The Band pass and energy Xfer of a transformer with no load is one thing but it all changes depending on the load and the DC involved. In class A balanced PP circuits the XFMR will still saturate at some frequency and load even if it is perfect balance on the PP circuit. XFMR saturation distortion in class A single ended service has a trapezoidal shape if the quiescent current is too high but in PP class A the shape is weird because the XFMR remains balance as for as DC is concerned but yet the XFMR will not produce the sign wave on the output if the frequency is too low. It resembles cross over distortion even though there is no cross over in class A push-pull.
My suggestion is to watch for this type of thing by using a audio signal generator. While on the air (DUMMY LOAD) slowly sweep down on the audio frequency generator, at some point (probably between 10 and 100 CPS) the output will become distorted. Design the preamps and drivers low frequency roll-off to be at or before this distortion happens. John, WA5BXO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of W5OMR/Geoff Sent: Sunday, March 12, 2006 10:43 PM To: Discussion of AM Radio Subject: Re: [AMRadio] Class AB and B audio XFMRS John Coleman ARS WA5BXO wrote: How difficult would be it be 'sweep' the mod iron? The reason I ask, is because so much of the surplus stuff we get is still of Mil-Spec design. Therefore, if the mil-spec transformer says it's freq response is +/- 1db from 100Hz ~ 3000Hz, how would one determine exactly what this particular peice of iron will be capable of handling, in the 'non-comercial' application? -- 73 = Best Regards, -Geoff/W5OMR ______________________________________________________________ AMRadio mailing list Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected] AMfone Website: http://www.amfone.net AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb
