DW300 project - one HiFI Audio Amplifier that can run stable on 2 ohm

[donpetru]

Hello everyone,

DW300 project - which I want to develop it with power supply diagram and other electronic circuits considered relevant - derived from an electronic scheme published by user @wahab on diyaudio.com. So, it's a project I've worked too and wahab. Initials DW come from Donpetru Wahab

In fact, in my version, I presented IRFP240/9240 transistors and added the protection and soft start. After that I changed some values ??of electronic components to bring them in the optimum functioning of the amplifier. Finally, I designed a PCB that meet the most stringent design rules.

I hope your's enjoy this project that I'm thinking of turning it into a much more laborious project which include: a power supply, input circuits and/or audio preamplifier (schematic and printed circuit). In this respect I'd really like to read some recommendations or opinions.

If you plan to use lateral MOSFET transistors, such as ALF16N20W / ALF16P20W, it is enough to make the following changes:
- replace with a jumpers these electronic components: D101 and R21;
- remove from the circuit components R22 and R23;
- connected in series with the emitter of the transistor Q13 one adjustable potentiometer: 100 or 250 ohms.

!!!! If you think use lateral MOSFET transistors, such as those exemplified above, then I recommend you do not use the amplifier on less than 3 ohms impedance. Do not forget that.

The project presented is a simple prototype, so, depending on the characteristics of bipolar transistors used might to need small adjustments (for example, changing the value of resistor from the bias circuit). This will set in the stage for achieving practical circuit. We can fix these issues - if applicable, remains to be seen - with continued discussion of this topic.

In the second PDF file listed below have submitted plans for achieving copper top and bottom in D.I.Y. regime of the audio amplifier.
The amplifier can be built and in a single layer, replacing the TOP layer with jumpers. In this case, supply routes sits solder.

I think, if anyone wants, to realize some PCB's after pass the practical test of the prototype.

Gerber files of the project below can make available to any user after a modest donation (minimum 20 USD) to my website. Donation can be made by accessing donation button on my website: www.tehnium-azi.ro
After making a donation, you will receive an e-mail Gerber files.

So, the project I would like to extend it will bring them and other useful circuits.

Dw300 project is an audio amplifier with multiple applications, from wide band audio applications and going to the subwoofer's. If you are thinking of looking for a reliable subwoofer amplifier, it is not bad to realize DW300. So, DW300 is an ideal project for subwoofer and not only that. Audio amplifier can charge 300Wrms into 2 ohms OR 150 ... 170W into 4 ohms with THD less than 0.01% (typic 0.007%).

Finally, I would like to read some opinions, a kind of first review, for this project, which can turn into something quite promising. That depends on your's.

[NiHaoMike]

If you're good with surface mount, TI has a few chips that will handle 2 ohms at up to 600W.

[donpetru]

NiHaoMike, you mean this chip from TI:
http://www.ti.com/lit/ds/symlink/tas5630.pdf

Sorry, but it's a big mess that chip. I read from the datasheet:

Total Output Power at 10% THD

And DW300 project has:

Total Output Power at 0.007% THD

There's a big difference and DW300 has a much better sound. And remember, DW300 is a Hi-Fi amplifier.

And maybe you did not know, an audio amplifier is Hi-Fi if the THD is less than or at least equal to 0.5% (at nominal power).

[T4P]

How sure are you that the THD you quote is at full power?
I know amplifiers that make max amount of power usually won't have 0.007%, did you use a DSA to see the amount of distortion?
Usually human ears won't even distinguish between 0.1% and 1% for real
You can pick a higher power amp and limit it to lower power figures (EG: 300W) and have lower distortion because i doubt a amp pushing 300W will have such low figures unless you pump a shitload of voltage into it as well as have really beefy transistors that have higher gain, keep in my mind that to push 300W you will likely have to use a FET that has high input capacitance as well and so requires lots of input current which means you need a beefy totem pole MOSFET driver that is capable of >6A depending on your fet and may i suggest something else as well? May i suggest something as well?

You need better FETs, 180mR is quite a lot and can dissipate quite alot of power at 8 ohm output impedances

What's your output stage class? You didn't mention but if you want to make a Class AB amp i'll tell you to MOVE ON. You're gonna waste 150W of power and you better know that upfront as well as requiring slightly more than 650W transformers per channel which makes it really pricey
And that 2ohm outputs are not really easy to implement in Class AB. And that according to the SOA of the lateral mosfets you will be hitting it's SOA at 50V (Likely to drive 2 ohms) if you want roughly 10amps and that just becomes worse as you increase the voltage, remember if you supply them with +/- 50V you probably only have +/-35V available swing on the output so you will have to find another lateral FET and 3ohms impedances won't really change things, you will probably have to use +/-80V voltage and switch about 6+amps and clearly you won't be able to do that especially if you have losses about 25V * 6A

I think if you use a discrete Class D instead you can achieve lower distortion figures than AIO Class D chips or you can use Digital PWM chips instead, NOTE! CLASS D IS NOT DIGITAL. CLASS D IS STILL ANALOG and Digital PWM really makes use PCM technology

Or you could attach a high voltage FET to a Class D chip output and make use of the class d AIO chip to drive the fet(s) and you will probably get lower distortion figures
I think we need doug ford around here now
You could look at the IRS2092 too

[donpetru]

Look simulation presented below. Idle current was set to approximately 100mA.

When the amplifier operates in 2 Ohm and charge 300W, each transistor power dissipation is about 25W. Indeed, the power dissipation is high, especially when the amplifier operates in 2 ohms.

Then, class D has a different structure than Class AB and Class D amplifiers have many disadvantages, such as the quality of sound reproduction, regardless if you use chips with PCM technology or not. 

