Power Supply help

[danielnaveen]

Hi,

I want to build a valve preamp and am goin the use 6SN7 tubes(they are the only ones available where i live) , i need help with a suitable solidstate powersupply to use with the attached schematic.

Thank You for all your help

[Eli Duttman]

What sort of power transformer(s) can you obtain? The topology of the PSU will be governed by the available "iron".

[danielnaveen]

Well i can get E core transformers i can't get a trasformer that can do high voltage and the low voltage for the heater in one box tho. I can get 2 individual transformers. And the mains voltage in my country is 230volts.

[Richard Ellis]

You could use an isolation transformer...as they tend to be easier to obtain. This will give you appx 320 volts of HT ...since it is a preamp perhaps you could regulate it down towards your target voltage.
Let us get an exact voltage you want & we'll go from there & get it drawn up for ya!
______________________________________Rick........ .

[danielnaveen]

hi richard, aren't isolation trasformers 1:1? how will the voltage become 320? Could you please expain. I'm new to this. And the schematic says anything between 250 to 300 volts will work

[Colt45]

230v RMS. 325v peak. The caps will be charged to this value, minus diode drop, more or less, in a SS design.

[Richard Ellis]

Daniel:
Transformers and most all "ratings" or designations of AC voltages are given as RMS voltages...What is RMS? It stands for Root Mean Squared.
RMS is derived from the mechanical generation of AC....It also has mathmatical significance...........The waveform we are talking about is called the Sinewave. Ever heard math people utter Sine or Cosine?........This waveform shape is what they are refering to.....very common in mathmatics.
The RMS voltage is .707 of its Peak.....The easy way to understand it is the total area of one upper curve of a sinewave is equivalent to 70.7 percent of the square box of the same time as one upper curve of a sinewave............Look at my drawing here, see if it makes sense for you.
_______________________________________Rick....... .

[danielnaveen]

Ah ok. Thanks for the explanation richard. So where do i go from there? And i found this power supply schematic will the 300volts out and the 6.2 volts out on this work with these tubes?

[Richard Ellis]

Daniel:
It looks like this schematic will work ,but it has some specific components....looks a little like overkill for your application as it has several "extra" voltages....and it has some FET devices which you may not be able to get from the sounds of things....your simple preamp deserves a simple power supply....look for an LM 317 or LM 123 series regulated high voltage supplies...if you note these say they work on low voltages but are "floating" regulators and with some supporting circuitry can indeed regulate high voltages.
The low voltage filiment regulators are a much simpler design & are easier to build.
Do a search on High Voltage regulators...trying to keep it simple.
I found some schematics in Morgan Jones book "Valve Amplifiers".
I can't reprint them here in this forum , but I'm positive schematics abound thruout the net.
Ther are some other issues we will have to talk about concerning implementing & integrating you design into a workable project. Hang in there we'll get this built & up and running for ya!
___________________________________Rick........... ..

[danielnaveen]

Thanks a lot for help'n me out richard i found a schematic at DIY paradiso http://diyparadiso.com/6sn71.htm . The only problem for me is that it has chokes and finding chokes in india is very hard. Is there something that can be done