is this a good design?
http://www.diyaudio.com/forums/solid-state/286992-irfp240-9240-amplifier-simulated-tina.html

http://www.elab.ph/forum/index.php?topic=49772.0

in ESP P27A, there is a 10 ohms resistor in series with the return path from the preamp. What's its purpose? Is it for isolating the preamp's common?

Also, is it necessary to connect the preamp's and the power amp's common? or can I just use a shielded wire, connect the shield ONLY in the power amp's common, NOT in the preamp's common? This way, their only common connection is through the power supply.

and make sure you made the right connections. I've tried powering up an LM1875 amp before and wondered why it won't work. After just 2 seconds, i turned off the power only to find that I made the wrong connections for my + and -

I was lucky no component was damaged. 
After that, I decided never to work in my electronic projects again when my mind or body is not in good condition. I was sleepy then coz I don't want to leave the project unfinished. 

Quote from: g1 on May 14, 2016, 11:48:13 AM

Quote from: phatt on May 14, 2016, 09:09:50 AM
There is no great tonal difference between complimentary paired outputs and sziklai paired output,,, just different configuration.

Google; Sziklai pairs for more info,

Do you mean quasi-complimentary rather than sziklai pairs?  Google says siklai is making a darlington out of an NPN and a PNP.

extinct01:  Very sorry to hear about your father.  Stay well.

Yeah, I googled sziklai and read that it uses npn and pnp pairs. The one using two npn's is quasi complimentary. Although I haven't read positive reviews for it, read it was used only because pnp's are so expensive in those early days.

Yes, those chipamps do run very hot and needs heatsink even without load. 
Or you'll fry it in seconds

I thought those tda's have long been gone and out of production? Where could they still be located?

I just tested my P27 preamp in breadboard, connected to my LM1875 power amp and it worked good. But I used old, used and all linear pots for the preamp so I'm planning on purchasing some pots for it tomorrow before I put it in pcb. So, which among those 5 pots should be log and which should be linear?

Also, is it necessary to shield the preamp from the power amp?

should i read it first, before sloan's and self's? I've just downloaded copies of those two books but I don't have time to read for these past few days as my dad just died and burial's tomorrow. Maybe I'll start reading those books the day after tomorrow.

More questions:
1. Can I use non-complementary power transistors? (e.g. MJ15003 and TIP36C, or 2N3055 and TIP36C, one is TO-3 paired with a TO-247?)
2. Can I use non-complementary output driver transistors? (e.g. Edit: MJE15032 and BD140)

My sources just don't have the complements.

Quote from: Enzo on May 12, 2016, 11:41:10 PM
Well, get over that, because transformers are inductors too.

:dbtu:

After some reading and thinking, I decided that a newbie like me should really start with building amps for a single driver speaker like guitar, then full range, then the biamped and triamped systems. Will take years though 
Have to study more.

Anyway, I never really liked the idea of a passive crossover because of inductors. I just don't want to work with them. I don't know why.

i removed it from its cab that time, so I think that's another factor I didn't consider. Thanks anyway 

Everything that you, good people of this forum, say are helpful  :tu:
I'll stop being too ambitious for now and settle on smaller projects. It's just that beginners have this urge of trying to know everything at once, but we know what happens next.

I'll just read a lot and take this road step by step. No more stupid questions for now, I guess.  I'll just focus on the current projects I have.

Thanks for the enlightenment  :dbtu:

I am not yet planning to build any large PA systems in the near future, but it aroused my interest especially since my father-in-law is a bit "obsessed" with it. He doesn't have it yet but plans to buy if he acquires a good amount of money. So, I think I need to gain knowledge about those things to impress him  8|
And, I'm a musician. Not really an audiophile but most things about audio captures my interest.

Phil, you mentioned I need to research crossover networks first. Do you mean active or passive? I read that active are used for biamped or triamped systems only so which should I need to learn first?

I am a bookworm who spends about 6 hours a day reading books and articles. It's summer here so I have lots of time, but I won't be at home again for maybe half a month, so no tinkering activities for now. Just reading and researching.

Sorry for double posting but is 25W enough for that woofer outdoors? say, for a car?