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Class D Switching Power Amplifiers and Power D/A conversion

Beomaster refit - controversial?
Beomaster refit - controversial?
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Old 14th September 2019, 10:46 AM   #21
Khron is offline Khron  Finland
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Well, you see, at least up until a few years ago, the "big boys" (ie. HP, Dell, Lenovo) got their laptop bricks OEM'd at one of a very short list of companies, like Delta, LiteOn, Astec etc. who are arguably at the top of their game in this particular field.

And yes, i would personally trust them infinitely more than some random no-name featherweight near-empty-box you get for 2$ brand new off Aliexpress or whatever. Which, in addition to being EMI hell, may well also be potential death-traps...

And while it's true that damn near everything is indeed made in China nowadays, it also depends WHOM it's made FOR - and thus, who and how well / stringently handles the quality control
How often have you heard of stock (ie. NOT aftermarket / 3rd party) laptop chargers catching fire, hmm? :roll: Not all that often, would be my guess.

Quote:
Originally Posted by Turbowatch2 View Post
Since I tried some very cheap Alibaba / eBay SMPS boards, Iīm cured of using these old laptop junk. You never know how it does with audio.
You get these in any voltage and they are remarkable silent.
Quote:
Originally Posted by TroelsM View Post
The ebay ones may "sound" better, but as for safety and EMC I would trust and old laptop-adapter much, much more.

Not saying that the ones you show are dangerous, just saying that its very hard to tell without proper (destructive) testing or analysis.

Kind regards TroelsM
Quote:
Originally Posted by Turbowatch2 View Post
Hi TroelsM, have you ever read the fine print on your holy brand brick?
HP or Lenovo buy their SMPSīs from some Chinese Manufacturer for less than a $ and put a label on it. These bricks sure meet the demands of a Laptop. Some work well with a D-amp, others not.
These cheap power modules linked here,from Ali or ebay, are produced in the millions. The design is proven, probably stolen from the US and works very well with D-amps. They have a lot more power than the usual laptop brick which ends at 90 watt.
The world has choosen to use medium-tech equipment from the yellow man for reasons of cost.
Sure some Danish high ender can ignore the fakt and be sentimental with brand names, but many here want the most for their money and look for proven low cost alternatives. Like the rest of the world. When the big manufacturers buy in China, why should I buy expensive? Just to waste money and in the end get the same China stuff, relabeled?
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Last edited by Khron; 14th September 2019 at 10:53 AM.
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Old 14th September 2019, 11:43 AM   #22
Turbowatch2 is offline Turbowatch2  Germany
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Safety is always a subject! Please take not all of my post too serious.

The metal cased SMPS from China are safer to handle than the naked ones, but for newbies with electricity the laptop power brick is the safest alternative. I think we all agree on that.
Batteries like LiPo can be dangerous, because of very high current, which can easily melt metal.
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Old 14th September 2019, 12:06 PM   #23
Turbowatch2 is offline Turbowatch2  Germany
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@Khron
I see anything from China very critical, as they have not the slightest sense of responsibility for what they sell. If you come from a culture of product piracy, this is no wonder.
But maybe you buy one of these SMPS and have a look at the build quality. They are really worth a try, run cold and radiation seems to be normal, if you put them into a closed metal housing. This is the only way to use them responsible. The minimum distances, a usual problem with Chinese power supplies, are VDE standard.

Please consider how many of these are build, sure the ones we buy are only a fraction of the numbers which go for OEM use. It is something I would call professional quality, not death traps. Sometimes even a Chinese dealer can not make a part he sells worse than it is. Would be more expensive to build sub industry standard than just deliver what is made to agree with European rules. You are right, there are still Eastern 230V products around, no one should use, but not these.

Off course you have to know how to use them! But that is the same with a kitchen knife.
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Old 14th September 2019, 12:57 PM   #24
tomtt is offline tomtt
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The Pass Labs section of this forum may be an inspiration,

As to what may fit in the original enclosure.
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Old 19th September 2019, 03:20 AM   #25
tallnutt is offline tallnutt  Australia
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I got the little bear chinese preamp today.. works fine, no nouse that I can detect at medium volume.
Now I need to get a stereo amp with treble / bass controls (that I can wire to existing sliders). I was going to use my 2.1 board but have realised it gives no bass control. I could use a 2.1 or 4.1, but it must have a way to control bass and treble in the stereo channel with separate pots.

Anyone please have any ideas for <$100???

Thanks.
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Old 19th September 2019, 05:57 AM   #26
Turbowatch2 is offline Turbowatch2  Germany
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Canīt you use the bass slider pot to adjust the .1 volume? Depends on the way you want to use it when itīs finished. 2.1 or 2.0?

