How to get started on making guitar amp portable?

Thread Starter

Jake502

Joined Jul 16, 2018
6
I have a Fender Squier SP10. It's a small (26x12x26cm) guitar amp. I would love to make it portable. Where do I begin? I'd love some pointers because I'm super psyched about this :) I've heard that I need to know the DC voltages of the capacitors, is that true? How do I do it?

This is the amp:
https://1drv.ms/u/s!AtXA6MVZxd8wgZ1WnhaU7OBNhNbvbA
 

Papabravo

Joined Feb 24, 2006
12,385
I have a Fender Squier SP10. It's a small (26x12x26cm) guitar amp. I would love to make it portable. Where do I begin? I'd love some pointers because I'm super psyched about this :) I've heard that I need to know the voltages of the capacitors, is that true? How do I do it?

Thus is the amp:
https://1drv.ms/u/s!AtXA6MVZxd8wgZ1WnhaU7OBNhNbvbA
No .. you don't need to know anything about the internals of the amp. You need an inverter and a battery. I don't know what you know or think you know, but the solution to running that amp from a battery will be about the same weight and volume as the amp which hardly qualifies as "portable".
 

Thread Starter

Jake502

Joined Jul 16, 2018
6
Really? The maximum output on this amp is 10 Watts. Someone told me to look into making a small 18650 battery pack, could that maybe work?
 

Papabravo

Joined Feb 24, 2006
12,385
Really? The maximum output on this amp is 10 Watts. Someone told me to look into making a small 18650 battery pack, could that maybe work?
The amp has what looks like a wall plug for 220V AC. A typical battery has an output od +12V DC. The someone has perhaps misinformed you, unless there are facts not in evidence.
 

danadak

Joined Mar 10, 2018
3,573
You start a conversion like this by first knowing how much
the amp takes in power from the AC line, thats how much your
inverter will have do deliver. Then factor it up by the efficiency
of the inverter. So if its 50W from the line, and inverter 80%
efficient then 50/.8 =~ 63W

So then I = 63W / 12 V into the inverter =~ 5A

So your battery has to supply 5A for as long as the play time occurs.

http://web.mit.edu/evt/summary_battery_specifications.pdf

There are of course a lot more power efficient amps thses days, Class
D for example.

Regards, Dana.
 

Papabravo

Joined Feb 24, 2006
12,385
Question. Do you want to get rid of the AC power supply entirely, and power the +12V section directly from a battery? That will require taking a knife and a soldering iron to the PC board inside the amp. This is a really lousy first time project unless you have a couple of those amps lying around to experiment with. If you have never done this kind of thing before there is a substantial liklihood you will ruin one or two while you learn the appropriate skills. Better yet find a dutch uncle to show you how it is done and maybe do it for you.
 

Thread Starter

Jake502

Joined Jul 16, 2018
6
There's multiple versions. the voltage etc is listed on the back of the amp like so: https://i.ebayimg.com/00/s/NTc2WDEwMjQ=/z/iRoAAOSwwXZbOfbb/$_86.JPG That's the one I have. 230V ~ 50Hz and 10W output.

@danadak So then how can I know how much power the amp takes in from the AC line?

@Papabravo Yeah that'd be cool to do too! Then I'd have something like this guy's 14 Watt portable guitar amp. I just want to use it as a portablespeaker tho (i've got a 6.35 mm adapter for a regular aux cord) and I need to be able to recharge the batteries.
!!

also this amp is not very important to me. I don't care if it breaks. But Maybe you can give me some directions and maybe I can ask my dad for help when he visits? :D (he lives abroad and he used to do stuff like this).
 
Last edited:

Reloadron

Joined Jan 15, 2015
4,499
This is your amp. If we look at the bottom of the schematic you will see the power supply and how it is configured. Really a pretty standard straight forward power supply. While I am not sure what +VCC and -VCC are the filter caps are only rated at 16 VDC maximum so I would venture + and - 12 Volts or less. The amp itself is only a 10 watt amplifier so I doubt we are talking about much current. A pair of 12 Volt 8.0 Amp Hour sealed lead acid batteries would weigh about 5 Lbs each for a 10 Lb total weight. They sell on Amazon for about $20 USD each. A cheap battery maintainer/charger can also be had under $20 USD. They would likely power the amp for hours.

