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THÖRESS
Parametric . Phono Equalizer . Series
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"THE PHONO ENHANCER MKIII"
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I N S T R U C T I O N M A N U A L
Thank you for purchasing a phono preamplifier from our Parametric Phono
Equalizer Series.
You have acquired a highly versatile phono preamplifier which allows for on-
the-fly adjustment of the de-emphasis characteristic, the gain versus frequency
behaviour of the amplifier, within wide limits by means of varying the defining
edge frequencies f1, f2 and f3 by means of three 6-position rotary switches
TCSW1, TCSW2 and TCSW3. These switches act as bass, middletone and treble
controls respectively. The favorable range of the tone selectors have been
determined and optimized by extensive listening tests. The tone selectors are
highly effective tools for restoring tonal imperfections of records (eventually
introduced during the recording or cutting process). Therefor we claim our
preamplifier to be a PHONO ENHANCER.
The amplifier is built with meticulous hand construction using our proven
point-to-point hard wiring techniques, whereas much care has been taken in
arranging each aspect of the internal construction to ensure low noise
performance, ease of service and the highest reliability for many years to come.
Please read the following explanations and instructions carefully to get the
most out of your phono preamplifier.
DE-EMPHASIS AND TONE CONTROL
The gain of a phono pre-amplifier varies with frequency so as to restore the
pre-emphasis introduced to the signal during the record cutting process.
Therefor a phono pre-amplifier is sometimes called PHONO EQUALIZER
(german PHONO ENTZERRER). The de-emphasis characteristic of a phono
equalizer is completely and unambiguosly determined by a set of edge
frequencies (equivalent to so called time constants)
f1 > bass roll-off,
f2 > bass turnover, f3 > treble roll-off.
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Summary of Contents for THÖRESS Parametric Phono Equalizer Series
- Page 1 THÖRESS Parametric . Phono Equalizer . Series ========================= "THE PHONO ENHANCER MKIII" ............I N S T R U C T I O N M A N U A L Thank you for purchasing a phono preamplifier from our Parametric Phono Equalizer Series.
- Page 2 The gain rises below f2 (bass boost) and decreases above f3 (treble attenuation/roll-off) with a slope approaching 6dB/octave. The difference between the various pre/de-emphasis prescriptions established by prominent record companies in the inception of high fidelity audio are rather small, often negligible, whereas in the most cases the crucial bass-turnover frequency f2 equals 500Hz.
- Page 3 Turn TCSW2 counter-clockwise to a lower position if a disturbing sharpness in the sonic presentation is observed. This manipulation increases the bass- turnover frequency f2 and such gives rise to a smoother (warmer) sonic presentation. Conversly, turning the middleton switch TCSW2 clockwise upwards lifts the presence of the sound image, whereas the most vivid presentattion is associated with position 6 (f2=500Hz, RIAA).
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Page 4: Phono Cartridges
Finally, attention should be given to TCSW3. This switch acts in a similar manner as the treble knob of a conventional tone control facility, altough its effect is much more subtle. Turning this knob clockwise upwards to a higher position lifts f3, thus reduces treble attenuation and such leads to a brighter sonic presentation. - Page 5 cutting head produces a monophonic groove when it is fed with identical signals on both channels. A groove obtained in this manner is significantly narrower than a FIRST-GENERATION monophonic microgroove, due to the new groove standards introduced for stereophony. Therefor a smaler stylus spike radius of 17 microns was specified for tracking SECOND-GENERATION microgrooves.
- Page 6 suitable for microgroove reading) is able to faithfully track stereophonic grooves and to re-combine the fairly well separated R and L signals back into a consistent mono signal whereby the signal generator of the cartridge converts only the lateral excitation of the stylus into signal while ignoring vertical movements.
- Page 7 The coding of lateral 78rpm record grooves (often refered to as STANDARD GROOVES) is similar to the coding applied for microgroove records (laterally excited triangular spiral grooves of constant depth). However, standard grooves are considerably wider (and deeper) than early or second-generation microgrooves and are meant to get tracked by a sperical stylus with 65-micron spike radius.
