Could try adding a MOS cap-multiplier to the B+
4.7uF [x1 or x2] MKT (cheap type is OK, as there is no current) and 1,5M resistor [and 12V zener]. Cheap FQPF3N80C is 800V isolated, and can easily do this [1 per channel]
FAIRCHILD SEMICONDUCTOR|FQPF3N80C|MOSFET, N, TO-220F | Farnell United Kingdom
4.7uF [x1 or x2] MKT (cheap type is OK, as there is no current) and 1,5M resistor [and 12V zener]. Cheap FQPF3N80C is 800V isolated, and can easily do this [1 per channel]
FAIRCHILD SEMICONDUCTOR|FQPF3N80C|MOSFET, N, TO-220F | Farnell United Kingdom
I'm altready planning to use Salas HV shunt regs.... one silicon junction in series with B+ it's enough for my taste! 😉
Thank you Rod anyway!
Thank you Rod anyway!
Thus the rectifier tube (#80) is still subject to cathode stripping.>>>
The 80 is directly heated - can you have "cathode stripping" with directly heated filaments?
andy
The 80 is directly heated - can you have "cathode stripping" with directly heated filaments?
andy
Ops..... #80 and its son 5Y3 are DH. What a noob I'm! 😉
What do you think about a double pwr on switch, Andy?
What do you think about a double pwr on switch, Andy?
"cathode stripping" normally means the electrostatic ripping of cathode layer from the active layer [or DHT filament] in **Transmitter** tubes.
With 600V and lower operation, you don't really risk this happening.
But you do risk the effect described by van der Weyer - active-layer particles being drawn to the grid (where they stick). This is not related to cathode stripping (as applied above).
But over many power cycles, you may end up with more noise and distortion than an unused valve.
The grid, and cathode active layer are present in direct- and indirect- heated tubes, so I would assume the same precautions apply. And since DHTs are usually more expensive to replace, I think the precaution is worth the trouble.
Personally, I think it is (aesthetic) rough-handling to crash the HT on to a valve before it is warmed up, like using a big nailed-boot, or a stick to operate the power switch. DHTs are fragile, and should be treated GENTLY, in all ways.
On the other hand, one may choose to believe that nothing will happen - many here do. That's OK, It's your money, and your tubes. This is DIY!
With 600V and lower operation, you don't really risk this happening.
But you do risk the effect described by van der Weyer - active-layer particles being drawn to the grid (where they stick). This is not related to cathode stripping (as applied above).
But over many power cycles, you may end up with more noise and distortion than an unused valve.
The grid, and cathode active layer are present in direct- and indirect- heated tubes, so I would assume the same precautions apply. And since DHTs are usually more expensive to replace, I think the precaution is worth the trouble.
Personally, I think it is (aesthetic) rough-handling to crash the HT on to a valve before it is warmed up, like using a big nailed-boot, or a stick to operate the power switch. DHTs are fragile, and should be treated GENTLY, in all ways.
On the other hand, one may choose to believe that nothing will happen - many here do. That's OK, It's your money, and your tubes. This is DIY!
Question for Andy: have you noticed a significant difference using 2 x 156C plate chokes instead of one? Or I should say, how much of a loss when using just one choke? I happen to have a couple 156C chokes and was thinking of using them one per channel.
Felipe, maybe. It will WORK with one.
But for best performance, one Trasfo for each side will protect the filament in channel L from the power supply current pulses, and diode noise, in channel R.
But for best performance, one Trasfo for each side will protect the filament in channel L from the power supply current pulses, and diode noise, in channel R.
Yes - there is a significant difference, because it halves the capacitance which is your enemy for the treble. It also doubles the inductance which is useful for a 26. Two are much better sounding.
I wire the two chokes bottom to bottom with the wires coming out the same side. Then connect the right side wire of one to the right side wire of the other (when the normal way up, not upside down!) so you wire them out of phase.
Try getting another two - they're very cheap and surprisingly effective. I'd prefer a really nice anode choke from a good maker, but for now this gets me some good sounds.
Andy
I will use separate box one for TX + inductor & the other one for tube preamp so my question is wich connectors & cable wire will be suitable for?
You will get a lot of different answers. I use Speakon 4 pole for the HT/ground and XLR 4 pin for the filaments. Both cheap, and this covers the voltage ratings.
andy
andy
I can get Speakon 4 pole or 8 pole, wich will be better: separate HT & filament or all togheter in one connector?
If it's permanent, speakon 8 pin is fine. But I use separate connectors because I may want to connect different HT supplies, or power the filaments from a bench supply etc. I experiment a lot.
andy
andy