
product which replaces all the models in the
original Groove Sleuth range. Please refer to this
block diagram of the Groove Sleuth Mk.II
preamplifier in the following description.
The Groove Sleuth Mk.II preamplifier is suitable for
high-output moving-coil (HMC) and moving-magnet
(MM) cartridges, and optional transformers may be
fitted for low-output moving-coil (MC) cartridges.
The Groove Sleuth Mk.II is also suitable for
Phaedrus Audio PHLUX (PHLUX II) active moving-
magnet cartridges. (See Chapter 5 for more
information about PHLUX active cartridges.)
Each base unit is equipped with a high-quality
looping path called iLOOP, and the Groove Sleuth
Mk.II preamplifier has an option for RIAA and
limited alternative equalisations.
In the base options, the unit simply presents the
cartridge with the correct impedance at the IN
phonos and amplifies the signal. The output is
presented on the phonos marked OUTPUT on the
rear of the Groove Sleuth Mk.II unit.
The gain of this preamplifier is a little lower than the
typical mid-band gain of an RIAA preamplifier
because, without RIAA equalisation, the crest-
factor of the signal is somewhat greater than
with a typical music signal (by about 4dB). The
signal amplification is designed for the lowest
possible distortion and noise-floor; a discrete
transistor stage with multiple, paralleled transistors
being necessary for the latter. This amplified signal
is sent to an external audio interface for digitisation
and subsequent recording equalisation in Stereo
Lab.
Transformer option
When ordered with the MC option (GS-MC), the
Groove Sleuth Mk.II preamplifier includes a step-
up transformer stage. Transformers are heavy and
expensive, but they sound great! And they do offer
the lowest possible noise-floor. The transformers
selected for the Groove Sleuth Mk.II preamplifier
are of the highest quality: they possess high primary
inductance, very low leakage and are fully mu-
metal screened.

Signal loop (iLOOP)
The Groove Sleuth Mk.II preamplifier features the
iLOOP; a wide-bandwidth, low-noise and distortion
buffered loop-through. This is especially convenient
for enthusiasts who already have an excellent LP
replay solution but who want to introduce
computer audio into their system. This is because
the Groove Sleuth Mk.II integrates transparently
into a pre-existing setup and provides new
functionality without upsetting what's there
already.
iLOOP always outputs the phono signal at high-
output HMC (or MM) signal levels. In fact, if moving-
coil cartridge transformers are fitted and the iLOOP
output is fed to a moving-magnet input, the Groove
Sleuth will function as a first-rate, wide-bandwidth,
low-noise MC preamplifier.
RIAA+
The Groove Sleuth Mk.II preamplifier may include
a high-quality equalisation stage (GS-RIAA+) so that
the "loop" signal is equalised and emerges at line
level on the phonos marked iLOOP/RIAA. The
equalisation filter is a high-precision, passive
network. Previously, we have only offered optional
RIAA equalisation for monitoring. However,
because Pspatial Audio's Stereo Lab software has
its greatest application in equalising the many
recording characteristics of historical recordings, it
was felt helpful to incorporate limited, variable
equalisation in the hardware preamplifier to make
record monitoring less fatiguing (it's hard work
listening to a 78RPM equalised with the RIAA
curve). Three carefully judged, generalised settings
are included:
RIAA, labelled RIAA
pre-RIAA (for late 78s and early LPs),
labelled LP; and
Early (which is for all records made up until
the late 1940s) labelled 78.
In this way record-monitoring may always be
comfortable and accurate. This is followed by
slightly more make-up gain (+24dB) than the mid-
band loss in the RIAA network because the signal
now has the crest-factor of the original music signal.
Power supply and warm up
The Groove Sleuth Mk.II preamplifier is designed so
that the analogue sections remain energised all the
time since this is consistent with the best audio
practice
The Groove Sleuth Mk.II incorporates the very low-
noise battery supply which was previously only in
the Groove Sleuth MINI. This means the
preamplifier can be powered from a conventional,
international-style power supply but be switched to
battery supply during needle-drops to ensure the
very best possible noise and aliasing performance.
This delivers first-rate quality at a very reasonable
price. A switch on the front-panel allows the battery
supply to be selected and a LED indicates battery
health and charge.
The Groove Sleuth Mk.II has well over 24 hours’
operational charge, but we recommend battery
play be limited to approximately 12 hours. The unit
may be kept in charge mode when listening with
only a minute loss of quality. By means of an
advanced power-supply design, this condition is
achieved whilst remaining compatible with
European Eco-Consumption directives.
If the unit is unplugged or the power is removed or
interrupted, the analogue circuitry is held in a
muted state for about 5 seconds until the various
bias voltages are stabilised. Therefore, do not be
alarmed if the unit does not produce an audio
output immediately after connecting power.

