Amps for PC Speakers

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#101
apassgear said:
Maybe there is another issue some place.

Antonio
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Highly likely. Settling in time is something I don't get too fussed about with cheaper gear, there are so many elements possibly involved - the time that would be taken to resolve precisely which item is the worst offender may not be worth it. Personally, if the sound is reasonable at startup and steadily improves the longer you listen then I would be fairly happy ...

Note particularly, DACs, especially the devil incarnate S-D variety - according to abraxalito, 🙂 - take hours to finally hit their full stride - could be what you're looking at ...
 
#102
fas42 said:
Highly likely. Settling in time is something I don't get too fussed about with cheaper gear, there are so many elements possibly involved - the time that would be taken to resolve precisely which item is the worst offender may not be worth it. Personally, if the sound is reasonable at startup and steadily improves the longer you listen then I would be fairly happy ...

Note particularly, DACs, especially the devil incarnate S-D variety - according to abraxalito, 🙂 - take hours to finally hit their full stride - could be what you're looking at ...
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Will have a look tomorrow but that’s the only thing I changed, sometimes pushing components can cause damage.

Getting there, the last cap replacement did away with the mids bump but also change the balance as could be expected, for the better so far, I had to cut back the bass to get a more linear response.

Antonio
 
#103
So far I haven't had problems "pushing components" - touch wood, 😀 - speakers particularly can be driven to what seems ludicrous levels and handle it well - if the sound starts to fall apart, pull back; while the sound remains clean they seem no worse for it.

What I have done is wear out a chip amp, the HT beast started to go a bit funny, steadily got worse and finally died, the chip amp gave up the ghost internally. Though, it was pretty old, due for retirement - and for about 2 years I was hammering it constantly at close to full power, on a daily basis - can't expect miracles, 😉.
 
#104
I suppose one thing you might have to watch out for, is that if the implementation of the chipamp is below par, then outside factors might play more of a role in influencing the sound. I am thinking mains noise and possible EM/RF grunge from somewhere that could come and go throughout the day.

I'd be surprised if the implementation was poor enough that the amps stability would be affected, but a less than perfect implementation could expose susceptability to outside influences that wouldn't normally be there.
 
#109
Thou I took away most of the camel’s back response problems with the small chip (TDA2822M) continues, it sounds gritty and no much left to do, can’t find a suitable replacement with better quality.

I was well advised by Arty that those chips don’t deserve any attention or effort from my part but have to convince myself the hard way.

I will continue to use this setup at the PC since provides acceptable casual listening until I decide (if) to build my own maybe something like Patrick or Arty proposes.

Frank,
I appreciate your encouragement and thanks for your help. But this seem to be the end of the road for this specific setup, maybe we can find another test bed or chip? Good exercise thou! One always learns something by doing things so no regrets. 🙂

Also appreciate all others for their good advice and time. 😱
 
#110
> is there more info besides the link you show?

Speaker : Mini dcaav con Hi-Vi B3n
Amp : http://www.ti.com.cn/cn/lit/ds/symlink/lm1876.pdf

Our PCB is of little use to you unless you can custom machine aluminium to fit.
But if you want, you can get PCBs and a Bill of Material from us.
PCB is proven.

> How difficult was to find those SMPS 24V 75W, they don’t seem to be very common.

Very easy if you would just google.

ACPS 90 - Ansmann Universalnetzteil, 90W bei reichelt elektronik
Buy Desktop Power Supply Desktop power supply,15-24V,90W Ansmann 5211003-UK online from RS for next day delivery.
http://targus.com/pdfviewer/temp/apa03eu_6.pdf
Buy 90W Digital Universal Laptop Power Supply (12V~24V) with LCD Display and USB 1000mA Power Port
Trust - Digital Lifestyle Accessories - 90W Notebook Power Adapter - Black
Maplin 90W Universal Laptop Power Supply with Travel Adapter Plugs | Maplin


Patrick
 
#111
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#112
Antonio, personally, I would persevere - the grittiness is a distortion problem, and it would be worth knocking over. I nearly fell off my chair when you said you had all this wireless gear right next to the speakers ... help!!! IME, the better a system gets, the more obvious becomes interference effects and similar considerations - very unfortunately, or so it would seem to many, the closer one gets to optimum sound, the fussier and more obsessive one must become - it never, ever gets easier!

