I have a MiniDSP 2x4 (non-HD). The line level input is the regular 2Vrms, but unfortunately it only outputs 0.9Vrms. Because of this, a more powerful power amp is required to compensate.
So I was wondering. Would it be hard to make a simple op amp based circuit board to increase the output to 2.0~2.1Vrms? It would be nice if this can be DC powered. The MiniDSP itself can be powered with anything between 5 ... 24VDC, it would be nice to use the same power source.
So I was wondering. Would it be hard to make a simple op amp based circuit board to increase the output to 2.0~2.1Vrms? It would be nice if this can be DC powered. The MiniDSP itself can be powered with anything between 5 ... 24VDC, it would be nice to use the same power source.
No, a power amplifier with more gain is required to compensate. Not the same thing.
Thanks, I'm very novice when it comes to electronics, but I'll give it a try. Might need some help, but we'll see.
True, but as the same speakers are used the impedance load will be the same, so an amp with higher gain will also have to be more powerful.
Unfortunately not, there's only a jumper for the input level, not the output. From the datasheet:
sounds like right direction.
If it needs .9 to 2v RMS input to reach full power
from various measurements over time being posted
it seems lots of portable music players or phones
seem to be around .6 to .7 volt RMS output.
Since max output is restricted by regulation.
and overall voltage is low as well.
Far as the board not sure what the actual power chip is.
Sounds regulated at 5 volts which sounds like a PAM
or similar, so it will never be more powerful.
But you might not even be getting close to full power
because it needs more input gain.
As mentioned changing the input sensitivity
higher with jumper would make it possible to
get closer to full power.
otherwise to power off same supply yes is possible.
be single supply opamp circuit.
older op amps dont do well on low voltage.
most would use a rail to rail to get decent output.
If it needs .9 to 2v RMS input to reach full power
from various measurements over time being posted
it seems lots of portable music players or phones
seem to be around .6 to .7 volt RMS output.
Since max output is restricted by regulation.
and overall voltage is low as well.
Far as the board not sure what the actual power chip is.
Sounds regulated at 5 volts which sounds like a PAM
or similar, so it will never be more powerful.
But you might not even be getting close to full power
because it needs more input gain.
As mentioned changing the input sensitivity
higher with jumper would make it possible to
get closer to full power.
otherwise to power off same supply yes is possible.
be single supply opamp circuit.
older op amps dont do well on low voltage.
most would use a rail to rail to get decent output.
Hello OP,
It would not be difficult. It appears the system would benefit from a preamp.
Along with the good 5532 suggestion, I might mention the LME49720 or LME49860 be added at the mini DSP’s output. You may want a volume control between the DSP and opamp, as the gain also amplifies whatever noise is present at the DSP’s analog output. A capacitor and unity stage might be beneficial in that case to isolate the potentiometer from both the gain stage’s input load and any previous offset. The gain stage could be a 1k source resistor in front of the op amp, and 2k feedback resistor (with 100pF in parallel with feedback) to provide a gain of 2x (6dB). An alternative feedback resistor of 3k will provide 3x gain (9.5dB).
Bypass the positive and negative power pins to the PSU common ground with 0.1uF ceramics for stability, and place 47k to the common ground for an output reference. On each opamp signal output to the audio jacks place 50 Ohms to limit current in the hypothetical event of accidentally shorting the plugs against something.
It’s not a lot of parts and a few little details could be added, but if it’s in the same chassis as the DSP it likely won’t need additional RF filtering at the input. I think a diagram might help you, but at this stage it’s an idea, at least.
It would not be difficult. It appears the system would benefit from a preamp.
Along with the good 5532 suggestion, I might mention the LME49720 or LME49860 be added at the mini DSP’s output. You may want a volume control between the DSP and opamp, as the gain also amplifies whatever noise is present at the DSP’s analog output. A capacitor and unity stage might be beneficial in that case to isolate the potentiometer from both the gain stage’s input load and any previous offset. The gain stage could be a 1k source resistor in front of the op amp, and 2k feedback resistor (with 100pF in parallel with feedback) to provide a gain of 2x (6dB). An alternative feedback resistor of 3k will provide 3x gain (9.5dB).
Bypass the positive and negative power pins to the PSU common ground with 0.1uF ceramics for stability, and place 47k to the common ground for an output reference. On each opamp signal output to the audio jacks place 50 Ohms to limit current in the hypothetical event of accidentally shorting the plugs against something.
It’s not a lot of parts and a few little details could be added, but if it’s in the same chassis as the DSP it likely won’t need additional RF filtering at the input. I think a diagram might help you, but at this stage it’s an idea, at least.
That does not follow. I am unable to understand this line of reasoning.
Jbarelds, the amp won’t be more powerful but you will be able to access more of the power it does have. Right now your input voltage is not enough to drive the amp to its maximum available power. It’s as if your accelerator pedal wasn’t able to push down all the way. The engine has more power, you just can’t get to it! You can look for a tiny preamp with a little gain too.
The way I understand it, gain is the product of Vin / Vout. If an amp has a gain of 20 this means an input voltage of 2V will be amplified to 40V. With a nominal impedance of 8 ohm's the current will be 5 amps (I = U / R). This means the amplifier would have to deliver 200W of power (P = U * I).
Following this math we'd require an amp with a gain of 44 and a max power of almost 1000W (at 2V of input) to deliver the same 200W with the lower 0.9V input.
Well with a single 5V supply you can't generate 2.1V rms, as that's about 6V peak-peak. You'd need a true rail-to-rail opamp for this, a 5532 would need more like +/-9V to ensure it had enough headroom. The way you might power things could be very different in the 5V case to the 24V case, you probably need to make a decision between buck converters and boost converters and involves constraining the supply voltage.
You are confused. The fact that you aren't changing the speaker proves that you don't need a more powerful amplifier. All you need is more gain. You can get it by modifying the MiniDSP, adding an opamp outside the amp, adding an opamp inside the amp, or increasing the amplifier gain some other way, that is to say increasing the NFB resistor. None of these things changes the total output power available, and they all increase the gain. The two are not connected.