Connecting the Groove Sleuth to your
sound card
The
Groove Sleuth Mk.II is connected to your sound-
card's line inputs (as shown above). Levels should
be set on the interface in the normal way and you
will find that the preamplifier delivers audio at a
sufficiently high level for all commercial sound-
cards, both internal and external.
Chapter 5 –Phaedrus Audio
PHLUX II - Active Phono
Cartridge
The Phaedrus Audio PHLUX II active phono
cartridge a new development in phono cartridge
technology in which a moving-magnet motor
system is buffered by a miniature amplifier thereby
securing the performance of a moving-coil cartridge
with the superior tracking and general convenience
of the moving-magnet type. Using a combination of
the PHLUX II cartridge, the Groove Sleuth Mk.II and
Pspatial Audio’s Stereo Lab software, first-rate
needle-drops may be obtained. More information is
available from www.phaedrus-
audio.com/PHLUX.htm
The power to the PHLUX/ PHLUX II active cartridge
is supplied via the signal cable: rather as phantom
power is delivered to modern microphones. In this
way, the PHLUX may be fitted to any standard
turntable without any rewiring. All that is required
is that the phono preamplifier supplies the
appropriate current and voltage to the turntable
leads. This circuitry is provided within the Groove
Sleuth Mk.II.
PHLUX-II digital correction
The PHLUX-II cartridge has a very level frequency
response. Variation is confined to ±1dB. This is a
very good result and is illustrated in the graph
above by the red trace.
Nevertheless, ±1dB is just perceptible; especially
when it is a monotonic 2dB drop as shown in the
graph. The result is a very slightly "warm" tonal
balance. So, before applying recording-
characteristic equalisation, it is possible to correct
this very slight response anomaly in Stereo Lab
software. The black trace indicates the corrected
response which brings the variation of the PHLUX-II
frequency-response to less than ½dB; a result
below accepted levels of perceptibility.
The combination of PHLUX-II, Groove Sleuth Mk.II
and Stereo Lab offers a solution with which to
extract the information captured on the original
record with forensic accuracy.
Chapter 6 - Recording "Needle-
drops"
To record a needle-drop,
you will first need a
program which records
audio. Pspatial Audio can
recommend Audacity, a
free, easy-to-use, audio
editor and recorder
which runs on the Mac
platform (and, in fact, on Windows and GNU/Linux
too). Audacity is free software, developed by a
group of volunteers and distributed under the GNU
General Public License (GPL). Audacity features, not
only the recording tools you need, but other tools
which you can use to enhance your needle-drops
like click and noise filtering and speed change. You
can read about and download Audacity on their
website (http://audacity.sourceforge.net/).

Setting parameters
You will also need to configure Audacity so that it
matches the settings you have made in the Audio
MIDI Setup utility. The selections are made in the
Preferences/Devices and Preferences/Quality
dialogues as illustrated above. You may also need
to adjust buffer depths in the software
(Preferences/Recording) for the higher sampling
rates. We’d recommend you adjust the Audio to
buffer parameter to 50 milliseconds as a good
starting point.
Recording levels
Set recording level so that peak music levels reach
between-12dBFS and -6dBFS. Do not be tempted to
over-record because this will cause distortion which
Stereo Lab cannot rectify. It is recommended that
loudness processing is also applied during the
Stereo Lab software equalisation process. In this
way you can be assured of the best dynamic range
from your music and of good matching between
needle-drops and other audio files (for example CD
rips). There is no need to anticipate the effect of the
RIAA filtering in Stereo Lab because the software
will automatically adjust the level of the input file
for best resolution of the processed file.
Remember to depress the front-panel switch of
the Groove Sleuth Mk.II to switch to battery
supply (green LED) before making a needle-drop:
this will ensure that the needle-drop recording is
of the highest quality. Reselect external supply
when the recording is made to preserve battery
charge.
Chapter 7 –Decoding
Quadraphonic and Ambisonics
discs
There were many interesting and important
recordings made in Quadraphonic sound and
versions of many classic recordings were mixed in
Quad'. Many still only available as vinyl records,
recording these LPs and decoding these recordings
in software allows us to revisit, and indeed
rediscover old friends.
Many beautiful and important recordings were
made in Quadraphonic
Stereo Lab allows decoding of SQ and QS
Quadraphonic and Ambisonics recordings to
multichannel audio files so that they can be played
over a square of four loudspeakers (as was the
intention in the 1970s) or over a modern 5.1
system. No special precautions need to be made in
recording needle-drops of quadraphonic or
Ambisonics discs. It is recommended that
equalisation is applied to the needle-drop in Stereo
Lab before decoding.

