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<blockquote data-quote="Ampdog" data-source="post: 675208" data-attributes="member: 144"><p>Me again,</p><p></p><p>Karel, before d.c. on heaters became convenient, we had to use a.c. One could get a pretty quiet phono stage, provided the wiring was premium (hum only with the ear right up to the loudspeaker.</p><p></p><p>But what with convenient modern ways of getting d.c. on heaters, even regulated, I cannot see a reason for not doing it. The cost is negligible compared to the total, and it removes one possible source of hum. (Believe me, once one has to start re-doing wiring in order to cure some persistent hum, it is not funny!)</p><p></p><p>Just a footnote - Karel will agree! D.c. on heaters is NOT simply rectified a.c. Some proper filtering is needed, otherwise one is stuck with high charging peaks into an ample capacitor, i.e. spikes, and worse off than with a.c. I prefer coming from 11 - 12V into e.g. an LM350 to give some ripple latitude; smooth d.c. without having to resort to expensive power capacity. (Provision must be made to get rid of the heat, heatsink required.)</p></blockquote><p></p>
[QUOTE="Ampdog, post: 675208, member: 144"] Me again, Karel, before d.c. on heaters became convenient, we had to use a.c. One could get a pretty quiet phono stage, provided the wiring was premium (hum only with the ear right up to the loudspeaker. But what with convenient modern ways of getting d.c. on heaters, even regulated, I cannot see a reason for not doing it. The cost is negligible compared to the total, and it removes one possible source of hum. (Believe me, once one has to start re-doing wiring in order to cure some persistent hum, it is not funny!) Just a footnote - Karel will agree! D.c. on heaters is NOT simply rectified a.c. Some proper filtering is needed, otherwise one is stuck with high charging peaks into an ample capacitor, i.e. spikes, and worse off than with a.c. I prefer coming from 11 - 12V into e.g. an LM350 to give some ripple latitude; smooth d.c. without having to resort to expensive power capacity. (Provision must be made to get rid of the heat, heatsink required.) [/QUOTE]
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