that is not what i said, read my post again.....
this is a public forum, you can not impose your will on another member...
this is a public forum, you can not impose your will on another member...
I remember my exchange with him couple years ago. The word "strange" sums it up.that is not what i said, read my post again.....
this is a public forum, you can not impose your will on another member...
Got it: I had connected one end of the 12V heater supply to the bias point, instead of the center tap. Pffft!
After so many years and dozens of builds one can still be surprised by the effects of a small (hihi) mistake. On the positive side is that this experience makes one think about the consequences of mixing AC into the power supply. Will that thingy Jones described come in handy after all..
After so many years and dozens of builds one can still be surprised by the effects of a small (hihi) mistake. On the positive side is that this experience makes one think about the consequences of mixing AC into the power supply. Will that thingy Jones described come in handy after all..
Ahhh! The classical fallacy, Bruno would say. Voltage doesn't exist on its own, it's always voltage with respect to!
If the voltage across the cap is less than 16V, what could be the problem that you need tech support for??
If it is more than 16V, you're in trouble! Everything else is irrelevant (in this context).
Jan
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Well... there was 2,9V ripple over those 16V caps and I (still) have no clue if that amount of AC is healthy. It would probably shorten their lifespan, but at what rate? Further I could not see what happens at startup when that 10uF gets loaded. The Fluke 87 DMM peak monitor function is not that fast.
It was the other way around than I thought: the heater supply was disturbing the HV. Silly thing was although anyone would have noticed that high pitched percussion, I was unable to measure a change in level of more than 0,25%. If the measurement had exacerbated, things would have been clear from the beginning but I have been listening (in disgust) to 50Hz modulated audio for a week, not understanding what was causing this trouble. It's a great hobby
there was 2,9V ripple over those 16V caps and I (still) have no clue if that amount of AC is healthy. It would probably shorten their lifespan, but at what rate? Further I could not see what happens at startup when that 10uF gets loaded. The Fluke 87 DMM peak monitor function is not that fast.It was the other way around than I thought: the heater supply was disturbing the HV. Silly thing was although anyone would have noticed that high pitched percussion, I was unable to measure a change in level of more than 0,25%. If the measurement had exacerbated, things would have been clear from the beginning but I have been listening (in disgust) to 50Hz modulated audio for a week, not understanding what was causing this trouble. It's a great hobby
Just hypothetical as I'm no EE, how come the valve does not oscillate at the applied frequency? From what I understood there's capacitive coupling from heater to cathode. Although above AF, the valve is certainly operating at these high frequencies. Doesn't it give distortions at lower (audio) frequencies?
In some cases like, the cathode in DHT is directly coupled with heater itself. The HF can be filtered out easily. Also the interaction with audio frequency will result in modulation products outside of audible range. IMHO
Well...
No, there isn't. There's an RC first order low-pass filter formed.
I had this on my 300B pp; when I changed around the heater connection to one of the tubes it was all silent: so little now that it can't be heard on a Lowther.
I use one AC winding (with a single 0,2ohm inrush stopper) for each channel.
Agree. I am struggling with this issue now: I see the rectified spikes from the filament DC in my output. Exactly in synch. So it is capacitative degrading the input cathode it seems. I use a toroid transformer. Such a transformer saturates easily .There might be 10A or higher transients easily.
- I get 6,1Volt with a high current (2A) DC through a LM350.
(But with AC to which I reverted this morning I see more junk ricght now). Yach.
i never had any humming issues with the 2 2A3 sets i built a couple of years ago,
one had a center tapped 2.5 volt filament winding i used as bias tapping point,
the other had a humdinger pot......
i set the humdinger pot to midspan and afterwards i found out that i did not
have to touch it at all....
one had a center tapped 2.5 volt filament winding i used as bias tapping point,
the other had a humdinger pot......
i set the humdinger pot to midspan and afterwards i found out that i did not
have to touch it at all....
...Were it not for that pesky 'filament damage', tubes may have never been invented, and this forum would serve the DIY steam-powered player piano community.
One can make a NAND logic gate with three steam controlled valves. With a NAND gate, any and all digital logic could be implemented. It is interesting to contemplate a steam powered internet consisting of a bunch of steam powered I5's, I7's and IPAD's chatting on the "steam-powered player piano community" forum. And everyone would use the term "valve". Might be a little hot though.
And slow.
True, I still wonder why it works, preamp tubes are without ref. Just why bother with 100R to ground if it works well floating them. I see all the books authors advocating a ref, why bother for small tubes?
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