Advice on powering my diy guitar amplifier

Thread Starter

Redfeo197@

Joined Jan 28, 2021
8
Hello, my name is matt. I have a few questions about supplying power to my audio amplifier projects.



I have made 4 Bluetooth speakers and 1 small guitar amplifier so far. All of the Bluetooth speakers have been powered by a 5v battery power supply. Simple Bluetooth amplifier boards and a simple setup. My first guitar amp was more complex. I used salvaged bits from a store baught Bluetooth speaker. It had a battery, amp, and aux in. The sound was not as loud as I wanted and I discovered that my overdrive pedal boosted the signal quite nicely. I used a 6 inch speaker of unknown specs ( I did test the resistance at 6 ohms) . When I put it all together in a cigar box,a usb battery bank (also inside) powered the pedal (9v boost cable) and the other USB port from the bank charge the Bluetooth amp and its battery. I worked very well for a time but it had some quirks with the volume pots I added ( I added them after the amplifier which was probably the problem). That was my first build and I really enjoyed it.



I am now making version 2 for my brother-in-law. This is to be a much better build. As well as more complex. I have several different little amplifier boards I bought from Amazon since then. I built a speaker testing station that allows me to instantly select between 8 speakers in any amount and combination. With volume pots correctly wired from line in (before amp) so I can also adjust the volume of left and right channels (it’s wired as dual mono basically from the guitar) This, in conjunction with a variable bench top power supply has allowed me to experiment with different speaker arrangements and voltages on the fly. I have found this quite helpful and have learned from this process. The goal is to use two different speakers as I have found the all have a different quality and color. My plan is to use two to ensure many different tones can be had. It’s really cool, the process of figuring it all out.



So then for this build I’m really putting forth some effort. So my question lies in powering it.

Here is a list of what needs juice.



-Amplifier board. 4.5-24 volts (my experiments have only been between 5 and 12v. It seems 9v to 12v is a good spot. 12 seems the best. How many volts I can give it will affect my choice of 2 speakers. In a perfect world I would like the 12 volts. As far a current. I was surprised at how little it draws. From the usb battery bank I had to also plug my phone in or it would not stay on. way less than .5 amps



-Overdrive pedal, requires 9v , also uses very little amps.



-couple of LEDs

-little guitar tuner. Works off a 3v coin cell battery.



-servo. I tested it at 3v and that seems to be the speed I want it to turn. It requires the most amps. From memory it looked to be about one amp. If you are curious as to why I’m putting a servo into a guitar amp, the answer is that I’m making a pick holder inside the box that can raise a single guitar pick up through a small slot and then back down to store it. I know it’s absurd but I thought it was funny and now I really want to make it happen.



So. Is powering all of this from a store bought usb battery bank a wise idea or should I look into something different. I want it to be safe and reliable. My thought was maybe boost one output (has two) to 9v and from that power the amp and pedal. The other I would buck to power the LEDs ,tuner, and servo all at 3v. I believe both ports from the bank are 5v 2.4 amps. Or rather it says max output is 12 watts from one or both ports. I do have some 18650’s and a couple different battery boards but just for a single battery. I know I can wire them up in series but I have been reluctant to try that as I want to be very sure if I do it, I do it right. My thought is that battery banks are cheap and easy to find and if possible to use in the way I would need that would be great.



Also,In general is it not so much a question of how many items you can hook up rather how many amps they all draw combined? Any thoughts or advice is appreciated.
 

BobTPH

Joined Jun 5, 2013
3,308
Does it have to be battery powered? If not, a 12V plug in supply at about 2A would be enough to power a bridged amp putting out 18W into 4 Ohms.

Bob
 

wayneh

Joined Sep 9, 2010
17,152
One of my favorite power supplies is spent laptop power bricks. They're free if you ask around. Or go to the local e-waste dump.

These tend to be fairly high quality, compact, and deliver 18-20V DC up to 4-5A. Tough to beat.
 

Thread Starter

Redfeo197@

Joined Jan 28, 2021
8
Yeah, I would like it to be battery powered. The other one I made was battery powered and I use a wireless guitar transmitter so the whole thing can operate without a single wire. The first one was about the size and shape of a lunch box. super portable and plenty loud.
Does anyone have any thoughts on if my current plans would be too taxing on a battery bank?
The laptop power brick is a good idea, might go looking for some for another project.
 

sparky 1

Joined Nov 3, 2018
540
Music tends to have a lot of op amp components that need positive negative supplies non polar may not be enough.
( the different modifications can be helpful )
The final stage amplifier would need large bricks and they can be incorporated less independent and more as voltage followers.
The video shows a hack to get a smaller split 15 supply up to +/- 18V so more details on what to modify to get 15V to 18V.
It can be handy also when you want to add a post filter board to a supply, so you need to raise it to allow for the voltage drop of the post regulators.
The eurotrack components sort of set a standard they mostly use same at least this is what I think might be fairly close ?
 
Last edited:

Audioguru again

Joined Oct 21, 2019
3,173
You did not link to or say which amplifiers you power with only 5V. You want to boost the 5V from the USB power bank to 9V or 12V but the amplifier maximum allowed voltage might be 6V if it is a PAM8403 bridged class-D stereo amplifier that has an output of 1.4W per channel at fairly low distortion per channel into 8 ohm speakers, when powered from 5V. A little louder than a cheap clock radio.

My 16000mAh power bank has a 5V output at 2A so it can be boosted to drive a class-D stereo amplifier that produces 4.3W per channel if the booster does not get hot. The supply voltage for a 4.3W into 8 ohms bridged PAM8124 amplifier will be about 18VDC.

A cigar box is much too small for a 6" speaker to produce any bass sounds. Also the thin box vibrates which cancels some of its sounds.
 

Thread Starter

Redfeo197@

Joined Jan 28, 2021
8
Thanks for the replies, I’m building the box this time and not using a cigar box. I will try and maybe take a video perhaps, of what I got going on sound wise, little demo maybe. Perhaps a visual could be helpful for inspection. Be warned though, I’m not good at playing guitar at all.
 

Thread Starter

Redfeo197@

Joined Jan 28, 2021
8
Ok so I re did all my links and before I posted the browser on my phone messed up. I will try from the laptop tomorrow. Here is a link to the amplifier board though

2Pcs Digital Amplifier Board,TPA3116D2 Dual Channel Audio Stereo AMP High Power Digital Subwoofer Power Amplifier Board 2x50W 5V 12V 24V for Store Solicitation Home Theater Square DIY Speakers https://www.amazon.com/dp/B08GYQTTX...abc_QK0MJ7MEVEFN0Z5Y0KRQ?_encoding=UTF8&psc=1

I guess it will have to be a copy paste
 

Audioguru again

Joined Oct 21, 2019
3,173
You are using a very common amplifier using a Texas Instruments IC and is sold by many Chinese vendors.
With a 12V supply its output is 7W per channel at low distortion into 8 ohms

The amplifier board is stereo. I wonder why Amazon sell two together? Oh, because Amazon does not know anything about electronics.
 
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