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LM317 and LM7906 supplied from same voltage source noise question
LM317 and LM7906 supplied from same voltage source noise question
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Old 5th December 2020, 04:28 AM   #1
dreamth is offline dreamth  Romania
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Default LM317 and LM7906 supplied from same voltage source noise question

I have a tube amp using two different types of valves with different heater requirments and due to some shortage of components, as i have 7 regulated heaters, i chose to regulate the last two heaters voltage using two different types of regulators supplied from same positive 12V rail.
I chose LM317 for the lowest noise tube with lots of gain which ask for 300ma of current and lm7906 for the power tube in the chain which is also the hungriest heater taking 750ma. I know lm317 could supply both of them but i don't need too much stress on my regulators .



The question is:

how is the 7906 line ripple on GND line going to affect the LM317 output noise and how should i wire those circuits the best way to get the best immunity, let aside the decoupling capacitors required for best performance?
Honestly the heater noise isn't critical in my system , the regulation is used just because i don't have 6.3v windings on my transformers, but i am really curious about the best technical solution for the future.
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Old 5th December 2020, 06:20 AM   #2
wiseoldtech is offline wiseoldtech  United States
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Forget about using DC on output tubes - it's rediculous and not needed.
As for input tubes, the only ones worth heating with DC are phono preamp tubes.
There's really no need for regulation of filaments - they self-regulate, always did.
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Old 5th December 2020, 06:31 AM   #3
dreamth is offline dreamth  Romania
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I don't think i am really interested in that aspect...i already told that i don't have a readily available correct voltage source for the fillaments so i need regulators to give the right voltage to those fillaments.I chose 6 v individual wiring and that is all about it.There is a phono preamp and a headphones amp what i am building and i build tube amplifiers and preamplifiers for 15 years.
All i am interested in is a theoretical aspect on regulator's noise in that particular instance.
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Old 5th December 2020, 07:21 AM   #4
wiseoldtech is offline wiseoldtech  United States
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Using the proper power transformer for a tube project is the simple answer.
You wouldn't put big truck tires on a sportscar, would you?
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Old 5th December 2020, 08:29 AM   #5
dreamth is offline dreamth  Romania
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....the answer to which question?
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Old 6th December 2020, 01:38 AM   #6
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someone else's opinion?
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