Yeah we did that. I couldn't get them to work but others did. Now then I like AC heating. Even 10volts at three amps is just fine and quite a few of us has heard my ongaku. 300b actually is easy, a problem to be adressed but can be done quite easily. It gets harder the more Watts are involved but on the whole I am really happy with ac. Maybe I'm just contrary and I have yet to hear really good dc heating. I've got some tent labs modules but haven't yet found a reason to use them. And using dc on idh valve s is just indulgent and a waste of time!
Anyway cheque in a son goute, eh and another factor is that I'm also lazy. I think that expression 'kiss' is aggressive and unnecessary so I'm sticking to actually heating. I am full of admiration though for t'other Andrew's hard work and if I can be convinced I'll relish my humble pie. In the meantime unless I'm. Doing gu48 I'm very happy with ac.
300B AC heating?
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andrew Ivimey
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#31
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
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Dave the bass
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#32
In that case 2A3 and 300B are almost identical...andrew Ivimey wrote:It gets harder the more Watts are involved
2.5V @ 2.5A = 6.25W
5V @ 1.2A = 6W
I dun maths and thinking. Proud smiley!
DTB
"The fat bourgeois and his doppelganger"
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IslandPink
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#33
Alex
I understand your trouble with DC heating , we have been working on a good solution ourselves, but it has been hard :
http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=4729
We are starting to understand the problem better at least .
Interestingly, John Camille understood the problem - of achieving the same AC impedance at both ends of the filament supply, over the 10 octaves of the audio signal - as early as 1993 in 'Sound Practices' magazine .
There is also interest in SMPS supplies, for instance laptop power supplies, for the bigger valves like GM70 :
http://www.audio-talk.co.uk/phpBB2/view ... c&start=75
http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=5033
I understand your trouble with DC heating , we have been working on a good solution ourselves, but it has been hard :
http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=4729
We are starting to understand the problem better at least .
Interestingly, John Camille understood the problem - of achieving the same AC impedance at both ends of the filament supply, over the 10 octaves of the audio signal - as early as 1993 in 'Sound Practices' magazine .
There is also interest in SMPS supplies, for instance laptop power supplies, for the bigger valves like GM70 :
http://www.audio-talk.co.uk/phpBB2/view ... c&start=75
http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=5033
"Once you find out ... the Circumstances ; then you can go out"
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andrew Ivimey
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#34
Yes of course they are! Watts wise.
What's that frank zappa song where they intone 'ac-dc'. As Clint Eastwood said in Two Mules for Sister Sarah, 'there are two sorts of people in the world... '
Until sonically shown otherwise I'm for a.c.
It's so frustrating trying to use a mobile phone when there is almost no signal grrrr
What's that frank zappa song where they intone 'ac-dc'. As Clint Eastwood said in Two Mules for Sister Sarah, 'there are two sorts of people in the world... '
Until sonically shown otherwise I'm for a.c.
It's so frustrating trying to use a mobile phone when there is almost no signal grrrr
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
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Alex Kitic
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#36
Thanks for the links, I will check your findings - but I am not having any trouble at the moment: on one hand, I am not blessed with really efficient speakers, thus I can use even 6B4Gs (6.3V heaters) on AC heating without hearing the hum from the listening position, even in late night "complete silence" conditions (of course, I refer to the music not playing and amps turned on).IslandPink wrote:Alex
I understand your trouble with DC heating , we have been working on a good solution ourselves, but it has been hard
On the other hand, I know how to make all three usual DC heating solutions, i.e. no regulation, voltage regulation, current limiting (regulation, if you like). The last one seems to be the preferred solution... if I needed to get rid of the hum, it would be easy.
Actually, I have no problems with my RH307A in the humming department, although it is a pentode amp, and the gain of the pentode is higher than that of a triode... thus I expect to extend that experience to the RH300B in the making (5V AC heating).
Dave,
the 300B and the 2A3 consume about 6W on heaters, and so does the 6B4G (6.3V x 1A) - but the 2A3 "hums" a lot less than 300B, while the 6B4G "hums" the most on AC heating. This is due to the fact that it is not current but voltage that is translated into hum, and the "noise" generated is proportional to the square of the voltage, thus 39.69 is a lot more than 6.25, and also more than 25. That is why I refer to the 6B4G as an "etalon" to define AC heating generated hum.
Furthermore, this voltage is amplified times the gain of the tube (mu) plus 1, since it comes from the cathode - but the difference between 2A3 and 300B is not that pronounced as the difference in heater voltage, while the 6B4G is identical to the 2A3 except for the heater voltage, thus the increase in hum is proportional to the above square.