Tube DIY Asylum

RE: New concept using circuit to replace cathode bypass capacitor

76.90.100.230

Tre'

P

In Reply to: RE: New concept using circuit to replace cathode bypass capacitor posted by Eric Chan on April 20, 2024 at 08:34:29

Can you please show me what's magic about 12 ma? Even at 12ma, a vertical load line would suck.
A high load impedance (horizontal load line) is very important if you want the lowest harmonic distortion. and if you want/need much total swing you will want more than 100vdc plate.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

Edits: 04/20/24

Follow Ups:

RE: New concept using circuit to replace cathode bypass capacitor - Eric Chan 17:44:42 04/20/24 (1)
Hi,

The first Stage ECC99 only need to produce 3V RMS to reach 30W at 845, lying on 100V 12mA OP is quite straight in the curve

I show the 6H30 schematic front end but the concept is the same as ECC99
- Yes - Tre' 19:00:56 04/20/24 (0)
  Only needing 3 volts RMS makes it easy and the CCS presents a very high impedance load for the tube resulting in a horizontal load line. That tube can be operated at a lot of different plate current levels and remain linear because of the horizontal load line.
  As long as the spacing between the grid lines is equal, following the load line, then the tube is not producing harmonic distortion.
  It's not about the straightness of the grid lines on the plate curves, it's about the spacing between those grid lines following the load line.
  You have to plot a load line. If there is no load other than the CCS (as in your first stage) then plotting a load line is easy. It's just a horizontal line with the operating point (voltage and current at idle) sitting right in the middle of it.
  The plate load for your second stage is the 220k grid resistor of the next stage. That is in parallel with the impedance of the CCS which is so high of an impedance that you can ignore it.
  Tre'
  
  Have Fun and Enjoy the Music
  "Still Working the Problem"
  
  Edits: 04/20/24 04/20/24

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