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I have had this MiniFX for a while now and the manufacture has stopped making them. It is used to mic a native American flute and add reverb/delay type effects to the sound. It is mono in and stereo out. I want to reverse engineer it and make my own version that would include:
- Better speakers/sound and the ability to get louder than it currently can.
- Add the ability to plug in an AUX cable that would have its own preamp and would route directly to the speakers without effects mixed to it
- Add the ability to remove batteries easily (currently the entire box has to be opened with four long screws to get at the battery pack inside)
- It would be great to be able to plug other types of lapel microphones since it can only take a mono plug currently.
I would have to create my own pcb board and I am thinking to 3D print the case (unless there are other methods that are possible).
I wanted to reach out to the DIY Perks group to get some ideas on how to accomplish this.
I also think there may need to be some design added to the case so that the speakers would have a proper enclosure in order to maximize the sound.
Oh and it should continue to be as light as possible so you can carry it will you on a shoulder strap.
Any ideas are most appreciated.
Posted : 16/02/2024 12:56 am
Speakers are the simplest modification to begin with. Different inputs (like an aux) are a little more complicated, it rather depends on your electronics skilled and test gear. The reverb DSP board is still made but you don't need to worry about that since it's a daughterboard.
I managed to read one of the chips in your picture as (to no surprise) is a TL072, a jellybean dual FET input op amp and one of my favourites when absolute quality isn't an issue.
I would guess the other 8-pin DILs are the same. The larger chip isn't clear but if you can get the part numbers from them I'd have a better idea of what they are doing.
Modifying these inputs is quite possible but you'd likely have to start by removing those input chips so you can socket them and make a daughterboard or inject your own inputs. I could be more help if you can get a little closer into those inputs and state which is which.
Let's look at louder speakers though. This is a simple job but it will require a little bit of soldering. Assuming the amplifier isn't in a bridge mode (which is more likely) you can tap the speaker outputs directly with a blocking capacitor (for sanity) and then feed that to a class D module like this one:
8Pcs PAM8403 Digital DC 5V Amplifier Class D 2*3W Audio Module | eBay
That's assuming it's not already doing that, of course. Class D modules are very cost effective and very, very loud compared to a classic Class A, B or AB because they are much more efficient.
I'd need to know which amplifier they are using to get a better idea.
The internal speakers look cheap and nasty but that's what you'd expect. Their impedance should be marked on there but a better quality unit (driver) would likely improve things considerably, even if they are just circular. Laptop speakers aren't suitable and the larger speakers get, the less sensitive they tend to be, so you need a better amp to make them work. It's also important to note that a speaker won't work correctly unless it's in a case to damp the inverse pressure wave. (You can hear this yourself operating the unit with the cover on and off.)
Take everything I say with a pinch of salt, I might be wrong and it's a very *expensive* way to learn!
Posted : 20/02/2024 11:09 am