The construction of the Silver Grand Mono closes ten years of the presence of Ancient Audio on the market. It is also, in my opinion [J. Waszczyszyn – editors note] the conclusion of the current art of making such constructions. The previous model, Silver 300, was made according to the canon of tube amplifiers construction made in the 70-ties in Japan. Those rules, perfected by Hiroyasu Kondo, stood ground perfectly in many hi-end products. However the ongoing improvement in loudspeaker and sound source design imposed the need of changing some of those assumptions. 20th century solutions became not sufficient for the 21th one. Hence the design of the Silver Grand Mono, using some of the canonical solutions as well some new ones, not used before.
Influence of the power supply on sound in audio devices is commonly known. An ideal power supply should be a voltage source, what means that its impedance for direct current and alternating current should be equal to zero – voltage does not change to any load, DC or AC. There is no such power supply. But we can approximate the ideal. When an amplifier works in class A (every Single-Ended amplifier) the supplying current is steady. But this is only true for the mean value. For circuits with inductive elements (chokes or transformers) during one cycle the amplifier is a current receiver, in another cycle it is the current source. Hence the big impulse changes in current draw from the power supply: their magnitude as well as their direction varies. To provide stable voltage, the power supply needs to have a very low internal impedance for alternating current. A classic design, with a rectifier tube, a big choke and small capacities provides satisfactory damping of the power current fluctuations, but is at the same time very sensitive to transient current changes – for those the impedance of the choke is very high. But to reproduce the dynamics of music, attack of the instruments, we need exactly the opposite. Experiments with the concept: “large capacities, solid state rectifiers, no chokes, active circuits lowering the impedance of the power supply” were the first step to construct the new Silver. Reproduction of dynamics and bass control were a class better, than with classic amplifiers with tube rectifiers.
The power supply turned out to be so worked out, that it had to be transferred to a separate enclosure. In addition separation to two monoblocks and two monophonic power supplies minimized their mutual interference, especially those caused by dissipated magnetic fields. Every power supply has three independent power transformers: high voltage and heating of the E88CC tubes, heating of the 300B and amplifier control. All voltages are stabilized. The amplifier has a battery of capacitors, which can hold a significant amount of energy. For example the high voltage capacitors can hold over 1000J of energy. This would be enough to start a gasoline engine or light a 100W bulb for 10 seconds.
This is an element, which is key for every tube amplifier. This is why the best manufacturers make their transformers themselves. Ancient Audio has come with a proprietary technology of making the windings from silver wire. The silver wire, prepared in a special laboratory (99.99% pure) goes through a full cycle of heat treatment. This wire is then used to hand wind the secondary winding of the loudspeaker transformer. The whole transformer is hand made using a “double C” core. The transformers are made in pairs, and after each technological step are undergoing tests and measurements. A novelty in this aspect is the usage of Teflon isolation. This material minimizes losses, provides low capacitances and lack of hysteresis. Silver Grand Mono is the only amplifier, which utilizes this technology.
Silver is a very good conductor. It has similar impedance to copper, but conducts current much better at low signals. Silver oxide (always present after melting) is also a conductor. In difference to that, copper oxide is a semiconductor, and the border between the oxide and copper has rectifying capabilities. This is why at low signals and zero crossing copper cables cause large losses of signal. Please remember, that high frequency currents flow on the surface of the conductor (skin effect). To further minimize the losses of acoustic signals, all connections are made by a silver ribbon, with 3mm2 cross-section and 20mm diameter. Only Teflon is used as dielectric.
Teflon signal capacitors
The difference between Teflon and other synthetics is noticeable already with small surface areas (like in interconnects). And the composite surface of the signal capacitor plates is measured in square meters. The quality of the dielectric and the plates has a significant influence on the sound. Yet commonly used dielectrics, like polyester, polypropylene or paper are non-linear. Their dielectric constant depends on capacitance, temperature, and worst of all, on voltage. In addition there is a memory effect – after discharge, the capacitor “remembers” some of the previous state. The solution is the best of the available dielectrics (besides vacuum), Teflon. Unfortunately the low dielectric constant, high costs and technological difficulties limited its usage. Mass production of elements utilizing it started only five years ago. And only a few companies offer those. The best, currently manufactured capacitors, are the V-caps, designed by Chris VenHaus, which have tin foil plates, better than the commonly aluminum dusted ones.
Fast electrolytic capacitors
Electrolytic capacitors are a necessary evil. In places where large capacity is needed, they have to be used. But they need to be as good as it gets. Black Gate capacitors were standard, due to their low impedance. But after 30 years of production, those were pushed out by modern elements, designed to work in switching power supplies. Switching power supplies impose very high requirements on those: high currents, low intrinsic inductance, low impedance, high operating temperature, high frequencies. Modern power supplies work in the megahertz range. This allows them to be smaller, with better parameters and higher durability. This is the reason behind the development of modern passive elements and quick development of their technology. The capacitors used inside the Silver Grand Mono amplifier use those abilities. The battery of capacitors in the heater circuit has an impedance in the mΩ range for the whole acoustic frequencies range.
The voltage tubes are the E88CC from old stock, NOS (Philips, Telefunken, Valvo, Siemens). The tubes are still available from significant stock. They work with low current, what makes them last for 10000 hours or more. The power tube is the 300B, designed by Western Electric, is the one, most commonly used in hi-end SET amplifiers. Due to high linearity it is able to work without any negative feedback loops, global or local. The demand for those tubes was so great, that the manufacturer decided to restart production after 50 years… But also here progress was achieved. The Taiwan company TJ designed a version of those tubes with a mesh anode. Those were splendid tubes, although the research for the optimal construction and materials continue. Two years ago, TJ created 300B tubes with graphite anode. Graphite has a large heat inertia, it also dissipates it well. Those are the best available tubes at the moment. Their durability is around 3000 working hours.
Anode current meter
Each 300B tube is different, this is why the tubes are prepared in pairs. But sometimes during transport, the mesh deforms slightly. That is why the amplifier is equipped with a bias current meter. This meter consists of a row of ten LEDs. Each LED means 25mA of anode current. The nominal current (two tubes) is 150mA, 6 LEDs lit. Higher current can be harmful for the tubes, this is why the LEDs indicating it are bigger. The 2006 edition of the Grand has automatic bias – no adjustments are needed. This solution increases the safety and durability of the amplifier.
Silver Grand Mono is mounted on a granite plinth. The 2006 version uses three granite elements separated by a soft, vibration reducing material (sandwich). In effect this is a splendid base: heavy, rigid and damping. The audio elements are mounted directly to the chassis. All connections are made point-to-point using silver foil.
two monoblocks + two monophonic power supplies,
output power : 2 x 18W/4-8Ω,
directly heated power triodes 300B,
no global or local feedback,
hand wound loudspeaker transformer,
silver secondary winding, Teflon isolated,
silver ribbon cabling, with Teflon isolation,
Teflon capacitors with tin foil V-Cap TFTF (signal path),
oil capacitors V-Cap OIMP (power supply),
full solid state power supplies,
six power supply transformers,
160 000μF heating circuit capacitance for the 300B,
1000J energy in the high voltage capacitors,
all voltages stabilized,
tubes: 4 x 300B, 4 x E88CC,
bias voltage meter,
bias current stabilization for power tubes,
input sensitivity 500 mV,
noise: - 100 dBA,
granite plinth for the monoblocks,