Altronics K 5171 Manual - Página 2

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K 5171

Fig.1: distortion across the entire range of audible frequencies is

extremely low, whether the tone controls are active or not. There

is a slight rise in distortion above 10kHz, but below that, the

distortion is below the noise floor.

Fig.3: the blue line shows the preamp's frequency response with

the tone controls switched out, and you can see that it's very flat,

varying by only 0.2dB across the entire audible frequency range.

The red and green curves demonstrate the range possible of bass

and treble adjustments.

Fig.5: distortion versus frequency of a simple low-pass filter using

either a 470pF MKT capacitor or a 470pF ceramic (non-NP0/C0G)

capacitor. As you can see, distortion rises dramatically at higher

frequencies with the ceramic capacitor due to its non-linearity and

its lower impedance at higher frequencies, which causes it to shunt

more of the signal and thus have a stronger effect.

ULTRA LOW DISTORTION PREAMPLIFIER WITH TONE CONTROLS

Fig.2: this shows the effect of noise; as you reduce the volume

and thus the output signal level, the fixed circuit noise becomes

larger in proportion and so total harmonic distortion goes up.

However, even at very low volume levels, it's below 0.01% so it

won't be noticeable.

Fig.4: the crosstalk and separation figures are good. Crosstalk is

how much of the left channel signal feeds into the right channel

or vice versa. Channel separation is how much signal from input

#1 couples into input #2 or vice versa.

Fig.6: if you must use a 20kΩ motorised potentiometer to build

this preamp, fitting the two extra 4.7kW resistors (R1 & R2)

will keep high-frequency distortion low, by lowering the input

impedance seen by the following buffer stage. This allows it to

perform optimally and also lowers thermal noise.