Hi guys, I'm looking to build the smallest 5 channels audio amp for a home theater system.
I have decent regular speakers (4 x KEF Cresta II and 1 GALE center) and a AE dolby decoder.
Now I'm using a huge H-K home theater amp. which is not passing the wife test after renovating my living room...
So I would like to build a decent somehow 15 to 20 watts per channel 5 channels amp. I've been working and fixing many vintage stuff for some years now and am perfectly able to build this kind of amp. (I've MOSFETTED a H-K CT12 per Mr Nelson Pass design using old Hitachi MOSFET and am very happy with the results BTW).
I'm looking for a good design that would be small. That brought me to the chipamp area. I have many toroidal trannies, bridges, capacitors, etc. Power supply is not a problem. I'm just looking for the amp section. As I wrote, I'll be using an AE dolby decoder who will serve as preamp. No treble neither bass control. And I'm not putting in a sub. so bass will have to come in front L + R speakers.
I've tried looking into this section but thought I could save time asking directly.
Thanks for any help!!!
I have decent regular speakers (4 x KEF Cresta II and 1 GALE center) and a AE dolby decoder.
Now I'm using a huge H-K home theater amp. which is not passing the wife test after renovating my living room...
So I would like to build a decent somehow 15 to 20 watts per channel 5 channels amp. I've been working and fixing many vintage stuff for some years now and am perfectly able to build this kind of amp. (I've MOSFETTED a H-K CT12 per Mr Nelson Pass design using old Hitachi MOSFET and am very happy with the results BTW).
I'm looking for a good design that would be small. That brought me to the chipamp area. I have many toroidal trannies, bridges, capacitors, etc. Power supply is not a problem. I'm just looking for the amp section. As I wrote, I'll be using an AE dolby decoder who will serve as preamp. No treble neither bass control. And I'm not putting in a sub. so bass will have to come in front L + R speakers.
I've tried looking into this section but thought I could save time asking directly.
Thanks for any help!!!
For 20watts you could do some Chipamp's or you can do a current boosted opamp design like I have done here,
http://www.diyaudio.com/forums/chip...own-supply-what-could-happen.html#post3695968
Although that one is not a final design but it worked great!!
If you wanted extreme performance at 20watt's there is a design in these threads that uses something like 4 or 8 LT1210 that are in parallel, this would be costly though.
Here is a great circuit I made using a LT1210,
http://www.diyaudio.com/forums/soft...re-capacitor-impedance-graph.html#post3848338
A Mini Aleph Class A amp comes to mind including Elvee's Class A amp that uses LM317/337 regulator chips is a possibility for that power range.
I once had a small comercial 5ch. HT amp that use the TDA2030's or TDA2040's in it and it sounded okay.
The highest power TDA2050 is a 32watt (50watt) amp in that series.
It just went out of production but there are plenty to be found inexpensively.
It is in a nice and compact 5 pin TO-220 package.
The possibility's are endless.
Maybe some thing like A MY-Ref amp would be good as it is in the 50 to 70 watt range, it uses the LM3886.
The LM4780's are dual Lm3886's for less space would work good.
A My-Ref design could be made with the LM1875 20watt chip as well.
Just a few thoughts,
FWIW
jer 🙂
http://www.diyaudio.com/forums/chip...own-supply-what-could-happen.html#post3695968
Although that one is not a final design but it worked great!!
If you wanted extreme performance at 20watt's there is a design in these threads that uses something like 4 or 8 LT1210 that are in parallel, this would be costly though.
Here is a great circuit I made using a LT1210,
http://www.diyaudio.com/forums/soft...re-capacitor-impedance-graph.html#post3848338
A Mini Aleph Class A amp comes to mind including Elvee's Class A amp that uses LM317/337 regulator chips is a possibility for that power range.
I once had a small comercial 5ch. HT amp that use the TDA2030's or TDA2040's in it and it sounded okay.
The highest power TDA2050 is a 32watt (50watt) amp in that series.
It just went out of production but there are plenty to be found inexpensively.
It is in a nice and compact 5 pin TO-220 package.
The possibility's are endless.
Maybe some thing like A MY-Ref amp would be good as it is in the 50 to 70 watt range, it uses the LM3886.
