Bridged TDA7294

[THChrist]

If I use this configuration

http://www.guitarraonline.com.ar/electronica/circuito1.gif

can i use an output transformer and make a NFB loop in a circuit like this?

http://www.runoffgroove.com/tc-tone.png

[J M Fahey]

Hi THChrist. The link is broken. Don´t understand why do you want to use a transformer. Those TDA´s already have a NFB loop that´s suggested by the factory. Do you mean that you´ll build a Bridged 7294 board and drive it with the Thunderchief? Thanks.

[THChrist]

Something like this (pardon the lame drawing)

[J M Fahey]

Hi TChrist. What you want to do is basically right, a "SS Plexi" driving a bridged TDA7294 (Loud!!). What you *don´t* need is an output transformer, the bridge drives directly an 8 ohms speaker with 140W RMS, and *don´t ever* make a negative feedback loop so wide, it will oscillate like crazy. Hook it to the original point, the source of the last J201 and leave it there.  You might make it even simpler; just one 7294 will provide 70W into 4 ohms or 50W into 8 ohms, loud enough for most situations. A friend built a bridged one, and the output waveform has a parasitic oscillation on the negative side of the output waveform. He will bring it to my shop to see what can be done. I guess it´s a grounding problem, but they´re difficult to cure by phone (or mail). Good luck.

[THChrist]

well, i'll take your advice and follow the KISS principle (you wanted the best... no, wait, Keep It Simple Stupid).

I guess 100w isn't necessary now (since the trend is to use mic'ed cabs or DI)

I'll use 1 TDA. Now, about the speaker, what do i need?

[J M Fahey]

Hi THChrist. Good for you. You can upgrade your amp anyday you like. Start with something good and simple, enjoy it, and in the future add what you want. The problem with speakers is that most available (besides expensive specialized guitar speakers) are built as Hi Fi woofers, or even worse, Car Audio. Low efficiency, muddy sound, the works. ¿What do you have available in Peru? You should look for "extended range" speakers, nor woofers or worse, subwoofers, no rubber or foam borders but plain paper ones, etc. Maybe the Selenium 12PW3 is available there, it´s acceptable as a guitar speaker.

[THChrist]

Hi THChrist. Good for you. You can upgrade your amp anyday you like. Start with something good and simple, enjoy it, and in the future add what you want. The problem with speakers is that most available (besides expensive specialized guitar speakers) are built as Hi Fi woofers, or even worse, Car Audio. Low efficiency, muddy sound, the works. ¿What do you have available in Peru? You should look for "extended range" speakers, nor woofers or worse, subwoofers, no rubber or foam borders but plain paper ones, etc. Maybe the Selenium 12PW3 is available there, it´s acceptable as a guitar speaker.

Well, since i don't have too much options here, i was thinkin' about using some recicled speakers (from broken 15w amplifiers). What scares me is the wattage of each speaker. I need to find a "Cabinets for Dummies".

Thanks for your patience Fahey.