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Old 22nd December 2012, 11:17 AM   #171
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Default Some tips to get the best out of TA3020 Audio Amplifier v2

Hi All,
I bought several of these amplifiers modules and I did a lot of testing so I try to summarize in one post all I have discovered.

These amplifier perform far better with SMPS rather than with "linear" power supply. It appears a regulated SMPS power supply is the one that yeld the best results.

If you decide anyway to use a linear power supply make sure that you've a DC trap on the High Voltage side of your main transformer especially if you use an high power toroidal one. Bypass the electrolytic capacitors in the DC trap with high quality plastic capacitors 2-4 uF of capacity. Make sure the working voltage of the capacitors is adequate. If the transformer "hums" with no signal chances are the amplifier self-oscillates because of poor cables layout or you've a DC offset on your mains (that's why you need a DC trap)

If you want to go for the best performance use a regulated SMPS. Chose the one that has a maximum output adequate for the usage of the amplifier. Using a 2Kw SMPS for an amplifier to be used at home is a nonsense and will introduce additional issues to deal with.. Same is to use a 150W SMPS for PA usage.. A wise decision is needed..
Take into considerations it's not always true that bigger=better (like in many other cases )

Same discussion applies to the working voltage.. if you don't need full power don't make the amplifier work with +/- 60V .. take into consideration that mains voltage can sometimes oscillate or contain peaks.. working near the maximum ratings could make these oscillations fatal especially if you don't have a regulated power supply, moreover the amplifier will develop less heat working with a lower voltage. I saw that +/- 40V regulated is ideal for home usage.

Self oscillations:

Like all the amplifying devices and in particular if they're switching high currents at very high frequencies this kind of amplifiers loves to self.oscillate if they're permitted to. This issue is commonplace for this class of amplifiers and not due to the amplifier design itself, almost all of the times it's due to poor knowledge of the phenomenon by who assemble the complete amplifier.

Symptoms of self oscillation are:

- The heatsink and the output chokes become warm/hot in a few minutes after the amplifier is switched on even if the amp is used at low power (or with no inpout signal at all). The quicker/hotter the heatsink becomes the worst is the issue
- a click is heard when the speakers protection relay connects the loudspeakers to the amp (if everything's ok no click at all should be heard)
- there is an abnormally high current absorbed by the amp even with no input signal. You can measure this current only with an oscilloscope by placing a 0.1 ohm shunt resistor in series with V+ or V- rail and displaying the voltage across it on the scope.. you will notice a distorted signal in the range 1-2Mhz that can reach 2-3V peak.
- your SMPS (or transformer) hums even with the amplifier not having any input signal. This could indicate abnormally high power level being fed to the amp
- the highs reproduced by the amplifier are distorted (very aggressive.. especially on the "s" being pronounced by the singer) .. low end is "dull".. Here don't buy expensive capacitors for the inputs, they won't help.
- noticeably high background hiss on the tweeters with no signal at the inputs.

Note that self-oscillation can happen more easily if an SMPS is used instead of a linear supply due to the high frequency noise generated by the SMPS itself being picked up from the amplifier inputs.

Some hints that resolved the issue in my assembled amps:

1 - I kept GND isolated from the metallic container of the amp. The only point where the amp GND is in contact with the container is in the 5th hole of the board (the one in the middle of the small capacitors behind the power connections hub)
2 - the cables V+ and V- coming from the SMPS and going to the amp must have a ferrite "choke" near to the point where they're attached to the AMP: Don't place the ferrite bead on the GND cable. It's better if these cables are twisted tightly together. Don't use cables whose thickness is more than 1,5 mm2.
3 - Don't use big capacitors (especially those high ends with wound film) if they're big enough and placed in the wrong position inside the container they can act as small aerials picking high frequency noise and creating unwanted feedback that could produce instability. If you decide to use this kind of capacitors make sure amplifier is not self oscillating in any condition
4 - output cables going to the speakers should be twisted together tightly as well
5 - in the container make sure that the inputs of the amplifier are alone and especially far from power supply cables and speaker output cables.
6 - DO NOT operate the amplifier with nothing connected to the inputs. Use shorting RCA caps if necessary. Always use shielded cables for inputs.
7 - DO NOT ground the inputs on the metallic frame of the container at the connector side

Moreover If you use an SMPS:

