Author Topic: Charge pump voltage drop  (Read 580 times)


Re: Charge pump voltage drop
« Reply #20 on: Yesterday at 05:04:50 AM »
Valvecasters can and do work off 9v with the series heater only getting 4.5v. Performance is improved with a 12v supply and series heaters but that is provided by a proper 12v external wall wart.

A midway solution might be to have a charge pump providing a 12v to 18v plate supply while the heaters carry on with 4.5v from the 9v supply OR give them 6v each from a regulator off the 9v supply but that wastes supply power into heat. The best solution might be a 12v PSU with series heaters and also charge pump the plate supply nearer 24v.

If you have balanced +/- charge pump outputs, you can hang the tube circuits between them for double effective plate voltage but any grid bias and cathode resistors now go to the -supply instead of 0v and the grid inputs will need DC blocking capacitors.

If you use multiple switching DC converters you run a big risk of audible whine due to the differences between their switching frequencies. A proper solution is convertors with master/slave clocking facility so no matter how many outputs you need, the switching frequencies are identical as only the master provides the clock.

Croeso i Diystompboxes.

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Ben N

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Re: Charge pump voltage drop
« Reply #21 on: Yesterday at 07:52:31 AM »
Another argument for a separate 12v supply: Whatever it is you are using to supply 9v to your whole shebang is going to be supplying a heckuva lot of current to this one effect. Maybe you have mA to spare, but maybe not. That, plus all the simplification that comes from not having to boost your voltages at high current levels.
Then again, why not power everything off a single hefty 12-18v 2-3A supply, with regulators, buck converters or even voltage dividers (and whatever filtering you need) to drop you down as necessary for all other required voltages? It seems to me that life is easier all around if you start with the highest voltage you need and drop, rather than boosting & dropping willy-nilly all over the place, with all the complexity, space & noise challenges that implies.


Re: Charge pump voltage drop
« Reply #22 on: Yesterday at 08:18:27 AM »
The proper power supply for this would be a 19-volt laptop battery and if you use a scrap laptop, you have all the charging circuitry included with it and the charger allows you to plug and play.  Most laptops have chargers available for 120 VAC or 220 VAC 50 Hz or 60 Hz for worldwide operation.  Use a switching regulator to bring the voltage down to 12.6 for the filaments.  You should be able to run a 12AU7 from 19 volts.  A neat solution would be to run a 20EZ7 which is a 12AX7 with 20 volt 100 mA filaments so you could run everything off a laptop battery with no regulators at all.