DIY ALTEC1570 Driver question

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I am building a pair of Altec1570 clones. The center tapped choke in the original amp driver stage has a dc resistance of 2*127 ohm. The chokes i have on hand have a dcr of 2*320 ohms. With a current of 25mA through the driver tubes i get a output tube grid bias of 8V instead of 3V as in the original circuit. The output tubes get overbiased by this. Which solution will be better to bring the output tubes grid voltage down to 3V again : Lower the driver tubes current to 10mA each or put a 83 ohm resistor between the center tap of the output tubes heater supply winding and ground? Any other suggestions?
Many thanks in advance, Volker

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Topic - DIY ALTEC1570 Driver question - Volker 03:42:46 11/07/06 (0)

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