tube amp power supply

[biker883]

Greetings to all.
Here is the question : With a Power transformer secondary 340V, SS bridge rectifier, choke 5H/200ma/65 Ohm
How can i calculate the capacitors and resistors for B+ 440V. (I need it for a PP 2xEL34)

I have built a 5e3 and a revibe, which are working perfectly, but i dont understand electronics. I can only read the schematic and build it. My knowledge in electronics is basic.
Any help is appreciated.
 

[kagliostro]

Do as I do, I look to schematics that has a configuration near those I want to build and "clone" it

so look to schematics of amps that has the same number and kind of final tubes an approximately the same number of preamp tubes

Kagliostro

[sluckey]

Here is the question : With a Power transformer secondary 340V, SS bridge rectifier, choke 5H/200ma/65 Ohm
How can i calculate the capacitors and resistors for B+ 440V. (I need it for a PP 2xEL34)

340VAC X 1.414 = 480VDC. That's unloaded. Depending on how beefy that PT is you may be very close to 440V with all tubes drawing current.

You can't really calculate accurately without knowing the PT current capacity and internal resistance and the load current.

[biker883]

Thanks for the replies.

What is the 1.41 factor?

here Is the amp circuit. 

[sluckey]

1.414V_RMS = V_PEAK

The FWB passes the positive peaks to the filter cap and the cap charges to this peak voltage under no load conditions.

[tubeswell]

What is the 1.41 factor?

Don't know if you remember much about high-school maths. (I'd sure forgotten a lot of it until a few years ago when I started getting in to this stuff).  Its all about the value of function curves. The peak value of a sine wave is 1.4142 x the average value of a sine wave, (or to put it another way around, the average value of a sine wave is .707 x the value of the peak). 1.4142 is the square root of 2 (which is where the 'average' comes from).  Mains AC is more or less a 'perfect' sine wave (in most places). So when someone says 120VAC they mean that 120 is the average value of the mains AC sine wave, but the peak value is 169.7. So if you rectify (i.e.: dump the -ve half of the AC cycle) and filter (i.e.: store the positive charge in a capacitor) a 120VAC signal, you will get 169.7VDC (all other things being equal).  

[sluckey]

I think you are confusing RMS and average values...

[tubeswell]

Yeah RMS - that's what I mean, which is kind of like an 'average', in as far as the RMS is like an approximation of a measure of central tendency, i.e.: its not the highest value nor the lowest value, but its somewhere in between :-)

[HotBluePlates]

Do you have the PT in hand? Can you measure the resistance of each of the windings?

That information may help determine if/how much the output voltage will sag under load.

[fdesalvo]

F'n love you guys.  I learn so much just by reading everyone's posts.

[HotBluePlates]

By the way, that schematic looks like a hi-fi power amp. Almost like a semi-update of a Williamson amplifier.

The EF86 is a change, and the inverter is changed to an early-style long-tail/differential amp. Also the output stage is switched from triode to ultralinear operation (with fixed bias rather than cathode bias). But the tweaky method of balancing the inverter and the output stage signal balance is reminiscent of the Williamson.

[jazbo8]

from Ducan PSU. http://www.duncanamps.com/psud2/index.html
close enough for r'n'r...

Jaz