DIY class D kit suited for 21ch multiroom amp?

Crest

Member
2018-05-31 2:49 pm
Hi all,

during the renovation of my house, 21 ceilling speakers have been installed and centrally wired to implement a multi-room audio system (there will be a dedicated system for high quality audio). Now, I am planning the required 21 channel amp. I read a lot about different class D boards, especially of the 3116/18 family, but I am not an expert and I hope you can help me selecting a sufficient chip/board.

Current state is as follows:
- source of the amp will be a PC (i.e., raspberry) with three 8Ch external sound cards
- speakers will mainly be Magnat Interior IC 82 ceilling speakers (100/180 watts, 4-8 ohms), a few Visaton DL10 and Sonance VP52R UTL

A design goal is to keep the power consumption low. Therefore, I am looking for a solution based on class D amps that can be muted to further reduce the power consumption if the amp is not needed.

A few years ago, somebody was building such an amp using 3118D2 PBTL mono boards, e.g., . DC 8-26V TPA3118 PBTL Mono Digital Amplifier Board AMP Module 1*60W for Ard D9J3 191466823774 | eBay

Of course, these boards are quite cheap and they have a mute connector, but the caps are only 25V and the 3118 have no heatsink. Therefore, and because its now a few years later, I am trying to find out whether there are chips or boards that are better suited to my project.

Although I can replace a capacitor or remove a resistor, the board should not need major changes, since a have no experience in designing amps. Moreover, I neither need bluetooth nor a volume potentiometer.

Possible alternative amp boards I identified based on discussions here of this forum are:
- boards based on the design of Danzz, e.g., JINSHENGDA TPA3116D2 50Wx2 Offizielle Version Fertig Stereo Digital Power Verstarker Bord-in Verstarker aus Verbraucherelektronik bei AliExpress or Yuan Jing Audio - ON SALE! - TPA3116 Class-D 2.0 Stereo Amplifier Board [50W+50W] - USD $17.99 (which seem to have 25V capacitors, too?)
- boards based on the XH-M590 design, e.g., TPA3116D2 Digital Audio Amplifier Board 2-CH Large Power AMP DC 12-24V 2 * 100W | eBay
- HW-447 such as DC5-28V 120Wx2 TPA3116D2 High Power Digital HIFI Amplifier Board Module | eBay

Unfortunately, I could not find out whether these boards have a mute connector or not. What do you suggest? Is the PBTL mono board still the way to go, or are there better (newer) boards based on the 3116/18 family, or is the 3116D2 chip outdated and amp boards with better (more efficient, better audio quality, easier design) chips available in between?

Many thanks and best regards,
Crest
 
Please look at the 4 Ohm RMS output with .1% distortion of these amps. You will not see more than 50W. As you have to consider quite some resistance from the wires leading to the load, it will be even less at the speaker.

To keep power under the clipping level even when over driving them by mistake (party mode?) , you might consider the TDA7498E instead. Prices are only a few $ more for it.
It has, IMO, a more stable and stronger bass and sound just as good as the 3116 in details.
I have very good experience with this board, an advantage is it´s switchable gain.
TDA7498E Dual 160W 2 Channels Digital Audio High Power Amplifier Board Module | eBay
Much cheaper at aliexpress.
I never managed to get the fan running, it stays cool.

The potentiometer is very convenient tool to set a maximum room/speaker level. If you rely on the sound card as a limiter, you can destroy a set of speaker on the other side of the house with a mouse click.

As low energy is a concern, you should use a SMPS. In your case I would use one of these (price is for 3 of them!). They are cheap but very reliable and easy to wire up. Because (crest factor) music never draws constant current, two amps will be well feed with such a constant 180W (250W peak) supply for two amps. Also, these boards have a very well sized capacitor array and store quite some energy for peaks.

3X(AC DC Inverter Module 110V 220V 100 265V to 36V 5A Adapter Switching K7A5) 191466821305 | eBay
Maybe cheaper at aliexpress.
For 22 channels, this makes 11 amps and 6 power supplies. Maybe, for lower level, 3-4 supplies will be enough. Get one amp and SMPS as a backup, sometimes such mass build electronic´s fail after a few hours/ on off cycles.

If you order from China, check tax free limits for your region. In the Eu we can order up to 25 US$ incl. P&P free. So we better don´t order 6 amps, but maybe place 6 orders over a few days (as the Chinese sellers often combine single orders without notice, which will cost you an additionell 25-30% tax and travelling to the customs office!).
Usually orders from China take 10-25 days.

One important hint: I would use twisted wires running to the speakers, as they do not produce and catch so much electromagnetic dirt as two conductors running in parallel.

