You are just repeating yourself. You have not supplied any evidence, you have not supplied any logical explanation, and you especially show no sign of using test gear proficiently.
You need to take your own advice - get scientific, understand the topic, do your own measurements.
Why have you not answered any questions that have been put to you?
We do of course already know the answer to one question. You do in fact sell filament supply regulators. With snake oil talk. I quote from your Post #20:-
The filament has a differential signal voltage across it, due to the gm and bias skew brought on by the filament voltage gradient. A voltage regulator - whose feedback is sourced directly across the filament - sees this music signal, and tries to null it out - clumsily, because it's an Ampere-level regulator.
Any beginning year electronics student would laugh at that. It makes multiple boo-boos. This "music signal" is 10's of millivolts (thats just Ohms' Law) - negligible compared to the cf 100V grid drive voltage. And a CV regulator just parallels the filament with a low impedance, making this "music signal" lower and even more negligible.
I just love that bit about "clumsy ampere level regulators". It should appeal to the ignorant. It's an emotional term presumably meant to conjure up in the gullible a comparison with using an enormous wrench to undo a wristwatch screw or something. Not a shred of science though.
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So, having lost the ACTUAL argument about IMD from ac-heating, you resort to attempting troll me.
You might at least add some more of that humour of yours though, or things will get very dull. Tell us more about being a DHT amplifier expert, on the strength of listening to an AM radio 30 years ago, for instance.
You might at least add some more of that humour of yours though, or things will get very dull. Tell us more about being a DHT amplifier expert, on the strength of listening to an AM radio 30 years ago, for instance.
You can repeat that nonsense on lost arguments all you like. I provided a technical explanation and you did not.
People can read this thread and note that you were the first to revert to personal attacks.
I have no problem with you selling CCS regulators for DHT tubes. If people want to buy them (for whatever reason) it's ok if someone sells them. Ok, that is, if you sold them on the basis of something like "Some people prefer const current power. I offer mine for experimental purposes and for those who want to try const current power".
But if you are going to make silly claims such as your claim that you can hear the difference, that's misleading advertising. In many countries, illegal, as it is not backed by technical fact.
I even have no particular problem with you using forums like diyAudio to push your product, though others may consider it unethical. I don't do it myself.
But if you are going for the gullible with words such yours I quoted in my last post, you are fair game. You should expect to have your claims refuted.
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Though I do plan on attempting to troubleshoot using some of the further suggestions in this thread.. Here's something I'm tossing around..
Just for comparisons sake even.. Solid state rectification. Eliminate the possibility of noise caused by the field created by the rectifier tubes.
I had originally planned to go solid state, but was having trouble finding diodes that would be suitable. Could someone make a suggestion for diodes that would be able to handle the voltages / current that I'm working with?
I liked the 6CM3 because it has a rating of 5500V PIV, and 1.7A peak plate current..
Based on my PSUD2 simulations, I think for a bit of margin, I think I need at least a 3000V PIV rating, 2.2A Peak current rating, and greater than 200mA continuous current rating..
I haven't been able to find anything that fits the bill.
Well, there's this R5000F Rectron | Mouser
But they look pretty slow.. 500nS recovery time..
Does anyone have any suggestions?
Just for comparisons sake even.. Solid state rectification. Eliminate the possibility of noise caused by the field created by the rectifier tubes.
I had originally planned to go solid state, but was having trouble finding diodes that would be suitable. Could someone make a suggestion for diodes that would be able to handle the voltages / current that I'm working with?
I liked the 6CM3 because it has a rating of 5500V PIV, and 1.7A peak plate current..
Based on my PSUD2 simulations, I think for a bit of margin, I think I need at least a 3000V PIV rating, 2.2A Peak current rating, and greater than 200mA continuous current rating..
I haven't been able to find anything that fits the bill.
Well, there's this R5000F Rectron | Mouser
But they look pretty slow.. 500nS recovery time..
Does anyone have any suggestions?
BY203-20S give 2kV and 20A peaks, 300ns RR.
You can series-connect them for higher voltage durability.
But with SS rectifiers, a bridge fed from a single winding is better (better use of the trafo, and lower voltage stress).
