Hi,
I'm looking for a soft start circuitry for both the heater and the B+ (Moglia CCS in mind for the B+) for a 6DJ8/ECC88/6922/E88CC. Whatever manual start for the heater before or better both PS with delayed start with one front-panel button !
Would like to avoid CT trafo, so no tube rectifier. I'm aware of some shematics, but I'm more looking for a ready made DIY bare pcb to avoid layout problems.
Are you aware of a good enough pcb(s) for both those purposes ? JIM Audio or else ?
Many thanks
I'm looking for a soft start circuitry for both the heater and the B+ (Moglia CCS in mind for the B+) for a 6DJ8/ECC88/6922/E88CC. Whatever manual start for the heater before or better both PS with delayed start with one front-panel button !
Would like to avoid CT trafo, so no tube rectifier. I'm aware of some shematics, but I'm more looking for a ready made DIY bare pcb to avoid layout problems.
Are you aware of a good enough pcb(s) for both those purposes ? JIM Audio or else ?
Many thanks
Is this because your existing PT doesn't have a CT and you don't want to purchase one that does? Or is it because you just don't want to use a tube rectifier?
A tube rectifier can be used with a non-CT PT by using a hybrid PS. An indirectly heated rectifier tube will give you a nice soft start.
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Hi,
No I have not the traffo with CT and they are expensive for me as the common chockes are.
I am only looking for an already made pcb with voltage multiplier perhaps for the B+ and a 6.3V heater pcb. But with soft-start design for the tube span life for both PS.
So no hybrid valve rectifier for me (not the aera room).
No I have not the traffo with CT and they are expensive for me as the common chockes are.
I am only looking for an already made pcb with voltage multiplier perhaps for the B+ and a 6.3V heater pcb. But with soft-start design for the tube span life for both PS.
So no hybrid valve rectifier for me (not the aera room).
I like the solution FlaCharlie provided.
Or, if you provide two 5V secondaries, you can use a pair of vacuum rectifiers to make a bridge rectifier.
Either use a rectifier that has a cathode for soft start such as 5AR4,
or . . .
Use two 6.3V filament transformers dedicated to the rectifiers, and two 0.65 Ohm resistors, one in each 5Y3 filament circuit (0.65 Ohm times 2A = 1.3V). The cold 5Y3 filament is far less than 1 Ohm, so the series 0.65 Ohm resistor will give a real good soft start.
I always enjoy it when people either paint theirselves into a corner, or they complicate the circuitry by an order of magnitude.
I am not a statistician, but with a more complex circuit, the more chance there is for a failure due to parts that fail; connections that fail; wiring that is not correct; bad warm up timing of the various circuits; Hot starts (a brief power outage, quickly followed by a power on again; and those often have over-voltage transients), etc.
Make your circuit robust without all the complications.
If you want a PCB with voltage doubler, how will you expect to modify it to have soft start.
Personally, I hate voltage doublers. Makes for very fast rise current transients with high frequency spectrum. Not nice for potential noisy ground loops, and hard to tame well enough to use to power preamp or line amp circuits.
Solid State diodes and voltage doublers are really noisy.
If you really want to use voltage doublers, you can use two vacuum tube rectifiers, and two rectifier filament windings. A pair of damper diodes and two 6.3 windings makes a good soft start voltage doubler. Or use the other vacuum tube solutions I listed above.
Of course, that does complicate it.
Just my opinions.
Or, if you provide two 5V secondaries, you can use a pair of vacuum rectifiers to make a bridge rectifier.
Either use a rectifier that has a cathode for soft start such as 5AR4,
or . . .
Use two 6.3V filament transformers dedicated to the rectifiers, and two 0.65 Ohm resistors, one in each 5Y3 filament circuit (0.65 Ohm times 2A = 1.3V). The cold 5Y3 filament is far less than 1 Ohm, so the series 0.65 Ohm resistor will give a real good soft start.
I always enjoy it when people either paint theirselves into a corner, or they complicate the circuitry by an order of magnitude.
I am not a statistician, but with a more complex circuit, the more chance there is for a failure due to parts that fail; connections that fail; wiring that is not correct; bad warm up timing of the various circuits; Hot starts (a brief power outage, quickly followed by a power on again; and those often have over-voltage transients), etc.
Make your circuit robust without all the complications.
If you want a PCB with voltage doubler, how will you expect to modify it to have soft start.
Personally, I hate voltage doublers. Makes for very fast rise current transients with high frequency spectrum. Not nice for potential noisy ground loops, and hard to tame well enough to use to power preamp or line amp circuits.
Solid State diodes and voltage doublers are really noisy.
If you really want to use voltage doublers, you can use two vacuum tube rectifiers, and two rectifier filament windings. A pair of damper diodes and two 6.3 windings makes a good soft start voltage doubler. Or use the other vacuum tube solutions I listed above.
Of course, that does complicate it.
Just my opinions.
Last edited:
diyiggy,
Simple soft start for 6DJ8 filament:
6DJ8 6.3V 0.365A
6.3V/0.365A = 17.26 Ohms
Cold resistance is much lower.
Use a 12.6V filament transformer, and a 20 Ohm series resistor (the 12.6V will be higher than 12.6V if it is not heavily loaded, for example a 1A or 2A transformer rating and only a 0.365A or 2x 0.365A load.
I have questions.
Are you using $1,000 Volt special 6DJ8 tubes?
Are they from an inheritance of your favorite relative?
What circuit is so hard on 6DJ8 tubes that a classical power supply will not protect them?
Can you sleep at night, or do you stay awake worrying about your Hi Fi?
Simple soft start for 6DJ8 filament:
6DJ8 6.3V 0.365A
6.3V/0.365A = 17.26 Ohms
Cold resistance is much lower.
Use a 12.6V filament transformer, and a 20 Ohm series resistor (the 12.6V will be higher than 12.6V if it is not heavily loaded, for example a 1A or 2A transformer rating and only a 0.365A or 2x 0.365A load.
I have questions.
Are you using $1,000 Volt special 6DJ8 tubes?
Are they from an inheritance of your favorite relative?
What circuit is so hard on 6DJ8 tubes that a classical power supply will not protect them?
Can you sleep at night, or do you stay awake worrying about your Hi Fi?
Yeah, the OP could just use his existing PT and add a couple of diodes which cost a few cents each. And to keep it super simple, there are a few 6.3v rectifiers (6X4, 6X5, 6CA4) which not only have soft start because they're indirectly heated, but they also have heaters that are not connected to their cathodes. Although I've never wired them like this, this means they can be heated using the same heater winding as the 6DJ8s. No additional heater transformer is needed.
But maybe that's not high tech enough.
He hasn't said what he's building but I assume it's a preamp. I'm not familiar with the 6DJ8 but I get the impression that it's not particularly expensive.
Couple that with the fact that I've often found vintage gear that doesn't have any type of soft start yet the original preamp tubes still test as new or nearly so after being used for 40 or 50 years.