Hi,
I'd like to build a 4 channel output power amp , with volume control using prebuilt mono boards. Required power is around 2x 40W @4 Ω for the woofer and about the same for 8Ω full range drivers. All of the drivers need to have separate amps, and will be fed from a mini-dsp crossover .
Is there a recommended (ebay) prebuilt board for building such an amp ?
My plan is to use 4 mono boards , run from a single power supply (36 v).
There is a (sure) 4ch amp on parts express : although it has 4 outs it only can have two input channels, and as I understand it will not work for this application.
I'm not sure if the single power supply is enough, assuming there will be voltage drop . I also suspect some of the pre-built amp boards might be low quality and even though cheap might not be worthwhile .
Any info appreciated.
Regards,
LXC
I'd like to build a 4 channel output power amp , with volume control using prebuilt mono boards. Required power is around 2x 40W @4 Ω for the woofer and about the same for 8Ω full range drivers. All of the drivers need to have separate amps, and will be fed from a mini-dsp crossover .
Is there a recommended (ebay) prebuilt board for building such an amp ?
My plan is to use 4 mono boards , run from a single power supply (36 v).
There is a (sure) 4ch amp on parts express : although it has 4 outs it only can have two input channels, and as I understand it will not work for this application.
I'm not sure if the single power supply is enough, assuming there will be voltage drop . I also suspect some of the pre-built amp boards might be low quality and even though cheap might not be worthwhile .
Any info appreciated.
Regards,
LXC
The only Chip which would fit your demands is the most popular ChipAmp LM3886 which delivers 68W into 4 Ohm and, depending on the Voltage, 38W @ +/-28V to 50W @ +/- 35V. So you get 40W with a little safety margin. You can get simple prebuild mono boards at ebay for about 12-20 €/$ if you want it cheap & easy, or you can invest 100 and more bucks for finest, highest Quality composite Amp Kits at, for example > Neurochrome Audio: High performance DIY audio circuits.. The choice is yours ... 
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.highest Quality composite Amp Kits at, for example > Neurochrome Audio: High performance DIY audio circuits.. The choice is yours ... .[/QUOTE]
I have looked at those and spoke with the designer; impressive and elegant to say the least, but they out of my budget.
It is hard to believe a $10 board can come close, but I treat it as a proof of concept and therefore willing to experiment.
.[/QUOTE]I have looked at those and spoke with the designer; impressive and elegant to say the least, but they out of my budget.
It is hard to believe a $10 board can come close, but I treat it as a proof of concept and therefore willing to experiment.
The mighty TDA7293 chip and it's modules also fulfill the requirements. The following video shows the ebay TD7293 module easily delivering a clean 92 watts into 4 ohms and 56 watts into 8 ohms.
YouTube
My whole town, and 20 towns around, is fed by ONE power source. (The dam at the falls, backed by a line to the City.)
When you have a lot of loads on one supply, you build a big supply.
Yeah, the folks on the Island had "voltage drop" on hot summer days. They recently ran a fatter wire out there and is fine now.
All of these consumer Surround Sound amplifiers with 7 or more channels run one big power supply.
Hi,
Following Grendel321's recommendation I found this:
TDA7293 Digital Audio Amplifier Mono Single Channel AMP Board AC 12V-32V 100W 665228655861 | eBay
Do you know of a good power supply to run 4 similar mono blocks?
Thanks,
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Before you order anything, learn everything you can about ground loops and how to prevent them causing hum.
Also check how reliable the chip is you want to use. Searching tda7293 or 4 and exploded or failed will give you some idea of what I mean.
It is important to know that the parts you are using are not fake. A fake ic or capacitor may fail.
Also check how reliable the chip is you want to use. Searching tda7293 or 4 and exploded or failed will give you some idea of what I mean.
It is important to know that the parts you are using are not fake. A fake ic or capacitor may fail.
I agree that it is important to be cautious when buying from ebay, but in my personal experience, if you buy from a reliable seller with good ratings you get the genuine item. In the video which i posted we can see the TDA7293 delivered 92 watts into a 4 ohm load without any significant distortion, which means its a genuine chip.
The seller below sells the same DIY kit and is a reputable seller, Julian Ilett, Big clive and other popular youtube electronic designers have tested his products and found them to be genuine. As i am from a poor country, I too have purchased from him for many years and found the items performed under load as expected. At the end of the day its just 8 dollars, less than the price of 2 cups of coffee.
MINI TDA7293 100W Mono Single Channel Amplifier Board Module DIY Kits | eBay
I didn't mention the TDA7293 because it has more than the double of the requestet output. I use 2 of them in parallel for my Subwoofer, and they work quite well. But, even if I never have built a LM3886 until now, I'd say the 3886 is more "musical" and easier to handle than the TDA.
One important thing: do as Mark Whitney said! Read, read everything about Chipamps you find. It will be worth it.
This would be a good start > Avoiding TDA7293 pitfalls
One important thing: do as Mark Whitney said! Read, read everything about Chipamps you find. It will be worth it.
This would be a good start > Avoiding TDA7293 pitfalls
Thanks Clueless But Avid .