Chapter 8 - Specifications
Size: Groove Sleuth Mk.II: 112 × 50 × 225 mm (W-H-L)
Preamplifier Supply: DC input on screw locking connector.
Power: Groove Sleuth preamplifiers are designed to be compatible with European Eco-Consumption directives.
Consumption is less than 4 Watts in all configurations and active. The unit is intended to remain energised all the time.
Groove Sleuth Mk.II Preamplifier
Sensitivity @ 5cm/s recorded velocity: Nominal 5mV RMS (-44dBu); or 500µV RMS (-64dBu) when GS-MC option fitted.
Input load: 47kohms // 220pF (MM); 100R (GS-MC option); 150kohms, 9V dc phantom supply (PHLUX)
Gain (to computer output): 33dB (× 45)
Frequency response: ±0.1dB from 20Hz to 50kHz
Distortion: 0.005% THD at maximum output level
Equivalent input noise (EIN): <500nV RMS (-124dBu), A-weighted. Input shorted.
Signal to noise (wrt nominal sensitivity and un-weighted): 80dB
Maximum input signal (prior to clipping at full charge): 75mV RMS
Maximum input signal (prior to clipping after 6 hours on battery): 60mV RMS
Headroom (wrt nominal sensitivity at full charge): 23dB
Headroom (wrt nominal sensitivity after 12 hours on battery): 20dB
Battery: 9V Ni-MH (nickel–metal hydride) E-block type.
iLOOP (Intelligent Loop)
Function: Wideband, buffered loop-thru
Frequency response: ±0.1dB from 20Hz to 50 kHz
Output load: 47kohms (non-critical). Suitable for feeding any MM input
RIAA+ correction circuit option
Gain (to RIAA output): 37db/58dB (MM /MC); RIAA curve; pre-RIAA curve: Blumlein curve
RIAA response accuracy: ±0.2dB from 40Hz to 20kHz (RIAA)
RIAA IEC amendment: Not implemented; rumble roll-off performed in software
RIAA Neumann Pole or eRIAA: Not implemented
1
Phædrus Audio reserves the right to change specifications without notice.
Chapter 9 - Warranty and service
Service
If you experience a problem with a Phædrus Audio product, contact [email protected]om. We will diagnose the
problem remotely and advise you of the warranty status. If a repair or replacement is required, we will issue a Return
Merchandise Authorization (RMA) number and tell you where to send the unit to be repaired. You MUST have an RMA
number before you return the equipment to Phædrus Audio's support service. Phædrus Audio will not accept responsibility
for loss or damage in shipping or for equipment returned without valid paperwork and/or a valid RMA number. Remember,
warranty is void if product serial numbers have been removed or altered, or if the product has been damaged by abuse,
accident or unauthorized modification and/or repair (see Phædrus Audio Limited Warranty for details). There are no user
serviceable parts inside.
PLEASE RETAIN YOUR SALES RECEIPT. IT IS YOUR PROOF OF PURCHASE COVERING YOUR LIMITED WARRANTY. LIMITED
WARRANTY IS VOID WITHOUT SUCH PROOF OF PURCHASE.
Phædrus Audio's Limited Warranty
Warranty service conditions are subject to change without notice. For the latest warranty terms and conditions and
additional information regarding Phædrus Audio limited warranty, please see complete details online at www.phaedrus-
audio.com.
1
The Groove Sleuth preamplifier's RIAA equalisation does not include the Neumann pole in the transfer-function of the equaliser. The truth is that the
inclusion of a zero in the playback RIAA de-emphasis at 3.18µS compensates for pole which never existed in the record equaliser (see
http://www.pspatialaudio.com/neumann_pole.htm

