I'm looking to build an amp with about 16 channels for cheap. Good news is that I only need roughly 3watts power into 4ohm speakers from it. I have never built an amp before, but I do know the basics of electronic circuits/schematics. Can anyone help with kit suggestions or design ideas? Thanks.
p.s. hi-fi is not a requirement of this design (just as long as it's reasonable fidelity)
p.s. hi-fi is not a requirement of this design (just as long as it's reasonable fidelity)
Pico, would you mind trying to be slightly more helpful/elaborate in your responses? I am a true beginner in amp building. In the world of digital audio (where I study) a buffer is a delay line - I assume you don't mean that.
I know that a car audio chip amp won't like 120V AC so I would assume a transformer would be needed. Would these chips also want a DC power source?
Is there any kit-style solution or maybe a schematic on the web that I can look into and understand more?
I know that a car audio chip amp won't like 120V AC so I would assume a transformer would be needed. Would these chips also want a DC power source?
Is there any kit-style solution or maybe a schematic on the web that I can look into and understand more?
good morning.
(low power) car amps need a +12V (+12V.......max. +15V) psu.........(digital chips need +5V i think).
with 16 channel each 3W Pout you need a transformer 48W min. - but in practice you should choose a better one.........48W x 1,5 gives you around 75W (or bigger).
low cost chip amp e.g. are tda2002,tda2003,...........or so.
can you give more information :
what is the goal of this design?
why 16 channels?
does every channel need a volume control - or do you have a preamp with volume controles?
(low power) car amps need a +12V (+12V.......max. +15V) psu.........(digital chips need +5V i think).
with 16 channel each 3W Pout you need a transformer 48W min. - but in practice you should choose a better one.........48W x 1,5 gives you around 75W (or bigger).
low cost chip amp e.g. are tda2002,tda2003,...........or so.
can you give more information :
what is the goal of this design?
why 16 channels?
does every channel need a volume control - or do you have a preamp with volume controles?
The goal is to amplify a line array of loudspeakers. Each loudspeaker is independently driven with a slightly different (phase delayed) signal and the paths for each speaker's signal need to be identical so the phase delay remains exact/intact.
Volume control could be universal (this would actually be preferable) or non-existent (and I'll just control them digitally).
16 channels is what I'm hoping to have at least. Currently I have 12 speakers ready to go, but I'm pretty sure I'll be buying more to make the array longer. Who knows, maybe the project will end up being 24 or 36 channels by the time all the math is crunched.
As it sits I can only output 8 channels from my soundcard, but the goal is to build the digital logic into a hardware board eventually. So for now feel free to help me with a eight channel amp that can be expanded later when needed.
So that I understand you fully, the 120V would need to be transformed down to either 13.8V (average car batt voltage) or 5V, then rectified to DC and smoothed. Are there general PSU units out there that amp builders rely on, or is this a general power issue that can be bought from most electronics stores/online retailers, or do I need to design and build my own for the exact need? If I set a 200W transformer rating goal that should give me enough headroom to draw the power for later expansion right? Or will it work like that?
Sorry. I can often write run-on paragraphs full of questions.
Volume control could be universal (this would actually be preferable) or non-existent (and I'll just control them digitally).
16 channels is what I'm hoping to have at least. Currently I have 12 speakers ready to go, but I'm pretty sure I'll be buying more to make the array longer. Who knows, maybe the project will end up being 24 or 36 channels by the time all the math is crunched.
As it sits I can only output 8 channels from my soundcard, but the goal is to build the digital logic into a hardware board eventually. So for now feel free to help me with a eight channel amp that can be expanded later when needed.
So that I understand you fully, the 120V would need to be transformed down to either 13.8V (average car batt voltage) or 5V, then rectified to DC and smoothed. Are there general PSU units out there that amp builders rely on, or is this a general power issue that can be bought from most electronics stores/online retailers, or do I need to design and build my own for the exact need? If I set a 200W transformer rating goal that should give me enough headroom to draw the power for later expansion right? Or will it work like that?
Sorry. I can often write run-on paragraphs full of questions.
You could power it from one or more "brick" power supplies from eBay or the junk box. If you search for 12V and 5A you'll also find metal-cased power supply modules in larger amp ratings. Visiting a ham radio swap meets might turn up a 12V supply, since they're commonly used to power mobile radios.
