Transformer with uneven ac out

[geminni]

I need 2x15v supply for preamplifier. I have a transformer with two output. One is 23v and second is 30v. Two windings are connected together.
Can i connect it to a rectifier? Will this voltage difference bother?
If it is ok then i will also use zener, transistor to lover voltage at 15v dc.

 

[Jan Dupont]

You can use 15V zener regulation to get your needed +/-15VDC with no problem as long as both the 23 and 30VAC outputs can deliver the Current you need 😉

 

[AndrewT]

or add the 7Vac winding to the 23Vac to match the 30Vac.

Check which winding has the smallest wire diameter. This becomes the effective limiter of your output current.

 

[geminni]

So, the voltage difference will not make things go bad 🙂
Ok, i'll try that and adding that 7 volt in seres with 23v.

Thanks guys!

 

[geminni]

It's working!
Now i have +-40,5V. How can i make +-15V for preamp?
I have been looking in LM317 data sheet, looking on net and found that its maximum input voltage is 40v.
Would the classic zener-transistor combination be enough for preamp?
I ask because i have made same setup for amplifier with TDA1516q and it distorted very bad on higher power output. When i replaced zener-transistor with 7815 it worked very nice. No distortion on louder volume.

 

[jaycee]

Use the transistor-zener as a "pre regulator" to drop down to about 25V or so... then use LM317/337 or 7815/7915 to supply the preamp.

Alternatively build something like the Jung or Sulzer discrete regulators, but that's a lot more complex.

 

[geminni]

Thanks! I'll try that with 2 stage voltage drop 🙂