From there Avoiding TDA7293 pitfalls
"A good amplifier begins with a high quality power supply. It should be capable to supply high currents while maintaining a stable voltage. Use therefore a toroid transformer. It should preferentially be potted to reduce hum. Long lasting low esr capacitors (e.g. BC components 051 or 056 series, Panasonic FC) should be used to smooth the rectifier output. The last important ingredient is proper grounding"
Can anyone link to a transformer suitable for 4 mono 7293 boards?
From there Avoiding TDA7293 pitfalls
"A good amplifier begins with a high quality power supply. It should be capable to supply high currents while maintaining a stable voltage. Use therefore a toroid transformer. It should preferentially be potted to reduce hum. Long lasting low esr capacitors (e.g. BC components 051 or 056 series, Panasonic FC) should be used to smooth the rectifier output. The last important ingredient is proper grounding"
Can anyone link to a transformer suitable for 4 mono 7293 boards?
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for music, you will rarely need the full 40w you are asking about. So I generally assume 50% duty. The TDA7294/3 chip will supply ~100w at 4r at clipping and you want 4 channels. That is a 400-watt transformer, but for me I generally spec a 160-200VA and you will have plenty of power on tap.
In the US, AnTek is a good company, that makes very capable transformers, and they have dual secondaries you can parallel and run all four channels easily. I would run this 200VA 25V transformer.
AS-2225 - 200VA 25V Transformer - AnTek Products Corp
In the US, AnTek is a good company, that makes very capable transformers, and they have dual secondaries you can parallel and run all four channels easily. I would run this 200VA 25V transformer.
AS-2225 - 200VA 25V Transformer - AnTek Products Corp
Very simple - I used a re-purposed amplifier case and the modules you linked do not require a separate PSU, they accept AC straight from the transformer.
I used a barrier/terminal strip for AC in and then combined wires for the amp modules. connected the input and outputs to the board and grounded the IEC plug to the chassis with a fuse.
Turned it on and played first time, no issues, with very very little hum from speakers. Probably could decrease the hum further with better wire/ground management, but was already very low and not worth that effort
I used a barrier/terminal strip for AC in and then combined wires for the amp modules. connected the input and outputs to the board and grounded the IEC plug to the chassis with a fuse.
Turned it on and played first time, no issues, with very very little hum from speakers. Probably could decrease the hum further with better wire/ground management, but was already very low and not worth that effort
I do not include volume controls - use my iPhone or laptop usually.
You can buy a 50k pot (dual gang) and include a passive volume control. If you want to add a buffer/gain, I would just buy a volume control board from eBay.
link to a passive on eBay (have not used it) - Amplifier / Preamp Passive Tone Board Volume Control Sound Enhanced 09 ALPS-16 | eBay
to use an active pre-amp, you will need another transformer/secondary, usually with dual 15V, but check the specs of the preamp, some will work with 12V.
You could also go with a larger AnTek Transformer, 400VA with 28V secondaries and it will have dual 15V secondaries as well.
200VA 25V is $32.00 versus 400VA 28V is $51.00 - up to you if it's worth the extra $$$$.
You can buy a 50k pot (dual gang) and include a passive volume control. If you want to add a buffer/gain, I would just buy a volume control board from eBay.
link to a passive on eBay (have not used it) - Amplifier / Preamp Passive Tone Board Volume Control Sound Enhanced 09 ALPS-16 | eBay
to use an active pre-amp, you will need another transformer/secondary, usually with dual 15V, but check the specs of the preamp, some will work with 12V.
You could also go with a larger AnTek Transformer, 400VA with 28V secondaries and it will have dual 15V secondaries as well.
200VA 25V is $32.00 versus 400VA 28V is $51.00 - up to you if it's worth the extra $$$$.
OK, computer volume will do for now. I read about the disadvantages of wood cabinet. What if the box was wood but laminated with sheets of metal inside? Twis way construction would be much easier than bending metal and alas much cheaper too . Aesthetically I like wood on the outside . Main concern would be if this provides adequate shielding . I'm also concerned about safety - maybe its better to stick to steel just for that reason , plus heat sissipation will be much better.
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wood case with metal will work just fine.
I made a wood case, and laid a 1/16" thick sheet metal (bought a sheet from big box store and cut to size) screwed to the wood case floor. Connected IEC ground and SMPS ground to the metal floor, then all other grounds back to the amp board. worked great.
Compared to a full wood case, with a single "star" ground connection for everything, the metal floor case was much quieter with less hiss. Exact same set-up, just different grounding scheme... plus much easier to wire.
Better ventilation can be easily achieved by cutting some holes/slits in the top and/or bottom of the wood case. I have had no issues with heat.
I made a wood case, and laid a 1/16" thick sheet metal (bought a sheet from big box store and cut to size) screwed to the wood case floor. Connected IEC ground and SMPS ground to the metal floor, then all other grounds back to the amp board. worked great.
Compared to a full wood case, with a single "star" ground connection for everything, the metal floor case was much quieter with less hiss. Exact same set-up, just different grounding scheme... plus much easier to wire.
Better ventilation can be easily achieved by cutting some holes/slits in the top and/or bottom of the wood case. I have had no issues with heat.
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