Trigon Vanguard III

Little phono technology and technical description of the Vanguard III

With the Vanguard III concerns it a phono pre amplifier for the equalization and
reinforcement of signal voltage coming from a record player.
Signal voltage coming from a pick-up system is unfortunately not as with CD-players or other audio devices over the shown frequency range linear, but contained with 20 cycles per second approx. 1000 time smaller signal than with 20 kHz. Without equalization the music would therefore sound itself extremely full of high tones.

The task of the phono amplifier or better said the equalizer pre amplifier is it now to produce a linear audio signal from this bent rendition characteristic, i.e. with all shown frequencies equivalent loud.
Thus however not enough, the signals of the pick-up systems are also still very weak (or quietly), so that a relatively high reinforcement is needed to raise the audio signal to the level, which is usually available with all other audio sources (except microphones). With MC pick-ups the task of the equalizer pre amplifier is more fastidious, because the output voltage of these systems is usually lower even again around the factor 10 (i.e. 20dB) than with MM pick-ups.

Furthermore the different pick-up systems need also another appropriate feed impedance, which can be adapted individually for each pick-up, to be able to unfold their qualities complete.

The demands, which are made against a phono amplifier, therefore are:
1. Exact equalization of the input signal
2. High, adjustable reinforcement
3. Individual adjustment of the feed impedance

The first task, exact equalization of the input signal, can be mastered only if you uses highly exact construction units in the equalizer part of the phono amplifier. Therefore we measure each construction unit for this stage with highly precise measuring instruments. The values of the assigned construction units are selected here on a deviation from less than 1%! Identical pairs of construction units are always formed for the two stereo channels, to exclude channel inequalities. In this way the Vanguard III produces an almost perfectly linear output voltage.

The second task, high, adjustable reinforcement, represents a problem of completely different kind. High reinforcement of the information signal means at the same time also high reinforcement of spurious signals. The main spurious signal is thereby the noise. This problem can be solved only satisfyingly with very efficient and at the same time low-noise amplifier stages. In the Vanguard III we use highly exact operation amplifiers, which besides exhibit extremely small distortion values.

The other spurious signal, which leads to problems in phono amplifiers again and again, is the so-called humming. This humming has usually three causes: Stray effect through nearby mains transformers, careless supply voltage and incorrect printed circuit board design. Over to avoid the stray effects by the mains transformer the power pack of the Advance is accommodated in a separate housing and so it can be set up in some distance to the set. The printed circuit board design is characterised among other things by a special star shaped arrangement of the pig pus courses, so that humming signals cannot disturb the sensitive amplifier stages.

The reinforcement can be adjusted individually in 16 stages by small mini switches, which are attached on the lower surface of the set. With the help of that table indicated far down you could make the correct attitude for the respective pick-up system there.

The third task, individual adjustment of the feed impedance, can be settled with the Vanguard III by a mini switch on the lower surface of the set. Here are six different adjustment resistances and this means 64 combinations are for the adjustment of one MC pick-up and 2 capacities, so there are four combinations for the adjustment of a MM pick-up at the disposal. Information about all combinations gives a table indicated far down. You recognize already by the larger number of possibilities of adaptation of a MC pick-up that the Vanguard III treats MC pick-ups preferentially. The reason lies in the fact that the majority of the offered High-end pick-up systems are nowadays of the type MC.
Because the Vanguard III is a separate phono amplifier that is connected with the pre- rather full amplifier via link cable, there are also placed high requirements to the output stages of the amplifier. Here we have decided us for an output stage, which makes a sufficiently small output resistance available, so that also cables of more than 2m lengths can be attached. This makes it possible to set up the Vanguard III in direct proximity of the record player and to keep so the cable length between record players and Vanguard III very small. This is of importance, because short cables can minimize transducer losses and offer at the same time external influences less attack region, so that the anyway very susceptible, low signal of the pick-up is impaired as little as possible.

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Reinforcement : 42 - 66 dB in 16 stages adjustable input impedance : from 25 ohm to 1800 ohm in 31 stages : without connected resistances 47KOhm capacity : Basic capacity = 60 - 100pF
: insert able capacity = 100pF, 220pF, 320pF entrance : 1x Cinch exit : 1x Cinch
Distance of weighted noise voltage : -73dB with 60dB reinforcement and : -95dB with 36dB reinforcement
frequency response : + - 0,2 dB RIAA equalized
distortion factor THD + N : 0,02%
Crosstalk attenuation : -96 dBA with 10KHz
power input : < 10VA
Dimensions h x w x d : 55mm x 133mm x 192mm