I had the idea of building a little amplifier/speaker module to monitor the modular output based on the classic TDA2030 amplifier in the pentawatt package (of course, @Stef already beat me to it). I am working with a 12V single supply (off an old 5A laptop switching PSU) and looking to build something similar to the datasheet (edited image off the datasheet below). I have a couple of questions for those who have played around with the 2030:
Am I okay with electrolytic capacitors rated at 25V, especially C7?
R6/C6 right before the speaker looks like a Zobel network. I am working with a salvaged 3Ω 75W speaker. Do I need a resistor rated at 1W instead of the typical 1/4W ones? How critical are the R6/C6 values for the kind of application I am looking for?
25V for the capacitors should be more than enough at 12V input voltage.
And for the Zobel network - yes, this is one - I used a 2W resistor for my input voltage of 19V, and its not getting very warm, but I think 1/4W would be a little bit too weak.
Or put several 1/4W in parallel.
(To add the wattage they must have the same value, or else it’s a bit more complicated to compute the resultant wattage)
Unfortunately, it’s not possible to use that calculator as I need the inductance of the voice coil of the speaker. I tried locating the speaker driver datasheet but had no luck.
hm, ok, but in this case - if you cant measure the inductance - you could use the values found in some speakers datasheets. I’ve found values of around 1.5mH for 75W/4Ohm speakers, and 0.7mH for 8Ohm.
So I think with a resistor of 2Ohm/2W (or 3 of your 0.68 Ohm in series) your should be close enough to the perfect value.
Thanks for the suggestion! A quick correction, the speaker is an Eastech at 7.5W, not 75W as I wrote by mistake. I checked datasheets of similar Eastech speaker drivers and the specs for the inductance were all over the place, which is not very helpful. I might just put a socket for a couple of resistors in series and try a couple of values around 1Ω as specified in the TDA2030 datasheet. If I ever find more information, I can replace them easily.
Here’s what I came up with, which unfortunately is not working. When I turn this on, I get plenty of noise and oscillation, and the circuit gets overwhelmed when I inject a signal at the input. I got no signal at all, just oscillation.
The specs of the build:
I used a, quite likely fake, TDA2030A desoldered from a little amplifier module that you can get cheaply online.
The IC is mounted at a 45-degree angle with a large heatsink.
The circuit was built on stripboard as shown below. All soldering is fine, no bridges etc.
Electrolytic capacitors are rated at 25 or 50V, the rest are film box capacitors, except the 100nF which is ceramic. The diodes are 1N4007 and I have a socket for the 1Ω 1W resistor (tried 0.57Ω, 1.6 and 5Ω).
Power comes from a 12V 5A switching laptop kind of brick.
Speaker, input, and supply grounds are connected with crocodile clips.
Tried both 3Ω 7.5W and 8Ω 0.5W speakers.
This had me scratching my head for a while. Unless I made a mistake in the stripboard layout (which is always likely), I am going to say that this is not likely to work because of the chip quality and/or limitations of stripboard design (i.e. jumpers and whatnot).
Even if the IC is original they are very sensible to pcb design and ground connections. I would not try this on stripboard. With an etched pcb with the design following the example in the datasheet I had no problems, nearly no noise and no oscillation.
But I will have a deaper look at your stripboard design.
This IC follows the rule #1 in oscillator and amplfifier design: ampflifiers always oscillate, and oscillators never.
ok, your stripboard design looks fine, only - in my opinion - too much hopping for the ground lane. Maybe you could try to change the orientation of the stripboard, from 17 rows/12 columns to 12 rows/17 columns, so that you could place all ground connections on one row without the need to place them all over the board.
If you can etch your own pcbs I could send you the kicad project.
Or maybe try to use the manhattan style, if you have some copper plated pcb material. Use a big copper plate for ground and glue small strips on it (just an example image):
In my case I bought an TD2030AV from UTC at the german shop reichelt.de for 0.60€.
Thanks for the suggestions! I figured that the ground jumpers might have something to do with it, but I did not expect things to be that bad. I mean, there is no signal whatsoever, just the nastiest motorboating and whining.
I could try another stripboard layout, but I suspect that it might be a huge difference. Or etching a board, as you suggested, but I am really trying to avoid the hassle of doing that. I looked to see if there is a board I could order from JLCPCB, but couldn’t find any on github, so I just ordered a couple of boards as kits. I also have a TDA2040 that I might try in a point-to-point build until the kits arrive, as you suggested.
Giving this another try, this time with a ittle PCB kit. I see, however, that the design does not include the protection diodes at the output. I guess I should hack those into the PCB just to be on the safe side?
I added the flyback diodes at the bottom of the board, replaced the Zobel network resistor with a higher rating one, added a heatsink and … it works! Loud and clear. It just needed that little PCB I guess! Now, its time to turn this into a proper module.
Not the tidiest build, but it gets the job (having a quick way to monitor the output) done nicely. I am working from home so I don’t have access to aluminium and I only have hand tools here, so I documented the build approach in case anyone wants to try something similar.
The idea was to mount a decent (and heavy!) speaker behind the panel. I used 1.5mm cardboard (I think it’s the bookbinding type) for the panel to be able to make decent-looking round cuts using simple hand tools. I cut two concentric holes to be able to wedge the speaker grill cloth in between and give it the necessary tightness.
Since the speaker is very heavy, I added 4mm and 2mm balsa wood at places for support. The challenge was that I could not add the support material uniformly due to the thickness constraints of the controls, etc.
The speaker was mounted to the board using 30mm M4 screws and nuts. I had to bend the top support to make it fit. The amplifier PCB is held in place on a piece of PVC profile with some hot glue.
How much difference the <1Ω will make for a 3Ω speaker?
