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My question is not about whether you run a 6.3v tube at above or under that figure - something different from that.My question is - when there are variants in a particular tube regarding heater voltage, e.g. an EL version at 6.3v and a PL version at 18v, whether you would be able to hear any difference? Or a DHT with either a 2.5v or 5v filament, since some 2a3s are assumed to be basically 300bs?
In other words, are two tubes with the same specifications but different heater voltages and consequently different current ratings the "same" tube sound-wise, or are they subtly different in sound in any way?
Edits: 09/30/20Follow Ups:
I don't think Andy is asking about running a given tube with high or low voltage. He is asking whether similar tubes, where the main difference is filament voltage, sound different: do different filament ratings affect sound?
I can't answer that question. I am curious though!
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
I did say at the start that this is about comparing the "same" tube with different heater or filament specifications. e.g. 6.3v and 12.6v versions. In some cases there are 25v or 50v versions even.
Yeah, With a quick read it just seemed at times a bit confusing below and was just trying to clarify. On reading again probably not needed, but may not hurt.
Cheers.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Andy,
I may have missed the question you pose-
My first answer works if you are talking about higher/lower voltage by 5% or less-
However if you are talking about running an 18 volt heater with a 6.3 volt supply - the tube will most likely fail to have sufficient emission from the cathode to operate-
and if you reverse the situation - 18 volt supply into a 6.3 volt load - the heater will likely burn up very quickly-
The situation does not improve for the 2A3 vs 300B...
Happy Listening
The 2A3 DHT has a 2.5V / 2 amp heater. The otherwise Identical 6A3 has a
6.3V / 1 amp heater. My SET amp can use either and I and prefer the 6A3, sound wise.
The 6A3 has a more dynamic sound and a more 'impactfull' bass.
I haven't heard many 2A3s and 6A3s so my opinions are just that.
I have 2 pairs of Tungsol 'black glass' 6A3s and they are a smaller glass envelope than other 2A3/6A3s. They are also single anode or 'mono plate' anodes instead of the far more common parralled anodes valves.
So they have 6.3V heaters but sound more like a higher-powered 45 DHT than either other 6A3s or 2A3s. Infact they are more similar sounding to my Hytron VT52s. So does the heater voltage affect the sound more than the construction ? Not sure.
'similar sounding to my Hytron VT52s'
no doubt ... because they're remarked VT 52's
odd that you mentioned this as it came up in a phone call I had last week
with a friend ... plus, see link
regards,
Hi, My limited understanding is that the markings on the glass bulb are always correct but that the writing on the valve base can be mis-leading.
I've read that 6A3s were sometimes used in place of VT52s but not the other way round due to the lower max plate current of the VT52s.
The four Tungsol valves are clearly marked as '6A3' on the bulb but only have 'Tungsol USA' on the black base. The glass bulb is only slightly taller than my RCA 45s and the single anode plate is about 50% taller.
BUT on my AVO mark IV, the Tungsol measure as 6A3s!
My NIB Hytron 38142 (VT52)and Sylvannia VT52s have larger glass bulbs and measure as VT52s.
I own a lovely Yamamoto A010 SET which uses one VT52 per channel as the output tube. The valves are cathode/auto biased and the heaters are solid state CCS. The heater current is regulated at 1 amp.
My VT52s run with a plate current of around 43 mA and between 6.5V to 6.8 V across the heater. I figured out that I can also use 6A3s in the A010 since the heaters are current not voltage regulated!
My NIB Sylvania 6A3s run at 45mA and 6.5V on the heaters which is within the allowed +/- 10%. The Tungsol 6A3s run at 52mA!! and 6.5V. So the plate resistance is lower than the VT52s which would be correct for a 6A3. Very confusing.
it sure is confusing ... there's plenty of tube experts around these here parts though and at least some of them who are will weigh in ...
my friend had told me his 'mono plate' 6A3's just looked like single plate tubes because of construction technique where the plates are tightly sandwiched ... thanks for your reply, it's been a slice
speaking of sandwiched and slices, it's almost lunch time!
adieu`
Lots of discussions on these if you do a search. Though the voltage difference is not as extreme as your examples.
Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
My thought is that its better to have less voltage across the heating element.Less voltage, less potential difference. Consider the function of the heater with a cathode type tube, and also the filament in a direct heated tube and the impact this may or may not have on electron function within the tube.
Edits: 10/01/20 10/01/20
I think that the biggest difference you will find will be the effect on heater life-
Higher voltage, shorter life
low voltage - longer life, with the possibility of lower efficiency due to lower emissions from the cathode...
Happy Listening
I don't think so. I think the heating power of a 6sn7 heater would be designed to be the same as the heating power of a 12sn7 heater so the emissions would be the same.
If they are both using AC then the circuit might pick up more hum from the 12 volt heater vs. the 6 volt heater.
I can't imagine there would be any other difference. But what do I know?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
From the Data sheet - the current requirement for the heater of the 12 volt version is half that of the 6.3 volt version- so Yes the Power is the same for both versions - but that is not the same as having the same heater. Running the 6.3 volt heater at 12 volts will burn it out FAST-
and the opposite will be a tube that never has any emission-
Additionally - a 1 volt drop for the 6.3 v heater is ~15.8%, and only about 8.3% for a similar drop on the 12 volt system-
Both are significant drops.
Happy Listening
I was trying to say the the 12.6 heater in a 12sn7 applies the same amount of heat to the cathode sleeve as the 6.3 volt heater does in the 6sn7. The rest of the tube doesn't care how the cathode sleeve gets the proper heat, as long as it does.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Generally, small variations from the desired filament voltages will not cause issues. If you run 6.8 vdc on a tube designed for 6.3 vdc, you will shorten tube life. Under voltage situations are not harmful to the tube life, but it does reduce the transconductance of the tube slightly. David Berning used 5.7 vdc on some of his earlier amps to improve longevity and reduce the heat generated by the tube.
I would have thought that focussing on one parameter misses the point in that the heater is consuming power to create the electron cloud so V&I combined. But I've never looked at similar/same valves that have different heater voltages 6SN7 vs 12SN7. However some valves can have the heaters in series or parallel. Can't imagine that would make a difference as it's the same power.
there will be no difference in theory. In practice, there's always the slight chance that there might be the smallest, tiniest difference if any.
If your looking to experiment, have absolutely nothing to do, and the desire to waste time to find out.......good luck. You'd be much better off with trying different brands of tubes.
"Bass is the place..the rest is filigree and lace" Doug Sax
If we assume heaters just generate heat, then if the heat is the same it shouldn't make any difference.
I was just curious - someone might have a view on the subject. Might be more relevant with DHTs.
Yep - just look at a 300B filament, it has 5V at one end and 0V at the other. Grid constant.
Now do you see ?
Inside clue, why easier to get 2A3 quiet more than 300B.
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