Appendices
Appendix 1 - Model Codes
The model/order codes for Groove Sleuth Mk.II preamplifier are:
GS-II- Cost-effective, battery-assisted preamplifier with iLOOP and support for MM (MC options) and
Phaedrus Audio PHLUX/ PHLUX II active phono cartridge. Optionally equalising. Supplied with basic
external, high-quality, universal power-supply unit.
GS-II SG - for Strain Gauge cartridge, battery-assisted non-equalising, iLOOP and plugtop PSU.
GS-II CYL - for cylinder replay, MM/PHLUX, battery-assisted non-equalising, iLOOP and plugtop PSU.
GS-SG-CD4 - adds recording line output to SG preamp for CD-4 decoding
Options
GS-RIAA+ - EQ option including: RIAA; pre-RIAA (for late 78s and early LPs); and Early (which is for all
records made up until the late 1940s). (Note that RIAA+ options replace iLOOP)
MC-INPUT2 –Addition of transformer input stage for all MC cartridges.
GS-COOLER –Input-stage electronic-cooling (Not available with MC-INPUT option)
Appendix 2 - Declaration of Conformity
The Manufacturer of the Products covered by this Declaration is
Phædrus Audio
Maidstone
Kent
UK
The directives covered by this declaration are:
2014/30/EU Electromagnetic Compatibility directive
2014/35/EU Low Voltage Equipment directive
The products covered by this declaration are:
Groove Sleuth Mk. II non-equalising phono preamplifier
The basis on which conformity is being declared: The manufacturer hereby declares that the products identified above comply with the
protection requirements of the EMC directive and with the principal elements of the safety objectives of the Low Voltage Equipment
directive, and that the following standards have been applied:
IEC INTERNATIONAL STANDARD 60065: 2005. - Audio, video and similar electronic apparatus –Safety requirements
The technical documentation required to demonstrate that the products meet the requirements of the Low Voltage Equipment directive
has been compiled and is available for inspection by the relevant enforcement authorities. The CE mark was first applied in 2020.
Signed:
Richard Brice, Technical Director Date: May 2020
Appendix 3 Disposal -
meaning of the dustbin symbol
Protect our environment: do not dispose of electrical
equipment in domestic waste. Please return any
electrical equipment that you will no longer use to the
collection points provided for their disposal. This helps
the potential effects of incorrect disposal on the
environment and human health. This will contribute to
the recycling and reutilisation of electrical and electronic
equipment.
Information where the equipment can be disposed of
can be obtained from your local authority.
Batteries/ rechargeable batteries must not be disposed
of in domestic waste.

Appendix 4 –Cylinder and Strain-gauge versions
GS-II CYL (Cylinder version)
For general and technical information about cylinder records see: http://pspatialaudio.com/cylinders.htm
Specification
Gain: 55dB (x 562)
Response: Less than 1dB variation from 20Hz to 20kHz
Max input: 18mV pk-pk (6.3mV RMS)
EIN: 500nV (weighted in 20kHz)
Channel separation: 60dB minimum
Power consumption: 150mW
Battery: 9V Ni-MH (nickel–metal hydride) E-block type.
Phædrus Audio reserves the right to change specifications without notice.
GS-II SG (strain gauge version)
Panasonic strain-gauge cartridges
Panasonic strain-gauge cartridges are peculiar in that the left output must be inverted to get it into the same
phase as the right channel and –because they are semiconductors –this may not be achieved by swapping the
wires on the pins on the cartridge. The Groove Sleuth GS-II SG is fitted with output transformers and these are
used to create this inversion for listening in stereo only. The stereo signal is available on the OUTPUT phonos.
For decoding CD-4 records in Stereo Lab software, needle-drops should be recorded from the iLOOP phonos
where a wideband signal is available when option GS-SG-CD4 is fitted.
For general information regarding displacement sensitive cartridges and Stereo Lab see:
http://pspatialaudio.com/primus%20inter%20pares.htm
Sensitivity @ 5cm/s recorded velocity: Nominal 5mV RMS (-44dBu)
Polarising supply to solid state cartridge: 4mA
Gain (to right output): 39dB (× 90), non-inverting
Gain (to left output): 39dB (× 90), inverting
Frequency response: ±1dB from 20Hz to 50kHz
Distortion: 0.005% THD at maximum output level
Equivalent input noise (EIN): <500nV RMS (-124dBu), A-weighted. Input shorted
Maximum input signal (prior to clipping at full charge): 75mV RMS
Battery: 9V Ni-MH (nickel–metal hydride) E-block type.
Phædrus Audio reserves the right to change specifications without notice.
NOTE: The iLOOP output presents the cartridge output at standard MM output levels but left-channel output is
inverted relative to right. When the GS-SG-CD4 option is fitted, the listening signal is at the output phonos and
the signal for needle-drop recording is supplied at the iLOOP output.

