6c33cb has Cathode – heater voltage of 300V. If the plate load is a choke or transformer that can swing higher than 300V, the heater needed to elevated so the rating is not exceeded, included also a high voltage e-cap for grounding and maybe a hum pot.
See 12.6 vac filament wiring 12AX7s
Something to try: AudioMirror-6C33 using 100 ohms to ground one side.
See 12.6 vac filament wiring 12AX7s
Something to try: AudioMirror-6C33 using 100 ohms to ground one side.
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SE, OTL, PP?
I would suggest that you not leave the cathode floating, but what you should do with it may depend a little on the design of the amp.
Of course, the heater cathode insulation is so robust on those things that grounding the center tap of the heater winding should be OK for most applications.
You were talking about plate load. Furthermore it would take a very freaky event for the cathode to rise to anode potential (shortage between anode and cathode & cathode voltage being able to rise substantialy, which most of the time is impossible because the cathode is connected to ground, either straight or through a cathode bias resistor).
You could also admit that you were wrong...
No schematic but you were talking about plate load, so not a cathode load.
Do you realize that if you were right, the biggest part of all tube amplifiers ever made are violating your 'rule'?
And I called shortages between anode and cathode, in combination with the cathode voltage being able to rise substantialy a freaky event.
Do you realize that if you were right, the biggest part of all tube amplifiers ever made are violating your 'rule'?
And I called shortages between anode and cathode, in combination with the cathode voltage being able to rise substantialy a freaky event.
It is better to wire the heaters in parallel if your power transformer has a sufficient current rating. If the heater supply is not centre tapped for a ground return you can use resistors 47 to 100 ohm from each end of the heater supply to ground to achieve the same result. There is no need to float the heaters as the 6C33C uses an indirectly heated cathode, assuming that you are not planning to use it as a cathode follower.
Moderators are there to uphold the forum rules. They are not there to judge over debates as long as they are conducted with arguments.
You made it clear that you take my point of view as an accusation. Looking for, and pointing out the truth with arguments, is not an accusation in my dictionary though.
I find it important that when a forum member asks a question, he/she doesn't get replies that are incorrect. I will not refrain from reacting under these circumstances because someone could feel that he/she is accused of something.
"If you can't stand the heat, get out of the kitchen". If you post on this forum, you have to expect reactions and be able to handle them without feeling accused.
You made it clear that you take my point of view as an accusation. Looking for, and pointing out the truth with arguments, is not an accusation in my dictionary though.
I find it important that when a forum member asks a question, he/she doesn't get replies that are incorrect. I will not refrain from reacting under these circumstances because someone could feel that he/she is accused of something.
"If you can't stand the heat, get out of the kitchen". If you post on this forum, you have to expect reactions and be able to handle them without feeling accused.
all heaters in series
Hello,
I've built a Circlotron (PPP) Amp with 2x 6C33 per channel, so the tubes are working as cathode followers on a low impedance output transformer. I put all the heaters of the 4 cathodes of the 2 tubes in series on a 24V standard industry switchmode power supply, whose output voltage could be adjusted to the 25V needed. Tied to ground at one end. PTC current limitation at startup is mandatory. Works perfectly.
best regards, Uli
Hello,
I've built a Circlotron (PPP) Amp with 2x 6C33 per channel, so the tubes are working as cathode followers on a low impedance output transformer. I put all the heaters of the 4 cathodes of the 2 tubes in series on a 24V standard industry switchmode power supply, whose output voltage could be adjusted to the 25V needed. Tied to ground at one end. PTC current limitation at startup is mandatory. Works perfectly.
best regards, Uli
Attachments
Than answer this question:
The maximum cathode to heater voltage of the EL84/6BQ5 is 100V. Even without voltage swing at the anode, the anode voltage in 99.99 % of the amplifiers with EL84/6BQ5 is way higher than 100V. So according to you all these amplifiers have a design flaw (as would designs with countless other indirectly heated power tubes...)?
PCL200 is right. Surely, if the tube breaks down, you are worrying about heater-cathode voltage?? If it breaks down, the anode is at cathode voltage, not the other way around, as there is a low cathode impedance and the high voltage will just collapse. Simulate it.
Heater-cathode voltage spec is exactly what it says. There is a reason for the 300V spec in this tube: it is designed as a series tube in a voltage regulator, and in that application there is high voltage between cathode (which is regulator output) and heater (around ground).
Bottom line: don't create issues that aren't there.
Jan
My answer is prevention is better cure, many well known designer forgot how protect OT from tube shorting out. Is some 20A of tube current meant nothing to you? It should blow a 10A use in primary of power transformer, also cathode resistor should be fused, the cathode is connected to plate, where do you think the current goes?? It depends on e-cap size of course, there is at least 100V remains, down from 150V for 6c33c shorting out.
Beside what other harms it's could do to raise the heater voltage by another 100V, foreseeing that it is additional insurance (to most) at least. I wish you could tone down your finger pointing habit, stick to the topic as moderator would put it. I certain wouldn't bother if same type of question posted again.
Beside what other harms it's could do to raise the heater voltage by another 100V, foreseeing that it is additional insurance (to most) at least. I wish you could tone down your finger pointing habit, stick to the topic as moderator would put it. I certain wouldn't bother if same type of question posted again.
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Why raise something to 100V without any logical reason? An SMPS or whatever that drives the heater isolated from everything because it is at 100V is a 'precaution'?? It's an accident waiting to happen. And for no good reason, nothing, nada, zilch.
You know, some of the smartest guys here are the ones that can say: 'Ahh, thanks, I didn't know that, I learned something today'. How smart are you?
Jan
You know, some of the smartest guys here are the ones that can say: 'Ahh, thanks, I didn't know that, I learned something today'. How smart are you?
Jan
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