50 volt and 9 volt supply voltage?

Question

I am in the process of gathering parts to build a guitar amplifier. I have a question about how to go about this. The preamp/amp requires 50 volts and the effects require 9 volts. The transformer the schematic specifies is a 220V Primary, 48-50V Secondary 75 to 150VA Mains transformer. My question is: How do I divide up the supply voltage from the wall outlet into two seperate circuits, one for the preamp/amp and one for the effects chain.
The schematic I would like to use is at
http://www.diy-electronic-projects.com/p27-60W-Guitar-Amplifier
Thanks!

Answer 1

There needs to be more information to help you, but here's a start.



First off, what country are you in. If you are in the US, you only need 110VAC not 220VAC. 220VAC is for europe and some other countris.



Next, do you want 50VAC or 50VDC? and how much current ?



This is true for 9V as well,. Again how much current?



The easiest and lowest cost solution is to transform down both at the same time using an AC transformer. The transformer will need to be rated for your input voltage/current (usually not a problem), and output voltage/current (usually a problem and custom).



A transformer will have separate windings on the same core that will be isolated and allow for two circuits at the same time, so not issue here.



Finding a transformer is tricky, but i have located some sources for you below. You will need to call and work out the details for your needs and custom ones can be wound to your specifications. Also you may need (2) separate ones if you cannot find one that does both.

Answer 2

It is a good idea to keep power supplies away from low level amplifiers to reduce interaction from stray magnetic and electric fields.



The effects chain would best be powered by its own separate supply. The wall outlet type of supply is commonly available, and it just plugs into any wall outlet. It could be a higher voltage unregulated voltage like 15V DC and regulated to 9V by a 3 terminal regulator. These are usually 8V not 9V, but the LM317 is one type that is adjustable to 9V (look it up). Otherwise it could be a regulated 9V DC supply. I expect almost any supply with proper voltage will suit as the current drawn by the effects chain is likely smaller than 100mA.



I would be inclined to make the mains transformer for the amplifier larger than 75VA, at least 120VA, as the amplifier will draw that much power to produce its 60W output. Also its input voltage and frequency should suit your local supply. Get help with wiring the mains cord and plug to the main transformer so it is safely grounded etc. Use suitable wiring for the power supply and output transistors as the current is up to 4A.

Answer 3

The simplest solution would be to get a 9 volt modular supply that supplies a clean, regulated output and wire that in parallel with the primary to the 50 volt supply (or install a small outlet inside the case you're using for the other electronics).



If the 9 volt circuit doesn't require much current, you could divide the 50 volt supply down using resistors (compute the power dissipation to decide if you want to waste that much energy in the form of heat inside your box, and also to get the right physical size resistors). Or you could use a 3-terminal regulator or other regulator circuit, but check the input voltage and power dissipation limits; going from 50 to 9 volts is a little uncommon, and I haven't surveyed PS regulators in decades.