- Measures with Complex Signal
In the audio area, except the « R2D2 » robot, nobody listens to pure tones. These are mainly used as references during calibration, adjustment and measurement procedures.
99,9% of musical signals are of a complex type : several waveforms of different levels and frequencies are mixed to form an overall signal, said complex. An electronic component may have a very different behaviour according to
the type of signal it needs to process.
Since an audio coupling capacitor handles, in 99,9% of cases, musical signals, thus complex, it’s to them that its behaviour must be beyond reproach. This is why we designed the LEFSON C-MOD as an audio coupling module for
complex signals and not as a classic capacitor.
- Measurement method
It’s possible to mesure the result of a complex or musical signal through different capacitors. We can use a spectrum analyser, multimeter or oscilloscope. However, the nuances between components remaining relatively low with
regard to the effective signal level, it is difficult to aspire to a serious exploitation of statements and measures.
As shown in the picture below, the lack of precision of measuring instruments must be taken into account. In this example, two capacitors of 1µF and of different quality are nevertheless well processed by the same musical signal.
When listening, the high quality (HQ.) POLYPROPYLENE capacitor gives better impressions than the standard capacitor (ST .) POLYESTER.
The most reliable method uses the phase reversal. If we add two strictly identical signals but of reversed phase, they nullify. For example, the two following signals are in phase reversal. Their theoretical sum is perfectly zero.
As a reference, we take a complex signal from a musical source. If we make it go through different capacitors (one by one) and also by a direct coupling (without capacitor), the capacitor causing less loss will be the one whose
addition in reverse phase with the direct coupling will give the weakest signal.
Similarly, if we add the signal obtained by the direct coupling whith its opposite in phase, the result will theoretically be null.
- Recording various signals
To proceed with the phase reversal method, we are going to record four musical samples from a common stereo source :
- DIRECT : Direct coupling, ideal capacitor (no capacitor)
- ST. POLYESTER : Standard quality film capacitor - 1µF/63V Metalized Polyester
- HQ. POLYPROPYLENE : High quality film capacitor - 1µF/200V Metalized Polypropylene
- C-MOD : LEFSON coupling module - 1µF/50V
We use the following configuration :
The four samples are recorded one by one after selection of the desired pair of capacitors. All recordings are made with the same wiring and on the same input of the digital multitrack recorder.
The « LEFSON – Comparative Box » is a stereo comparator box for coupling capacitors. It consists only of sockets, rotary and lever switches. Below is a picture of the 1µF comparator box used for our tests, and its electronic schematic :
The recordings give nearly similar levels. Impossible to use the results at this level.
We select a very short period of music and proceed to four new internal recordings in the multitrack recorder, according to additions of signals with others, in phase reversal, as follows :
. DIRECT + ɸ(DIRECT) = -116.9 dBFS (peak)
. DIRECT + ɸ(C-MOD) = -60.5 dBFS (peak)
. DIRECT + ɸ(HQ. POLYPROPYLENE) = -57.6 dBFS (peak)
. DIRECT + ɸ(ST. POLYESTER) = -57.5 dBFS (peak)
At this point in our experience, we already understand that the LEFSON C-MOD causes a level of loss lower than the one of the two others. In order to view the results on the oscilloscope, we apply a digital amplification (Full Scale)
of gain Gfs=4 to each of the four previous recordings. So we get the following levels :
. DIRECT + ɸ(DIRECT) = -29.2 dBFS (peak)
. DIRECT + ɸ(C-MOD) = -15.1 dBFS (peak)
. DIRECT + ɸ(HQ. POLYPROPYLENE) = -14.4 dBFS (peak)
. DIRECT + ɸ(ST. POLYESTER) = -14.37 dBFS (peak)
- Visualization of loss levels on the oscilloscope
Each stereo recording is summed to a mono output channel connected to the oscilloscope input. The ideal capacitor (direct coupling/ no capacitor) is obviously the one which causes no loss.
The displayed small wave is in fact the noise of the digital multitrack recorder.
The ST. POLYESTER capacitor causes, depending on the period, slightly more losses than the H.Q POLYPROPYLENE.
The LEFSON C-MOD is indisputably the one whose electric loss level is the closest to an ideal capacitor. The LEFSON’s « WIRE LIKE » technology allows a smaller level of audio loss than a high quality polypropylene capacitor :
- When hearing meets measurement
Accuracy, detail, fastness of transients, dynamic conservation, are among the words pronounced by all the professional of sound, in audiophily and recording studio, who listened and compared the LEFSON C-MOD.
These hearing sensations directly come from the « WIRE LIKE » technology developed by LEFSON, that allows an ultra-low ratio of audio loss.
- High Fidelity up to 1000µF
The « WIRE LIKE » technology allows to use the C-MOD with such high capacitance as 1000µF in a really small case (4,2 x 4 x 2,5cm).
In the contrary to the very big size and the values limitation of polypropylene capacitors, it becomes possible to design true audiophile coupling with high capacitance values in many audio gear.