I had a nice 8vdc regulated, filtered supply, acouple bypass caps along a resistor string even.
Why that is much noisier than a bias string... AC290v>R>Diode>*R>*Pot>R>Gnd.
* designate the bypass filter capacitors [10uf/160v].
...is what I don't understand.
I had to alter the values [schematic of 2w PP power amplifier at ax84] of the R's to get it to adjust the output between -8V and -8.5V, it works nicely now.
My experience with regulators has been that they are solid DC, ripple free, apparently not in this case for some reason. Ie the regulator was wired up with R and C values, adjusted voltage as expected [lm317], I even added another small resistor and another bypass cap to the LM317 output...still too noisey.
The Grids I'm driving are obviously sensative, but the noise from the regulator makes me re-think 'ripple free' in relation to Vregs.
Quote from: petemoore on June 01, 2011, 06:41:04 PM
I had a nice 8vdc regulated, filtered supply, acouple bypass caps along a resistor string even.
Why that is much noisier than a bias string... AC290v>R>Diode>*R>*Pot>R>Gnd.
* designate the bypass filter capacitors [10uf/160v].
...is what I don't understand.
I had to alter the values [schematic of 2w PP power amplifier at ax84] of the R's to get it to adjust the output between -8V and -8.5V, it works nicely now.
My experience with regulators has been that they are solid DC, ripple free, apparently not in this case for some reason. Ie the regulator was wired up with R and C values, adjusted voltage as expected [lm317], I even added another small resistor and another bypass cap to the LM317 output...still too noisey.
The Grids I'm driving are obviously sensative, but the noise from the regulator makes me re-think 'ripple free' in relation to Vregs.
most Vregs state 80db of ripple rejection. I would look at the power supply with an oscope..
All regulators are feedback based DC amplifiers. Get them a bit wrong and they oscillate. I'm with Iccaros - get a scope on it and see if it's oscillating.
More output capacitance may make oscillation *worse* in some cases.
And a bad one, or a bad reference voltage solder joint, is always a possibility.