But I think you will be fine with the 6CM3. And the slow ramp-up of the voltage is always nicer. They only need to be positioned on a chassis carefully, wired in short, twisted 5kV rated cable.
You could use the twisted cable method now, to reduce loop area, and see if your buzz reduces.
You can series-connect them for higher voltage durability.
But with SS rectifiers, a bridge fed from a single winding is better (better use of the trafo, and lower voltage stress).
But I think you will be fine with the 6CM3. And the slow ramp-up of the voltage is always nicer. They only need to be positioned on a chassis carefully, wired in short, twisted 5kV rated cable.
You could use the twisted cable method now, to reduce loop area, and see if your buzz reduces.
Ah yea, hadn't seen that diode.. The diff in recovery speed between the BY203, and that R5000F that I posted isn't huge..
I was just thinking for experimentation's sake could try solid state.
I have twisted my heater wiring for the 6CM3's, but you're talking about twisting my HV wire, right?
You made it my business yourself - when you entered this thread against me.
Yes, twist the HV trafo -> rectifier pair, 5kV cable. Massive loop-area reduction, certainly lower noise.
Why on earth would you do that? You will add to your problems.
The noise does not actually come from the rectifier tubes. The noise comes from the power transformer leakage inductance due to the short conduction. This will still happen if you use solid state diodes.
If you use solid state rectification, you will add another problem. Unlike tubes, semiconductor diodes don't turn off as soon as the voltage reverses. They continue full conduction in the reverse direction, until the charge carriers are swept out of the junction.
Then, when the charge carriers are gonem, the diode stops conduction - but by then the AC input voltage has built up the transformer current again (in the reverse direction). So the delayed diode turn off causes a larage inductance back EMF in the trasformer leakage inductance. This doesn't happen with tube rectifiers.
So, using semiconductor rectification is likely to add to your buzz problem.
Semicionductor diodes are used succesfully in commercial equipment, but they have good layout that you don't have, and they take other measures to control the hash generated. Some diyers use shottly diodes as these turn off much faster than standard power rectifier diodes. But they are only available in low PIV ratings, and there are other, better ways to address the problem.
I strongly recommend you fix the buzz first, before considering solid state diodes.
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My thought process was just that it seemed like shielding around the rectifier seemed to affect the buzz slightly, and the vicinity of those tubes to the grids of the 845's could possibly contributing to the noise.. But I hear you! I'll kybosh that idea..
I'll keep troubleshooting my current build.
Back at the beginning of this discussion, you ignored your best clue. When you grounded the grid, the noise stopped. The grid resistor really is too big. Try 1.5K instead. You could also reduce the 250K to ground as well to 100K and not suffer much loss. It sounded like a ground loop at first - you never showed your layout - "ground" isn't ground all over. Ground that 250K to the same spot as the cathode ground. I see this a lot.
Soemthing else to try, if you have the requirments on hand, before you do a whole lot of work rebuilding:-
While you have used a shottkly bridge rectifier in the filament supply, and effectively a choke input filter, the bridge could still be a source of noise. And because DC feeding provides a straight run from filament -ve, you have another two possible contributors to the buzz.
Try disconnecting the filament current regulator, and temporarily powering the filament in one channel direct from a battery. A battery is a perfect noise free DC source (apart from droop under load and limitted life)
Two possibilities for the battery:-
1) 7 D-size (or C-size at a pinch) 1.5V torch cells connected in series by wires soldered on the ends. I often solder cells up in series when I need a few low noise DC volts to check something. Soldering wires on the ends doesn't appear to hurt them. I solder the wires to the side of centre so that I can still put them in a torch afterwood - or in some vintage battery powered electronic items I have.
2) A "12V" motorcycle or car battery temporarily removed from the vehicle. Since a charged lead acid battery actually puts out about 13.8V on moderate loads, and the 845 filament requires 10V @ 3.25A, you will need a series dropping reistor of (13.8 - 10) / 3.25 = 1.2 ohms. The power dissipated in the resistor will be 12.4 Watts, so use something rated to take it. A 1.2 ohm 10W resistor will be ok for a short test, thoough it will get very HOT! Or two 2.2 ohm 5 watts resistors in parallel. Or three 3.3 ohm 5 watt resistors in parallel.