PS usually you can solder a mute line at the underside of the board.

PPS These amps are high quality audio, even if that hurts owners of expensive amps.
 
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Might be interesting to look at the minidsp pwr-16, that gets you 16 channels in a std chassis, you could then get remaining five channels from a home theater power amp or buy 3 icepower 50asx boards from parts express.
If I had gone through the trouble of installing 21 speakers in my house I would not be dealing with Chinese boards bought on eBay :)

If you have a bigger budget take a peek at the new NAD distribution amps
 
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Crest

Member
2018-05-31 2:49 pm
Hi Turbowatch2,

many thanks for your quick feedback. I just read the infos about the 7498(E) which took a while...

Please look at the 4 Ohm RMS output with .1% distortion of these amps. You will not see more than 50W. As you have to consider quite some resistance from the wires leading to the load, it will be even less at the speaker.
First two general questions: Where do you get this info from? I read the spec of the 3116D2 and could only find the info that in PBTL mode you get with 24V and 3Ohms about 85W with 1% THW. Is there a general rule how to calculate the RMS output with 0.1%, or have you measured it? Secondly, is [email protected] per channel in your opinion really to low for ceilling speakers? They will mainly be used for background music, of course a little bit louder during a party. But my expectation was that [email protected] or [email protected] are sill enough...

To keep power under the clipping level even when over driving them by mistake (party mode?) , you might consider the TDA7498E instead. Prices are only a few $ more for it.
It has, IMO, a more stable and stronger bass and sound just as good as the 3116 in details.
I have very good experience with this board, an advantage is it´s switchable gain.
TDA7498E Dual 160W 2 Channels Digital Audio High Power Amplifier Board Module | eBay
Much cheaper at aliexpress.
I never managed to get the fan running, it stays cool.
Looks very interesting, thank you. My only concern is, as mentioned above, that I will never use the power of this amp with ceilling speakers.

The potentiometer is very convenient tool to set a maximum room/speaker level. If you rely on the sound card as a limiter, you can destroy a set of speaker on the other side of the house with a mouse click.
The raspberry will be controlled by a logitech media server, so there is no risk that somebody can directly destroy a speaker. I read that a poti can reduce the sound quality, therefore I tried to get a board without. But of course I can try and remove it if I really get problems with it.

As low energy is a concern, you should use a SMPS. In your case I would use one of these (price is for 3 of them!).
Yes, I planned to use SMPS. For safety reasons, I planned to use a high quality product, e.g., from Meanwell. Are these modules form aliexpress reliable enough? Is it, in general, possible to connect even more amps to one SMPS, e.g., if I use a 10A one?

One important hint: I would use twisted wires running to the speakers, as they do not produce and catch so much electromagnetic dirt as two conductors running in parallel.
This is too late now. During renovation, 3x2,5mm2 NYM cables have been used. Of course, the PE will not be used, but 3x2,5mm2 was cheaper than 2x2,5mm2...

Another question: In two rooms, I want to use four speakers with two cables. With the 3116 in PBTL mode I planned to connect them in parallel, but with the 7498E it would be better to connect them in series, right?

Many thanks,
Crest
 

Crest

Member
2018-05-31 2:49 pm
Hi cph2000,

Might be interesting to look at the minidsp pwr-16, that gets you 16 channels in a std chassis, you could then get remaining five channels from a home theater power amp or buy 3 icepower 50asx boards from parts express.
Thanks for the hint. In general, such a multi-channel amp is a good alternative. However, this amp seems to be out of stock. The website is not correctly working and it is not available on amazon any more..
Moreover, I read that it can only provide continuous output of [email protected] for all channels. Isn't this a little bit low? According to Turbowatch2 above, 50W/channel could be too low..

If I had gone through the trouble of installing 21 speakers in my house I would not be dealing with Chinese boards bought on eBay :)
Why?

If you have a bigger budget take a peek at the new NAD distribution amps
Typically, ceilling speakers do not provide a very good audio quality, therefore NAD amps are IMO too expensive compared to what they have to deliver.

Best regards,
Chris
 
You wrote that your speakers where 100-180 watt 4-8 ohms.
You can have a look in the amp chips data sheets. There you find diagrams for power, distortion etc. in any resistor / power supply configuration.

Speakers are usually destroyed by clipping amps, not by to much program power.
If you equalize just a bit, the 3116 will run out of steam very soon. If the control amp is far away from the loudspeaker, you may easily distort this small amp.
Sure you will have only low background music most of the time. This is true for almost any HIFI speaker. It is always this last half hour of a party, that burns your tweeters.
So having some more headroom might pay off.

