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DHT heater specs.

74.121.164.141
Posted on October 17, 2014 at 18:47:33
jorisdallaire
Audiophile

Posts: 356
Location: Quebec city
Joined: July 26, 2012
 Hello to all!

Currently building a current-regulated supply for the heater of a DHT.
The spec is 1A/6.3V. However if i run it with 1A, the drop accros the heater is 8.5V.

Ok i say, so the spec is incorrect, and i can adjust the current easly. But what is the most important parameter, the right current or the right voltage on the heater? Or the right power?

My guess is that i should not go over the voltage spec, but then the current is down at 750mA. Will that suffice for correct operation?

Thank you in advance.
Joris

 

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Answer...., posted on October 17, 2014 at 20:52:44
jorisdallaire
Audiophile

Posts: 356
Location: Quebec city
Joined: July 26, 2012
 ... in this interesting paper by tentlabs.
Seems i must stick to the voltage spec. The current will be 75% of the spec tho.

 

RE: DHT heater specs., posted on October 17, 2014 at 22:12:31
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 What tube are you dealing with?

What current source are you using?

I'd guess 6B4G or 6A3. I agree that you should trim the current until the voltage is correct.

 

RE: DHT heater specs., posted on October 17, 2014 at 23:06:50
jorisdallaire
Audiophile

Posts: 356
Location: Quebec city
Joined: July 26, 2012
 Hello,

None of the above :-) It is for the russian 6P21S. Normally i prefer AC but this is an amp for electrostatic headphones and those are mercyless - Any trace of hum is heard.

The current source is a simple LM117 job, with a "standby" setting, taken from Morgan Jones's book. I hooked to a computer-type switching PS's 12V supply. to reduce the power waste. The current source circuit wastes as much power as the tube :-(

 

RE: DHT heater specs., posted on October 17, 2014 at 23:21:51
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002

Where did you get the idea that the filament is supposed to draw 1amp?

This is the second reference (that I found with a quick google search) that says 750ma. (+/- 60ma)

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

I was operating from memory...., posted on October 17, 2014 at 23:39:57
jorisdallaire
Audiophile

Posts: 356
Location: Quebec city
Joined: July 26, 2012
 ... which is defenitely defective :-( I remember i saw this info on Bartola's site but didn't even bother to re-check... Yes i am *that* lazy...

Thanks for the reminder! The poor tube has been abused a bit... At least now i know my reg is now spot on!

 

RE: DHT heater specs., posted on October 18, 2014 at 16:34:29
Paul Joppa
Industry Professional

Posts: 7296
Location: Seattle, WA
Joined: April 23, 2001
 Cute little bugger! Here's a spec through TDSL at 0.75 amps:

 

Cute indeed!, posted on October 19, 2014 at 12:35:59
jorisdallaire
Audiophile

Posts: 356
Location: Quebec city
Joined: July 26, 2012
 I have great hopes for this beauty in triode mode... We shall see in the next few days!

 

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