How I would approach it in a simple, easily testable fashion is to warm up the system until it sounds as good as you've heard it, but still has that grittiness. Then, while still running, switch off and pull the plug on every electrical device nearby, switch off all mobile devices, tablets, etc; the area around the system has to become an electrical desert - what you're listening for is the level of grittiness, does this unpleasantness vanish or strongly attenuate when doing the exercise?

I've completely shut down the house at times, it becomes electrically dead - apart from the the bit supplying the system; this has told me a great deal over the years ...

Unfortunately, once one starts blaming a key component inside as not being good enough then one starts losing the way - that's how I see it, sorry, 😀 ...
 
#113
I'd hook up the little loudspeakers to an amplifier that you know isn't gritty and see if it goes away. If it does you know it isn't the loudspeakers.

I say this because raggedness/breakup in the upper range of the drivers can make things gritty/harsh/hashy and unpleasant, it's a large failure of some full range drivers.

The more you improve things however the less susceptible the system should be to the influence of any interference as hopefully you should be making the amplifier and surrounding circuitry 'reject' or be uninfluenced by any high frequency gubbins. To do this you'd need good decoupling, well thought out grounding, a zobel on each output of the amplifier and an RF filter on the input. Most of this is pretty standard, but it's easy to skimp for extra profit providing the amp wont explode.
 
#114
Yes, what is improved is key, so doing the right changes would help interference rejection. To be honest, there are so many areas that can be targeted, and one has only so much time and patience - I have never had a system where everything that matters has been dealt with, optimised - with each exercise I've focused in a different area, seeing what the impact is when certain strategies are tried.

So, I've always listened to compromised sound, there have always been weaknesses remaining - however, this has not stopped me getting convincing sound when I pull enough levers ...meaning, how good can it become when absolutely everything is done ... 😀, 😉 ?
 
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#115
Thanks guys, I’ll do some testing in the next few days to see how RF could be affecting. Unfortunately here at the home studio have other electronics that could also affect besides the ones I told. Two PC’s sometimes also a tablet and laptop besides the requisite cell phones up to 4 plus scanners and printers, so this environment does not look promising for the speaker set and here is where I reside most of the day.

Antonio
 
#116
uhh, many questions.

first, the tda car radio IC series is not a flawless one, quality wise lm1875/3886 or tda72 whatever will do a far better job. the car radio ICs are verry easy to work with, and for the efforth and the money You get a lot of joy. actualy i would say for the few minutes it takes to build it, the sound it delivers is quite fantastic. price/value wise its a mirracle of its own.
gross quality wise.. well, ya know it ain't a good amp in just too many ways.

input caps.
well, if the source has de-coupling, then you do not need any caps on the input.
supposedly quality wise that would be the best choice.
i use a tda 1557q as my computer speaker amp, and i have no input caps.
bet'ya that will not color the sound, and will need no time to break in, or what so ever.

replacing the tda2822m would be .. a good choice, as that chip will deliver no more than 1 watt. and at roughly 1/3 watt it will distort to 0.2 %.
an absoholutely bad chip for anything else than low grade headphones.
 
#117
Arty said:
..............input caps.
well, if the source has de-coupling, then you do not need any caps on the input.
............
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I expect you mean coupling capacitor.
The High Pass input filter uses a series capacitor that also acts as the DC blocking capacitor.

Between a Source and a Receiver one generally uses a DC blocking capacitor to prevent passing through a faulty (or deliberate) DC offset. This only needs to be blocked ONCE, at each interface.
The Source OR the Receiver can have the blocking capacitor. NOT both.

Decoupling usually applies to Power supply rails.
 
#119
Arty said:
first, the tda car radio IC series is not a flawless one, quality wise lm1875/3886 or tda72 whatever will do a far better job.
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Interesting that my own experience is the polar opposite...😛

the car radio ICs are verry easy to work with, and for the efforth and the money You get a lot of joy. actualy i would say for the few minutes it takes to build it, the sound it delivers is quite fantastic. price/value wise its a mirracle of its own.
gross quality wise.. well, ya know it ain't a good amp in just too many ways.
Click to expand...

Another question - detail some of the ways that to you the TDAs are inferior to the LM38xx and TDA729x? I accept they're lower power but what else?
 
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