I have both D-amps, a good implementation of the 3116 and the 7498E. The second amp, driving a serious speaker, has a much better bass control.

If I run trough the trouble of wiring up a dozen amps, I will not think about 80 $ more for a more solid product.

The power supplies I showed you, are some of the most sold on all platforms. They are cheap, but a very good, reliable design.
It is up to you what you prefer, one large expensive or 3-5 small power supplies. I would plan for at least 50 W of constant supply power for each stereo amp. So if you take 3 of the 36V 7A version, each should give enough program power for 4 amps.
Personally I do not like to be on the weak side.

Because of the long wire runs and the 8 Ohm speakers, an amp optimized for 2 ohms does not deliver much voltage in a high resistance load. So your 100W/2 ohm amp will not even give 25 W into 8 ohm speaker.
Sure, you can parallel some speakers, but then you lose individual volume control.
NAD distribution amps will not give better sound quality than these chips, but cost multiples. Convenience is expensive.

PS NAD has always produced in the far east. Most of their gear is made in China internally. So what is the difference? Nice case, high price tag.
 
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Crest

Member
2018-05-31 2:49 pm
Hi Turbowatch2,

You wrote that your speakers where 100-180 watt 4-8 ohms.
You can have a look in the amp chips data sheets. There you find diagrams for power, distortion etc. in any resistor / power supply configuration.
As I already wrote, I already read the data sheet of the 3116D2. While re-reading it, I just noticed the diagrams "Total Harmonic Distortion + Noise (xxx) vs
Output Power". According to them, the THD heavily increases (4 ohms, 24V) between 50W and 60W. In contrast, the THD of the 7498E is higher than 0.1% between 70W and 80W at 36V. Is this a correct interpretation of the figures (sorry for these beginner questions...)?

If I run trough the trouble of wiring up a dozen amps, I will not think about 80 $ more for a more solid product.
:) I don't care about the $80, but I want to understand what I do and why. Therefore, your comments are very helpful.

The power supplies I showed you, are some of the most sold on all platforms. They are cheap, but a very good, reliable design.
It is up to you what you prefer, one large expensive or 3-5 small power supplies. I would plan for at least 50 W of constant supply power for each stereo amp. So if you take 3 of the 36V 7A version, each should give enough program power for 4 amps.
I understand and agree that 36V/7A would be a good compromise. Another advantage of smaller SMPS is that I can turn them on/off more fine granulated. Nevertheless, I have two issues with the modules you suggested. Firstly, it is not enclosed in any way, which makes is a little bit more dangerous to work with them (compared to a laptop smps, for example). Secondly, there are neither safety functions nor a PFC-function documented.

Are you aware of alternative SMPS modules that fulfill more of these requirements, e.g., similar to the HRP line of Meanwell? I could only find a 48V model with this properties: Ac zu dc SMPS PFC funktion 350w schalt netzteil 13,5 V 25a led treiber quelle schaltnetzteil 13,5 volt-in Schaltnetzteil aus Heimwerkerbedarf bei AliExpress

Many thanks & best regards,
Crest
 
I use two well working varieties of the 3116 amps and the pictured 7496E board. They all sound very good in the high/ mid range. Much better than most amps of the past and many amps multiples of their price. They have been extensively tested, used and modified by forum members and are some of the better implementations of these chips.

The 7496E has better control of the bass chassis. I first wanted to use 3116, but switched to 7496E because of it´s better sound quality with woofers.
Please notice, there may be other, more expensive 3116 boards around, that should (theoretically) be able to match the 7496E´s bass performance at low levels if you look at data sheets, but I wanted to keep cost limited.