As for suitable amp chips, LM383/TDA2002, or TBA810 are a couple of mono chips that'll do around 7 to 8 watts into 4 ohms. LM377 is a stereo amp chip rated at about 2 watts. LM380 is mono, about 2.5 watts, and needs very few external components. Those are all chips which have been around a very long time, so there are probably newer chips that are more available or cheaper.
However, by the time you buy the chips and add the ancillary parts, buying ready-made stereo amp modules starts to look attractive. The TA2024 T-amp boards are available for under $7 shipped from eBay, and those are stereo. Outputs are bridged, though, which could be a problem since the speaker negatives can't be common.
Searching eBay for cheap amplifier modules, I spotted a TDA7297 stereo amp for $4.50 including shipping. That's about as cheap as it gets, but, they have bridged outputs. For $6.50 to $7.50 (shipped) there's kits for a TDA2030A boards, which appear to be stereo, and not bridged.
As for suitable amp chips, LM383/TDA2002, or TBA810 are a couple of mono chips that'll do around 7 to 8 watts into 4 ohms. LM377 is a stereo amp chip rated at about 2 watts. LM380 is mono, about 2.5 watts, and needs very few external components. Those are all chips which have been around a very long time, so there are probably newer chips that are more available or cheaper.
However, by the time you buy the chips and add the ancillary parts, buying ready-made stereo amp modules starts to look attractive. The TA2024 T-amp boards are available for under $7 shipped from eBay, and those are stereo. Outputs are bridged, though, which could be a problem since the speaker negatives can't be common.
Searching eBay for cheap amplifier modules, I spotted a TDA7297 stereo amp for $4.50 including shipping. That's about as cheap as it gets, but, they have bridged outputs. For $6.50 to $7.50 (shipped) there's kits for a TDA2030A boards, which appear to be stereo, and not bridged.
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Just for clarification, what signals are you working with? The 20Hz to 20kHz range I assume? How handy are you with a soldering iron? Could you give us the output specs of your soundcard? How cheap do you need this to be? Also, some of the geniuses around here might have some suggestions if you'd say what you're trying to make!
As for pico's earlier comment regarding buffers, you would want to put one in front of the amp to increase the input impedance and drive the amp(s) a little better. There are innumerable options here, and if fidelity isn't a huge concern you could use a simple opamp buffer. You could use quad packages (ie 4 opamps in one 14 pin package to save on space if needed, and only require 2-4 external components per channel (depending on how you go about doing things). However, depending on the power amp specs, input buffers may not be necessary.
Sorry if I misinterpreted your message, but it sounds like you need however many amplifiers with independent inputs and outputs, and a universal volume control for all the channels. A single volume control to control multiple channels with individual sources could be a bit inconvenient, if you're comfortable with digital volume control I would recommend that you stick with that, plus it would probably simplify things if you wanted to expand later.
A good option for your situation might be an IC with several class D amplifiers in one package. They have a lot of advantages, including extremely high efficiency (and by extension lack of heat dissipation) and in many cases they're very easy to implement. However, they might be expensive, and many are only available in tiny SMD packages.
Lastly, the power supply. Just an initial heads up, this section could easily be the most expensive- transformers aren't cheap. The voltage(s) you need will depend on the specific parts you use, and it would probably be a wise decision to pick the parts before you pick the transformer. And yes, you could use a prebuilt PSU unit, but even the decent ones can be pricey, plus it probably wouldn't be easy to modify later if your requirements change. A 200W transformer could probably get you up to 50 channels if you really needed to push the limit and you're careful!
As for pico's earlier comment regarding buffers, you would want to put one in front of the amp to increase the input impedance and drive the amp(s) a little better. There are innumerable options here, and if fidelity isn't a huge concern you could use a simple opamp buffer. You could use quad packages (ie 4 opamps in one 14 pin package to save on space if needed, and only require 2-4 external components per channel (depending on how you go about doing things). However, depending on the power amp specs, input buffers may not be necessary.
Sorry if I misinterpreted your message, but it sounds like you need however many amplifiers with independent inputs and outputs, and a universal volume control for all the channels. A single volume control to control multiple channels with individual sources could be a bit inconvenient, if you're comfortable with digital volume control I would recommend that you stick with that, plus it would probably simplify things if you wanted to expand later.
A good option for your situation might be an IC with several class D amplifiers in one package. They have a lot of advantages, including extremely high efficiency (and by extension lack of heat dissipation) and in many cases they're very easy to implement. However, they might be expensive, and many are only available in tiny SMD packages.
