This is a tool I have been needing for a long time. Being the type who likes to scour the local classifieds and flea markets for bargains, I often wish I had something with which to test speakers when I happen upon them. A while ago, I bought some Bluetooth class D amplifiers for just this purpose.
The idea was to have a small batter-powered amp with leads that I could carry around with me. This is what I came up with:
Modification:
[Audio] The Bluetooth amplifier was bought off one of the Chinese online shops. The performance was not the best, because there was some radio noise breakthrough from the BT module into the audio. To be fair, my review here https://www.avforums.co.za/index.php/topic,59970.0.html did not make mention of it. The conditions under which I tested it (max volume into low efficiency speakers) minimised its effect. However, after using it some more, it did begin to bother me. I subsequently stumbled upon some information about modifying the board to eliminate this noise, which I posted about here https://www.avforums.co.za/index.php/topic,71713.0.html.
[Connector] The board came supplied with screw-down terminals. I needed a quick-connect system, so I removed those connectors and replaced them with a pluggable pair. This would enable me to plug in leads with various termination options.
Power:
[Portable] I initially toyed with the idea of using a set of Li-ion cells in series (3 or 4) but the special charge requirements for this type of cell would over-complicate this simple project. I found a sealed 12V lead-acid battery that was just small and light enough. I made a lead with a DC connector on one and a pair of insulated quick-connect terminals on the other end. I have a complementary socket on alead which I connect to a desktop DC power supply for charging the battery. A future addition to theis project will be a stand-alone charger.
[Fixed] I have a 12V 3A wall wart to power the amp, should I need to use it for extended periods of time.
Enclosure:
I found a small plastic box at Communica, which I roughly modified to accept the amplifier assembly, with a cutout for the power and connectors.
Connecting leads:
I have 3 pairs of leads with terminations as follows:
(a) bare wire
(b) banana plugs
(c) crocodile clips
Controls:
There are just two holes in the cover as I write. One is to view the Bluetooth LED indicator. The other is to access the power switch.
Portability:
Everything fits into a six-pack cooler bag. However, I found a less user-friendly but nicer-looking and harder-wearing bag at a street vendor (robot sellers), with separate compartments. It is a slight bit larger than I had been hoping for, but still compact.
Safety:
With such a potent power source (the battery), it is all too easy to cause a fire via a short-circuit. I ensured that the connectors on the battery terminals are insulated. I also sleeve the DC power connector with a snug-fitting piece of heat shrink tubing so that live power points are not exposed.
Further development:
1. I want to mount buttons on the lid that will give me access to the volume controls and the other onboard controls.
2. I need to make a stand-alone charger for the battery.
Pics to follow.
The idea was to have a small batter-powered amp with leads that I could carry around with me. This is what I came up with:
Modification:
[Audio] The Bluetooth amplifier was bought off one of the Chinese online shops. The performance was not the best, because there was some radio noise breakthrough from the BT module into the audio. To be fair, my review here https://www.avforums.co.za/index.php/topic,59970.0.html did not make mention of it. The conditions under which I tested it (max volume into low efficiency speakers) minimised its effect. However, after using it some more, it did begin to bother me. I subsequently stumbled upon some information about modifying the board to eliminate this noise, which I posted about here https://www.avforums.co.za/index.php/topic,71713.0.html.
[Connector] The board came supplied with screw-down terminals. I needed a quick-connect system, so I removed those connectors and replaced them with a pluggable pair. This would enable me to plug in leads with various termination options.
Power:
[Portable] I initially toyed with the idea of using a set of Li-ion cells in series (3 or 4) but the special charge requirements for this type of cell would over-complicate this simple project. I found a sealed 12V lead-acid battery that was just small and light enough. I made a lead with a DC connector on one and a pair of insulated quick-connect terminals on the other end. I have a complementary socket on alead which I connect to a desktop DC power supply for charging the battery. A future addition to theis project will be a stand-alone charger.
[Fixed] I have a 12V 3A wall wart to power the amp, should I need to use it for extended periods of time.
Enclosure:
I found a small plastic box at Communica, which I roughly modified to accept the amplifier assembly, with a cutout for the power and connectors.
Connecting leads:
I have 3 pairs of leads with terminations as follows:
(a) bare wire
(b) banana plugs
(c) crocodile clips
Controls:
There are just two holes in the cover as I write. One is to view the Bluetooth LED indicator. The other is to access the power switch.
Portability:
Everything fits into a six-pack cooler bag. However, I found a less user-friendly but nicer-looking and harder-wearing bag at a street vendor (robot sellers), with separate compartments. It is a slight bit larger than I had been hoping for, but still compact.
Safety:
With such a potent power source (the battery), it is all too easy to cause a fire via a short-circuit. I ensured that the connectors on the battery terminals are insulated. I also sleeve the DC power connector with a snug-fitting piece of heat shrink tubing so that live power points are not exposed.
Further development:
1. I want to mount buttons on the lid that will give me access to the volume controls and the other onboard controls.
2. I need to make a stand-alone charger for the battery.
Pics to follow.
