OTL Asylum

Nice circuit!

75.168.123.245

Ralph

M

In Reply to: RE: Study of a circlotron with cathode and current feedback posted by cellailuca on October 12, 2024 at 10:05:51

Have you tried Voltage feedback?

The driver tubes could have their cathodes tied together to improve CMRR, using a CCS to ground.

The Voltage feedback then coming from the output terminals to the grids of the input tube (which IMO/IME is the right way to apply feedback in any tube amp).

Since most speakers are designed to be driven by a Voltage source, this might make for a more practical application.

Follow Ups:

Output impedance is 2.8 Ohm - cellailuca 09:08:02 10/16/24 (6)
If I replace the speaker with a 330 Hz-1V voltage generator the current is 350 mA, that is, 2.8 Ohm output impedance.
It is quite an acceptable value for all commercial speakers.

Omnes feriunt, ultima necat.
- It's actually lower, it is 1.8 Ohm - cellailuca 09:15:13 10/16/24 (5)
  As you can see in the LTSpice screenshot I set 1 Ohm of series resistance in the 1V voltage generator.
  
  Omnes feriunt, ultima necat.
  - Current feedback usually raises output impedance FWIW nt - Ralph 09:19:01 10/16/24 (4)
    -
    - RE: Current feedback usually raises output impedance FWIW nt - cellailuca 09:03:53 10/17/24 (3)
      I agree with you but in this case the effect of cathode feedback on output impedance is the strongest.
      
      Omnes feriunt, ultima necat.
      - In that case I would surmise its actually Voltage feedback nt - Ralph 09:11:59 10/17/24 (2)
        
        In Reply to: RE: Current feedback usually raises output impedance FWIW nt posted by cellailuca on October 17, 2024 at 09:03:53
        
        -
        
        RE: In that case I would surmise its actually Voltage feedback nt - cellailuca 03:12:43 10/18/24 (1)
        
        In Reply to: RE: In that case I would surmise its actually Voltage feedback nt posted by Ralph on October 17, 2024 at 09:11:59
        
        Correct, because cathode feedback can not be eliminated without destroying circuit topology and current feedback is only 5 dB.
        For sake of completeness the input impedance with and without current feedback is 83 Ohm and 104 Ohm respectively.
        A very low value for tube standards.
        Thank you for your comments.
        
        Omnes feriunt, ultima necat.
        
        +1 good work! - Ralph 11:48:12 10/18/24 (0)
        
        In Reply to: RE: In that case I would surmise its actually Voltage feedback nt posted by cellailuca on October 18, 2024 at 03:12:43
        
        -

Post a Followup:

FAQ

Post a Message!

Forgot Password?

Moniker (Username):
Password (Optional):
	Remember my Moniker & Password (What's this?) Eat Me
E-Mail (Optional):
Subject:

Message:	(Posts are subject to Content Rules)

Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:	Automagically notify you when someone responds.

To view your new posting or follow-up, click on the RELOAD or REFRESH button on your browser.

This post is made possible by the generous support of people like you and our sponsors:

VH Audio