Hi,
having built a lovely Ale Gyrator loaded 2p29l /filament bias preamp, (Thanks Ale) I would like to use the same power supply for some old cv1045 DHTs I have. Old bright tubes for"special occasions". Though meaty enough for the 440mA filament of the cv1045, the 15v (14v at 440mA) wont be enough headroom for the Rob Coleman regs, 2V filament and -10v grid bias needed. Could I use this filament supply to get say 8v of the -10 needed for the grid, then add a couple of diodes to ground to get the rest. A sort of hybrid approach, or would this suck? Thoughts?
Thanks.
Nick.
having built a lovely Ale Gyrator loaded 2p29l /filament bias preamp, (Thanks Ale) I would like to use the same power supply for some old cv1045 DHTs I have. Old bright tubes for"special occasions". Though meaty enough for the 440mA filament of the cv1045, the 15v (14v at 440mA) wont be enough headroom for the Rob Coleman regs, 2V filament and -10v grid bias needed. Could I use this filament supply to get say 8v of the -10 needed for the grid, then add a couple of diodes to ground to get the rest. A sort of hybrid approach, or would this suck? Thoughts?
Thanks.
Nick.
Don't use DHT filament supply for other purposes than filament heating or filament bias (raw filament supply must be floating).
Direct heated tubes cathode is the heated filament wire (BTW the filament two end has different potential -referred to grid-).
Direct heated tubes cathode is the heated filament wire (BTW the filament two end has different potential -referred to grid-).
The V8 Regulator needs ca. 16V input, for 12V out. The new V9 can work as low as 14.6V, but 15V or more is best.
Are you asking to run the Filament regulator into the filament and 8V of bias, and then add diodes under the filament regulator's negative to ground? So outside of the filament current loop? If so, you will probably be OK. As euro21 says, be sure the whole Raw DC and regulator is floating, except to the filament bias resistor and the diodes.
Are you asking to run the Filament regulator into the filament and 8V of bias, and then add diodes under the filament regulator's negative to ground? So outside of the filament current loop? If so, you will probably be OK. As euro21 says, be sure the whole Raw DC and regulator is floating, except to the filament bias resistor and the diodes.
You could change the -10v bias to something lower.
Or you could add another filament transformer in series to boost the AC voltage by e.g. 6v and than add a dropper resistor as needed.
Or you could just use cathode bias and use Rod's regs to just heat the filaments. A cathode resistor with a 40uF DC Link bypass isn't too bad.
Or you could add another filament transformer in series to boost the AC voltage by e.g. 6v and than add a dropper resistor as needed.
Or you could just use cathode bias and use Rod's regs to just heat the filaments. A cathode resistor with a 40uF DC Link bypass isn't too bad.
Thanks all,
Yes Rod, Like the sketch above, sic diodes to ground, Reg floating as usual . Is this likely to sound good while allowing use of the existing power supply? I dont want to burn up these really old tubes watching TV and thought I could just swap the 2 preamps to the one power supply as I felt like it. I will order some v9 Regs to try this.
Yes Rod, Like the sketch above, sic diodes to ground, Reg floating as usual . Is this likely to sound good while allowing use of the existing power supply? I dont want to burn up these really old tubes watching TV and thought I could just swap the 2 preamps to the one power supply as I felt like it. I will order some v9 Regs to try this.
Yes, that should be fine for bias. Low impedance bias parts, like those diodes, are the best when they are between FILAMENT - and the anode supply-negative.
The new V9 gives a much lower impedance to ground, making 50Hz pickup much less of a risk than before.
The new V9 gives a much lower impedance to ground, making 50Hz pickup much less of a risk than before.