Tube DIY Asylum

RE: SE output transformers never have enough inductance.

24.27.41.140

Triode_Kingdom

In Reply to: RE: SE output transformers never have enough inductance. posted by Tre' on December 05, 2024 at 10:48:58

Insufficient inductance should present as a loss of amplitude at low frequencies, even at very low power levels. That's not the case for the FS-100 transformers I'm using. They're flat to below 20Hz at levels like 1W. It's only at higher levels where the low frequencies suffer. I believe this indicates transformer saturation.

Follow Ups:

RE: SE output transformers never have enough inductance. - Tre' 17:49:06 12/06/24 (4)
I agree, that sounds like transformer saturation.

Check this out from VoltSecond.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
- https://web.archive.org/web/20120618185607/http://www.sitesw (Open in New Window)
- FYI: My site it back up - VoltSecond 23:24:54 12/07/24 (2)
  This may be the image you are looking for.
  
  My site is back up and I hope to have more new stuff in it fairly soon. I also have a few inductor design articles from friends of mine that I posted on the new site.
  
  Play safe and play longer! Don't be an "OUCH!" casualty.
  Unplug it, discharge it and measure it (twice) before you touch it.
  
  . . .Oh!. . .Remember: Modifying things voids their warranty.
  - What does the transformer inductance do to the load line of (Open in New Window)
  - That's great news! - Tre' 09:11:23 12/08/24 (1)
    This is what grabbed me the first time I read it years ago.
    
    "It does not matter if your speaker does not go down to 31.25 Hz or not. If you are sending low frequency information to the amplifier, the amplifier will make the plate voltage move. If the plate voltage moves, the tube must spend bias current to charge and discharge the primary inductance as well as the actual primary load impedance. If the plate voltage or current "clips" because of low frequency plate excursions, the sound will suffer."
    
    This changed my outlook and I took steps to keep the low frequencies out of my single ended midrange/tweeter amplifier. The sonic results are very positive.
    
    Thank you.
    
    Tre'
    Have Fun and Enjoy the Music
    "Still Working the Problem"
    - Active Bi and Tri amp-ing solves a lot of issues! - VoltSecond 22:05:53 12/08/24 (0)
      Excellent method to make the issues go away. Active Bi and Tri amp-ing solves a lot of issues!
      
      What ever is picked for the lowest frequency, to support transients the iron will need to deliver full power at 1/2 that frequency.
      
      Good job with the cross over!
      
      Play safe and play longer! Don't be an "OUCH!" casualty.
      Unplug it, discharge it and measure it (twice) before you touch it.
      
      . . .Oh!. . .Remember: Modifying things voids their warranty.
- Very interesting - Thanks! - Triode_Kingdom 18:56:13 12/06/24 (0)
  The FS-100 transformers are 10K. I've always known a higher reflected load would result in a more favorable load line, but I think it must be very difficult to make a conventional transformer like that without sacrificing upper frequencies. I suppose this is the downside of the 211 and similar tubes, as opposed to those with a lower Rp.

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