The LM4780's are dual Lm3886's for less space would work good.
A My-Ref design could be made with the LM1875 20watt chip as well.
Just a few thoughts,
FWIW
jer 🙂
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That is a quite efficient and good sounding class AB amp indeed.
It can be made very small. I even have PCB designs that could fit your needs.
Got lots of measurements of THD IMD and so on. But i have to find them first.
I have currently listening to this: Posr#42 http://www.diyaudio.com/forums/chip...n-supply-what-could-happen-5.html#post3696344 But I used NJW0281G / NJW0302G as outputs and MJE340/50 as drivers.
You may try this outputstage too because this one is ultra efficient class AB and delivers 1W at 0.0007% THD+N
The design belongs to Mr palstanturhin.
It can be made very small. I even have PCB designs that could fit your needs.
Got lots of measurements of THD IMD and so on. But i have to find them first.
I have currently listening to this: Posr#42 http://www.diyaudio.com/forums/chip...n-supply-what-could-happen-5.html#post3696344 But I used NJW0281G / NJW0302G as outputs and MJE340/50 as drivers.
You may try this outputstage too because this one is ultra efficient class AB and delivers 1W at 0.0007% THD+N
The design belongs to Mr palstanturhin.
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LM4781 has three amplifier per channel, roughly equivalent to 3xLM1875 in a single package.
I think two of those will be enough for an HT system, the additional channel can be used for the .1 channel.
With decent sinks, you should get about 25W per channel out of them. They say 35, but I wouldn't bet on it. Keep the rails below 25V if possible for 6 ohm speakers, for 4 ohms you may need to drop it to 20V.
No PCBs are available so you have to roll your own. There's a nice Italian site with a single-sided design.
I think two of those will be enough for an HT system, the additional channel can be used for the .1 channel.
With decent sinks, you should get about 25W per channel out of them. They say 35, but I wouldn't bet on it. Keep the rails below 25V if possible for 6 ohm speakers, for 4 ohms you may need to drop it to 20V.
No PCBs are available so you have to roll your own. There's a nice Italian site with a single-sided design.
Well thanks a lot!
After quick looking, the LM4781 seems the smallest and easiest way to go... Thanks sangram!
On the datasheet here:http://www.ti.com/lit/ds/symlink/lm4781.pdf they show a double sided PC board layout. Can one of you tell me where I could have 2 made?
And Mikhus, can you show me how big is your PCB? Can be quite small too...
But I'm still open to opinions! Ain't decided yet...
Thanks again!
After quick looking, the LM4781 seems the smallest and easiest way to go... Thanks sangram!
On the datasheet here:http://www.ti.com/lit/ds/symlink/lm4781.pdf they show a double sided PC board layout. Can one of you tell me where I could have 2 made?
And Mikhus, can you show me how big is your PCB? Can be quite small too...
But I'm still open to opinions! Ain't decided yet...
Thanks again!
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45x63mm
Its quite large compared to LM4781 but has better perfomance and is well balanced.
I would like to see that single sided board for LM4781. How could you possibly fit that on single sided board?
Its quite large compared to LM4781 but has better perfomance and is well balanced.
I would like to see that single sided board for LM4781. How could you possibly fit that on single sided board?
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^^ here it is: Servisystem • Ver Tema - LM4781 - 3 X 35W (L + R + Sub Woofer) [DIY]
I'm quite amazed at it too, and can't verify that it works. I had a buddy print out a board but haven't yet tested it.
There's a link to a pdf.
I might want to add that these chips - LM4780, 4781, 4766, with more than one amp in the package - can get super toasty. The board may be small, but don't assume the heatsinks will be tiny. If you want it really compact, you'll get more savings by using lower voltage and smaller sinks than trying to find the most physically compact board.
I'm quite amazed at it too, and can't verify that it works. I had a buddy print out a board but haven't yet tested it.
There's a link to a pdf.
I might want to add that these chips - LM4780, 4781, 4766, with more than one amp in the package - can get super toasty. The board may be small, but don't assume the heatsinks will be tiny. If you want it really compact, you'll get more savings by using lower voltage and smaller sinks than trying to find the most physically compact board.
