Tube DIY Asylum

RE: DN2540 CCS, cascade or not cascade, what you prefer?

76.90.100.230

Tre'

P

In Reply to: RE: DN2540 CCS, cascade or not cascade, what you prefer? posted by Triode_Kingdom on April 11, 2024 at 07:05:51

"non-linear idiosyncrasies of the SS junction within the device"

The CCS is such a high impedance vs. the plate resistance of the triode that it is loading that the non-linearity of the device will have very little influence over the total. A tiny fraction.

If the non-linearity of the MosFet causes a 10% decrease in the load as seen by the triode then you have say 9 megs vs. 10 megs. The distortion and gain of a triode loaded with 9 megs vs. 10 megs is right next to no difference at all.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

Follow Ups:

RE: DN2540 CCS, cascade or not cascade, what you prefer? - Triode_Kingdom 13:42:42 04/11/24 (3)
"The CCS is such a high impedance vs. the plate resistance of the triode that it is loading that the non-linearity of the device will have very little influence over the total. A tiny fraction."

You can't know that. Impedance is a RMS measurement. It does not communicate the extent or duration of any non-linearities that may be created by the device under test.
- RE: DN2540 CCS, cascade or not cascade, what you prefer? - Tre' 16:46:21 04/11/24 (2)
  But regardless of the duration of the non-linearity, that non-linearity would have to substantially lower the impedance of the CCS or it won't make an audible difference. Or at least I don't see how it would.
  
  Tre'
  Have Fun and Enjoy the Music
  "Still Working the Problem"
  - RE: DN2540 CCS, cascade or not cascade, what you prefer? - Triode_Kingdom 18:45:35 04/11/24 (1)
    "But regardless of the duration of the non-linearity, that non-linearity would have to substantially lower the impedance of the CCS or it won't make an audible difference."
    
    No one knows how much (or which type) of SS non-linearity is responsible for degrading sound quality. Any SS device that isn't bypassed introduces this possibility, and I simply won't take the risk.
    - RE: DN2540 CCS, cascade or not cascade, what you prefer? - PakProtector 08:52:39 04/18/24 (0)
      There is magic in that box.
      
      What kind of magic?
      
      Don't know, but it may be bad.
      ............................................
      Just trying to round up the 'omg it is solid state and that can be bad' comments... :)
      
      First time I built a LTP is was a long resistor. Then tried a current reg diode. Then a cascode CCS from Gary Pimm. Then thought the simple single depletion mode would be darned near as good and *FAR simpler. Nope. Cascode depletion mode came next and that worked well, just like Gary's enhancement-mode stuff worked.
      
      The 10M45 has 2x the bias voltage vs a DN2540N5. A very useful thing to provide the DN3545N3 I prefer in the bottom spot.
      
      Douglas
      
      Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

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