4V Tentlabs filament supply

ianc13 · 22nd March 2007, 11:19 AM

Hi,

I have a quick question about wiring up a Tentlabs filament supply.

The supply is 4V and looking on the Tentlabs page for fitting instructions it seems that 'ground' side of the supply should be connected to the top of the cathode resistor for auto bias.

Would I need to look at biasing my output tube slightly differently in this instance - i.e. shifting the bias by 2V so that the filament is bias(-31V) + 2V at one end and bias - 2V at the other end.

This is on a Chinese PX25 which should be biased at around -31V for 400V/62.5mA operation.

Thanks,

Ian

pmillett · 22nd March 2007, 03:53 PM

Technically, yes, it will shift the bias. But +/-2V on a 31V bias point is inconsequential; the tube characteristics will vary more than that. So you really don't need to change anything.

Pete

ianc13 · 22nd March 2007, 08:02 PM

Many thanks Pete, most appreciated.

22nd March 2007, 11:19 AM	#1
ianc13 diyAudio Member Join Date: Oct 2005	4V Tentlabs filament supply Hi, I have a quick question about wiring up a Tentlabs filament supply. The supply is 4V and looking on the Tentlabs page for fitting instructions it seems that 'ground' side of the supply should be connected to the top of the cathode resistor for auto bias. Would I need to look at biasing my output tube slightly differently in this instance - i.e. shifting the bias by 2V so that the filament is bias(-31V) + 2V at one end and bias - 2V at the other end. This is on a Chinese PX25 which should be biased at around -31V for 400V/62.5mA operation. Thanks, Ian

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22nd March 2007, 03:53 PM	#2
pmillett diyAudio Member Join Date: May 2005 Location: Dallas (but I am not a Texan!)	Technically, yes, it will shift the bias. But +/-2V on a 31V bias point is inconsequential; the tube characteristics will vary more than that. So you really don't need to change anything. Pete

22nd March 2007, 08:02 PM	#3
ianc13 diyAudio Member Join Date: Oct 2005	Many thanks Pete, most appreciated.

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