|
|
silvercore preamp 812A
Our preamp 812A is a one stage single ended preamp with line and headphones output. The power supply is separated in extra case. Thus, to achieve the best sound this amplifier is built without any limits in view of costs. That’s why those high-class components and the resonance optimised case are the reasons that this preamp is a real sop in the pan. Moreover, it is definitely a serious competitor for the best preamps in the world.
The sound can be described as airy and easy. It is very seldom that we hear music like this. But what are the reasons? Is it because we do have only a few components in the signal’s path? Or is it because of the good material? It is best to say, that both aspects play a certain role in it.
The Concept
The music signal is selected at the input by an gold plated rotary switch from Elma. Hence, the volume control happens inductively with our 12-switch stepper transformer. The voltage gain is done by the huge transmitting tube 812A triode in a class A2 application. The output transformer has the task to provide the headphones and the output stage with an as low-ohmic as possible signal.
The power supply is situated separately to the amp. We decided to build it like this to reduce every negative influence of the mains transformer on the sensitive circuit of the preamp.
Why a Transformer?
We use the “stepper” transformer for the volume control in the amplifier’s input. It is true that right at this place, we could also use a potentiometer. But the sound wouldn't be as light as with the “stepper” transformer.
It is almost the same with the output transformer. We need this device for the low resistant output also for making the amps personal sound. For this reason we take the biggest core possible to get spectacular deep bass response and the phantastic huge soundstage.
The power supply
In a tube amplifier we have a DC voltage, that is also called anode voltage with the anode current. When the music’s AC voltage modulates the frame, then the anode voltage is also modulated with the higher amplitude and its factor of the amplification.
Put simply, the tube amplifier modulates the supply voltage in time of the music. It can be argued, that the importance of the adapter, which generates the supply voltage, is very often not understood in full term. However, the adapter is an essential element of the amplifier. We can build a controlled adapter to obtain a humming free AC voltage. Fact is, a controlling in the adapter is almost like a strong degeneration: when it is too high, as a result, it is darkened too much. Usually then the sieving is clear, but the sound image is dark and undynamic.
Therefore, it is much better, even though connected with more effort, to use a conventional built adapter with inductor sieving and smoothing capacitors. This adapter should have a low-impedance and be built well dimensioned. Furthermore, to obtain a great sound one should use MKP capacitors filled with oil instead of electrolytic capacitors. Moreover, we do not want any silicon noise and, that’s why, we use a tube to rectify the current.
The handcraft
The cases are made of a combination of Delrin and stainless steel. As a result, we have an almost resonance free case. This fact is very important for the tubes, which have the tendency to stimulate vibrations and to make the sound unclear with the microphony. Furthermore, we mould the transformer and the inductors in solid mantles in favour to suppress any vibrations.
However, modern CNC milling machines and laser alone do not characterise the complete case. The stainless steel elements are engraved by hand and polished; this underlines the technical aspect. To present an amplifier with an altogether excellent appearance, we use solid turned operating buttons and hard gilded RCA jacks.
We link the power supply to the preamp with a high voltage connector and six-pole silver hybrid wire.
The Facts
measurements come soon
dimensions per unit in mm: 250 x 340 x 210
Weight: the power supply weight is 15 kg and the amplifier’s is 12 kg
|
|
