I always had the impression that Allen preferred current regulation, and that is what I use in both my RTP3 and SVP.
Current regulation is no hassle either! Use a 9V transformer secondary, and put an LM317 or LM1085 after the reservoir caps with the appropriate resistor (4,1 ohms for the 6922) between output and adjust terminals to get the current for your chosen valve type, and connect the adjust to the filament. No voltage dividers or capacitors needed for the regulator.
Alex
Current regulation is no hassle either! Use a 9V transformer secondary, and put an LM317 or LM1085 after the reservoir caps with the appropriate resistor (4,1 ohms for the 6922) between output and adjust terminals to get the current for your chosen valve type, and connect the adjust to the filament. No voltage dividers or capacitors needed for the regulator.
Alex
I'm using these Single Pole Change Over Switch | Rapid Online
Not very substantial, but they do the trick. I used one CS for each tube. It's a long time since I implemented it, but I'm sure I used LM317's with the jumper switches and paralleled resistors to give the 3 currents.
I get 5.6V across the heaters. Is it normal? Tubes - 6N23P, for 2 tubes I measure 0,61A with 2 x 8,2Ohm resistors.
The only part of this circuit which should need regulated heaters is the phono front end. The line level will be totally hum free with AC heaters biased at a suitable DC potential.
However if you correctly apply Constant Current to the heaters then the voltage drop across them could vary from 6.3V by as much as +/-0.6V and this is what you should expect.
Shoog
However if you correctly apply Constant Current to the heaters then the voltage drop across them could vary from 6.3V by as much as +/-0.6V and this is what you should expect.
Shoog
Ok, I have finished the line stage and have the following problem: there's only 30v on the upper tube plate of the gain stage after 25K resistor though it should be 150v. The rest reads ok: CCS 6 mA, the input tube plate 52v, the upper tube grid at 50v. CF CCS 12,5 mA, voltages are OK. Salas reg supplies 300v with 50mA. When I disconnect CF stage I can read 150v on the upper tube plate. But when I connect it again - 30v. Where to look, guys?
In the pictures from Alex you can see HT minus connected to 3 way terminal strip but in the manual it connects to the ground point of the lower tube in CF. Also there is a connection mistake in the manual with one of 2M resistors in the voltage dividers section in CF. Also I don't quite follow what those yellow caps under the strips in CF section do. In the manual they are actually parallel to other caps in voltage dividers section. If they are meant to be for heater elevation then it is a wrong place to connect them. Maybe someone who has a working unit will explain.
I found errors in two manuals from Allen (2004 & 2008). Send me a PM with a picture of your manual and your e-mail and I'll send you the corrected pages.