OTL Asylum

Output impedance is 2.8 Ohm

79.31.239.25

cellailuca

In Reply to: RE: Nice circuit! posted by Ralph on October 16, 2024 at 08:38:42

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.

Follow Ups:

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)
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  - 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)
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      - 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
        
        -

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