What fuse does the Presonus ACP88 use? and why does it blow?

Not sure what your issue is, as long as you have the ASIO drivers installed you'll be able to get a decent copy of the main mix into and out of presonus. Even if not the standard windows sound drivers will recognise it as an external sound card and you can map this into / out of presonus so you don't actually need ANY drivers other than standard windows ones. If you were hoping to get access to the individual channels to do the mix in presonus forget it, this is not what what your mixer is designed for, get an X32 or other professional mixer.

http://www.presonus.com/uploads/products/1918/downloads/PreSonus_StudioLive_24.4.2.pdf

Did you figure out the problem? I am having the same Problem!

This kind of noise is caused by so called dirty AC signal, I installed a surge protector which has a noise filter in it, almost all do, even the cheapest ones. .

Transformers rarely need replacing unless they plugged into wrong voltage (high) source. Still, a fuse should have opened. Transformers are dipped in varnish and often look damaged when they are fine. I have Presonus mixers but those all use switching power supplies. You can probably assume that the output of the regulators are around +/-15 volts and that the DC to the regulators will need to be about 20 volts for headroom. With a single diode drop assuming FWB with center tap, we need around a 15 volts either side of center transformer... you MIGHT get by with a 27 volt center tapped... probably not a 24 volt one. Recommendation... get an original one... In audio equipment the transformers often are specially designed to run low on the saturation curve or have magnetic shielding to avoid hum. If you call Presonus, DIRECTLY ask for "Parts" or "Repair Parts" else you are likely put on hold for sales or marketing.

Sounds like this Presonus is causing alot of people issues. Its not your pad thats the problem i think presonus needs to update there stuff. Im seeing alot of questions on here about PreSonus and there all the same. Contact them and ask them whats up, especially after paying so much for it

What latency do you have the Presonus set to? Too low of latency can cause this issue.

The signal SHOULD be line level which you can run into most any line level input. This level is considerably higher than a mic by itself...around 50 Db or so higher.

Check your latency settings and try something higher that what it is currently set to. 1024 samples is usually a good starting point for most newer PCs.

Assuming you are connecting a microphone to this, if the mic is a condenser mic, make sure you have Phantom power on the PreSOnus turned on. You have given us almost no info of your configuration of mics and other devices connected to this unit.