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DC Filament power supply
DC Filament power supply
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Old 18th September 2002, 11:55 AM   #21
Petter is offline Petter
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Default Batteries and AC

I recently had a friend attempt battery based heating on his '211 amp.

He reported the results were worth it.

Then he went back to AC heating and said it was much closer than he had thought it would be.

I have a theory on the effect of "DC" heating if heater power is taken from the same transformer. If you use AC in such a scenario, you are not stressing the core . If you rectify to DC you get take the power out in short spikes at the same time you are trying to deliver it to the main supply. Go figure if that is good or bad

I thus believe that if you want to use DC power, you should also use a separate transformer. I would also guess that CCS based DC supplies will sound even better than normal voltage regulated ones in such a scenario. If you have only one transformer, it is likely that AC heating will sound best. Your mileage will vary with circuit topology, tube choice, signal level etc. but you should consider separate transformer or SMPS for filament power anyway.

This is my guess anyway

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Old 21st September 2002, 08:57 AM   #22
eduard is offline eduard  Netherlands
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What about using a so called common-mode choke to filter out some noise coming from the powersupply, Ed
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Old 22nd September 2002, 01:02 PM   #23
john is offline john  Philippines
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Hey Guys,

I am refering to Regulated DC ... Here in my country, AC from the power company is really terrible. Can someone give me an idea on how can i listen to my music and relax when i have to keep adjusting on the HUM pot when voltage fluctuations are occuring?

I would go against tube life expectations for the enjoyment of the SET amp Audionote quest...

Lucky You if you don.t have the same problem as with me...

Over or Under voltage be it AC or DC can shorten your tube life!!!

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Old 27th September 2002, 01:01 PM   #24
fdegrove is offline fdegrove  Europe
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Default AC DC

Hello John,

Powergrid that bad,he?

Ever thought about a good isolation transformers (1/1 ratio)?
Common mode rejection chokes?
Any voltage regulator will need to work within a certain range,usually a bit higher voltage at the input will not throw them off track.
Too low a voltage at their input and they can't do their job anymore.

It's a dilemma,I know.

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Old 10th October 2002, 07:59 PM   #25
oldstyle is offline oldstyle
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Smile My tests report

Thanks for all these kindly reply. I have tried a couple of ways. Here are results

1) DC. unless you have a very quite DC supply with enough capacity. It doesn't do anything good. a cheap regulated power supply only add more noise

2) raise center of the filament winding 30 - 50 V. above ground reference.
I have read this on a couple of website. However, this method
does not really improve anything in my system.

3) Finally, I went back to the basic, layout. I simply cut the wiring on the PC board. Re-wired filament supply with twisted wire. And make it away from input stage as far as possible. This way gave me best result

So, my conclusion is that the basic ways are always better. Don't use PC board if possible. Cuz you cannot twist you lines on PC board ;-)


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Old 10th October 2002, 08:32 PM   #26
Petter is offline Petter
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Thorsten Loesch actually recommends SMPS (with stuff behind it) these days. That is good enough for me.

However, based on my reading, I believe AC heating when supplied from a separate transformer, twisted wires etc. is also good.

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Old 2nd November 2002, 01:26 PM   #27
Tomatito is offline Tomatito
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I tried central star grounding first which gave me about 5mV hum. Then I tried grounding the separate stages together and from there to a central ground: no difference. I'm now going to try Steve Bench's hum balancing trick. Has anyone ever tried this ?

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