Hey Chip amp family,
I am putting together a 24ch amplifier for an active line array. Long story but most channels will only ever see <1W. Running 24 drivers per side, in 2P. 4ohm load for each amp channel. Crossed over around 125hz.
I settled on this TDA7850 IC. It looks like a great little amplifier that needs very few external parts. There are complete boards available on AE for $5/6, but questionable whether they're using authentic parts.
I found a nice clean layout on OSHW that I was able to make small adjustments to. this way I can include quality parts. I'm going to try out JLCPCB's assembly service, so I had to source the parts through LCSC, which is mildly annoying. Did my best. BOM is below.
Total for 10 boards fully assembled is looking like $75 (shipping to US another $30). I only need 6 pieces for my project, but orders are in mult. of 5.
Any tips you can share or issues you see are greatly appreciated. I am operating way out of my level of understanding- I can connect nets and the board looks logically like it could work-but I don't actually have a background of real EE knowledge+experience to troubleshoot. Thanks for your time!
I am putting together a 24ch amplifier for an active line array. Long story but most channels will only ever see <1W. Running 24 drivers per side, in 2P. 4ohm load for each amp channel. Crossed over around 125hz.
I settled on this TDA7850 IC. It looks like a great little amplifier that needs very few external parts. There are complete boards available on AE for $5/6, but questionable whether they're using authentic parts.
I found a nice clean layout on OSHW that I was able to make small adjustments to. this way I can include quality parts. I'm going to try out JLCPCB's assembly service, so I had to source the parts through LCSC, which is mildly annoying. Did my best. BOM is below.
Total for 10 boards fully assembled is looking like $75 (shipping to US another $30). I only need 6 pieces for my project, but orders are in mult. of 5.
Any tips you can share or issues you see are greatly appreciated. I am operating way out of my level of understanding- I can connect nets and the board looks logically like it could work-but I don't actually have a background of real EE knowledge+experience to troubleshoot. Thanks for your time!
Amazon is selling the boards in India, so no need to get them made, seem to be a generic item.
Assembled (populated), and bare PCB seem to be available at some time, I did not look too closely as you are not in India.
The other parts should be available from reputed vendors.
The best way would be to accept the ready built boards, or assemble them yourself if you are choosy about parts quality.
Assembled (populated), and bare PCB seem to be available at some time, I did not look too closely as you are not in India.
The other parts should be available from reputed vendors.
The best way would be to accept the ready built boards, or assemble them yourself if you are choosy about parts quality.
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Generic TDA2030A and LM1875 boards are less than $1.50 each here, fully populated.
That is $30 or so for 24 boards, plus shipping.
That is $30 or so for 24 boards, plus shipping.
That’s good to know. I’m really looking for feedback on the board design, parts, and placement.
Low cost isn’t the only factor especially since this is still under $100. I would rather spend extra to know I’m getting something that can operate near hi-fi level quality.
$30 on an unknown vs $75 to know I’m using original premium parts is probably good money to spend.
The ready boards work well enough for others to appreciate, some comparisons are here on this forum. Nearly hi fi.
Sound quality depends on your expectations really.
Your board is a generic, BOM may be in data sheet, it is simple enough to assemble by a person who knows minimal soldering, and all parts are commonly available, no surprises there.
You can compare boards from different vendors to check for layout.
But all said and done, the chips are well reputed, so it is your decision which to use.
Sound quality depends on your expectations really.
Your board is a generic, BOM may be in data sheet, it is simple enough to assemble by a person who knows minimal soldering, and all parts are commonly available, no surprises there.
You can compare boards from different vendors to check for layout.
But all said and done, the chips are well reputed, so it is your decision which to use.
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Yeah I’m sure It would be successful duplicating the schematic/sample board from the datasheet. However I feel like there are nuances that having an expert look over it might catch. Maybe I’m using the wrong type of capacitor somewhere? Or using a cheaper one would be sufficient? Things like this the datasheet doesn’t go over.
Capacitors are cheap, go for regular Japanese, or Vishay, not fancy audio types. Film caps, again regular quality, not military grde, are enough.
Resistors, again, good are enough, not super precise ones.
The power supply, and origin of the chip amps, are the main issues here.
And do put too big a heat sink.
Resistors, again, good are enough, not super precise ones.
The power supply, and origin of the chip amps, are the main issues here.
And do put too big a heat sink.
Just for fun, I also did a layout.
