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THÖRESS
Parametric . Phono Equalizer . Series
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"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 the THÖRESS Parametric Phono Equalizer!
You have acquired a highly versatile vacuum tube phono preamplifier offering MM
and MC amplification with excellent signal-to-noise performance in purely active
operation mode (without the aid of built-in step-up transformers) and unique on-
the-fly tone adjustments by means of three 6-position rotary switches TCSW1,
TCSW2, TCSW3, which we call tone selectors. The tone selectors give rise to subtle
bass, middle tone and treble control functions which are highly effective tools for
restoring tonal imperfections of the replayed vinyl program (eventually introduced
during the recording or cutting process), implemented without involving clumsy and
sound destructive conventional tone control circuitry!
The amplifier is built with meticulous hand construction using our proven point-to-
point wiring techniques, whereas much care has been taken in arranging each aspect
of the internal construction to ensure highest reliability, low noise performance and
ease of service for many years to come. Please read the following explanations and
instructions carefully to get the most out of your phono preamplifier.
INPUTS
The amplifier comprises 6 phono inputs with gain pattern (5xMC+1xMM), five inputs
with 65dB MC gain and one input with 45dB MM gain (presenting a standard 47K
load to the cartridge). Alternatively, a gain pattern (1xMC+5xMM) can be
implemented on request. However, it is not possible to install an arbitrary MC+MM
gain pattern on the amplifier for technical reasons. The cartridge loading is
(100, 200, 300, 500, 1000 / 47.000) ohms and (500 ohm/47K, 47K, 47K, 47K, 47K).
on (5xMC+1xMC) and (1xMC+5xMM) standard units respectively. Other load values
can be easily installed on demand.
The MC load values installed on each individual MC gain input are printed on the rim of
the rear panel for reference!
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Summary of Contents for THÖRESS PHONO ENHANCER MKIII
- Page 1 THÖRESS Parametric . Phono Equalizer . Series ========================= "PHONO ENHANCER MKIII" ..............I N S T R U C T I O N M A N U A L…..Thank you for purchasing the THÖRESS Parametric Phono Equalizer! You have acquired a highly versatile vacuum tube phono preamplifier offering MM...
- Page 2 It is not possible to install arbitrary MC+MM gain patterns on the Phono Enhancer for technical reasons! OUTPUTS The output impedance of the amplifier is sufficiently low (around 300 ohms) to simultaneously drive (up to 3) long cable runs and line inputs with an input impedance as low as 10.000 ohms without compromising sound quality.
- Page 3 same record company in the same period of time) vary much more widely than the tonal differentiation even between the most distinctive de-emphasis prescriptions, hence Humble de-emphasis curve selectors are not suitable for restoring optimal tonal balance of analogue disc records. They are useless, misleading and puzzling to the user! By contrast, the Phono Enhancer allows for highly impactful yet subtle tone control via edge frequency shift! Tonal manipulations of this kind have a much stronger impact in restoring a satisfactory tonal balance of a given record when adjusted...
- Page 4 The boosting effect is obtained by attenuating the mid band gain of the amplifier with respect to the low frequency end. Consequently, in order to maintain the listening loudness of the previous sound image, the volume needs to get adapted on the line device after moving TCSW1.
- Page 5 RECORD THE OPTIMAL CONTROL PATERN FOR LATER REFERENCE. Record the positions of TCSW1, TCSW2 and TCSW3 established so far as a temporary result. Then critically check and re-consider the settings by comparing and re- evaluating the sound images while switching the selectors one or two steps upwards and downwards from the previous optimum.
- Page 6 ability, although this type of stylus was originally intended for tracking (WIDE) first- generation microgrooves! Conversely, every phono cartridge with a spherical 17-micron stylus (or one of its modern derivatives) can faithfully track (WIDE) first-generation microgrooves although this type of stylus was originally intended for tracking (NARROW) second-generation microgrooves! Stereophonic grooves are mono-compatible in a two-fold sense...
- Page 7 Mono-flexible single-coil MC cartridges are currently produced by MIYAJIMA LAB in Japan, all of which models (unfortunately) come with simple spherical stylus profiles. The highly outstanding TEDESKA mono cartridges made in Berlin by Hyun Lee are other examples of mono-flexible single-coil MC cartridges of current production. Whereas the ORTOFON Mono CG-25 and the EMT OMD-25 are widely known classic single-coil MC cartridges (pick-up heads).
- Page 8 SINGLE-COIL MONO INSTALLATION (with MKII and MKIII units) Precautions at the Input onnect the L-plug of the (stereophonic) tonearm cable with the L-jack of the desired phono input. Insert the R-plug of the tonearm cable in one of the RCA jacks (labelled SINGLE-COIL MONO) below the phono inputs.
- Page 9 mono signal appearing at the L-signal output of the phono amplifier over the L+R channels of the line device (Y-connection). The system is will be ready for replaying mono records in dual channel mode with the chosen single-coil cartridge once input MO has been switched active on the line device.
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Page 10: Noise Performance
Nevertheless, lower bass-turnover frequencies than 500Hz can be easily implemented on some positions of TSCW2 on demand, for those users who specialize in 78rpm playback and place importance on more finely graduated bass- turnover frequency selection. SUBSONIC ARTIFACTS Coupling capacitor values between the amplifier stages of the Enhancer have been carefully chosen so as to give a very low cut-off frequency while providing a certain amount of attenuation of subsonic frequencies (unwanted but not always avoidable artefacts). - Page 11 where component damage may occur in case the switching transient is not blocked out within the line device. The Enhancer also produces moderate switching noise when the input selector it is moved in between the pos(1, 2,...,5). This is not a peculiarity of our preamplifier and would arise in a similar manner with any kind of phono amplifier with on-the-fly selectable MC gain inputs due to the extreme input sensitivity of such devices.
- Page 12 3. Move all tone selectors into default position, pos(6,6,1)=(RIAA, RIAA, RIAA), RIAA de-emphasis. 4. Bring the ground switch (GS) on the rear panel into position ERDE (earth/ground). With this GS setting the amplifier is grounded in the sense that there is a conductive connection between the central zero point of the circuit and the ground terminal of the power inlet module (and thus a conductive connection between circuit zero potential and earth/ground through the respective lead of the power chord).
- Page 13 playback in the foregoing step, respecting the remarks made in the paragraph about dual-channel mono installation. Note that the system will replay the L-signal on both loudspeakers (rather than a consistent stereophonic signal) when you play a stereophonic cartridge through MO! Conversely, when you play a single-coil cartridge trough STE the mono signal is replayed on the L-loudspeakers only (while the R-Loudspeaker runs at idle)! 11.
- Page 14 Let the records rotate in the bath of an industrial grade (6 liter, 6L) ultrasonic cleaning machine (USCM) for at least half an hour with the aid of the KUZMA rotator kit or similar device. (Note 6L machine, not a 4L or 10L device!) Use demineralized water and a few drops of dish cleaning concentrate as cleaning fluid heated up to about 45deg Celsius.
- Page 15 • MC gain with state-of-the-art signal-to-noise-performance in purely active operation mode (without the aid of step-up transformer gain). • Minimalist single-ended zero-feedback schematic with passive de-emphasis installation utilizing (2x6J5GT+1xPCC88) vacuum tubes. • Edge frequencies of the de-emphasis characteristic independently on-the-fly adjustable within wide limits by means of three 6-position rotary selectors.