I have a comparable project with an old Yamaha CA-V1 integrated amp.

https://www.hifiengine.com/images/mo...maha_ca-v1.jpg

The amplifier will be a unity with new build 2-way speakers. In the end I will only use the passive input selector and the power switch from the old amp. It will drive each chassis with a single amp, so 4 channels. No electronics inside the "active" loudspeakers at all.
For x-over I found the DSP from 3e-audio in the version with 3 separate pots for bass tremble and volume. Maybe have a look, this could fit for you too.
Iīm going to combine it with a motorized pot, which will give me on/off and volume control over a remote. I donīt need more (old man).
I will see how to match these parts...

Maybe use the DSP as a volume /tremble /bass control if this is an option for you. You can program at which frequency it will work, a huge advantage over a fixed version and even fix room related problems. No need to use all 4 outputs.
It has symmetrical outputs and you can easily convert any cheap D-amp for such an input. Just look for the two input capacitors each channel has, lift one leg of each and you are there, symmetrical in. I will use two TDA7498e modules, one per side, which sound very good, even unmodified, with two out of the box SMPS.

ADAU1701-2In4Out | 3e Audio

The quality of the DSP is very good and 4 times the value of the Sure DSP at least. 38US$ inc. P&P fast delivery, took about a week China-Germany.
The programming is not that comfortable as expensive DSPīs, but since the ADAU 1701 is used so much, there is help to be found anywhere. Need a 4$ programmer to make it complete.

Last edited by Turbowatch2; 19th September 2019 at 06:18 AM.
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Old 19th September 2019, 06:03 AM   #27
tallnutt is offline tallnutt  Australia
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Thanks gor the info Turbowatch. I will not use the bass channel because I have powered stereo speakers that don't need it, so I need bass control on the stereo. I hadn't thought of a dsp, but I have no idea how to use symmetrical outputs. Do you have a link to the amps you used with that dsp?
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Old 19th September 2019, 06:34 AM   #28
tallnutt is offline tallnutt  Australia
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Also, is there a GUI to control the dsp? The link doesn't mention how it's done.
Thanks.
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Old 19th September 2019, 11:24 PM   #29
Turbowatch2 is offline Turbowatch2  Germany
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The DSPīs
boards based on the ADAU1701 are usually programmed by a software called Sigma Studio. It is free, you can download it. No cost to try. Maybe do that and load one of the DSP files into it. So you can see how it works. You can use a ready made file, change the values or add elements. Itīs graphical and for some might be very easy to use. Depends only on you, how you get along with it. The finished file is then loaded to the DSP via a small interface. Like using these three pots for volume ect.

You also can use it with the DSP connected, while listening, to use equalizers, x-over or whatever you want, to match to your loudspeakers. This would be a chain of "computer-interface-DSP-amp-loudspeaker". The input to the DSP comes from your pre-amp.

In your case, the 3e-audio DSP, which got the potīs already in hardware, would simply be used as a tremble/ bass/ volume stage. You use only two in- and outputs. You can program it as you like once and leave it as it is without interface etc.

Maybe have a look at the internet pages, weather you could make friends with such a device. Sound is very good, you find this DSP chip in many expensive active speakers today.
In my opinion the only way to go today, since the price is so affordable. There is hardly any audio that does not profit from such a device, even the the simplest full range speaker can get rid of the passive correction and sound better.
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Old 20th September 2019, 01:16 AM   #30
Turbowatch2 is offline Turbowatch2  Germany
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The amp:
Usually the cheap D-amp modules we use are finished with asymmetric inputs.
The chips hardly all have symmetrical input in native form.
On most modules you can access the "pure" input by tapping into the input caps, directly before the Chip, ignoring the other parts on the board. This will be an advantage in most cases, I think.
If you take, as an example, this board with the TDA7498e, you see 4 red caps in a row betwwen the RCA and volume pot. One side goes to the input circuit and the other one to the legs of the D-chip. You need the caps connected to the chip only. Just removing the caps and re-positioning them, gives you the input you need for the symmetric output of the 3e-audio DSP.
An advantage is the broken ground connection, preventing hum.

If you are still unsure which amp to use, the pictured board is really nice. Two points: 1. the fan did never start while using it, even at 34°C in summer.
2. be sure to get the "e" version, the quite similar looking 7498 is not made for the lower, usual 4 ohm loads, so it will not drive any speaker.

It sounds quite as nice as the TDA3116, but while, with larger speakers, the smaller one lacks some authority with bass, while the 7498e deliveres. Something like 10US$ more might not make a difference for most here.

Maybe go the most easy way and buy one of 3eīs amp, they are very good as far as I could read. Even more $...
Attached Images
File Type: jpg tda7498e.jpg (448.6 KB, 62 views)
File Type: jpg 3e_audio_DSP.jpg (502.1 KB, 62 views)
File Type: jpg remote.jpg (406.5 KB, 61 views)
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