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Old 1st January 2010, 02:57 PM   #171
Salas is offline Salas  Greece
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hi salas,

i tried 10k anode resistor and it sounded much better.all of the frequency spectrum opened up especially the bass. the harshness was gone and most of all i now have a usable range on my volume pot. what happened when i made the change?i know that increasing the load lowers THD. do i need to change the cathode resistor value if so what?


happy new year to all,

ivan
In my case 5k was best, had tried 10k too. If your amplifier does not mind higher source impedance, then the THD with 10k is surely less, and you must have lessened the current also. OTOH the gain is supposed to go up? Then you use it as I/V so I don't know. What kind of voltage you got across Rk, and on plate, with how much B+? So to see on the chart. The main idea is to use the 6V6 as a triode line amp, find your best load and operating point in your system, by all means. Which make of 6V6 you got? The buffer arrangement has the less THD of all due to local feedback BTW. Cheers, happy new year.
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Old 1st January 2010, 03:57 PM   #172
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Anything that can give 100mA at 400V without stress will do. So about 340V will be feasible counting the Vdif needs of regs. 45mA is for two channels, but 100mA is good for headroom or in case of shunt reg extra constant current needs.
Thanks.
How much current the Maida regulator draws and what's the minimum voltage drop across it?
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Old 1st January 2010, 05:59 PM   #173
Salas is offline Salas  Greece
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Maida is series, around 45mA for two channels with 5k loads at 340V B+. Needs about 30V diff to work good.
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Old 1st January 2010, 06:20 PM   #174
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Thanks.
I'm not sure how the regulator for filaments in your schematic works. Does the regulated voltage go up slowly as the filaments warms up?
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Old 1st January 2010, 06:26 PM   #175
Salas is offline Salas  Greece
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No, the filament goes up slowly since its a current source heater, the tube rectifier goes faster but rather slow enough too, compared to ss diodes. Haven't experienced any early wear due to cathode stripping yet. Of course the slower the rectifier tube, the best in that regard.
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Old 1st January 2010, 06:41 PM   #176
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Between current source and voltage source filament rectifier, which makes the filaments draw more current during warm up and which works slower?
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Old 1st January 2010, 06:43 PM   #177
Salas is offline Salas  Greece
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Constant current is tell tale, can't diverse on the amount of current, hence the filament warms up slower. Good for its long life too.
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Old 1st January 2010, 07:01 PM   #178
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Wouldn't electrolytic cap in parallel to the filament improve DC smoothness?
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Old 1st January 2010, 07:23 PM   #179
Salas is offline Salas  Greece
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I used a 100uF Pana HFZ once locally on the heaters, but I took it out because it was underneath the 5W burning when I went from noval to 6V6. Maybe a 0.1uF MKP for decoupling the cable inductance. But I have no noises in practice.
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Old 5th January 2010, 06:20 AM   #180
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Salas, you feed your 6V6 line stage from Maida-like series regulator. Yet, in your "Simplistic Mosfet HV Shunt Regs" thread you say that the Shunt regulator sounds much better than the Maida one, which makes a lot of sense. Usually, when all else is equal, shunt regulators are much better and quieter than series ones. So, wouldn't this 6V6 line stage benefit from Shunt regulator?

I'd rather start the project with one type of regulator and I trust your experience.
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