What wattage practice amp needed to drive 4 x 12 cab?

[Jdansti]

Unfortunately, your question is over my head, so I'll leave it to someone such as PRR to answer it.

For reference, this is what I'm suggesting.



The TDA7267A data sheet says that the Vs for the chip is 5-18V and recommends 14V on the application note. You could probably use 9V and get good volume. I'm not sure if you'd have to make any changes to the preamp above to use 9V.

[caspercody]

Thanks!!!! That is what I thought of in my head when you told me about the Tiny Giant.

Also thinking of using the other op amp as a buffer and being able to switch it into the circuit or not. Is there a buffer that does not really change the tone of the sound? I know there is a lot of hype about the Klon buffer....

Thanks
Rob

[caspercody]

Also, I got that information about the gain stage from this:

http://www.generalguitargadgets.com/richardo/distortion/index.html

Very interesting if you have not read it before.

[Jdansti]

Great article-thanks!

I'm not sure about op amps changing tone, although I have heard that op amps can potentially degrade the signal more than a transistor. I'm not sure if this is myth or truth.

My personal favorite is the Tillman preamp, which uses a J201 JFET: http://www.till.com/articles/GuitarPreamp/index.html.  To me it adds body and tone (and other subjective adjectives). I'm not sure if the Tillman would work as a front end to the TDA 7267A. You might want to try bread boarding op amp and JFET preamps and play with them until you find what you like. There's only a handful of parts involved.  You can play with the gain and diode clipping too while you're on the bread board.

[ozzu2000]

Bit of-topic: I've heard an Orange Micro-Terror connected to a 4x12 Mesa Cab, and it sounded Really good! It has a tube pre-amp and an ss power amp.

[caspercody]

Final note on this 3 watt kit from Radio Shack. I added the op amp gain stage before this little amp, and after turning volume up over 10% it started to distort. I tried just the amp using the volume on the guitar and same thing. Adding a 50K pot before the amp seems to work the best. I can turn it up to around 75% before it starts to distort.