Picture of C-MOD Audio precision coupling module

Picture of C-MOD

The LEFSON C-MOD is a very high performance audio coupling module. It’s named «coupling module» instead of «capacitor» because it was designed with care in the point of view of an audio coupling system. Extremely low loss operation is one of its best features, this is our «WIRE LIKE» technology.

Specially designed to process small AC signals (instrument, microphone, line), the LEFSON C-MOD is the perfect solution when a DC blocking capacitor is needed, in low voltage circuitries.

The LEFSON C-MOD is fitted with an internal shielding and can be placed in high magnetic flux environment. A dedicated clamp (patent pending) can be optionally used to achieve a perfect mechanical ground.

Main features of the LEFSON C-MOD are :






The LEFSON C-MOD is non-polar : both audio pins can be either used as input or output for analog signal. It is designed to be used as a precision audio coupling module. The LEFSON C-MOD is sold with a 20 hours burn-in time. To achieve optimum results, it needs to be burned-in with audio signals during at least 80 hours.

We designed 16 values, from 1µF to 1000µF working at low DC voltage (25V/35V/50V), as follows :

1 50V A C1M50 77€
2.2 50V A C2M250 80€
3.3 50V A C3M350 83€
4.7 50V A C4M750 85€
10 50V A C10M50 87€
22 35V A C22M35 93€
22 50V B C22M50 97€
33 50V B C33M50 101€
47 50V B C47M50 106€
100 50V B C100M50 114€
220 35V B C220M35 120€
220 50V C C220M50 131€
330 25V B C330M25 128€
330 50V C C330M50 140€
470 35V C C470M35 151€
1000 25V C C1000M25 168€

Recommended retail price

- The ideal audio coupling

Ideally, we shouldn’t have to use any capacitor to design an audio coupling. They cause, because of their properties, a variable ratio of losses of any AC signal that runs them. The best capacitor should be « no capacitor ». The preservation and stability of DC polarization voltages between electronic stages sometimes forces the designer to use an audio coupling capacitor.

The purpose of the LEFSON C-MOD is clear : get closer to the quality of a direct (wire) coupling.

- Measures with Pure Tones

Traditional measures using a pure tone show that the LEFSON C-MOD has quite standard characteristics.

Picture of ESR vs Frequency Picture of TAN D vs Frequency

Picture of Capacitance vs Frequency

We can notice the ESR (Equivalent Serie Resistance) consistency and the linearity of the dissipation factor (Tan δ) between 10kHz and 100kHz. But that’s when it’s used with complex or musical signals that the LEFSON C-MOD, with its « WIRE LIKE » technology, brings its incredible performances.

- 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.

Picture of Classical measure

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.

Picture of reversed phases

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 :

LEFSON-C-MOD - Recording 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 :

Picture of the C-MOD Audio Comparative Box

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.

Niveau de pertes - DIRECT vs HQ. POLYPROPYLENE

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 :

Niveau de pertes - C-MOD vs HQ. POLYPROPYLENE

Ecoute comparative du C-MOD aux Studios de La Chine - Paris

- 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.

Hasta la vista, Baby !

- 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.