To return little to the example above Class D audio amplifier. I mean TAS5630 chip from TI. I said above that that chip is a mess, as the datasheet specifications, which are quite swollen (especially the power amplifier specifications). If we look at how constructive that way you'll see that it contains four channel Class D amplifier powered 50V each. Channels are configured in stereo -> two 'bridge', or, two ch. in parallel and then bridged. A single channel can charge the maximum output a voltage of 50V peak to peak. That means, on 4 Ohms, about 78W rms power, but at 10% THD, which is very much THD (inadmissible). Man audible harmonic distortion with values equal to or greater than 2%.

Then, as recommended TI company, you should connect two such channels bridged (two by two). I do not want to think about how hard it is to adjust the two channels to operate in Class AB bridge, not to mention two-channel Class D which are more difficult to adjust. And if you adjust the bridge configuration, then the THD - I speak from experience - will increase even more (much more than the 10% stated by the TI company). So, the result is deplorable and unacceptable for an audio application that needs to be HI-FI.

For this reason I have chosen a solution in class B or AB which, though dissipate more power, will sound much better.

[T4P]

You totally forgo'd one thing, those amp chips ARE TUNED FOR MAXIMUM POWER not minimum distortion, PCM technology = digital, easy to correct but slightly harder to setup
Class AB + Class D = ANALOG! And i don't see what you mean by "sound reproduction" unless you have been listening to 10$ class D amps meant for maximum output again and comparing it to a 400$ Class AB amps. I have good class D amps around and they sound great placed to one of my LM3886 amps AND MIND YOU, i am a somewhat audiophile. I'm not kidding and well i hate audiophile nonsense
One very odd thing is, why do you need 300W anyway? Are you planning to make some PA amp or what? Why would you need 300W constant at 0.007% for HiFi?

And plus you talked about Class B, tell me what you know about them.
One thing i can tell is that it's distortive but even so i have a Class B car amp which achieves 0.2% at 60WX4 which is alot for a car amp in the 90s

AND REMEMBER, distortion is in % and % doesn't add up if you think it does go back to your maths because really in decimal it adds up but when you calculate the amount of distortion VS amount of power which is increased it's still 10% not some stupid 20% calculation of yours! They don't work that way!

[donpetru]

You totally forgo'd one thing, those amp chips ARE TUNED FOR MAXIMUM POWER not minimum distortion,

I did not forget anything. Indeed, the TI chips - I refer to those in class D, I like the one exemplified above - are designed for applications where it is necessary, first of all, a great power. Such chips are suitable for applications like audio conference, in large halls or auditoriums.  If you want to tell me that TI chips are suitable for Hi-Fi quality auditions, then, excuse me, but I think you need further studies.
On the other hand, TI chips have more disadvantages such as: very sensitive to overloading, high harmonic distortion, low dynamic and low SNR, a lower current capability etc.

Class AB + Class D = ANALOG!

Class D, through construction and operation, not part of the domain "ANALOG". Class D of amplifier is a switching or PWM amplifier. The audio signal is used to modulate PWM carrier signal which drives the output devices, with the last stage being a low pass filter to remove the high frequency PWM carrier frequency. Class D amplifiers take on many different forms, some can have digital inputs and some can have analog inputs but both constructive forms out of area "ANALOG". Remember that. So, to say that: AB + D is totally ANALOG is a big mistake.

And i don't see what you mean by "sound reproduction" unless you have been listening to 10$ class D amps meant for maximum output again and comparing it to a 400$ Class AB amps. I have good class D amps around and they sound great placed to one of my LM3886 amps AND MIND YOU, i am a somewhat audiophile. I'm not kidding and well i hate audiophile nonsense

When I said "sound reproduction" I mean the sound reproduction quality: tone, timbre, you know, that stuffs. And amplifiers with discrete components (transistors) are superior to any monolithic technology intensive solutions such as TI or LM3886 chips or anything like that. I said "superior" in terms of "quality sound reproduction".

One very odd thing is, why do you need 300W anyway? Are you planning to make some PA amp or what? Why would you need 300W constant at 0.007% for HiFi?

I don't want (necessarily) 300W, that was not the main target. The main goal was to design a Hi-Fi audio amplifier stable into 2 ohms.
2 ohms because of that: many of the solutions that sound I created and I have sold on various clients, some of them, after a while, wanted to add another parallel speakers besides one or two existing. For this reason, not force customers to buy another amplifier, I decided to design one that works well with loads below 4 ohms. Then, considering that many sound solutions that we have designed are designed for ambient sound at various restaurants, even at low load operation (below 4 ohms), is needed as Hi-Fi reproduction. Indeed, we must not overlook the sound recording performance (those losses very high power amplifiers in class AB), but so far, considering the use of the amplifier, there was no problem.

And plus you talked about Class B, tell me what you know about them.
One thing i can tell is that it's distortive but even so i have a Class B car amp which achieves 0.2% at 60WX4 which is alot for a car amp in the 90s

Class AB or B are very close and constructive working, just different idle current output stage. Then, if we seek to obtain an audio amplifier with low distortion and a special stamp, as DW300, matters a lot when obtaining low distortion, even if 0.01 instead of 0.2%. What I mean is that, we should not only report a low THD, but to look at all aspects of the construction of the amplifier which optimized once may result in us getting a quality amplifier. On I based this when I designed DW300.

AND REMEMBER, distortion is in % and % doesn't add up if you think it does go back to your maths because really in decimal it adds up but when you calculate the amount of distortion VS amount of power which is increased it's still 10% not some stupid 20% calculation of yours! They don't work that way!

Please do not categorize my calculations wrong because you have not seen it all. I understand your frustration but you watched it start in the wrong way, which makes me think that you had little tangent with the theoretical and practical aspects (in the audio area I mean).