VS-20 Voltage Stage module

With this VS-20 Voltage Stage (input) module we built the most audiophile input module we have.
We sell this one mostly in setups where the classy, linear EXICON Mosfets are used!

VS-20 Voltage Stage (input module)

At first sight this VS-20 looks about the same as our VS-10 module, but in order to increase the sound quality there sre some significant changes.

The mirror input stage is based on 4 exactly matching transistors, mounted on an IC-housing. It is positioned exactly in the middle at the backside of the PCB. The temperature (drift) is about zero and the same for all, making it at stable amplifier, regardless it's temperature. There are NO compensating parts for drift stability required. At first glance this rare IC looks like an Opamp circuit but it's NOT. There are just 2x NPN and 2x PNP transistors on board, matched within 500uV) where the substrate of the chip is grounded. There is no way to do it better than this. All the symmetrical connected parts have exactly the same track lenghts and in a mirrored position. The driving transistors for the CS-board are low-noise, mid power, mid voltage SMD transistors.

The frequency limiting RC-network is using a Mica type of capacitor, which is about the best possible. All resistors are 0,1% Metal Oxide Film (MOX) resistors. The PCB tracks on this double sided FR4 board have a thickness of 35um (VS-10 is 18um).

At the left and right connector, the power supply voltages are available for extra add-on modules and there is an AC- and DC input, where the PCB mounted MKP capacitor (Mundorf MCap250) is bypassed. You could use this DC-input if you want to drive the amp from DC on, but then you have to be sure that the preceeding device is totally free from a DC-offset, f.e. due to the output capacitor this device most probably already has. You could also decide to use the DCin and add a, mostly large, input capacitor from a type/brand you want. Just a matter of taste, space and wallet.
We were able to develop the PCB in a way that the inputs and their required parts can be mounted either left or right, so the inputs will always be as close as possible to the input connector.
In a similar way, the DC-offset trimming parts (blue multi-turn trimpotmeter) can be mounted at the opposite side. In the VS-10 picture, the input- and trimming parts are at the other side in order to show you what we mean.

We can decide to mount an angled mid-connector (as in this picture) at the front, mounting this VS-20 board L-mounted to a CS-board, or mount a straight connector at the back as in the VS-10 picture). In that case we become a "sandwich" construction with lowest possible total height (32mm) in the LP versions (See chapter 4). While doing so, this board comes closer to the CS-board track, loosing some of the high quality though. So, only do this if you need a limited height of the VS/CS pack.
Horizontal mounted                                                        L-mounted module

This board can handle supply voltages of ± 20-63Vdc without any changes to be done. With any CS-module you only need to trim the DC-offset and the idle current of the pack. The simple allignment procedure can be found at our parts website.
While operasting at supply voltages >63Vdc, you will also need a Voltage Regulator board, bringing down the Power Supply voltage to around ±30V for this board only.