Hello, everyone,
I'm looking for a simple and cheap amplifier with 20 - 50 watts that is as insensitive as possible. Class D, Chip Amp or Solid State does not matter.
Sound, noise etc. does not matter either, a circuit board or a DIY board.
I just want to use this amplifier to test speakers, individual chassis, components or cables, even over several hours. In addition, the amplifier should be very insensitive and damage-resistant, and should be easy to repair if the worst comes to the worst.
Does somebody has any idea?
I'm looking for a simple and cheap amplifier with 20 - 50 watts that is as insensitive as possible. Class D, Chip Amp or Solid State does not matter.
Sound, noise etc. does not matter either, a circuit board or a DIY board.
I just want to use this amplifier to test speakers, individual chassis, components or cables, even over several hours. In addition, the amplifier should be very insensitive and damage-resistant, and should be easy to repair if the worst comes to the worst.
Does somebody has any idea?
Second the LM3886. That´s a pretty robust chip.
If testing 4Ohm speakers I´d watch your supply voltage though.
+-35V is too high for 4Ohm but needed if you want 50W into 8Ohms.
(see datasheet)
Maybe you find yourself a nice board with parallel LM3886. Then +-35V are OK for 4-8Ohm speakers.
(Same goes for TDA7293 which I´m playing with at the moment.)
Also have a look here:
'Best' LM3886 PCBs (both single & parallel)
I´m using the LM3886-PCBs from the "open source LM3886" and they are very well done boards and the gerber files are free to use.
If testing 4Ohm speakers I´d watch your supply voltage though.
+-35V is too high for 4Ohm but needed if you want 50W into 8Ohms.
(see datasheet)
Maybe you find yourself a nice board with parallel LM3886. Then +-35V are OK for 4-8Ohm speakers.
(Same goes for TDA7293 which I´m playing with at the moment.)
Also have a look here:
'Best' LM3886 PCBs (both single & parallel)
I´m using the LM3886-PCBs from the "open source LM3886" and they are very well done boards and the gerber files are free to use.
Audiophonics have a couple of populated PCBs with LM3886, 2x and 3x parallel:
AUDIOPHONICS APD85 Amplifier Module Mono LM3886 100W / 8 Ohms - Audiophonics
AUDIOPHONICS APD87 Mono LM3886 Amplifier Module 150W / 8 Ohm - Audiophonics
If these aren´t fakes, the prices are OK. (considering the LM3886 is not that cheap)
You might want to tune the resistors though. Don´t think they would match them enough for same gain but that´s easy to do.
AUDIOPHONICS APD85 Amplifier Module Mono LM3886 100W / 8 Ohms - Audiophonics
AUDIOPHONICS APD87 Mono LM3886 Amplifier Module 150W / 8 Ohm - Audiophonics
If these aren´t fakes, the prices are OK. (considering the LM3886 is not that cheap)
You might want to tune the resistors though. Don´t think they would match them enough for same gain but that´s easy to do.
My recommendations for speaker measurements are
-Provide an output that swings symmetrically around ground. This requires some half bridge amp fed by a split supply.
-Avoid class-d as you will not like the rf-residual on your signal.
-For the sake of ruggedness choose either chip-amps or discrete latFET, certainly neither discrete BJT nor V-FET.
So I ended up by building a latFET class AB-amp with +-35V split supply.
For all other amplications I am a TPA3118/TPA3255 fanboy.
-Provide an output that swings symmetrically around ground. This requires some half bridge amp fed by a split supply.
-Avoid class-d as you will not like the rf-residual on your signal.
-For the sake of ruggedness choose either chip-amps or discrete latFET, certainly neither discrete BJT nor V-FET.
So I ended up by building a latFET class AB-amp with +-35V split supply.
For all other amplications I am a TPA3118/TPA3255 fanboy.
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I have regulator cct for LM3886 power in my test amp.
I switch (before power up) between +/- 35 for 8R and +/- 28 for 4R.
I use +/- 35 for driving 1K series for impedance testing.
Theoretically 2xLM3886 should be OK, three probably better.
Practically I haven´t tried.
But see here and the AN-1192:
PA150 (3x LM3886) 2 ohm capability ?
Also here, DUG´s trick to use some kind of adjustable power supply would be nice to have.
(or two different transformers that can be changed via switch; or a variac)
At 2 Ohms something like +-16V (at least < +-20V) would do the trick for ~50W without too much stress on the chips.
Practically I haven´t tried.
But see here and the AN-1192:
PA150 (3x LM3886) 2 ohm capability ?
Also here, DUG´s trick to use some kind of adjustable power supply would be nice to have.
(or two different transformers that can be changed via switch; or a variac)
At 2 Ohms something like +-16V (at least < +-20V) would do the trick for ~50W without too much stress on the chips.
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Lm3886 looks fine, the most important part I believe is never use a bridge amp. A lot of chip amps and class D are bridged.
Any measurement on oscilloscope might wind up accidentally shorting output to ground.
Oon
Any measurement on oscilloscope might wind up accidentally shorting output to ground.
Oon