PURE CLASS "A" - MONOBLOCK 20W - Power Amps

Dear lover of music and quality, emotional listening. As you already have on our website Every OldStep device at our customer is a never-ending commitment for us, which is why we strive to deliver uncompromising quality and reliability.
 
This combination, along with a turntable and headphones, is all you need to get the most out of your favorite music.
 
You can complete the set with a top integrated Comfort preamplifier.
 
The power amplifiers can of course be combined with all standard audio components, but we have taken the utmost care to match the OldStep Comfort preamplifier and Nadral speaker systems and we believe this set is an excellent choice in this price range.
 
The Monoblock PCA-PA-20W power amplifier is designed as a Monoblock, ie the left and right channels are amplified in a separate amplifier, which is a separate component. This solution has the major advantage that the power amplifier is placed as close as possible to the speaker, so you can minimize the length of the speaker cable and thus eliminate its effect on reproduction. The monoblock design solves any crosstalk, interconnections and influences between the left and right channels in a completely ultimate way. The Monoblock concept is used in the highest category of High End devices.
 
The second and more fundamental aspect of the concept is the construction in class A. The term "class A" is very often used in connection with many different devices, different categories. It is marketed as a brand of quality equipment, but in reality its use is often completely beyond the reality and meaning of this involvement. As an example, I would mention class A preamplifiers. In my decades of audio practice, I have not encountered a different type of preamplifier design than in class A unless it was digital. There is no reason for voltage preamplifiers and it makes no sense to use a connection other than class A. Quiescent current is not a design problem and the fact that class A completely eliminates transient distortion predetermines this connection for this type of use. Simply put, you can be sure that every preamplifier is built in the "A" and to state this fact as an advantage of a particular model has no real value. However, the situation is completely different for power amplifiers. With a power amplifier, this type of connection completely eliminates transient distortion as with preamplifiers, but the quiescent current required to achieve output power becomes a major design complication. The quiescent current is in relation to the output power and flows through the output stage of the amplifier even when there is no signal at the output. This current causes considerable heating of the entire component and becomes a central factor for the design of the entire structure. In other words, the class A used in the power amplifier has only one advantage in eliminating transient distortion and on the other hand the disadvantages, consistently high consumption, high warming, which requires robust and expensive design of heatsinks and power supply with enormous filtration of capacitor banks, problematic stabilization of operating point in a wide range of working temperatures and many more. However, this single advantage is a fundamental difference from all other connection classes, because it has a characteristic spectrum of harmonic signal content (odd 3,5,7 are dominant), which forms the overall sound perception of listening, and music is what we are talking about. Again, simply put, the final "A" has, according to our many comparisons, a different and exceptional character of the sound that we like in OldStep.
 
Many manufacturers manufacture Class A power amplifiers, which contain very sophisticated and complex circuits that compensate for the disadvantages of this connection, and significantly reduce the cost and simplification of the entire design so that it can still be remotely labeled as Class "A" and still be manufactured and sell well. With a bit of exaggeration, we dare say that when you take in an amplifier with an output power in the order of tens of watts, your back does not hurt and it does not burn you in your hands, so it is not a native but just a mutant with an uncertain character of real class A. experiments, in OldStep we chose a different and rather unusual path. We accepted all the disadvantages of class A as a fact and decided to accept all the consequences such as output power limit, high weight and size in relation to output power, complicated thermal design and heating reaching up to 50C on coolers and the need for precise component selection and individualized manual production. and settings. As a reward, we acquired a gem that we honed into an exceptional sound expression from our point of view. If you've come to the same humble acceptance of the laws of physics on your journey through the world of audio equipment, and you trust your ears more than sophisticated marketing claims, we believe you'll be as excited about this choice as we are at OldStep.
 
Power supply
 
The amplifier circuits are powered from a robust source of linear concept, which minimizes the formation of interfering components in the power supply. The power supply is preceded by a discrete, high-quality mains filter and Standby control circuit. In the off state, the amplifier consumes very minimal energy in the 2VA series. The source consists of a 150VA toroidal transformer in audio design, followed by a diode rectifier and filter batteries with a total capacity of 80,000uF. The last part of the source consists of a semiconductor filter with a capacitance multiplier, so that the total equivalent filtration capacity is in the order of hundreds of thousands of uF. The design of the power supply is absolutely essential for an amplifier in class A, because this class of connection does not in principle suppress interfering components of the power supply and it can be said that everything interfering from the source appears transparently at the output in the music signal. The power amplifier is powered by a symmetrical voltage +/- 22V with a consumption of about 1.3A. The continuous consumption in the on state and the "lossy" power of the amplifier, which must be radiated by the heatsink, is therefore about 50W.
 
Power amplifier
 
At the heart of this part of the amplifier are two pairs of complementary, paired Toshiba power transistors in a special Darligton circuit. This stage is excited by a symmetrical voltage amplifier. The overall design is subject to the philosophy of the most direct and shortest possible audio signal path through the amplifier. OldStep's philosophy is to achieve the simplest possible construction but strictly never easier. This means that when an element must be in the connection, we will use it regardless of the price and complications associated with it. The entire amplifier is DC coupled and the signal from input to output does not pass through any capacitor. The stabilization of the quiescent current has a very slow control constant in comparison with commercial amplifiers, and the nominal value of the quiescent current is reached only at complete temperature stabilization in the order of about 20 minutes. So when using it, you can choose two ways, turn on the amplifiers 20 minutes before you start listening or enjoy how your audio plays minute by minute better at the beginning.
 
Auxiliary and protective circuits
 
Monoblock PCA - PA - 20W is designed for connection with high quality components of a higher price category. For this reason, we paid uncompromising attention to protective circuits during development. The basic element is the starting circuit, which delays the connection of the output connectors after switching on in the phase of initial stabilization of quiescent current. The disconnect circuit contains a power relay that is controlled to minimize knocking and transients when turning the amplifier off and on. The second circuit is a DC component monitor at the output of the amplifier, which immediately activates the disconnection and grounding of the outputs in the event of a fault or improper handling. The third protection circuit is a signal size monitor at the output, which again immediately activates the disconnection of the outputs when the normal level of the nf signal is exceeded, eg in case of incorrect handling of signal cables in the on state, thus protecting especially speaker systems.
 
OldStep construction philosophy
 
The value we honor and pass on to our customer is the repeated long-term joy and experience of listening to music. Our constructions are uncompromisingly subordinated to the overall perception and feeling of the music, they are built on the effort to find the most direct path of the audio signal from the carrier to the listener's ears. We love vacuum tubes, but we use a wide range of electrical circuits and wiring concepts and carefully choose to use them in the right place in the audio chain.
 
Every detail of OldStep components is based on our many years of development, many experiments and experience. The products are handmade and each piece is uncompromisingly controlled for sound, quality and parameters.
 
Price: 59 900, - CZK (incl. VAT per pair in black or silver colour)
 
Specifications
Nominal power output:                                             20W (20Hz - 20kHz)
Output impedance:                                                   8 OHM
Harmonic distortion:                                                 <0.06%, @ 10W, 1kHz
Frequency Response:                                             -0.5 dB, 5Hz - 100 kHz
Input Sensitivity:                                                       0.5V, @ 10W / 8OHM
Input Impedance                                                      33 kOHM
Signal to noise ratio                                                 > 90 dB
Slew rate                                                                 12V / us
Power consumption:                                               50 W max on, <2 W in Standby
Mains voltage:                                                         230 V AC ± 10%, 50 Hz
Dimensions - Line stage:                                         240 (w) × 110 (h) × 360 (d) mm
Weight in total (1pcs):                                              12 kg