There are other options but if "portable" includes the weight of 10 Lbs plus the amp I would just use SLA batteries. The schematic should be of use to anyone else looking to help.

The 9V1 diodes while not drawn as zener are likely 9.1 volt zener diodes.

Ron
 

Thread Starter

Jake502

Joined Jul 16, 2018
6
@Reloadron Awesome, but I've googled a bit and they're all too big to fit inside the amp.

So, now, I'm thinking the only way i can do this project, is by modifying the amp so it looks like the amp from the YouTube video I linked earlier.
 

Reloadron

Joined Jan 15, 2015
4,499
@Reloadron Awesome, but I've googled a bit and they're all too big to fit inside the amp.

So, now, I'm thinking the only way i can do this project, is by modifying the amp so it looks like the amp from the YouTube video I linked earlier.
No, they will not fit inside the box. :) I doubt any power supply used for portability will fit inside the box. My thinking was the battery pack would be external to the amp in a separate box allowing an easy connection.

Ron
 

Thread Starter

Jake502

Joined Jul 16, 2018
6
@Ron Okay I'm going with the external battery idea then.
I'm also beginning realize just how in over my head i am herel. I really need help from a person.

If I bought those batteries you described, could I then easily figure out on my own how to install them?
 

ian field

Joined Oct 27, 2012
6,543
Really? The maximum output on this amp is 10 Watts. Someone told me to look into making a small 18650 battery pack, could that maybe work?
12V sealed lead acid batteries are sort of traditional, lithium is lighter if you can handle the complexities of charge balancing without burning your house down.

not sure if powerful enough, but you can get pretty decent PC speakers that are easy to power.

A new build is another option - I'd go for a BTL car stereo chip which usually do around 17W. Some manufacturers do audio chips with bootstrap rails that charge on peaks and can deliver a boost on heavy passages.

There are tone control circuits online, you'll probably need something to match the high pickup impedance - a simple JFET buffer usually gets it done.

A cheap crap second hand practice amp case can be tidied up and put to use - you might get lucky and win a springline.
 

BR-549

Joined Sep 22, 2013
4,936
It's looks like it might be done with a power switch replacement and a power plug install.

One might replace power switch with a multi-function switch....maybe a double throw double pole. Oops...three pole.

When the power switch is in the off position....it dis-connects the rectifier and connects to a three terminal battery plug. It appears you have the physical mounting room.

If none of this makes any sense at what I'm getting at.....have someone do this work for you.

My mod will power up amp as soon as plug into battery....with no power off switch. Unless you want to add another switch.
 

Reloadron

Joined Jan 15, 2015
4,499
When I reload on the range I use my digital scale & powder dispenser running off a 12 volt battery like those I linked to. A handy carry case can be made using a 50 Caliber ammo can available at any Walmart. The can will easily hold two 12 volt 8 amp hour batteries and a small battery tender which can be used to charge them one at a time when not in use.

I see BR549 just posted. I had the same in mind give or take a little. :)

The batteries are a simple affair, connecting them in series. That means the (+) of one to the (-) of the next and that junctions becomes ground. If you wish I can make up a simple drawing. The diode bridge can be removed or left in. I would likely remove it or depending on things use it to maintain the batteries. Pretty much however you wish to go with this? BR-549 pretty much outlined things.

Ron
 

ian field

Joined Oct 27, 2012
6,543
It's looks like it might be done with a power switch replacement and a power plug install.

One might replace power switch with a multi-function switch....maybe a double throw double pole. Oops...three pole.

When the power switch is in the off position....it dis-connects the rectifier and connects to a three terminal battery plug. It appears you have the physical mounting room.

If none of this makes any sense at what I'm getting at.....have someone do this work for you.

My mod will power up amp as soon as plug into battery....with no power off switch. Unless you want to add another switch.
You can just stick the battery on the DC side of the rectifier - but you have to disable mains power with battery on and protect against reverse connection.
 
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