Keep the filament powering wires as short as possible during the battery test.
Don't forget what I said before: At the very low level of buzz you are reporting, and the results of the tests you reported, there seems to be multiple causes of the buzz. Therefore there may be no single cure.
If you find that powering the filament from a battery reduces the buzz, tell me, and I'll give you a solution or two so you don't need to always have a battery.
While you have used a shottkly bridge rectifier in the filament supply, and effectively a choke input filter, the bridge could still be a source of noise. And because DC feeding provides a straight run from filament -ve, you have another two possible contributors to the buzz.
Try disconnecting the filament current regulator, and temporarily powering the filament in one channel direct from a battery. A battery is a perfect noise free DC source (apart from droop under load and limitted life)
Two possibilities for the battery:-
1) 7 D-size (or C-size at a pinch) 1.5V torch cells connected in series by wires soldered on the ends. I often solder cells up in series when I need a few low noise DC volts to check something. Soldering wires on the ends doesn't appear to hurt them. I solder the wires to the side of centre so that I can still put them in a torch afterwood - or in some vintage battery powered electronic items I have.
2) A "12V" motorcycle or car battery temporarily removed from the vehicle. Since a charged lead acid battery actually puts out about 13.8V on moderate loads, and the 845 filament requires 10V @ 3.25A, you will need a series dropping reistor of (13.8 - 10) / 3.25 = 1.2 ohms. The power dissipated in the resistor will be 12.4 Watts, so use something rated to take it. A 1.2 ohm 10W resistor will be ok for a short test, thoough it will get very HOT! Or two 2.2 ohm 5 watts resistors in parallel. Or three 3.3 ohm 5 watt resistors in parallel.
Keep the filament powering wires as short as possible during the battery test.
Don't forget what I said before: At the very low level of buzz you are reporting, and the results of the tests you reported, there seems to be multiple causes of the buzz. Therefore there may be no single cure.
If you find that powering the filament from a battery reduces the buzz, tell me, and I'll give you a solution or two so you don't need to always have a battery.
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If you mean that the filament negative terminal is connected to the raw dc supply, then no, that is not true.
My Filament Regulator provides broadband isolation of BOTH sides of the Filament from the raw rectified dc, expressly to prevent noise ingress.
solid state rectification = abs. NO for true tube device
Not correct. Millions of commerical products, tube based, were made with solid state recification, including audio equipment of the highest quality, without any trouble. As soon as silicon diodes became available, tube rectifiers were avaioded by factories, as rectification, whith its high peak-to-average current ratio is something tubes were never really suitable for, and they were the most failure prone parts in any equipment.
You just have to know how to use solid state rectification correctly:-
a) Good layout, keeping the power supply away from sensitive circuits
b) short wires,
c) Routing grounding wiring so that the power supply capacitor ripple currents don't flow in wires powering the amplification stages - that helps eliminate hum as well.
d) Installing snubber capacitors across the diodes.
e) Ensure the power transformer core and cheek plates are properly earthed.
f) If necessary, with bridge rectification and choke input filtering, use a shunt diode across the bridge output, so the choke flywheel current flows in the diode, and not through the bridge and thus the transformer.
Usually the first three measures are sufficient, sometimes (d) is needed. Many manufacturers, especially Japanese, always included (d) as a matter of course.
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In my view, the "susceptibility loop" should be corrected first: i.e. the receiving "search-coil" formed by the loop : anode -> OT primary -> -> HV+ -> HVcap -> Ground.
Move Cap-3 and rewire the OT primary in parallel or twisted 5kV cable.
The advantage of doing this first is that is reduces noise caused by ALL non-conductive sources - whether from within the amp, or from some nearby equipment.
Move Cap-3 and rewire the OT primary in parallel or twisted 5kV cable.
The advantage of doing this first is that is reduces noise caused by ALL non-conductive sources - whether from within the amp, or from some nearby equipment.
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Exactly how is this broadband isolation implemented?
Incidentally, what is the minimum input voltage your regulator requires? I don't mean the average DC level, I mean what is the minimum permitted volatge during rectification ripple troughs?
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