Need some calculation assist for a psu

[phrarod]

I'm making a 5AR4 rectified psu. I worked with Duncan PSU II but I'm concerned I'm inputing the right value for R1 (being the output it sees)

The psu will see a 100R primary of an OT and the plate of the 5965 running at a bias of 12mA. The plate resistance of the tube is 7200. I'm not sure the value I calculate for R1. A friend said 5K and another said 4.5K Naturally this all makes a difference in spec'ing the PT.

Right now I have it as 233VAC secondary to get an output of 200vdc.

[Arnulf]

The PSU will see R = V+ / I(total), where I(total) is the total current consumption of your circuit (use quiescent values). An odd way to design a power supply by referring to load resistance, if I may add ...

[phrarod]

Is there any easier more accurate program? I need to figure it out to order the proper PTs. I've been flailing on this one...

[jrenkin]

From all the prior discussions on PSUD II, it seems to be most accurate using a current source as the load.
Total up all the currents in the amp, at least at idle, and plug it in. You do better if you use the "stepped load" function, but I am not clear how to figure out the step.
For example, the EL34 PP I am working on has one power supply for both channels, Each EL34 idles at say 50mA, the drivers are pulling 6mA via CCS each and I am dropping about 20mA through some voltage regulation tubes I have included.
50 x 4 + 6 x 2 + 20 = 232
I might move up to 55mA and load changes with operation, so I figure modeling 250mA is close enough.
With that much current, watch for warning about current draw through the 5AR4, try using soft start mode, or the "stepped load" option.
That's my take on it. Hope it helps.

[phrarod]

Hmmm. Well I plan do create dual mono so each PT should see, according to the tube data sheet 8mA of anode current and I'm running the cathode at 12mA. I'm far better at building than designing. So would my total current be 20mA?

http://scottbecker.net/tube/sheets/009/e/E180CC.pdf

[jrenkin]

Originally Posted by phrarod

Hmmm. Well I plan do create dual mono so each PT should see, according to the tube data sheet 8mA of anode current and I'm running the cathode at 12mA. I'm far better at building than designing. So would my total current be 20mA?

http://scottbecker.net/tube/sheets/009/e/E180CC.pdf

Seems to me that if you are setting the operating parameters of the tube to get 12mA at the cathode, you would get the same 12ma at the anode and the PT would see 12mA ,since it is all the same current running through the tube.

I don't know your circuit, but add up the idle current (cathode current) of each tube in the channel and then try to figure out if there are any other currents (like my voltage regulator tubes) and add that and there you go.

[vinylkid58]

Originally Posted by phrarod

I'm making a 5AR4 rectified psu.

Isn't that a bit overkill for a preamp, or did I miss something?

Jeff

[phrarod]

Its always all about the PSU. Even in dac's. I started off with an anemic Audio Note supply then moved up to a clone of Jadis preamp and the difference was astonishing. Now I want to dump the nightmare of the regulated supply and concentrate on simpler mono block supplies.

[aardvarkash10]

ok - what is the working voltage (B+) that you want? What is the TOTAL current draw of the circuit (include the cathode current of the tube(s)).

Find a PT that best approximates what you think you will need eg if you need 25ma per channel at 250V B+, Find a PT capable of delivering 60ma+ at 280VAC to give you some headroom.

Put the values for the transformer into the model, and then start building up your model. Don't use a resistive load - make your load a current sink set to the total working current of the circuit. If its a two-stage circuit, use two current sinks.

Now you can fiddle with the RC filter (or LCRCLCCC or what ever floats your boat) to get to the right B+ and ripple etc for your application.

Cool?

[phrarod]

I want 200VDC at the plate. I want 12mA of cathode bias current. The manual says the plate is 8mA but as the posts above show it should be the same as what I am biasing for the cathode. I did place the valve in to the program (5AR4) but I don't know how to build it out to cover the whole circuit.

I showed the results to a friend who builds amps and he thinks the program is providing incorrect info. Others believe its very accurate.