I'm a newbie to CBGs and amplifiers so there's a whole lot I don't know. This forum has been great in helping with most questions, but I am having an issue I haven't been able to resolve.
As an experiment to go electric I got a couple of pickups and these little amps (LM386 DC 5V-12V Mini Micro Audio Amplifier Module Board Mono AMP Module HIFI)
.
Wired it all up with a piezo pickup and a 12 volt battery for power and I get severe buzzing from the speakers. Sometimes the tone will come through a bit but then it degrades into a buzz. Based on advice from this forum I have tried the following - all to no avail.
1. Tried another amp (same type).
2. Tried better speakers.
3. Tried a different guitar with a magnetic pickup rather than the piezo.
4. Checked and rechecked all solder joints.
5. Grounded strings to the jack.
6. Reversed pickup leads (getting desperate now - trying everything I can think of).
7. Turned off all fluorescent lights.
So all I'm left with (I think) is the amp itself. And since I tried a couple of them it must be a design issue rather than a specific fault in the amp.
I have a different type of amp on order but I'd really like to resolve this issue as I think these should work. Does anyone have any sage advice?
Thanks all.
Replies
One out-of-the-box-sides thought...if it's a "HI-FI" amp board that might means it is designed for LINE level signal, which is much stronger than a piezo pickup can make.
as a test: take your favorite mp3 player with the aux cable plugged into the earphone jack, touch the tip to the "IN" and the sleeve to the "GRND" and see what the output sounds like.
(side note: very useful to have a set of jumper wires with alligator clips on each end for troubleshooting)
If the MP3 player sounds a lot better than your git, than an in-line powered EQ will probably help, like the one CBGitty sells that shane turned into a stand-alone eq in a box.
Just wanted to get back to everyone who offered advice and suggestions with an update.
First problem - I had a crappy battery. A fresh battery made a world of difference.
Then I went over all the connections to make sure they were tight, no cold solder joints, etc. Joined all the grounds together in a star ground (including the strings).
And now the buzzing is gone. Hooray!
The sound is a bit "tinny" to my ear, but that could be a tone issue. I will pick up a tone pot and hook that into the circuit next.
So, progress.
The sound is still good with the computer power supply I'm using, especially if I take it off the 5 volt lead. Problem is it's too bulky to fit in a small box, so I'll be looking for another power supply, perhaps one off a laptop rather than a desktop unit. That way the transformer is actually out side the amp.
Still lots to play with, so I may be back. But thanks for all the help and advice. This is a great group for that.
Cheers.
If you have several boards, and they all do the same thing (buzz), the problem is most likely with polarity or ground. Speaker polarity is important. So is ground reference. I buy a slightly different flavor of this PCB and they work for me. A battery is less noisy than a supply. The input polarity and output polarity must be the same.The problem is most likely how you connect to the circuit. You are using what type of harness to interconnect? Normally LM386's work well. Let us know how you make out !
Jerry's right here on the power source... if you are using a wall wart, they are super noisy.
Lots of ideas to try out. I did a quick test with a repurposed computer power supply. It was much quieter than the battery and much, much better at 5V than 12V. Not sure why that would be. However I hope to get a few free hours at this in a day or so and will report back on what I find.
Thanks to all for your ideas and suggestions.
Cheers.
Do you have a pic of the wiring?
That's what I expected, but it was cleaner on the power supply than on battery. I need to do some playing around to make sure I've got everything wired up right. No wiring pictures, but I'll put together a rough schematic when I get back at it.
that is weird.. maybe a photo or two would help us see whats going on. running from a battery should be the least noise.. is the battery new? if its old and the voltage drops it possibly could do weird things.
the pot is input volume. the gain is fixed at 200.if you want to reduce the gain then you are going to have to mod the circuit. R1 is a 0 ohm resistor. Removing this ad replacing it with a 100k pot 1 leg and wiper. then you will get variable gain as well as input volume.
If you are getting a lot of buzzing then your strings and bridge are not earthed to the jack.
Thanks for that. I think modifying the circuit on this little amp may be beyond my abilities, but I will see if I can figure that out. As for grounding to the jack, I did that and it made no difference.
-
1
-
2
of 2 Next