I need a very small mono amplifier board that can operate on 5Vdc and power an 8 ohm speaker.
I do not know exactly what power output I need. Maximum 5 watts I think.
I have one of these
https://quarterarcades.com/products/galaga-arcade
I added this speaker to it behind one of the grill openings
https://www.parts-express.com/Dayto...xtended-Range-Driver-8-Ohm-285-145?quantity=1
as the original speaker couldn't reproduce the lower end of the game audio very good.
The module needs to have a volume control as well.
I do not know exactly what power output I need. Maximum 5 watts I think.
I have one of these
https://quarterarcades.com/products/galaga-arcade
I added this speaker to it behind one of the grill openings
https://www.parts-express.com/Dayto...xtended-Range-Driver-8-Ohm-285-145?quantity=1
as the original speaker couldn't reproduce the lower end of the game audio very good.
The module needs to have a volume control as well.
LM384 will do that. 🙂
But maybe not on 5v. :/
LM2002 can be found at 10watts.
and the LM1875 does 20watts.
They all require about 12v minimum, check their datasheets to find out what their minimum operating voltage would be, else count on building a small bipolar (or single ended) supply to run them on.
A 5Vdc supply will get you about 2 watt of output at best.
You may be able to do something using a class D amp at that voltage, but not at any much more of a power level.
V^2 /R= Peak Pwout
(Pwout/2)*.707_RMS Pwout.
Or 25/8+3.125 Watts Peak thus rms power equals 3.125*.707= 2.209 Watts RMS in ti 8 ohms on a 5v supply,not to mention voltage losses across the amps devices within itself.
https://www.ti.com/product/LM384
jer 🙂
But maybe not on 5v. :/
LM2002 can be found at 10watts.
and the LM1875 does 20watts.
They all require about 12v minimum, check their datasheets to find out what their minimum operating voltage would be, else count on building a small bipolar (or single ended) supply to run them on.
A 5Vdc supply will get you about 2 watt of output at best.
You may be able to do something using a class D amp at that voltage, but not at any much more of a power level.
V^2 /R= Peak Pwout
(Pwout/2)*.707_RMS Pwout.
Or 25/8+3.125 Watts Peak thus rms power equals 3.125*.707= 2.209 Watts RMS in ti 8 ohms on a 5v supply,not to mention voltage losses across the amps devices within itself.
https://www.ti.com/product/LM384
jer 🙂
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You might be able to do something with an 'RRIO' CMOS op-amp and tack on an output stage. Though you might have to ask around if you want good results right out of the box.
I would experimentally try a pair of small N+P MOSFETs like a scaled down push pull amplifier, but with a simplified bias scheme consisting of 2 resistors and a trimmer.
Bear in mind it may be a cat and mouse of the FETs suddenly switching on and getting hot due to thermal positive feedback if the control circuit is too simple.
I would experimentally try a pair of small N+P MOSFETs like a scaled down push pull amplifier, but with a simplified bias scheme consisting of 2 resistors and a trimmer.
Bear in mind it may be a cat and mouse of the FETs suddenly switching on and getting hot due to thermal positive feedback if the control circuit is too simple.
"25/8+3.125 Watts Peak" contains a (shift) typo: 25/8 = 3.125 Watts Peak.
This is true for bridge mode, but for a single opamp the ac-swing on one side of the load is +/-2.5V, so the output power is 1/4 of 3.125 is 0.78125Wrms...
Best option is to find a IC with a bridge amplifier inside running on a 5Vdc supply.
Fast search result: TI LM4863.
H
HAYK
With 5v supply you cannot get more than 1w 8ohm in bridged mode. It will be necessary to use dc-dc booster, step up converter and get 14v to use one of those car amp chips to get 7w 8 ohm.
Best bet would be a 5V-capable filter-free class-d IC. There should be loads of them out there somewhere on Mouser, Digikey, Farnell, LCSC and co. It will 100% come bridged already.
Citzen1240323, Yes ,Thank you for catching that, I calculated by peak voltage and by RMS you must divided that peak voltage by 2 and then multiply by .707 to get RMS voltage.
I knew I was missing something, Thanks !!
when I am designing circuits I don't pay much attention to RMS, I only use it as reference to know the final output in to the load.
I mostly concern myself with Peak voltages as it is those when they get too high , they blow stuff up !!! 😉
If the OP didn't want to mess with chipamp's or can't find one, a simple current boosted opamp can be made out of most anything one might have laying around in their junk box, here is one I cobbled up one day,
https://www.diyaudio.com/community/...-supply-what-could-happen.244818/post-3693072
https://www.diyaudio.com/community/...-supply-what-could-happen.244818/post-3695968
Cheers!!
jer 🙂
I knew I was missing something, Thanks !!
when I am designing circuits I don't pay much attention to RMS, I only use it as reference to know the final output in to the load.
