Hey guys, I have to adjust a difference of aprox. 11V between anodes of the two tubes, I'm using OPT for each tube but only one SSHV2 for the two OPT.
It seems possible to reduce one tube anode voltage using a RC between the SSHV2 and the OPT?
Using Ohms Laws for 11V & 20mA I need 550 ohms 0,22W so 1or 2 watts will be enough but how to calculate the value of the capacitor to do RC an avoid the resistor used as load togheter the OPT?
It seems possible to reduce one tube anode voltage using a RC between the SSHV2 and the OPT?
Using Ohms Laws for 11V & 20mA I need 550 ohms 0,22W so 1or 2 watts will be enough but how to calculate the value of the capacitor to do RC an avoid the resistor used as load togheter the OPT?
Is this a PP OPT, with different RDCs? Doesn't sound like it...
Or two SE OPTs, do these have a different RDC? Or, asking differently, if you use the same PS, how can the offset develop (different RDC and/or different currents through each tube).
Or two SE OPTs, do these have a different RDC? Or, asking differently, if you use the same PS, how can the offset develop (different RDC and/or different currents through each tube).
Unmatched tubes could give this effect. Is it not possible to obtain a matched pair to test with ?
Probably old DH tubes, one is more used than the other, so they produce different operating points.
This (equalising anode voltages) won't help, the current AND the gain will be different ... more or less.
Felipe, draw the operating points to tube's datasheet curves.
This (equalising anode voltages) won't help, the current AND the gain will be different ... more or less.
Felipe, draw the operating points to tube's datasheet curves.
Hey Merlin,
What circuit are you referring to?
I am not sure if relevant but I made this yesterday.
https://www.bartola.co.uk/valves/2019/06/23/iron-and-sand/
Originally I had it the preamp version for the 4P1L but because of the oscillation and the microphonics, I switched it to the 2P29L. Oscillation was fixed by a 0.1uF PP cap close to the gyrator. I use LL1660 4.5:1 ratio (prim in series and secs in parallel to be suitable for a 300ohm HD600. BTW, I am using the 50ohm cathode resistors not the diodes.
I am impressed by the freq response > 600kHz before out starts to get attenuated, cleanest square wave you'll ever see.
Believe it of not, I read Ale listening impressions after listening to mine and found his take very much in line with mine.
I'll be measuring some thd today.
The hifiman headphones are much lower imp, right? A 12:1 OPT will be required at least.
What circuit are you referring to?
I am not sure if relevant but I made this yesterday.
https://www.bartola.co.uk/valves/2019/06/23/iron-and-sand/
Originally I had it the preamp version for the 4P1L but because of the oscillation and the microphonics, I switched it to the 2P29L. Oscillation was fixed by a 0.1uF PP cap close to the gyrator. I use LL1660 4.5:1 ratio (prim in series and secs in parallel to be suitable for a 300ohm HD600. BTW, I am using the 50ohm cathode resistors not the diodes.
I am impressed by the freq response > 600kHz before out starts to get attenuated, cleanest square wave you'll ever see.
Believe it of not, I read Ale listening impressions after listening to mine and found his take very much in line with mine.
I'll be measuring some thd today.
The hifiman headphones are much lower imp, right? A 12:1 OPT will be required at least.
Fixed guys, was when I tried starved filaments possible going to low, now is going all ok with only 1V of difference.