I do not care that much about some data that are measured with some reverence board, but judge what I have on my table. I use my ears for a final conclusion when it comes to amps. There are a million amps around, that measure perfect and sound awful.
Any amp has rising THD with falling output. At some mV any noise that is generated by electronic components, PS, power grid, phones or what ever, adds to the music signal. If you hold the tweeter directly to your ear, almost any amp will have a weak hiss. This is not the signal at the input. Because of this fact, you measure at, for example 1 watt. You will not be able to hear this hiss at any normal listening distance, even half a meter away, with speakers on your desktop.
On the other end, with high power output, any amp starts to distort the closer the output signal gets near the supply voltage. For real listening 1% distortion can be seen as an audible limit, with sub woofers even 10% may be tolerated. Important for the sound you really hear is how these distortions are placed in the spectrum. If there was a fixed % number, no one could listen to a tube amp, as most produce quite a lot of distortion with music. With a good design they just fit well into the signal.
If you think you can hear the distortion you see on the data sheet, go for another chip, or buy one of them, add the cheap power supply and listen to them. Take a really good loudspeaker and use a CD or other high quality signal (not high compressed MP3). If you can afford to spent 25$, the way to know for sure. Anything bought at eBay or Ali-e, to some extent, is experimental.
For a test, you can even risk to use a PS that has not all the fancy safety logos printed on them. You have set up such an amp on a board, with a screwdriver and some wires, in 12 ½ minutes.
Please don´t ask me what I think about anything printed on a Chinese Ali express part. Some cultures have the habit of copying anything, if they see profit. Also, they ignore Western legal standards as a hobby. If you feel safer with a colorful TÜV, VDE or whatever sticker, buy a Chinese product with it or make one by your self and attach it, practical value is the same. Maybe send the sellers an email and ask for any documentation. Good luck!

I would advise you to get some kind of metal housing for the amps, as they (any D-amp!) might radiate EMF. So it does not really care if the PS is closed, as you will enclose it anyway. Because of EMF I advised to use twisted wire if practical.

None of these amp modules has anything of value documented. They are only parts, not functioning appliances, that is why you can import them in the EU. If you go by EU laws, you are not even allowed to power them up or give them to any other person in working order. You first have to have your finished product tested and certified by an institute like the TÜV. DIYS is not for anyone...
If you want to stay 100% legal, buy a finished amp, like the NAD or look at Monacor.

The power consumption of these amp/ SMPS combinations at idle is ridiculous low. From the ecological standpoint, you can leave them on all year long. The 365 day consumption is about the same your coffee maker needs to power up and make one single latte. Never the less do I switch of anything not in use. It´s up to you.
 
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Crest

Member
2018-05-31 2:49 pm
Hi Turbowatch2,

the amp will be installed into one (or more) 19" cases which themselves will be mounted to a 19" rack. As said, I prefer the use of a SMPS with some basic safety features, maybe also with the PFC function.

Interesting are the HRPG series from meanwell, since they provide several safety functions and a standby mode that uses only 0,5W (I don't like systems consuming a lot of energy if not used). The 324W model is about 80€.

Maybe someone is aware of a similar alternative from another vendor?

Best regards,
Crest
 

Bergarth

Member
2018-07-03 9:11 pm



This is a very interesting thread. I've been hunting for a solution to my problem also. A 12 channel class D is hard to find and the cheapest one I found is Dayton Audio for $600. I'm going to order some- is there a Noob guide for hooking all this stuff up?

Sofar I have 6X TDA7498E boards linked.
2X ----3X ac dc inverter modules linked...what else would you recommend?

Or better yet sofar my cart total is $159USD, I have a $250-$300 USD budget- so I'm open to suggestions.
 
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Basically this is quite easy, if you can read and don´t have a tendency to "try" things, instead of sticking to rules.
Such an amp should meet some safety standards. So, if for some reason it burns out, it should not inflame anything outside of it´s box. So a metal housing is a good idea, wood not.
This brings up electrical safety: The metal housing should be connected to the power grid´s earth. This makes sure the breaker get´s into action if any dangerous part touches the inside.
If you have addressed this part, another problem, the electro magnetic radiation (EMF) should be under control too.

Then the audio part. The enemy number one of any amp builder is hum, noise, anything that you can hear when no music is playing.
As the AC wall power in your life (120 Volt /60Hz in the US, 230 Volt/50 Hz in most of Europe) is alternating between +and - 60 times per second, a hum of 60 and 120 Hz is everywhere.
The trick is to power an amp with this AC, but not let any of it to the loudspeaker.
You can reach this aim if you stick to some rules that are common practice with audio designers (you are an audio designer if you start building amps). You will find problems with hum in any amplifier thread here. Only one earth wire wrong can make the difference between complete silence and annoying noise from the speaker.
It is no real problem to get these amp modules silent. In most (all?) cases the builder "thought" something had to be done "that" way. If you simply stick to the rules, you should have no unsolvable problem with this.

The simple rule is not to form any circle with ground wires. An easy way to get anything right is to have a single ground point, where all ground wires are connected.

Then, to keep electro magnetic fields from radiating, all wires should be drilled together. I attach a picture, where you can see this.

If you go with these TDA7498E boards, you will only have input, output and power wires to twist. Keep the input away from the SMPS a few inches and you are fine.

This is only the amp. Sometimes the signal source can add problems to a perfectly silent amp, so this should always be considered as part of the system, but to any problem in audio there is at least one solution...
 

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