I mostly concern myself with Peak voltages as it is those when they get too high , they blow stuff up !!! 😉
If the OP didn't want to mess with chipamp's or can't find one, a simple current boosted opamp can be made out of most anything one might have laying around in their junk box, here is one I cobbled up one day,
https://www.diyaudio.com/community/...-supply-what-could-happen.244818/post-3693072
https://www.diyaudio.com/community/...-supply-what-could-happen.244818/post-3695968
Cheers!!
jer 🙂
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If logic level FETs or BJTs are oriented as common source/ common emitter, the output could be driven rail to rail. I'm not sure what would be easier to bias though.
Perhaps a current-sensing NTC thermistor can be placed in the output stage path, and used as +ve or -ve for a bias voltage divider? So if the thermistor gets hot, the bias voltage gets wider, reducing output current. (Common source polarity only.)
Perhaps a current-sensing NTC thermistor can be placed in the output stage path, and used as +ve or -ve for a bias voltage divider? So if the thermistor gets hot, the bias voltage gets wider, reducing output current. (Common source polarity only.)
Class D amp like PAM8403 is bridge-mode and runs cool... You'll need 4 ohm speaker to get 3W from 5V supply. Or two 8 ohms in parallel perhaps.
I actually wanted to use two of those speakers in parallel as there are two vent holes in the back of the game cabinet just like what the real full sized arcade cabinet would have, but the cabinet is not deep enough at the top vent hole.
That said is there a shallow mount small 8 ohm (using two in parallel) or 4 ohm speaker that has a low frequency response to 100Hz?
The amp I did use originally powered a very small speaker in an all in one PC and I think it was a chip operating in bridged mode.
The added speaker is not quite loud enough to match the stock speaker the cabinet has.
I can only assume the cabinet's amp runs on 3.3 volts as the only 5 volt source that I know of is the USB port used to charge the battery and I'm not going to probe around the board to find a 5 volt source.
On a side note, the battery is bad.
It's a typical modern rechargeable battery. Am thinking a standard 18650 with battery holder may work. If so I'd be able to run a boost converter and set it to 12 volts.
I also used a 6 db/octave passive crossover, but I think I will eliminate that and figure where I can add a cap to the amp for the larger speaker to make a low pass filter.
That said is there a shallow mount small 8 ohm (using two in parallel) or 4 ohm speaker that has a low frequency response to 100Hz?
The amp I did use originally powered a very small speaker in an all in one PC and I think it was a chip operating in bridged mode.
The added speaker is not quite loud enough to match the stock speaker the cabinet has.
I can only assume the cabinet's amp runs on 3.3 volts as the only 5 volt source that I know of is the USB port used to charge the battery and I'm not going to probe around the board to find a 5 volt source.
On a side note, the battery is bad.
It's a typical modern rechargeable battery. Am thinking a standard 18650 with battery holder may work. If so I'd be able to run a boost converter and set it to 12 volts.
I also used a 6 db/octave passive crossover, but I think I will eliminate that and figure where I can add a cap to the amp for the larger speaker to make a low pass filter.
Returning to the KISS principle. 12V boost = bad idea.
#1 would be find out what voltages are actually available. Even 3.3V / LiPo should be fine, based on the levels mobile phones are capable of.
#2 Sanity check. Have you tried just cutting (or unplugging) the speaker leads and connecting a bigger diameter speaker with the same nominal impedance to the existing sound module? You may be surprised.
#3 for more bass the #1 limitation may be the available air volume in the cabinet.
#1 would be find out what voltages are actually available. Even 3.3V / LiPo should be fine, based on the levels mobile phones are capable of.
#2 Sanity check. Have you tried just cutting (or unplugging) the speaker leads and connecting a bigger diameter speaker with the same nominal impedance to the existing sound module? You may be surprised.
#3 for more bass the #1 limitation may be the available air volume in the cabinet.
#1 I can get 5 volts.
#2 I think the internal speaker is real low ohms plus I want it to work. Believe I did try the larger speaker on it and it wasn't very loud.
#3 The full size arcade cabinet I think had a 4" speaker so deep bass response wouldn't have been there to begin with.
Using the speaker I did, the sound sounds closest to what I remember the full sized cabinet sounding like.
#2 I think the internal speaker is real low ohms plus I want it to work. Believe I did try the larger speaker on it and it wasn't very loud.
#3 The full size arcade cabinet I think had a 4" speaker so deep bass response wouldn't have been there to begin with.
Using the speaker I did, the sound sounds closest to what I remember the full sized cabinet sounding like.