K&K Audio / Lundahl Transformers

Posted by Dave Davenport (M) on July 09, 2006 at 20:28:36

In Reply to: Oscillation on the EL34 grids. Can this be CCS related? posted by Francois Robichaud on July 9, 2006 at 18:57:45:

Hi Francois,

Yes, indeed. I have spent many hours chasing oscillation in circuits with a CCS. Here are a few hints. Make sure that every tube has a grid stopper. Also make sure that every MOSFET has a gate stopper. I would start with 1K for each of these except for the EL34 and use 100 Ohms there.

For the input tube, since it is single-ended, you will need to bypass the cathode resistor. Then that will screw up the feedback so you will need to do something with it.

For the driver, try replacing the two CCSs in the plates with one in the shared cathode circuit.

There are several ways to use CCSs in the output stage. I don't know what you did there so I can't help you.

If it were me doing the project, I would start with no CCSs an then add a CCS to one stage at a time and make sure that it doesn't oscillate before moving on to the next stage.

Dave

• Re: Oscillation on the EL34 grids. Can this be CCS related? - Francois Robichaud 06:27:39 07/10/06 (4)
  • Re: Oscillation on the EL34 grids. Can this be CCS related? - Dave Davenport 17:29:34 07/10/06 (3)
    • Thanks Dave (last question): Oscillation on the EL34 grids. Can this be CCS related? - Francois Robichaud 19:13:13 07/10/06 (2)
      • Re: Thanks Dave (last question): Oscillation on the EL34 grids. Can this be CCS related? - Dave Davenport 20:11:55 07/10/06 (1)
        • Most sincere thanks, Dave (nt) - Francois Robichaud 03:04:12 07/11/06 (0)

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