Appendix 5 –LOCKDOWN version
Phædrus Audio's Groove Sleuth LOCKDOWN is a rechargeable-battery powered, very wide bandwidth, very-low
distortion, ultra-low noise MC (or PHLUX-II) phono preamplifier for high-quality listening and for recording
needle-drops.
For background information regarding this model, see: http://www.phaedrus-audio.com/lockdown.htm
Incorporating the features of the existing Groove Sleuth Mk. II, the Lockdown incorporates the following
innovations:
Wide bandwidth signal path (>2 Hz to 2MHz)
Highest-quality external power supply
Battery controller (removes the need for CHARGE/PLAY switch)
Electronic, ultra-low-noise MC front-end (replaces transformers in GS MK. II)
Block diagram of the Groove Sleuth LOCKDOWN

Specification of Groove Sleuth Lockdown
Size: 112 × 50 × 225 mm (W-H-L)
Preamplifier Supply: Low-noise +12V DC input on screw locking connector
Power: Compatible with European Eco-Consumption directives*
Inputs: Unbalanced MC cartridge or PHLUX-II active-cartridge
Sensitivity: 500µV RMS (-64dBu) or nominal 5mV (-44dBu) @ 5cm/s
Outputs: Gain (to computer output): × 500 or +54dB**
Gain (to iLOOP output): 0dB
Gain (RIAA equalised option): +58dB @ 1kHz
Frequency response: 2Hz to 2MHz (-3dB) to computer output and iLOOP
Distortion: Better than 0.0005% THD on 1kHz at 0.5mV RMS input
Equivalent input noise (EIN MC): -134dBu†
Equivalent input noise (EIN PHLUX): -124dBu‡
Max input: Greater than 6mV RMS (22dB above nominal level)***
Max output: 3V RMS (+12dBu)
* The unit is intended to remain energised all the time and still conforms with the European Union's Ecodesign Directive (Directive
2009/125/EC).
** × 50 (34dB) in PHLUX-II mode.
† Main output, measured in 20kHz bandwidth, A-weighted. Input shorted. 70dB signal to noise ratio.
‡ Main output, measured in 20kHz bandwidth, A-weighted. Input shorted. 80dB signal to noise ratio.
*** Greater than 60mV RMS in PHLUX-II mode.
Phædrus Audio reserves the right to alter specifications without notice.

Appendix 6 –Groove Sleuth EC8020 version
The Telefunken EC8020 is probably the best vacuum tube (valve) ever made. Today, originals are almost
impossible to obtain. And, in any case, good examples must be selected for precision audio work.
Phædrus Audio have recently introduced the EC8020-pH Supertube™, our re-creation of this unique device.
The Groove Sleuth EC8020 incorporates a couple of these tubes to create an incredible non-equalising phono
preamplifier.

Product features
Pair of Ph&aedrus Audio EC8020-pH Supertubes™
Ph&ædrus Audio designed moving-coil step-up transformers, or for PHLUX-II active cartridges
Separate HT power-supply box
Direct-coupled input circuit (no capacitors)
Designed for needle-drop recording or for operation with the PHOCUS software preamplifier
Resolve HT power-supply
Power for the Groove Sleuth EC8020 is provided by the supplied, separate Resolve HT power supply. The
internals of the power-supply and the back panel are illustrated.

Specification GS8020 with Resolve HT
Size: 2 boxes - 112 × 50 × 225 mm (W-H-L)
Preamplifier Supply: Low-noise high-tension DC input on screw locking connector
Power: Less than 10 watts*
Inputs: Unbalanced, MC cartridge or PHLUX-II active-cartridge
Sensitivity: 500µV RMS (-64dBu) or nominal 5mV (-44dBu) @ 5cm/s
Outputs: Gain (to computer output): × 630 or +56dB**
iLOOP output: Used to adjust cartridge loading
Distortion: Better than 0.05% THD on 1kHz at 0.5mV RMS input
Equivalent input noise (MC): -144dBu†
Equivalent input noise (PHLUX): -122dBu‡
Max input: Greater than 18mV RMS (31dB above nominal level)***
Max output: 10V RMS (+23dBu)
* The unit is intended to remain energised all the time.
** × 50 (34dB) in PHLUX-II mode.
† Main output, 20kHz bandwidth, A-weighted, input shorted.
‡ Main output, 20kHz bandwidth, A-weighted, input shorted.
*** Greater than 200mV RMS in PHLUX-II mode.
Phædrus Audio reserves the right to alter specifications without notice.