Lastly, the power supply. Just an initial heads up, this section could easily be the most expensive- transformers aren't cheap. The voltage(s) you need will depend on the specific parts you use, and it would probably be a wise decision to pick the parts before you pick the transformer. And yes, you could use a prebuilt PSU unit, but even the decent ones can be pricey, plus it probably wouldn't be easy to modify later if your requirements change. A 200W transformer could probably get you up to 50 channels if you really needed to push the limit and you're careful!
Szechuan, the range will likely be 200Hz-20kHz range and 20-200Hz will be fed to a subwoofer with its own amp. I can solder pretty well, but I haven't done any surface mount stuff, though I'm sure this project will lead me down that path and I'm confident my hands can manage it fine. I actually have some QFN chips right here, waiting for me to learn how to solder them.
The project itself will essentially be a DIY version of the Yamaha YSP product line (not identical, but close enough that you get the picture). I'm playing with beamforming array algorithms. Like I mentioned at one point digital audio is my strong point, not analog electrical, so things like opamp buffers I'm totally new to.
I am fine with digital volume control if it will simplify the overall process - I think that's where it would have ended up in the final design anyways.
My soundcard is a PreSonus Firepod (they probably call it by a different name now) but this is just the temporary testing bed for this project (8in/8out). Eventually there will be a hardware ADC/DAC implemented internally in the processing board - no idea what the spec on that will turn out to be.
I'm totally open to class D amps on an IC chip. This sounds like it's probably best for this application.
The project itself will essentially be a DIY version of the Yamaha YSP product line (not identical, but close enough that you get the picture). I'm playing with beamforming array algorithms. Like I mentioned at one point digital audio is my strong point, not analog electrical, so things like opamp buffers I'm totally new to.
I am fine with digital volume control if it will simplify the overall process - I think that's where it would have ended up in the final design anyways.
My soundcard is a PreSonus Firepod (they probably call it by a different name now) but this is just the temporary testing bed for this project (8in/8out). Eventually there will be a hardware ADC/DAC implemented internally in the processing board - no idea what the spec on that will turn out to be.
I'm totally open to class D amps on an IC chip. This sounds like it's probably best for this application.
How about some TAP3110 based amps? Just add a reasonable switched PSU at 12-15 VDC or so. Easy to hook up and reported as quite good.
2 x 8Watt Class D Audio Amplifier Board TPA3110 2W Stereo Power Mini Amp | eBay
Or the TDA7850 based amps which obviously are not High-End but simple and compact.
http://www.ebay.com/itm/1PC-TDA7850..._Audio_Amplifiers_Preamps&hash=item4ac05c9447
2 x 8Watt Class D Audio Amplifier Board TPA3110 2W Stereo Power Mini Amp | eBay
Or the TDA7850 based amps which obviously are not High-End but simple and compact.
http://www.ebay.com/itm/1PC-TDA7850..._Audio_Amplifiers_Preamps&hash=item4ac05c9447
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Another good choice might be the TPA2008 (datasheet) which is easy to use in that it doesn't need output filtering. It comes in a TSSOP-24 package, which is pretty easy to solder by SMD standards. I don't know of any kits, however, so you'll be left to handle the physical development.
I notice TI has a handful of quad amplifier chips. Would that route help me save some coin? Audio Operational Amplifier | Products for Audio Operational Amplifier
Oh, now I've got the full picture. Those are Operational amplifiers ( Op Amp)
that work with small signal; with those you can make buffers, amplifiers, filters but if you want power you need devices that work with high current, such as the common LM 1875 ( 20 W) or LM 3886 (60 W) or TDA7294 .
They need dual supply ( plus and minus potential referred to 0V=ground)and
many amplifiers need accurate layout to work flawlessly.
I don't know anything about class D amplifiers, only that they are more efficient - smaller transformer needed.
There are many others ( so-called) chip amps, available in stereo in one package ( LM 1876 for example, LM 4766 etc) and there are maaaaany working
with single supply voltage, like the LA series . I've got one LA 4551 with 36 V supply. Less voltage, less power -it depends also on the load, if 4 or 8 Ω and the sensitivity of the speaker.
Now all the chips feature a stand-by mode and a muting, which you can select with a switch but mostly with digital logic
that work with small signal; with those you can make buffers, amplifiers, filters but if you want power you need devices that work with high current, such as the common LM 1875 ( 20 W) or LM 3886 (60 W) or TDA7294 .
