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Category: Tubes Page 1 of 2

6SN7 Preamp With Parallel Sections + CCS

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:

6SN7 Load line and biasing
6SN7 Load line and biasing

ECC88 Preamplifier / buffer

This is a quick entry to demonstrate a simple topology used in this ECC88 preamplifier. I’m using 7V heater variant – PCC88. It seems like the term “preamp” is not quite suitable here because the stage is actually a buffer and there is no amplification whatsoever. The schematic is shown below:

ecc88_preamp

Tube Manual by Western Electric – part 3

This is the third part of the manual.

Western Electric Tube Manual. Part 2 – >>>[ LINK ]<<<

Tube Manual by Western Electric – part 2

The second part of the Western Electric tube catalog.

>>>[ LINK ]<<<

Tube Manual by Western Electric

Part 1 from a tube catalog by Western Electric, USA.
The collection show almost complete range of tubes manufactured by Western Electric including the WE300B, WE417A, WE437A and many many others.

More parts of the manual to follow soon…

1941 Western Electric Tube Manual. Part 1 – >>>[ LINK ]<<<

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