Hello. I recently constructed a GC using the OP548. Using my benchtop PS is sounds great, but I now want to move to a battery PS. Tonight, I attempted to do this but it seems I may have damaged my GC circuitry. I attempted to connect the +/- 12V battery supply (2 power sonic 1.2AH 12V) rail by rail since I did not have an appropriate switch handy. I first connected the the common, then the +, but then disconnected the + and saw a spark. I then attempted to run the GC off my benchtop supply again and I got nothing. Any ideas what I may have done? What precautions do I need to take when using a battery supply. And, finally, how do I eliminate the speaker "popping" when I power up and power down.
Thanks !
Mike
Thanks !
Mike
Mike anytime that you use a different power source to a circuit, verify it before hooking it up with a meter and a load.
I think that you may have blown the chip because of this but without any diagram of your hook up its hard to tell.....test yor battery supply with the GC not connected and go from there
DIRT®
I think that you may have blown the chip because of this but without any diagram of your hook up its hard to tell.....test yor battery supply with the GC not connected and go from there
DIRT®
I tested the two battery set up before using it. I had +/- 12.65 V. The circuit operated perfectly with the benchtop supply at +/-10V.
I don't think I blew a cap since all my caps are rated at at least 16V (except for the decoupling cap).
My main questions are:
1) Is it possible to damage the OPA548 by connecting the power supply in this oder (with out switches): ground, then positive, and then negative (i.e. do both positive and negative rails have to be switched on simultaneously?)
2) How does one eliminate the popping heard in the speaker upon power up and especially power down of a GC?
I don't think I blew a cap since all my caps are rated at at least 16V (except for the decoupling cap).
My main questions are:
1) Is it possible to damage the OPA548 by connecting the power supply in this oder (with out switches): ground, then positive, and then negative (i.e. do both positive and negative rails have to be switched on simultaneously?)
2) How does one eliminate the popping heard in the speaker upon power up and especially power down of a GC?
GC Battery PS
I've only played with LM3875 chips but connecting a +/- supply one leg at a time can cause a massive dc offset at the output resulting in scarry voice coil movement. Check to see if you didn't fry your speakers and always use a junker speaker to test a new build. A switch that switches both sides at the same time(DP) will help, and caps ~1000 uf help smooth the turn on(though some use smaller film caps ~10 uf when using battery supplies).
The LM3875 has protection circuits built in and all my brutal treatment doesn't seem to have harmed them but I'm unfamiliar with OPA548 and it's possible they could be fried.
So, an appropriately rated DC double pole switch will be a good start once you find out what is fried. And don't forget the fuses-batteries can supply huge currents that can weld and melt things pretty easily.
good luck,
Scott
I've only played with LM3875 chips but connecting a +/- supply one leg at a time can cause a massive dc offset at the output resulting in scarry voice coil movement. Check to see if you didn't fry your speakers and always use a junker speaker to test a new build. A switch that switches both sides at the same time(DP) will help, and caps ~1000 uf help smooth the turn on(though some use smaller film caps ~10 uf when using battery supplies).
The LM3875 has protection circuits built in and all my brutal treatment doesn't seem to have harmed them but I'm unfamiliar with OPA548 and it's possible they could be fried.
So, an appropriately rated DC double pole switch will be a good start once you find out what is fried. And don't forget the fuses-batteries can supply huge currents that can weld and melt things pretty easily.
good luck,
Scott
Just DON'T CONNECT the speakers until you connected both rails to the PS. If you don't have load (speaker) connected you'll have the same spikes at the output of the amp, but no damage well occur.
So:
1. Disconnect the speaker and any other loads connected to the output of the IC
2. Connect the +V and the - V.
3. Connect the speakers.
No damages should occur that way.
I have a switch that disconnects the speakers (as in the original GC) and I disconnect the speakers first every time I turn the amp on or off.
So:
1. Disconnect the speaker and any other loads connected to the output of the IC
2. Connect the +V and the - V.
3. Connect the speakers.
No damages should occur that way.
I have a switch that disconnects the speakers (as in the original GC) and I disconnect the speakers first every time I turn the amp on or off.
There shouldn't be any thump when powering GC on or off. It only happens when the grounding is done incorrectly or substantial DC off set (300mV or so ) is present at the output.
Otherwise there is no need to disconnect speakers when switching the amp. Actually there is no need to use a power switch at all. It plays better when you run it constantly ON.
The above doesn't apply when you play with rail voltage. Although it shouldn't damage the amp when connecting only one rail, it may do something to the speakers
Otherwise there is no need to disconnect speakers when switching the amp. Actually there is no need to use a power switch at all. It plays better when you run it constantly ON.
The above doesn't apply when you play with rail voltage. Although it shouldn't damage the amp when connecting only one rail, it may do something to the speakers
Thanks to everyone for all your help. This has been very educational for me.
As it turns out, my pesky experimental GC decided that it would
WORK Again today. I strongly suspect the problem to be a crappy aligator cable.
I will push forward and attempt (again) to implement a battery power supply.
thanks again,
Mike
As it turns out, my pesky experimental GC decided that it would
WORK Again today. I strongly suspect the problem to be a crappy aligator cable.
I will push forward and attempt (again) to implement a battery power supply.
thanks again,
Mike
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