1 - If you've the version of the amplifier with RM filter capacitors (marked "for audio") and you use SMPS change the capacitors with a couple of high quality capacitors with low inductance (for switching). I used a couple of 15.000 uF nippon chemical with better results reducing RF ripple. Other brands may work equally well (like ELNA provided by connexelectronic as option) but I didn't test.
2 - Since you've already DC produced by the SMPS you don't need the rectifier bridge.. so short out the diodes bridge by removing the two small SMD capacitors in parallel to two of the bridge diodes and place a small "short" wire in their place. This way the amplifier (and the capacitors in particular) will be directly fed by the SMPS. I notices that there's a significant HF ripple decrease with this move.
3 - if you buy a new amplifier ask connexelectronic to provide it without the bridge (so you can short the appropriate terminals) and buy it with the best filter capacitors available
4 - it could be a good idea, especially if you don't have a very stable SMPS (and if it's a regulated one), to reduce the filter capacitors value to a "safe" value.. 3300 uF - 4700 uF fed at the SMPS working frequency should be enough. Don't eliminate the capacitors from the board or the amplifier will for sure self-oscillate.


Potential damages of self-oscillation:

1 - audio quality will be noticeably worse compared to the same amplifier that is not self-oscillating
2 - in one case the self oscillation was so bad I fried the amplifier after a few seconds (I left inadvertently the inputs open) and the SMPS was damaged as well
3 - as a general case the self oscillation in these amplifiers happens to frequency so high that it's less likely to be able to damage you speakers (they have a so high reactance at these frequencies that there is a negligible power transfer) however potentially you can have damages

Having said this, these amplifiers have a very good fidelity of music reproduction and they're my favorites.

Hope the above will help.

Last edited by Cristi; 23rd January 2013 at 05:00 PM.
 
Old 10th March 2013, 10:24 AM   #172
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Quote:
Originally Posted by Ryssen View Post
What is the input sensitivity on this module?

Click the image to open in full size.
Is the schematic for this module "open"/free, thus one could make his own board layout ?
BRGDs
Klavs.
 
Old 15th March 2013, 06:14 PM   #173
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since this forum is not always accessible from my location, I set-up a small forum on the connexelectronic domain, don't be shy and click: Forum Connexelectronic • Index page
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www.connexelectronic.com complete assembled amplifier and SMPS
 
Old 29th March 2013, 01:27 AM   #174
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Cristi, any chance we can convince you to build TI TPA3116/8 and/or TPA3100D2 Amps (as used in the MGI Millenium Amp for instance)? I think these chips are the next wave to replace Tripath and <100w Class D. There are some threads on the forum already, and right now the MGI Millenium is the only commercial amp using the chip and it is becoming very very popular with the audiophile crowd.

Also these chips sound really, REALLY good.
 
Old 29th March 2013, 05:08 AM   #175
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tbi millenia ? mg3 ?
 
Old 29th March 2013, 06:12 AM   #176
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Quote:
Originally Posted by norman bates View Post
tbi millenia ? mg3 ?
google
 
Old 29th March 2013, 07:11 AM   #177
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wushuliu: thank you for proposal. I will consider it, and if there are requests, why not ? although my main interest is (was) on above-50W amplifiers, it might worth to consider lower power ones if they have special features which make them worth considering.
how about a version with on-board SMPS ? :-)) Don't know if would be suitable, but worth to try.
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www.connexelectronic.com complete assembled amplifier and SMPS
 
Old 29th March 2013, 08:30 AM   #178
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Quote:
Originally Posted by Cristi View Post
wushuliu: thank you for proposal. I will consider it, and if there are requests, why not ? although my main interest is (was) on above-50W amplifiers, it might worth to consider lower power ones if they have special features which make them worth considering.
how about a version with on-board SMPS ? :-)) Don't know if would be suitable, but worth to try.
 
Old 29th March 2013, 10:32 AM   #179
nesha is offline nesha  Serbia
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Location: Beograd, Serbia
Speaker Amplifier and Modulator - Mid/High-Power Amplifier - TPA3116D2 - TI.com

I'm interested too, this one is 50W/ch...
 
Old 29th March 2013, 11:55 AM   #180
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Default I'd be interested

Quote:
Originally Posted by wushuliu View Post
Cristi, any chance we can convince you to build TI TPA3116/8 and/or TPA3100D2 Amps (as used in the MGI Millenium Amp for instance)? I think these chips are the next wave to replace Tripath and <100w Class D. There are some threads on the forum already, and right now the MGI Millenium is the only commercial amp using the chip and it is becoming very very popular with the audiophile crowd.

Also these chips sound really, REALLY good.

I'd be interested in a board. With clearly marked terminal block hookups so you can easily hook up the DC power supply, inputs, and speaker outputs.

If it's a DIY type board only then someone smarter than I please provide a bill of materials with part numbers linked to say Mouser or Digikey.

Keep it easy.

Last edited by Mark2727; 29th March 2013 at 11:58 AM. Reason: To revise a sentence/thought
 

 


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