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Page 8: Phono Inputs
input 4 or 5) in case our Full Function Preamplifier is used for line amplification! PHONO INPUTS The amplifier comprises 6 phono inputs, 5 of which are suitable for low-output MC (moving coil) cartridges (equal gain 65dB@1KHz). One input is reserved for MM amplification presenting a standard 47.000 ohm load to the cartridge (gain 45dB@1KHz). - Page 9 DUAL-CHANNEL MONO PLAYBACK The Phono Enhancer allows for hum-free dual-channel mono playback with single-coil phono cartridges on each individual input without the aid of accesoires! When the 4 input terminals of a stereophonic phono preamplifier (L-hot, L- ground, R-hot, R-ground) with SINGLE-ENDED (non-balanced) circuit topology are wired to a single-coil cartridge trough a stereophonic toneramcable, in an attempt to distribute the monophonic signal over the stereo channels for dual- channel mono playback, L-ground and R-ground will unavoidably meet at the...
- Page 10 Precautions at the Input. Insert the R-plug of the (stereophonic) tonearm cable into the R-jack of the desired phono input. Let the L-plug of the cable hang freely and isolate the armature of this plug with the aid of a smal test glass (or similar accessoire) in order to prevent unwated contacts.
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Page 11: Noise Performance
signal in the initial amplifier stages cancels away during the mixing process. Obviously a clumsy and sound destructive concept. Mono switches are sound destructive as they go along with clumsy ciruitry and therefor are not suitable for dual-channel mono playback when ultimate sound quality is the aim! NOISE PERFORMANCE Much care has been taken in arranging each aspect of the internal construction... - Page 12 blocks) are part of the setup. However, there might be worst case scenarios beyond our imagination (solid state amplifiers with huge power output and too inertial protection circuitry, exceptionally fragile loudspeakers etc.) where component damage may occur in case the switching transient is not blocked out by the line device.
- Page 13 Coupling capacitor values between the amplifier stages of the Enhancer have been carefully chosen to give a very low cut-off frequency while providing a certain amount of attenuation in the subsonic range. Yet it is important to note that the FFPre does not incorporate dedicated subsonic filters. The Phono Enhancer does not feature high-slope subsonic filters! The amplifier will therefore not mask but reveal subsonic artifacts which eventually have creeped in the signal due to improper phono installation...
- Page 14 3. Remove the top lid from the amplifier case and install all tubes carefully. Take care to tighten the screws properly when closing the amplifier case to ensure a conductive connection of the lid with the chassis. Never power on the preamplifier unless ALL tubes have been installed! Never pull a tube out of its socket while the preamplifier is powered on! 4.
- Page 15 amplifier remains powered off. Wait for at least 30 seconds until the warm-up process on the unit has come to an end. 11. Power on the line device, while the power amplifier remains powered off. Again wait until the warm-up process on the line amplifier has come to an end. 12.
- Page 16 EXAMPLES OF DE-EMPHASIS PRESCRIPTIONS RCA New Orthophonic (RIAA) (f1, f2, f3)= (50, 500, 2124)Hz > (3180, 318, 75) microseconds. EMI HMV (His Master-s Voice) (f1, f2, f3)= (50, 400, 1590)Hz > (3180, 318, 100). TELDEC (Telefunken & Decca) (f1, f2, f3)= (50, 500, 2124) Hz > (3180, 318, 50). Columbia (f1, f2, f3)= (100, 500, 1590) Hz >...
- Page 17 via jumper setting), 220Vac (Thailand, China-ML, Russia, Korea, Indonesia, 100Vac (Japan) or 245Vac (Australia) available on request. Non-magnetic aluminum casework, front and rear panel with anodized printing, powder coated lids. Dimensions: 434x434x154 mm, 154=134+20 (feet). Dimensions of the shipping box: 650x650x350 mm, weight 11.4Kg.............