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Heatercathodeshort · 21st Aug 2019, 8:38 am

Yes David, the 1768 series always did produce Tom cat sounds when it warmed up presumably due to the pre amp anode load supply being from obtained from the boost rail via that 2.7m resistor.
It's a long time ago but something jolts my memory that the cathode by pass capacitor could be O/C causing this. We are going back to 1964 here! The O/C capacitor had little effect on the sound other than a slight lack of bass. I will dig the manual out when I have a quiet moment. John.

21st Aug 2019, 8:38 am	#42
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Stella ST1007U Yes David, the 1768 series always did produce Tom cat sounds when it warmed up presumably due to the pre amp anode load supply being from obtained from the boost rail via that 2.7m resistor. It's a long time ago but something jolts my memory that the cathode by pass capacitor could be O/C causing this. We are going back to 1964 here! The O/C capacitor had little effect on the sound other than a slight lack of bass. I will dig the manual out when I have a quiet moment. John.