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In Reply to: RE: Is this regulated filament supply any good? posted by Nickel Core on October 25, 2014 at 01:28:16
Rod Coleman has been designing his regs for DHTs for several years and has gone through about 5 or 6 versions. They are a whole level up from Ronan Regs (hissy) and another world from LM317s. I can't see any reason not to use them for directly heated tubes.
The only other filament DC supplies I would ever think of would be choke input ones, maybe with more than one choke. Choke input gets you most of the way there.
Of course, the best solution is choke input followed by Rod Coleman regs, which is what I use. Hammond chokes have been cheap and very good for this. Perfect for 10Y, 26, 4P1L and those kinds of tubes. In addition those are tubes I always use in filament bias, which goes a whole step further in quality because you can eliminate the cathode bypass cap, and that's pretty important.
Follow Ups:
I did a clone of the Colemanreg clone with a 2SC3852A CCS transistor and TIP121 for the buffer . To be honest with you I could not tell any difference whatsoever when taking the cathode connection from the 4P1L centre tap between using the whole Colemanreg or straight ring of two CCS . In future I will be just using the ring of two which simplifies matters and means the heatsinked CCS can easily be built skeleten-style and mounted from one of the loctal socket mounting screws
Al
"I can't see any reason not to use them for directly heated tubes.
The only other filament DC supplies I would ever think of would be choke input ones, maybe with more than one choke. Choke input gets you most of the way there."
"My version" of the voltage regulator for DC heaters on direct heated tubes is extremely simple:
- low drop Schottky diodes forming a bridge
- one cap (let's say 4700uF or so)
- L4940V05 - a very-low drop fixed voltage (5V) regulator (1.5A max)
- another cap (let's say 1000uf)
and that's it.
The main advantage of this solution, which I tend to use from 6.3V AC outputting 6.3V DC (thus suitable for 6B4G, 2E22... and easily reduced via series resistors to 5.5V for 307A or 5V for 300B) is the fact that you can apply it to already existing transformer secondaries - and the low drop of both diodes and regulator also implies very low dissipation. Plus, the simplicity of the build is such that simpler is almost impossible.
Now for the sound - a DIY friend has compared this solution with the Coleman regulator, and has found that the difference in sound quality is minimal (might be even placebo, for that matter). I must add that he has tried standard AC as well, and while AC had unacceptable hum levels on his efficient speakers, he did not find AC sonically superior as well to "my" DC solution.
Now, why "not use..."?
1) Price (much more expensive than other simpler solutions) - which might be irrelevant to those who consider it sonically superior.
2) Heat (being a DC solution, it implies more power consumption, and more heat dissipation: some resistors have to be installed rather high above the board because they are going to get rather hot, etc.)
3) Last but not least, why not use a custom HF AC solution? Besides being cheaper, it will probably have lower hum/noise levels, and since it is AC, the cathode will be at the same potential throughout...
Just giving an opinion and a suggestion.
******
http://rh-amps.blogspot.com/
Hi,
Where can I order these regulators. Google doesn't help me much. Does Ron has his own site? I'm a bit unable to find it.
NC
Rod Coleman doesn't have a website. Easiest way to contact him is a personal message on DIY Audio where he's an active poster.
For example he contributes here to the 4P1L line stage thread
http://www.diyaudio.com/forums/tubes-valves/190857-4p1l-dht-line-stage-66.html
Too bad he's not active over here. I really despise the administration style at DIY Audio. I cancelled my "membership" two days in.
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