Fader + trafo buffer

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Matt Syson

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Dec 17, 2005
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Reverting to the original sketch, 220 uF as an output cap will give a significant 'bass boost' which can be 'corrected' by the resistor splitting as mentioned or making the capacitor value much larger, at least 1000uF. Having some resistive or preferably a 'zobel' network on the secondary (the output connections) is also helpful to flatten the high frequency response, assuming you want flat!
Getting transformers to 'behave' when you have the possibilities of a few metres or a couple of hundred metres of twin screened wire on it takes a bit of work. Most 'simple' circuits work well enough on a bench but making then predictable, stable and reliable in the real world takes a bit more effort.
 

JAY X

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Jan 9, 2009
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524
Hi Matt! Thanks for your reply!.

I try to make work the single opamp (one section of an NE5532) transformer driver of the attached drawing, driving a 1:1 600:600, sowter 8403 trafo that i had around, and it did not work properly. I got sound, but also a sort of thump/latch up/saturation/oscillation, with half of the waveform disappeared...:eek:. But the dual opamp driver version from the lundahl 2811 spec sheet worked fine.(y)

Jay x
 

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abbey road d enfer

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Hi Matt! Thanks for your reply!.

I try to make work the single opamp (one section of an NE5532) transformer driver of the attached drawing, driving a 1:1 600:600, sowter 8403 trafo that i had around, and it did not work properly. I got sound, but also a sort of thump/latch up/saturation/oscillation, with half of the waveform disappeared...:eek:. But the dual opamp driver version from the lundahl 2811 spec sheet worked fine.(y)

Jay x
The value of the 45r resistor must be adjusted to the DCR of the xfmr you use. The Sowter probably has a lower DCR than the LL.
 

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