thanks Phil
But, can I use same concept for building a 2.1 system using 2 lm1875 for Left/Right channels and a single lm3886 for a sub?

I need a simple crossover for that project but even though it's not exactly a crossover as long as the sub power amp will only play low frequencies, then it's enough right?

I opened a small amp circuit out of curiosity as how these things are designed. Also, I want to see how it separated the signal to use for the low end driver. Speakers are only 3W stereo and 8W for the low end. Below is the schematic I drew from it. From preamp, it goes to volume then treble then goes to Con2 (Red & White). I don't understand how from Conn2, it passes through a dual opamp then to the bridged TEA2025. Can someone explain what's the purpose of that opamp circuit?

Quote from: joecool85 on April 05, 2006, 07:37:26 PM
First - Have a good power supply circuit and a big enough/proper voltage transformer
Second - Big heatsink, there is no such thing as too large of a heatsink

Proper heatsink size for two LM1875 chips, or one LM3886:

He said it. Proper size for the LM3886 accdg to Joe

I don't know why I'm always worried that it won't work unless I follow the recommended parts
I don't even feel satisfied unless I build it with overkill parts :loco

I'll try to build it then using parts I can afford, then try to upgrade if necessary.
Thanks Phil.



~ Stephen

when you say "running an amp hard" what does it truly mean?

and is a 160 VA 25-0-25 AC transformer enough for stereo LM3886? Unfortunately, Rod Elliott's P19 does not include details about power supply.

thanks Juan. I was hesitant to use the sink in the first link because almost all sinks I saw being recommended for Lm3886 mono is about 200mm long, 100mm wide and 10mm thick. That first one i linked is only 100x100x40 with 10mm thick so I thought it's not enough.

Is this enough for a mono LM3886 (two for stereo) guitar power amp?
http://ph.rs-online.com/web/p/products/1898274/
I'm planning to build a stereo amp using two LM3886 now that I'm finished with my LM1875 one. If placing the heatsink fins outside amp chassis would help for better dissipation, then I'm willing to do it with that heatsink.

If not, how 'bout one of these for stereo?
http://ph.rs-online.com/web/p/products/5074876/

http://ph.rs-online.com/web/p/products/1898684/
I know they show their thermal resistances were given but I still need your advice.

is it okay to play distorted and compressed guitar sound through speaker box that has both woofer and tweeter? Won't it damage tweeters?
How about in PA?

how about that tda8932 amp in a thread in diystompboxes http://www.diystompboxes.com/smfforum/index.php?topic=114335.0?

about the power amp pcb and supply, i put it in a plastic bag and my brother in law mistakenly thought it was garbage so he threw it away

I think it would be better to just sell this traffo and buy a lower voltage one. Unless I would be stubborn enough and not follow Phil's advice of avoiding high voltage projects for now 

okay, not recommended for guitar amp
how bout bass amp or subs?

  yeah AC, so about +/-60V rails
any good project with that power?

As the title speaks, can you recommend a power amp project for my 42-0-42 300watts traffo? I remember I scavenged it from a powered mixer with 2 pairs of 2SC5200 and 2SA1943 but I'm prepared to use better power trannies for the amp. I prefer it to be versatile enough for use as guitar or hifi power amp, something in the middle I think. I don't have any ideas as to how many watts it will put out but doesn't matter for me right now. Traffo must be put to use 

it's clear enough for me :tu:

thanks a lot to both of you  :dbtu:
illustrations are much better than text, since I honestly don't understand some ideas or terms here.
Another question, what if the two equipments have different power supply, is it still okay to cut that ground path? For example I use a pedal, is it enough to just connect the signal path from pedal to preamp, and not the common path?