OTL Asylum

:) I found out about Futterman soon enough of course

71.34.0.165

Ralph

In Reply to: RE: "Those who dot not study history will de doomed to repeat it." Santayana. nt posted by viridian on August 12, 2019 at 14:07:08

And studiously sidestepped a lot of the pitfalls in his design. That's why our OTL is unconditionally stable.

Follow Ups:

Somewhere I have an old hi-fi mag from the 50's and... - viridian 19:18:09 08/12/19 (11)
....there is an ad in it for an OTL amp with a matching very high impedance loudspeaker. I'm coming off the top of my head here but around 100 ohms. Have you heard of that Ralph? I should dig it out and post it here.
- Beveridge? - Lew 18:44:29 08/13/19 (4)
  For the Beveridge models 2 and 2SW a direct-coupled amplifier is situated in the base of the gigantic speaker(s). No coupling capacitors OR transformer, driving a totally unique take on ESL, not really an ESL as we know it because the diaphragm does not carry a bias voltage; it's at ground reference. Which is maybe why after nearly 40s years my 2SWs still sound divine. (Knocking on wood.) I've owned the 2SWs for about 6-7 years now, but the amplifiers are dated inside, "1979".
  
  Other later models of Beveridge speakers (models 3 and up) are much more like conventional ESL speakers and require an outboard amplifier.
  - No Lew, much earlier, the mono era. Nt - viridian 09:22:40 08/14/19 (3)
    Nt
    - Thanks, V. - Lew 10:15:05 08/20/19 (0)
      I think I just wanted a chance to talk about Beveridge.
    - Definately the Phillips then. nt - Ralph 09:58:03 08/14/19 (1)
      -
      - Thank you, Ralph. Ill be diggin' this weekend. nt - viridian 10:34:31 08/14/19 (0)
        
        In Reply to: RE: Definately the Phillips then. nt posted by Ralph on August 14, 2019 at 09:58:03
        
        Nt
- RE: Somewhere I have an old hi-fi mag from the 50's and... - Jim Dowdy 11:15:43 08/13/19 (3)
  Stephens and Philips Norelco offered high impedance speakers with matching OTL amplifiers.
  I believe the high impedance Stephens TruSonic speakers were 500 ohms; while Philips Norelco had both 400 ohm and 800 ohm offerings.
  As I recall, each of their OTL amplifiers were cap-coupled SRPP designs.
  
  Edits: 08/13/19 08/13/19
  - Thanks Jim, Ill have to do some digging this weekend. nt - viridian 16:09:50 08/13/19 (2)
    Nt
    - Stephens link - Jim Dowdy 07:57:06 08/15/19 (1)
      Lots of interesting material here - scroll down for info on their OTL amplifier.
      http://www.itishifi.com/search/label/Stephens%20Trusonic (Open in New Window)
      - Wow, Jim thanks for sharing that.... - viridian 10:05:24 08/15/19 (0)
        
        In Reply to: RE: Stephens link posted by Jim Dowdy on August 15, 2019 at 07:57:06
        
        ...I wouldn't mind a pair of those corner horns, and that mid-century modern house to listen to them in.
- RE: Somewhere I have an old hi-fi mag from the 50's and... - airheadair 11:04:23 08/13/19 (0)
  This combo (OTL + high impedance speaker) sounds interesting. I hope you can find it.
  
  My Stax F83 speakers have a variable but overall very high impedance, around 160 ohms in the midrange. The NYAL Stax combination works very well. (But I now have a subwoofer to take
  care fo the low frequency, where the speaker's impedance strangey goes back down to 4 ohms).
- Wouldn't be a Phillips would it? nt - Ralph 10:30:13 08/13/19 (0)
  -

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