Here is an article to show how I designed my 6SN7 preamp with CCS based on DN2540N5 or IXCP10M45S D-MOS transistors. The article is an addition to my design which showed a 6SN7 tube in parallel connection. Here I will continue to develop the schematic. I will introduce a popular solution for a reliable constant current source.
Category: Tubes Page 1 of 2
Here is my design of a 6SN7 (6N8S) based preamp with parallel sections of the tubes. I plan to use just two tubes, one for each channel. As we all know 6SN7 is a double triode and for my design I will tie the two sections in parallel. The main design parameters fall into three points – low-distortion, low-gain and low output impedance without using a output buffer/cathode follower. In order to achieve some of these goals I will be using an active load – constant current source(CCS).
Setting the bias point
First of all lets begin with the obvious – setting the tubes into the desired operation point. Lets consider a fairly typical power supply voltage of around 300V and a 30kohm plate resistor which results in a plate current of 10mA. From these three values it’s easy to draw the load line, so here’s what it looks like: