I sent off an email to
Matt Sespaniak with a question about Frequency Response and Output Transformers. I thought his response was interesting.
Basically frequency response is a function of two main characteristics of an OT:
Bass - is a function of the primary magnetic inductance created by the laminated core & number of winding turns. As a general rule bigger iron means more inductance and more bass. If you use thick or low quality lams, you can negate this. Since the normal frequency range of a guitar is 82Hz (Low E) & most standard guitar speakers roll off at 80 to 100Hz, unless you're striving for the ultimate dropped tuning rig & have a clsed back cabinet there are arguments that too much iron on a guitar OT renders it unbalanced thru the mids.
Treble - is a function of the coupling between the windings which is directly related to physically proximity of the two windings. If you lower the losses/spacing between the input and output windings you get better high end response. That said, a good guitar speaker rolls off at 6Khz, so the multiple interleavings (spilts) of the primary and secondary windings in a HiFi audio OT aren't really necessary. I've settled on a simple interleave with a 2x1 split in my OT's after using 3x4 (PP) and 2x3 (SE) in my 1st run. Users of both have reported no difference and keeping the transformer simple means it's potentially more reliable.
Matt has been asked to evaluate & quote some manufacturers current OT's & found that the Chinese amps OT's are generally not interleaved at all. It kind of makes sense then that if you take one of the VJ's or other low cost SE amps and pop in an MPS, Mercury, or Heyboer with a little bigger core and interleaving you awaken the amp.
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