Solid State Guitar Amp Forum | DIY Guitar Amplifiers

I'm putting together my first stereo chipamp circuit boards that I intend to use as a guitar amp.  I'm assembling the the amplifier PCB at this point.  In section 1.7 it refers to a feedback capacitor being optional.  Should I be using the feedback capacitor for guitar?  Please help me with this I'm stuck.  What are the implications either way?  Thanks

Quote from: Zappacat on August 28, 2009, 05:25:38 AM
I'm putting together my first stereo chipamp circuit boards that I intend to use as a guitar amp.  I'm assembling the the amplifier PCB at this point.  In section 1.7 it refers to a feedback capacitor being optional.  Should I be using the feedback capacitor for guitar?  Please help me with this I'm stuck.  What are the implications either way?  Thanks

I used all of the optional things when I did my chipamp.com kit.

Hi Zappacat.
¿Can you please post the schematic and show us the feedback capacitor?
Thanks
J M Fahey

I think he can only refer to either one of these two

1. A low-capacitance cap bypassing the feedback resistor that connects the output to the inverting input. Often has a series resistor too. Fitting one in shouldn't do any harm and shouldn't reduce audible bandwidth either. It just prevents instability by decreasing high-frequency gain and is likely "transparent" under normal operation. Yes. Fit it in.

2. A high-capacitance cap in series with the feedback loop's ground shunt resistor (in the inverting input). This is an important part because it ensures that DC gain is unity, thus preventing any DC offset at the input from getting amplified. Yes. Fit it in.


All of those "optional" parts likely have a very meaningful purpose discussed by the chip's datasheet. You can build a working circuit without them but if you fit them in the amplifier likely becomes a lot more reliable.

Here is a link to the build sheet that has a schematic on it: http://chipamp.com/docs/lm3886-manual.pdf

Mojo
Mumbo jumbo
Kaboonga !
OMMMMMMMMMMMMMMMMMMM!!!!!!
Polish Pletska produced platinum plated plate capacitors
Dc response amplifiers and speakers
Audible impedance peaks at 500 khz
Chip encapsulation ground off to shorten feedback path
1914 vintage NOS capacitors, hand wound by Nikola Tesla himself with hand-wrought tinfoil, insulated with Yak leather and sperm-whale oil
Nuclear waste powered ionic dischargers
Power chips compass oriented *exactly* North-South so the Earth's magnetic field helps electrons travel freely: more transparent-yet-firm highs
...............................................
mmmmmmh !, do I have all I need to build a "better" gainclone?
...............................................
I guess not, I'll continue searching.
...............................................
By the way, I despise all those crazy SSGuitar guys who (¿Dare I say it?), build ..... ¡Guitar amplifiers with them!!
and not only that, ¡they actually use them!!!
Blasphemy.