New DHT heater - Page 13

Alastair E · 12th July 2010, 07:10 PM

Add another pair if you can please....!

vanofmonks · 12th July 2010, 11:29 PM

Depending on price I would take 4 or more.

Chris

mach1 · 12th July 2010, 11:34 PM

and another 2 please

.

Wavebourn · 12th July 2010, 11:44 PM

Hi Rod;

since it is a thingy for a tube gear you may easily use IRF parts biasing them from B+.

Just an advice, for flexibility.

jims · 12th July 2010, 11:49 PM

Hi Rod

I am interested in at least a couple.

Thanks

JimS

Hearinspace · 13th July 2010, 04:19 AM

Quote:

Originally Posted by Wavebourn

Hi Rod;

since it is a thingy for a tube gear you may easily use IRF parts biasing them from B+.

Just an advice, for flexibility.

Can you say more?

Wavebourn · 13th July 2010, 06:57 AM

Quote:

Originally Posted by Hearinspace

Can you say more?

Yes, I can.

Rod Coleman · 09:40 AM

Hi Anatolij, I thought a lot about FET solutions, but in this circuit, we try to run Vds very low (1.5 .. 2V) to keep the heatsinks cool. The devices work OK, but the capacitance is huge (400pF++ even at little IRF510 level) at low Vds, and changes very rapidly with Vds change (supply ripple).

For best quality DHT heaters, we are trying to make the (ac, small-signal) impedance as large as possible, to keep cathode current from leaking out of the circuit - and from one end of filament to the other. This leakage has a very bad effect on the sound quality, and is one reason that ordinary dc heating made with voltage regulation sounds bad. In fact voltage-controlled dc sounds even worse than ac-heat - no lustre, no sparkle. With voltage regulation, the big capacitor across voltage regulator output (even if 0.1uF) presents direct ac-short-circuit across the filament, and is enough to ruin the quality of DHT-sound.

Anyway, I think you're teasing me about having B+ present before heater can switch ON!!

Rod Coleman · 13th July 2010, 09:28 AM

Good to see the interest in the new board - Thank You!

I'll order as many PCBs as I dare, to keep the cost low!

bravi · 13th July 2010, 09:36 AM

Please add my name for 4 boards

B.Ravi

12th July 2010, 11:34 PM	#123
mach1 diyAudio Member Join Date: Sep 2004 Location: Brisvegas	and another 2 please . __________________ Au rutti wop-bop-a-loom-bop-a-boom-bam-boom - Richard Penniman

12th July 2010, 11:44 PM	#124
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	Hi Rod; since it is a thingy for a tube gear you may easily use IRF parts biasing them from B+. Just an advice, for flexibility. __________________ If I disappear suddenly, that means I finally created a time machine and pushed wrong button that brought me to Stalin's Russia. In any experiment any result is the result. Even if it is negative.

13th July 2010, 09:24 AM	#128
Rod Coleman работник diyAudio Member Join Date: Jul 2004 Location: Warwickshire UK	Hi Anatolij, I thought a lot about FET solutions, but in this circuit, we try to run Vds very low (1.5 .. 2V) to keep the heatsinks cool. The devices work OK, but the capacitance is huge (400pF++ even at little IRF510 level) at low Vds, and changes very rapidly with Vds change (supply ripple). For best quality DHT heaters, we are trying to make the (ac, small-signal) impedance as large as possible, to keep cathode current from leaking out of the circuit - and from one end of filament to the other. This leakage has a very bad effect on the sound quality, and is one reason that ordinary dc heating made with voltage regulation sounds bad. In fact voltage-controlled dc sounds even worse than ac-heat - no lustre, no sparkle. With voltage regulation, the big capacitor across voltage regulator output (even if 0.1uF) presents direct ac-short-circuit across the filament, and is enough to ruin the quality of DHT-sound. Anyway, I think you're teasing me about having B+ present before heater can switch ON!! Last edited by Rod Coleman; 13th July 2010 at 09:40 AM.

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12th July 2010, 07:10 PM	#121
Alastair E diyAudio Member Join Date: Feb 2004 Location: South Wales	Add another pair if you can please....!

12th July 2010, 11:29 PM	#122
vanofmonks diyAudio Member Join Date: May 2006	Depending on price I would take 4 or more. Chris

12th July 2010, 11:49 PM	#125
jims diyAudio Member Join Date: Mar 2007	Hi Rod I am interested in at least a couple. Thanks JimS

13th July 2010, 09:28 AM	#129
Rod Coleman работник diyAudio Member Join Date: Jul 2004 Location: Warwickshire UK	Good to see the interest in the new board - Thank You! I'll order as many PCBs as I dare, to keep the cost low!

13th July 2010, 09:36 AM	#130
bravi diyAudio Member Join Date: Mar 2004 Location: Wellington, New Zealand	Please add my name for 4 boards B.Ravi

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