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Tech 21 Power Engine

Started by jmdfd415, February 22, 2007, 07:19:37 PM

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J M Fahey

Hi Zappacat.
To begin with, I fully agree with all of Teemu´s suggestions.
I told you to search for the "zillion" Gainclone projects, or LM3886 projects, which of course use a PCB and all necessary components, to save you the chore of designing your own PCB.
I pointed to the "minimalistic" one for you to see just how simple it might become, compared to the LM4780 and its close spaced pins, but of course I agree that a guitar amp, specially a "combo" type , mounted inside the very speaker box, gets handled roughly and should be built sturdily.
You can use the GGG project as a guide.
http://www.generalguitargadgets.com/pdf/ggg_lm3886_amp.pdf
Not the best in the world, but, hey!, it´s free!
It follows exactly the manufacturer´s recommendations, http://www.national.com/mpf/LM/LM3886.html  including the non-use of a Zobel network.
Personally, that makes me nervous; I´d add a .1 ceramic in series with a 4,7 ohm 1/4W resistor from pin 3 (output) to speaker ground.
I´ve searched a lot,it seems that everybody and his brother is offering 3886 kits, but of course nobody posts the PCB design.
If you dare to design your own, go for it.
Yes, I suggest you build two 3886 amps instead of one 4870.
I think it will be easier to get 8 ohm speakers.
Yes, most (¿all?) the stuff published refers to Hi Fi amps, and minimalistic by the way, not guitar amps which get a rougher treatment.
I´m not at home now, later I´ll draw and post a rough sketch of a "guitar version" 3886, including all of Teemu´s suggestions.
Bye.

Zappacat

Quote from: J M Fahey on May 06, 2009, 10:05:18 AM
Hi Zappacat.
To begin with, I fully agree with all of Teemu´s suggestions.
I told you to search for the "zillion" Gainclone projects, or LM3886 projects, which of course use a PCB and all necessary components, to save you the chore of designing your own PCB.
I pointed to the "minimalistic" one for you to see just how simple it might become, compared to the LM4780 and its close spaced pins, but of course I agree that a guitar amp, specially a "combo" type , mounted inside the very speaker box, gets handled roughly and should be built sturdily.
You can use the GGG project as a guide.
http://www.generalguitargadgets.com/pdf/ggg_lm3886_amp.pdf
Not the best in the world, but, hey!, it´s free!
It follows exactly the manufacturer´s recommendations, http://www.national.com/mpf/LM/LM3886.html  including the non-use of a Zobel network.
Personally, that makes me nervous; I´d add a .1 ceramic in series with a 4,7 ohm 1/4W resistor from pin 3 (output) to speaker ground.
I´ve searched a lot,it seems that everybody and his brother is offering 3886 kits, but of course nobody posts the PCB design.
If you dare to design your own, go for it.
Yes, I suggest you build two 3886 amps instead of one 4870.
I think it will be easier to get 8 ohm speakers.
Yes, most (¿all?) the stuff published refers to Hi Fi amps, and minimalistic by the way, not guitar amps which get a rougher treatment.
I´m not at home now, later I´ll draw and post a rough sketch of a "guitar version" 3886, including all of Teemu´s suggestions.
Bye.

Can I power two 3886 chips from a single transformer or will I need two transformers?  I'm really looking forward to your sketch.  Thanks for the help.
I put my pants on just like the rest of you - one leg at a time. Except, once my pants are on, I make gold records.

joecool85

One transformer (so long as it's large enough) will power two LM3886s no problem.  In fact, Brian at chipamp.com has a kit designed for that type of use.  He's a good guy and his PCBs are really high quality.
Life is what you make it.
Still rockin' the Dean Markley K-20X
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