6bx7gt Se Amp

nafunga · 14th June 2007, 11:41 AM

Hi,
Found a cct. for a 6BX7GT SE Amp on the Electra Print site. Could someone check it out for me as it appears to exceed the 6BX7's max. dissipation? The ht supply is from a 240 - 0 240v winding which should produce around 320v DC. The 6BX7's bias resistor is 180 Ohm and the O/P transformer is marked at 70mA. The 6BX7 is rated at 12w (both sections paralled). The cct. produces around 21W dissipation! The spec. sheet says - 10W per section & 12W for both, or does this mean 24W for both? which would mean the Electraprint cct. is ok?

Any help appreciated.
Thanks,
David.

ilimzn · 14th June 2007, 02:09 PM

You may be assuming too much.
First, if the transformer is marked 70mA, this is it's maximum primary DC, which by no means implies this is the current used in the circuit. In fact, it will be signifficantly lower.
Second, you need to subtract the bias voltage and the DC voltage drop across the transformer from the power supply voltage, to get the voltage across the tube.

nafunga · 14th June 2007, 02:12 PM

Thanks.

14th June 2007, 11:41 AM	#1
nafunga diyAudio Member Join Date: Jul 2005 Location: Whitstable , Kent. UK	6bx7gt Se Amp Hi, Found a cct. for a 6BX7GT SE Amp on the Electra Print site. Could someone check it out for me as it appears to exceed the 6BX7's max. dissipation? The ht supply is from a 240 - 0 240v winding which should produce around 320v DC. The 6BX7's bias resistor is 180 Ohm and the O/P transformer is marked at 70mA. The 6BX7 is rated at 12w (both sections paralled). The cct. produces around 21W dissipation! The spec. sheet says - 10W per section & 12W for both, or does this mean 24W for both? which would mean the Electraprint cct. is ok? Any help appreciated. Thanks, David.

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14th June 2007, 02:09 PM	#2
ilimzn diyAudio Member Join Date: Feb 2005 Location: Zagreb	You may be assuming too much. First, if the transformer is marked 70mA, this is it's maximum primary DC, which by no means implies this is the current used in the circuit. In fact, it will be signifficantly lower. Second, you need to subtract the bias voltage and the DC voltage drop across the transformer from the power supply voltage, to get the voltage across the tube.

14th June 2007, 02:12 PM	#3
nafunga diyAudio Member Join Date: Jul 2005 Location: Whitstable , Kent. UK	Thanks.

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