From: info@turneraudio.com.au   
      
   Andre mentioned to me............   
      
   Hell, Patrick, what Jac said on his site, and what Phil's saying is something   
   every engineer and technician and rigger in a recording studio or on a film   
   set knows.    
      
   To be honest, I've never had much to to with cores that are magnetized easily   
   and remain magnetized after a steady DC flow has ceased, ie, the magnetic   
   properties are changed after the DC has been used, perhaps by someone using a   
   meter to measure winding    
   resistance.   
      
   But I am well aware of how easy it is to magnetize a core temporarily with   
   Idc. This can apply in any OPT with no air gap. In a toroidal OPT with GOSS   
   strip the µ may be 30,000+ so very little Idc imbalance in a pair of output   
   tubes can cause hard core    
   saturation. Bdc in Tesla is the product of µ x turns x Idc and the full   
   formulas for all this stuff are at my website. But permanent magnetization   
   does not occur in such cores after the Idc has ceased.   
      
   I've never had to measure the Rw of a microphone tranny winding, and I'll have   
   to be careful if I do and learn about de-magnetization afterwards. Phil   
   obviously has more knowledge on this but Phil's website has ZERO content from   
   which I can learn so I'll    
   learn as I go from elsewhere online and from old books and from careful   
   examination of the properties of all things I come into contact with as I have   
   since 1993.   
      
      
   They'd be amazed that a guy in the sound business doesn't know. This worthless   
   little wanker "hugeshows" shoots off at the mouth all the time and three   
   minutes later is forced to retract and apologize. Valve has already identified   
   for you the reason this    
   wretched little man contradicts Jac, that he is a Magnequest Scummie returned   
   under a new name. If I remember correctly, Jac is an importer and seller and   
   booster for Lundahl transformer, which are far, far, superior to Creepy Mike   
   LaFevre's Magnequest    
   Crap, and cheaper too, and I seem to remember Jac also being a distributor for   
   some solidly designed and made Italian transformers (Bertolucci?). Jac knows a   
   thing or two, which is why such a useless clown contradicting Jac is already   
   an outrage, but to    
   do it by making such a dumb, obvious mistake, really takes the cake. Still,   
   the foolish little motormouth has backed off and apologized, so I shall say   
   nothing more unless he's stupid enough to open his mouth again.    
      
   Andre Jute    
      
   Well, that's the kind of paragraph for all to wonder about but I don't have   
   the urge or time to comment. I'm here for the engineering practices rather   
   than the personal issues, knowing all the while that I sure ain't perfect, and   
   that there is much about    
   existence I could learn, but like everyone, I'll die while remaining ignorant   
   about so many things........... and hopefully quite happy to have not had   
   Eternity granted to me to learn Infinite Knowledge, well, at least a correct   
   Phil-proof version of IK    
   at least.   
      
   But I do recall Bertolucci OPTs being advertised long ago. They seemed just   
   dandy, IMHO, and in ways that 99% of everyone wanting an OPT could not   
   understand. I have no idea if they are still made. But the freight to Oz from   
   USA or Italy is a killer, and    
   prices ppl paid me for custom made amps were abysmally low, so buying Bertie's   
   OPTs or buying ANY OPT made by any maker was financially ruinous. So after   
   1994 I learnt all there was to know about OPTs and I wound all the OPTs in   
   amps I sold. I've retired    
   happily because the old age pension is far more than I ever could have earned   
   from tight arsed Australian audiophiles wanting perfection lower than the   
   online price of an asian made lump of junk.   
      
   Over the last 10 years, 5 university undergraduates and post graduates have   
   attempted to convert the many pages of my logic involved when designing iron   
   wound items such as PTs, OPTs, and chokes. None succeeded beyond the basics,   
   and they realized they    
   couldn't make a buck from time spent. There's nothing at my site about winding   
   microphone or MC step up trannies etc all with "strange" core material one   
   does not see often. There's nothing about use of cores which may be   
   permanently magnetized with a    
   low amount of Idc applied either by  circuit malfunction, measurement dc, etc.    
   The "strange" core materials usually give a very high µ thus allowing fewer   
   turns of wire for a given amount of inductance, plus the iron caused   
   distortions are usually much lower than if one ties to use GOSS at low Bac   
   levels.    
      
   So, if one does need to measure Rw of a delicate transformer then be sure to   
   check if the core will be affected. But for all OPTs, PTs and chokes, I have   
   never for one moment seen any evidence of permanent magnetic behavior after   
   Idc has been turned off.   
      
   Jus' mi 2c,   
   Patrick Turner.    
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)