Yes, for a small footprint and high quality you can't beat the current boosted opamp design.
And you don't need anymore than a +/-18v power supply either for 20 watts in to 4 ohms.
Although it does require a 17.88Vpeak signal in to 8 ohms so a +/- 22V supply may be in order.
Make sure you use an opamp rated for that high of a voltage as there are many to choose from in dual and quad packages for that range.
A bridged configuration is another way to get a higher voltage swing to the load with a lower supply voltage as well.
Take a look at this LM1876 My_Ref design,
http://www.diyaudio.com/forums/chip-amps/184165-miniref-schematic-pcb-layout.html#post2505819
Read through the whole thread as there might be more later revisions.
jer 🙂
And you don't need anymore than a +/-18v power supply either for 20 watts in to 4 ohms.
Although it does require a 17.88Vpeak signal in to 8 ohms so a +/- 22V supply may be in order.
Make sure you use an opamp rated for that high of a voltage as there are many to choose from in dual and quad packages for that range.
A bridged configuration is another way to get a higher voltage swing to the load with a lower supply voltage as well.
Take a look at this LM1876 My_Ref design,
http://www.diyaudio.com/forums/chip-amps/184165-miniref-schematic-pcb-layout.html#post2505819
Read through the whole thread as there might be more later revisions.
jer 🙂
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The nice thing about the current boosted opamp designed is that you can bias the output stage high so that it runs in to the class A region for the First watt or so.
jer 🙂
jer 🙂
Hey Mihkus, the LM4781 use a double sided board. Not single.
Do you have boards of this cct. made I could buy ? I tend to have more confidence to regular NPN/PNP stuff... Strange in the chipamp section...
If I use the LM4781 I sure would use a heatsink wall for it... with some of this nice white paste.
Do you have boards of this cct. made I could buy ? I tend to have more confidence to regular NPN/PNP stuff... Strange in the chipamp section...
If I use the LM4781 I sure would use a heatsink wall for it... with some of this nice white paste.
For the smallest size (and heat), class D is the way to go. Parts Express has a number of modules that would fit the bill and would be a simple solution.
If you want finished board from me they would be 50$ each at least. They are expensive to make... If I dont take any money for making them. So for 5 Id ask 300 which is very expensive. My design needs large heatsink at 22V/rail when driving 8 ohm speaker
For all 5 channels You would need minimal of 1.6°C/W and with 0,1% resistors even smaller but when you turn volume to the max you will need even bigger one. Or you can use the same but run it around 80°C+ 🙂
So go for class D if you dont want ultra high performance
Like this one: Mini 2CHANNELS TPA3123 Class D Digital Amplifier Board Assembled 20W 20W | eBay
Some say that class D has poor highs but thats for the older ones 🙂
You may check for TI's class D chipamps, they all sound fine. Ebay isn't the safest place to order those amp kits. But I don't think those chinese fakers will copy TI's class D designs successfully.
For all 5 channels You would need minimal of 1.6°C/W and with 0,1% resistors even smaller but when you turn volume to the max you will need even bigger one. Or you can use the same but run it around 80°C+ 🙂
So go for class D if you dont want ultra high performance
Like this one: Mini 2CHANNELS TPA3123 Class D Digital Amplifier Board Assembled 20W 20W | eBay
Some say that class D has poor highs but thats for the older ones 🙂
You may check for TI's class D chipamps, they all sound fine. Ebay isn't the safest place to order those amp kits. But I don't think those chinese fakers will copy TI's class D designs successfully.
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Some classD chips have poor highs - TDA8932 is one I've been trying to tame. TPA3116 has better highs but much poorer bass. Take your pick.
Class D performance is highly dependent on the interaction between filter and load, and hence varies considerably from application to application.
Not to say Class AB etc are immune to this effect, but much more resistant.
The problem with Class AB is the heat and power consumption, both of which are directly going to impact the size of the amp. Since the topic is about the smallest possible amp, the size benefit of the switching variety cannot be ignored.
However chipamps offer a reasonable middle ground and you can control the heat quite simply by lowering the supply voltage. With 15V rails, you should easily get about 15-20 watts out of the amp and still have a small heatsink. Beware though that for HT use 20W/ch is very low, just about enough for nearfield.
