Paralell 10M45's for 71A DHT filament?

regal · 5th March 2010, 02:08 AM

For a headamp with high efficiency low ohm phones where no hum can be tolerated general rule is that one must buy the Tentlabs modules to use DHTs.

I know the standard solution are LM317 CCS's but these require capacitance on the output to avoid ascillations which defeats the purpose of a CCS.

However given the low .25A current requirement of the 71A, how would a regulated supply feeding 5 10M45's in paralell be for a DHT supply? Anyone tried it?

woody · 5th March 2010, 02:28 AM

What about the dn2540n-5 instead in the to-220 case it,s good for .5A

Sheldon · 5th March 2010, 02:48 AM

Not as complicated as it looks: New DHT heater

regal · 5th March 2010, 03:26 AM

Quote:

Originally Posted by Sheldon

Not as complicated as it looks: New DHT heater

Not sure where you adjust the gyrator to deliver .25A vs the higher 300B current requirements.

astouffer · 5th March 2010, 04:03 AM

Not sure what you mean about the LM317. The datasheet doesn't show any output caps for a CCS. A discrete CCS with a few transistors should handle 250mA easily.

Sheldon · 5th March 2010, 04:53 AM

Quote:

Originally Posted by regal

Not sure where you adjust the gyrator to deliver .25A vs the higher 300B current requirements.

You don't. R2 and R3 are a divider that set the voltage at DC. At AC, the gyrator looks like a high impedance source at the output. It acts like a choke, but it can't swing above the input voltage. In principle, you could use a choke in this position.

Sheldon

regal · 5th March 2010, 06:05 AM

Quote:

Originally Posted by astouffer

Not sure what you mean about the LM317. The datasheet doesn't show any output caps for a CCS. .

I know it doesn't, but I spoken to several who have tried and all found high freq oscillation without caps on the output rails. Headphones are very sensitive and pick up things speaker guys never notice.

regal · 5th March 2010, 06:09 AM

Quote:

Originally Posted by Sheldon

In principle, you could use a choke in this position.

Sheldon

I guess thats my issue with the gyrator. PMillet has a DHT fillament design basically an LM1085 voltage regulating into a choke. Yet in his commercial DHT headamp he had to use something better for the DHT filament supply, some sort of very high freq oscillator. So I'm not sure the gyrator would have the performance I need based on this limited info.

dsavitsk · 5th March 2010, 06:58 AM

.

regal · 5th March 2010, 08:01 AM

Thankyou dsavitsk, I imagine with a separate PS chassis its best to put the CCS portion in the tube chassis?

5th March 2010, 02:08 AM	#1
regal diyAudio Member Join Date: Jan 2004 Location: MD	Paralell 10M45's for 71A DHT filament? For a headamp with high efficiency low ohm phones where no hum can be tolerated general rule is that one must buy the Tentlabs modules to use DHTs. I know the standard solution are LM317 CCS's but these require capacitance on the output to avoid ascillations which defeats the purpose of a CCS. However given the low .25A current requirement of the 71A, how would a regulated supply feeding 5 10M45's in paralell be for a DHT supply? Anyone tried it?

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5th March 2010, 02:28 AM	#2
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	What about the dn2540n-5 instead in the to-220 case it,s good for .5A

5th March 2010, 02:48 AM	#3
Sheldon diyAudio Member Join Date: Dec 2003 Location: San Diego	Not as complicated as it looks: New DHT heater

5th March 2010, 04:03 AM	#5
astouffer diyAudio Member Join Date: Jun 2004 Location: Pittsburgh, crumbling wasteland	Not sure what you mean about the LM317. The datasheet doesn't show any output caps for a CCS. A discrete CCS with a few transistors should handle 250mA easily.

5th March 2010, 08:01 AM	#10
regal diyAudio Member Join Date: Jan 2004 Location: MD	Thankyou dsavitsk, I imagine with a separate PS chassis its best to put the CCS portion in the tube chassis?

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