PCM 1794 with tube output problem

[kevinkr]

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baldrick: one thing I don' understand: on the BCF schematics, the lower tube grid has two connections. The one that I circled is the same as the one from pin nr. 2, and is connected like this to have a more clearly schematic?

R4 is the input resistor, and R5 is the feedback resistor, both are connected to the grid pin (2). The schematic is drawn in an unconventional way and can result in just this sort of confusion.

 

[stefan646]

Thank you for the answers !
I will start building the BCF with 6N1P and anode voltage = 165V. I chose the recommanded values for R1,2,4,5 = 47K, R7=1M. For C1=2,2uF, C23=0,1uF and C2=3,9uF. I omitted the C3 and C4. Correct me if I am wrong or if you have better suggestions.
The problem is that I don't know witch value to use for Rk. The BCF manual recomands 300ohms for 6N1P with B+ voltage 240V, but I have 165V. I should compensate this voltage diference putting a bigger resistor than 300ohm or it will work fine with lower voltage too?

http://ep.yimg.com/ay/glass-ware/bcf-9-pin-pcb-user-guide-6.gif

 

[baldrick]

Why did you pick that anode voltage?

If you keep the same value cathode resistor your tubes will conduct less current, but I suspect that it will not impact the operation of the circuit very much due to its symmetry.

 

[stefan646]

Why did you pick that anode voltage?

Because I order the transformer to match the specification of the lampizator tutorial -120V . I am currently using a 470uF cap followed by a simple MOSFET regulator like this one Basics, Introduction, Calculation, Theory,PCB DIY Kit Mosfet stabilized power supply
I am wainting for a 1000uF capacitor to see if the tension before the MOSFET will rise significantly, and if so, I will add another zener diode to the regulator to rise the final anode voltage.

Attached is a table using different anode voltages and sizes for Rk(last 3 one), so I am guessing a 330ohm will be a good choice in my case