It uses the H version of the chip and is designed to fit directly onto a Fischer SK08-100-SA heatsink.
But in principle any suitable heatsink with a flat back and larger than 88x100mm will do.
The PCB is then mounted above the IC with 6mm standoffs.
Power supply caps are 20x SMD 1000µ 16V low ESR (e.g. Panasonic SVPF), plus 2x ECPU 1µ 16V closest to the supply pins.
ACG cap is WIMA MKS02 1µ, SVR cap is Nichicon UKA 100µ 16V.
And star Gnd also very close to the chip.
High current connections are Molex 0.325" screw terminal strips.
Input coupling caps WIMA MKP2 330n 63V.
The R/C's for Mute and Standby are of no sonic importance and are just standard 1206 SMDs.
A 2-wire connection is added to allow manual muting externally.
Pin 25 is connected to 10k to Gnd in parallel with an LED+R.
Certainly not the lowest cost solution. 🙂
Ebay has plentys of those to offer.
Cheers,
Patrick
It uses the H version of the chip and is designed to fit directly onto a Fischer SK08-100-SA heatsink.
But in principle any suitable heatsink with a flat back and larger than 88x100mm will do.
The PCB is then mounted above the IC with 6mm standoffs.
Power supply caps are 20x SMD 1000µ 16V low ESR (e.g. Panasonic SVPF), plus 2x ECPU 1µ 16V closest to the supply pins.
ACG cap is WIMA MKS02 1µ, SVR cap is Nichicon UKA 100µ 16V.
And star Gnd also very close to the chip.
High current connections are Molex 0.325" screw terminal strips.
Input coupling caps WIMA MKP2 330n 63V.
The R/C's for Mute and Standby are of no sonic importance and are just standard 1206 SMDs.
A 2-wire connection is added to allow manual muting externally.
Pin 25 is connected to 10k to Gnd in parallel with an LED+R.
Certainly not the lowest cost solution. 🙂
Ebay has plentys of those to offer.
Cheers,
Patrick
You make it look so easy! Im hoping mine works out ok. I had to swap out most of my original bom because the assembly service interface was very picky.
Are you able to sell/share your design+bom? Id feel much better having an expertly made one even if it means purchasing another batch.
I’ll see if I can pull up the final bom from my order, would you be able to review it for any major faults? I intended to keep it all as through hole in case I chose poorly somewhere.
I'll let you know when we want to order a batch.
Then you can have one at cost.
Patrick
Then you can have one at cost.
Patrick
Thats a very kind offer that I will take you up on. I need 6 and a few spares though 🙂
If you can't find a reliable supplier.
You can contact me LJM_ LJM@FOXMAIL.COM
I don't care about making this little money. But I have many such amateurs. You can help by the way.
From PCB processing to IC production, Chengdu can.
Of course, you can arrange it yourself. If you have any questions, please consult me.
You can contact me LJM_ LJM@FOXMAIL.COM
I don't care about making this little money. But I have many such amateurs. You can help by the way.
From PCB processing to IC production, Chengdu can.
Of course, you can arrange it yourself. If you have any questions, please consult me.
Ugh I just reviewed my order and they aren't including the actual TDA7850 IC, only had 8 pieces on hand so it was marked DNP.
So it was a good practice run at ordering (ugh) and I'll have 10 mostly-complete boards to play around with in a few weeks.
So it was a good practice run at ordering (ugh) and I'll have 10 mostly-complete boards to play around with in a few weeks.
if possible. You can send a PCB file to my email.
I also make some pieces to try. I can also help you with APSYS 2722 measurement data.
This thing is very simple for me. So I'm too lazy to design it.
LJM_LJM@FOXMAIL.COM
So I see that it is not your own PCB, but an open source one at easyeda :
https://easyeda.com/modules/TDA7850-STPA00x-PCB_3cb6451df8254b5993574f088ee6ae81
https://oshwlab.com/bassblaster505/tda7850
Patrick
https://easyeda.com/modules/TDA7850-STPA00x-PCB_3cb6451df8254b5993574f088ee6ae81
https://oshwlab.com/bassblaster505/tda7850
Patrick
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i see. But I think this PCB can be modified.
Some welding places are too small. Easy to damage.
Yes I mention that in the first post. I did a layout of my own but it was nowhere near as clean as this one. I have no commercial intent, so afaik I’m ok to use and modify it under the license.