cs port Phono equalizer amplifier C3EQ

Thought of C3EQ phono amp

The mission of the equalizer amplifier is to accurately convert the current generated by the MC cartridge to the voltage, accurately equalize it to the RIAA curve, and amplify it to the level required by the preamplifier without adding extra things.

The I-V conversion is a C3EQ phono amp concept, which amplifies with a small number of stages while driving with a MC transformer with high linearity (linearity) and drives the CR network with low impedance.

Use ultra-reliable tube C3g

The voltage amplification of the high linearity is advantageous for a triode which is a constant voltage element. Also, since the distance between the electrodes and the thickness of the wire are effective for linearity, it is advantageous that the grid line is thin and the gap between the electrodes is large.

Deutsche Telekom developed for a telephone repeater, C3g is a highly reliable pentode that realized it with a Roctal tube, but in C3EQ it is used for triode connection.
In order to avoid noise generated at the contact point, C3g is directly soldered to the printed circuit board without using a socket. Moreover, since the exterior is completely shielded with an aluminum case, even if it is used for a circuit with high gain, it is structured to be less susceptible to external noise.

CR Equalizer

There are NF type and CR type in the phono equalizer method. Since C3EQ uses C3g and FET follower, it drives the CR equalizer circuit accurately with high linearity and low impedance. For the CR filter, a 1% accuracy foil-wound capacitor developed for communication is used to ensure stable operation.

MC transformer built-in, transformer output system

Since MC transformer is built in, you can use it only by connecting phono cables. Because the output can also be separated from other equipment by the transformer method, it is less susceptible to noise and does not add extra things.

In the transformer, we used super permalloy core of high magnetic permeability that allows micro signal to pass as it is, and has obtained high linearity characteristics.

Balanced, unbalanced input selectable

For connection to cartridges, either balanced input or unbalanced input can be selected. Output with high signal level is only imbalanced.

Non-NFB technology reproducing original sound in high fidelity

Key technology is no NFB

A negative feedback circuit was invented in 1927, and the performance of the amplifier improved markedly. However, looking at the micro level, the negative feedback circuit (servo control) returns underexposed signals back to the “+” and returns underexposed signals back to the original, and this vibration And Odd’s different words will cause cross-modulation and become different from the original sound.

In order not to cause this oscillation, it is necessary to perform ideal servo control, or use non-feedback as a linearity (linearity) for components such as amplifier elements and capacitors.

Intermodulation distortion scarier than harmonic distortion

Harmonic distortion means that, when a signal passes through the element, it generates an integer multiple signal, which can be heard comfortably to humans in a sense.

Among the distortion, it is intermodulation distortion that is scary, generating uncorrelated signals that are not in the original signal, resulting in an unpleasant sound.

For example, when a signal of 1kHz and a signal of 1.1kHz pass through a rectifier or an amplifying element, a sum signal and a difference signal of the respective signals are generated. 100Hz and 2.1kHz were not found in the original signal. Since the audio signal is a collection of many frequency components, the frequency component of noise also causes intermodulation, invades the audio signal, and loses the three-dimensional effect of the sound. Again, components with good linearity are less likely to cause cross-modulation.

Realization of low distortion rate by two stage configuration

You can not escape distortion as long as you use an amplifying element. It is a measure to use elements with good linearity or reduce the number of elements.
In C3EQ, it is configured with only two amplification tubes C3g of high linearity, suppressing harmonic distortion and intermodulation distortion to a minimum while returning non-return.

C3g is a new old article, but since it is in stock at the CS Port in large quantities, there is no worry about maintenance.

Noise generation at the contact point

Amplifiers have many contact points. When looking at the micro level, there is a rectification effect there, and noise is emitted.
Especially the rectifying action of the metal oxide film is the most scary factor.
The signal path other than the input terminal and the output terminal is designed not to use a connector to prevent noise generation, and the gilding connector is adopted for the portion where direct current flows.

Battery-driven system ensuring quite high quietness

Disconnecting from a line driven by a battery

Various noise is misplaced on the AC line. From the outside of the audio system, switch noise of large equipment and noise due to current distortion etc. come in through the cable. Also in the audio system, the AC cable of each equipment creates a loop and generates electromagnetic noise. In an equalizer amplifier that handles a very small voltage, these noises become a major obstacle.
C3EQ shuts out these noises by performing battery operation and realizes silent music playback.

Operating time during battery operation

For the battery, use a large-sized nickel metal hydride battery. It is possible to operate for 5 hours with one charge, but it can be increased to 9 hours by option.
When the battery runs out, the charger automatically operates and puts it in a fully charged state. In the unlikely event that the battery fails, safety will be secured by temperature monitoring.

Switching power supply + analog power supply

It is not exaggeration to say that the sound of the amplifier is determined by the power supply. Transformer type power supply suffers from mechanical vibration generated by the transformer and processing of generated magnetic flux, but this unit adopts switching power supply without risk.
Suitable for the reference machine, it responds more quickly to the voltage regulated by the switching power supply. We arrange highly accurate analog power supply independently on the left and right channels, and are making it clean. From there, it produces a sound like a clear stream of the Alps.

Outstanding noise processing technology

Rectifiers and contacts used for general power supply are sources of noise. Since these are sharp noise of rising, they occur over the band of 50 Hz to several hundred MHz, entering the audio band and making the sound muddy, causing intermodulation. Of course, the switching power supply also generates noise greatly, causing the same phenomenon.
CS Port noise processing technology cultivated over many years of switching power supply design suppresses / cuts unnecessary noise and achieves clear sound.

Phono equalizer amplifier C3EQ

Specification