Transformers and rectifiers.

[afourtrackmind]

Hello EEVblog members!

I'm about to try something without knowing what the result will be. Maybe I can call on your experience to predict what is going to happen and perhaps avoid releasing magic blue smoke.

I have an amplifier with a very nice torrid transformer. I'd like to integrate a preamp inside that housing. My preamp PCB requires AC for a split supply that has the rest of the rectification and filtering on it's own, preamplifier PCB. My amplifier has another rectifier for itself. I want to know, can I connect the AC winnings of the secondary to both of those PSU/rectifiers?

My mind sees it like this; Either one will only draw only what it needs so i think this should work, no problem. All of the my devices and caps have been upgraded to handle the voltage from the secondary. Am I making a mistake? Can anyone forsee any issues I'm going to create?


Thanks for taking the time to read this, I hope you have an opinion and possibly some facts you can throw at me.

Cheers,
Aftm

[Fank1]

If the voltage on the transformer is correct and you don't over load it you will be fine.

[afourtrackmind]

Thanks mate, going to start termination in the next hour or so.

[singapol]

I think it would be better if you add a small transformer to feed your preamp. This being audio you do not want extra noise from a big transformer and the higher voltage drop will strain the regulators in the preamp by dissipating excess voltage in the form of heat. There is the surge voltage and current that your preamp power supply will have to deal with everytime you turn on and off the main power supply although you have upspec the caps voltage ratings. It would be advisable to use surge protection devices like TVS diode, MOVs or NTC resistors if you want to tap from main transformer but take into account the pros and cons of using such surge devices. As they say garbage in, garbage out.

[Kleinstein]

The voltage needs to match, at east resonably. Power audio amplifiers tened to have a rather high voltage.
The voltage from an extra rectiifer will also have a connection to the supply of the amplifier - so you may get troube if you connect the preamp with the amplifier, as there is a gonnection through the supply. At best you have to take care of possible ground loops an hum from this.

So a separate transformer is likely the easier way.