They need dual supply ( plus and minus potential referred to 0V=ground)and
many amplifiers need accurate layout to work flawlessly.
I don't know anything about class D amplifiers, only that they are more efficient - smaller transformer needed.
There are many others ( so-called) chip amps, available in stereo in one package ( LM 1876 for example, LM 4766 etc) and there are maaaaany working
with single supply voltage, like the LA series . I've got one LA 4551 with 36 V supply. Less voltage, less power -it depends also on the load, if 4 or 8 Ω and the sensitivity of the speaker.
Now all the chips feature a stand-by mode and a muting, which you can select with a switch but mostly with digital logic
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It sounds like bridged outputs won't be a problem. Anyway, with bridged outputs, both sides of the speaker go to amplifiers which operate in opposite phase. That provides much more power from a given supply voltage, but in certain situations it's inconvenient to have both speaker wires "hot" with respect to ground.
I can't see much point in scratch-building amps when you can buy working boards from China for less than the parts would cost. The TA2024 T-amp chips have "mute" input pins, but I'm not sure how many amp boards make those available.
I can't see much point in scratch-building amps when you can buy working boards from China for less than the parts would cost. The TA2024 T-amp chips have "mute" input pins, but I'm not sure how many amp boards make those available.
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Actually you don't need a dual supply for opamps. You could easily run it off 5V and ground (0V) along with the class D amp, you'll just need a bias voltage of 2.5V. You'll probably want rail-to-rail opamps, meaning the signal at the output can swing very very close to, and in some cases even pass the supply voltage. However, nearly any opamp will do. If you use DIP chips you should probably socket them, that way you could start out with garden variety parts and easily upgrade later if need be.
Oh- another question. What is the impedance of the speakers you are using?
Oh- another question. What is the impedance of the speakers you are using?
I did mention in the first post the speakers are 4 ohms.
I have to admit I'm getting fairly lost here. I don't understand what a dual supply might even entail.
I should also mention once again that the signal phase really does matter. The whole project is based on phase shifting each loudspeaker signal.
I have to admit I'm getting fairly lost here. I don't understand what a dual supply might even entail.
I should also mention once again that the signal phase really does matter. The whole project is based on phase shifting each loudspeaker signal.
Dual or split supply voltages need a center tapped <CT> transformer or two equal transformers where the windings are connected in phase, so the central tap assumes for 0 V and after rectification with Graetz diode bridge ( same as with single supply) and ripple smoothing with 2 capacitors (mind the polarity)
you'll get a positive and a negative potential referred to 0V. With single supply you get a positive voltage referred to the negative which is fixed/defined as 0V.
The advantage of a dual supply is a slight difference in circuit's architecture and brings some benefits such as CMRR ( common mode rejection ratio ) and the opportunity of eliminating the output capacitor.
But for such low power-3W ( but for a dynamic signal the peaks may require more than double power ) the difference is small, as the output cap is not asked to transfer high current. I would focus more on building a single amplifier
that is indipendent -so no interchannel crosstalk that may happen in two-amps-on -the-same-chip (die); a little 12-0-12 V or 15-0-15 V AC(30 W)
with a diode bridge and two 1000 uF/25 V electrolytic capacitors would be handy for the first try, and it might be useful for powering preamplifiers-buffers later. A benefit you'll be finding with dual supply, is that they can be reversed to a single supply...indeed it's a single supply with a zero in the middle
you'll get a positive and a negative potential referred to 0V. With single supply you get a positive voltage referred to the negative which is fixed/defined as 0V.
The advantage of a dual supply is a slight difference in circuit's architecture and brings some benefits such as CMRR ( common mode rejection ratio ) and the opportunity of eliminating the output capacitor.
But for such low power-3W ( but for a dynamic signal the peaks may require more than double power ) the difference is small, as the output cap is not asked to transfer high current. I would focus more on building a single amplifier
that is indipendent -so no interchannel crosstalk that may happen in two-amps-on -the-same-chip (die); a little 12-0-12 V or 15-0-15 V AC(30 W)
with a diode bridge and two 1000 uF/25 V electrolytic capacitors would be handy for the first try, and it might be useful for powering preamplifiers-buffers later. A benefit you'll be finding with dual supply, is that they can be reversed to a single supply...indeed it's a single supply with a zero in the middle
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