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For years and years I hear about benefits of using sophisticated filament supply for DHT tubes yet even a statement commercial products costing many tens of thousand (or more ) use simple solutions like for example AN UK in their top tier level 5 amps . Just a simple 7805 regulator is all there is. I guess the importance of filament supply is overrated.
Edits: 04/02/15Follow Ups:
Besides the need to avoid hum, which guides people towards DC for DH tubes, an additional concern should be the sound quality achieved with various DC solutions, and what can be had from AC and HF-AC.
While I do hear the difference between AC, DC, and HF-AC, it seems that many are not capable of discerning any relevant difference. Thus from a manufacturing standpoint, the simpler and cheaper, the merrier.
Using ultra-low drop rectifiers and regulators allows you to get 6.3VDC from 6.3V AC, and the difference in sound quality should already be heard, which allows for simple and cheap conversions of amps running with 300B, 6B4G, and similar. Nevertheless, even that is too expensive for a manufacturer like AN.
I must add that in my view AC sounds better and HF-AC "rules" both in terms of sound quality and background noise.
******
http://rh-amps.blogspot.com/
Alex
A regulator based filament supply looks like a much more expensive proposition to implement than simple rectifier and Pi filter . Also it provides fairly stable and consistent voltage irrelevant of mains line fluctuations in many countries a manufacturer like Audio Note sells their wares.
In my opinion its perfectly OK if Audio Manufacturer is becoming wealthy from making a product. We don't mind rich shoemakers , plumbers or corporate lawyers but somehow a manufacturer of audio buying a Bugatti is a major offense , why ?
@Wojciech
Your reply shows that you have done no work / experiment on the subject (DH tube heaters), otherwise you would know exactly what I am referring to.
As for someone becoming rich by doing one job or another, there is nothing wrong with that - besides the side effect called greed. I do not accept greed, and thus I do mind whichever professional getting rich through the exercise of greed on naive customers.
Business requires profit in order to survive and thrive: the difference between thriving and getting rich usually lies in the profit margins, often dictated by greed.
******
http://rh-amps.blogspot.com/
@Wojciech
"""Your reply shows that you have done no work / experiment on the subject (DH tube heaters), otherwise you would know exactly what I am referring to."""
Alex , that would be true :)
Basically ,I wanted to establish where on the importance/audibility leader in the amp filament supply really sits.
I believe customers are not that naive, giving the choices nowadays.
Best , W
A 7805 kills hum but does not sound particularly good
I would go for a separate filament transformer at the very least . You would not believe the horridness that a capacitor input filament supply does until you see the crud it puts onto other windings on the mains transformer .
Good sounding filament supplies go even further than this : schottky rectification and choke input supplies are a good starting point along with a separate filament transformer . CCS filaments IMO are the way to go but this adds even more complexity and requires a separate transformer per filament for best results
Al
NT
It really depends on what your goals are. There are a few 7805's that are rated to deliver enough current (most 7805's are 1A regulators), and those will certainly work to deliver 5V at 1.25A. There's some convenience here, as you could probably put a Schottky bridge on a 6.3V winding with a cap input filter and get enough voltage for the 7805 to operate.
For most of these efforts, the hum generated by AC on the filaments is the driving force behind altering these design aspects. If your 7805 regulator gets your noise floor down below 1mV, but you can add ten more components and get the noise floor down to 700uV, should you really do that? Who is going to notice? Will you then need a 7V winding to make all this work?
Maybe , maybe not. Addition of $50 for better supply to $70k retailed amp may rise up the final price to $70.500 .I'm not convinced serious manufacturer would pas on opportunity to greatly improve the performance for such a small premium .
Never equate quality with MSRP alone.
as I am rapidly finding out,
You would be incorrect.
The Mind has No Firewall~ U.S. Army War College.
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