Since nobody passed the wife test, I have a nice 6-channel chipamp for the nearfield system and a mid-sized Marantz receiver for movies along with a monster 8x10" sub. Bachelor life has its upsides 😀
Not to say Class AB etc are immune to this effect, but much more resistant.
The problem with Class AB is the heat and power consumption, both of which are directly going to impact the size of the amp. Since the topic is about the smallest possible amp, the size benefit of the switching variety cannot be ignored.
However chipamps offer a reasonable middle ground and you can control the heat quite simply by lowering the supply voltage. With 15V rails, you should easily get about 15-20 watts out of the amp and still have a small heatsink. Beware though that for HT use 20W/ch is very low, just about enough for nearfield.
Since nobody passed the wife test, I have a nice 6-channel chipamp for the nearfield system and a mid-sized Marantz receiver for movies along with a monster 8x10" sub. Bachelor life has its upsides 😀
Hi all,
I've found this 6 channels class D TDA-7498 (320-307 at parts express) for $60. It would cost me at leist double to build a thing like that...
All it needs is heat sink and power supply which I have lying around in numbers...
RCAs are on it as well as terminals for power...Can't really beat this !
Anyone have experience with TDA7498?
I will probably go with that. I don't care much with sound quality (this is my TV setup, not my hi-fi one...) but I don't want background noise. I know there is a fan always on on this board, I will find a way to "muff" it. I plan to leave it on at all time.
As I don't use subwoofer, I'll have plenty of power with it I think.
Opinions?
Thanks fort the suggestion! Really appreciated!
If no ones gets back to my with comments on the TDA7498 I'll get back to this thread with mine.
I've found this 6 channels class D TDA-7498 (320-307 at parts express) for $60. It would cost me at leist double to build a thing like that...
All it needs is heat sink and power supply which I have lying around in numbers...
RCAs are on it as well as terminals for power...Can't really beat this !
Anyone have experience with TDA7498?
I will probably go with that. I don't care much with sound quality (this is my TV setup, not my hi-fi one...) but I don't want background noise. I know there is a fan always on on this board, I will find a way to "muff" it. I plan to leave it on at all time.
As I don't use subwoofer, I'll have plenty of power with it I think.
Opinions?
Thanks fort the suggestion! Really appreciated!
If no ones gets back to my with comments on the TDA7498 I'll get back to this thread with mine.
You can put bigger heatsink on it... I think its the way to go.
I dont know how that chip sounds but I think its ok.
I dont know how that chip sounds but I think its ok.
Here it is. I just need to add a DC power supply to it...
I'll see what I can get. Reading the comments on this amp (on parts Express) it looks like I won't need to add heathsink, even I may be able to remove the fan covering it... I think I'll build a PS with tranny & capacitors, separate it from this amp in the box. I'll get the RCAs out on a panel side and I'll wire Banana female on the facing panel side.
I should not forget about the fan and give some airways to it... I usually tend to leave the things I buy like they are... too many crashes after "customizing" equuipments... "OHH that is why they did put that...".
I'll see what I can get. Reading the comments on this amp (on parts Express) it looks like I won't need to add heathsink, even I may be able to remove the fan covering it... I think I'll build a PS with tranny & capacitors, separate it from this amp in the box. I'll get the RCAs out on a panel side and I'll wire Banana female on the facing panel side.
I should not forget about the fan and give some airways to it... I usually tend to leave the things I buy like they are... too many crashes after "customizing" equuipments... "OHH that is why they did put that...".
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I've just thought I may use a PC power supply... Switching 19.5 Volts 6.5 amps. Don't know about damping. I'll try it and compare.. It sure could do as for voltage & current I need. For now I'll only use 3 channels and I, by far, won't need 100 watts per channel...
Go for it, it will work just fine if the voltage is in range. I doubt you will have any issues with sound quality in HT environment.
It's just as well you didn't build the 4781 with that PCB. I got my first board done yesterday and need to fix a show-stopper before it can be put into active service duty.
It's just as well you didn't build the 4781 with that PCB. I got my first board done yesterday and need to fix a show-stopper before it can be put into active service duty.
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