Keantoken's CFP cap multiplier

[merlin el mago]

I don't know the input ripple: I will use CRCRC and CLCLC between the tx & the cap multiplier, for sure I will use a hybrid SS+silicon rectifier Graetz type with tubes AZ1 & 6AXGT, load will be #26 tube preamp or other tube preamps, SSHV2 spends 20mA to operate for #26 or other tube preamp I will set the SSHV to 30mA.

[keantoken]

If you have 30mA load current and 470uF capacitance after the rectifier you should have .5V ripple. Input ripple for the Kmultiplier needs to be lower than 1.8V. For 1.8V ripple you need at least 140uF, if the Kmultiplier were right after the rectifier. Tell me if your supply is not beefier than this.

[merlin el mago]

Well AZ1 now have connected only 2 x 40uF capacitance ASC386X MKP in oil = 80uF. 6AX4GT still not installed waiting to arrive. I have now the Valve Itch phono tube preamp that I have installed 4 UF4007 as bridge rectifiers followed with CRCR 220uF/220R/220uF/220K bleeder resistor, I think can I use here?

[keantoken]

What is the transformer secondary voltage?

[merlin el mago]

240VAC & I need minimum 320VDC before SSHV2.

[keantoken]

So if I understand correctly 240VAC->340VDC. 30mA*220R=6.6V. So I have 13.4V to work with.

Merlin, what do you think about this? The 220R/220u RC is from your supply. It took some determination to make it safe from overvoltage and inrush current, but I like how it turned out.

Don't put more than 330uF between the Kmultiplier and the HV2. Capacitance after the HV2 is okay because it will be limited to 30mA inrush.

[KlipschKid]

Originally Posted by keantoken

Thanks KlipshKid. I haven't messed with the BUP40/41. My focus has always been on parts that are easy to get and that can be bought from authorized vendors with the certainty they are not counterfeit. This has just been my preference so far, as I don't want unexpected problems while I am testing and developing my circuits. If they are still easy to find not counerfeit, I may consider making designs with them.

If BC550C is the NPN part then that's what it should be. I mix them up all the time! Must fix that...

Hi,

I'm in the same situation but I can't get 2SA1930 / 2SC5171; Q2 and Q3. Could I use Q2 BC560C and Q3 BC550C instead (for applications under 50mA) and still get good psrr and stability ? I'll still use Q4 BC327-25 and Q5 BC337-25 as your page recommends.

Is anyone intrested in doing a PCB and group buy ? I can see this becoming very popular if it can be made suitably small.

Thanks for your help Kean !

[keantoken]

If you use smaller outputs you need to mind inrush. At 50mA TO92 outputs may work but may blow up when trying to fill a 470uF output cap. This was my problem with the HV Kmultiplier. A TO92 output would work great for this but would be destroyed the first time it was turned on.

The BC327/337 are more suited as outputs than the BC5x0C, I would use them instead.

An SMD version could be made, NXP has some ideal BISS transistors for this purpose I think. Scratch that, the only way you can get them is through the sample kit!

[KlipschKid]

Hi,

I can't get the MJE easily either, so perhaps a BD is needed ? Bd139/140 or 433/434 ?

Thanks

[keantoken]

BD139 will do I think though I haven't tested it myself. You have to get it from the right manufacturer though, or it'll be something aweful. The BD433 is one of the slowest transistors I've ever seen, 3MHz at 250mA! That is a new one, for me. It's slower than an MJL21194!

BC639/640 from NXP/Phillips are a good bet if you can get them anymore. IIRC BD139/639 from ONSemi are no good.

Dunno if any of this helps. The BUP40/41 will probably work great if you have them.