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Class D Switching Power Amplifiers and Power D/A conversion

TPA3255 - all about DIY, Discussion, Design etc.
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Old 16th November 2019, 10:41 AM   #1521
CowCat is offline CowCat
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Originally Posted by FauxFrench View Post
A logical reply would be "apparently" but it is unusual. First, you have to make sure that the white noise does not enter via the input from a previous stage.
So, unless you have already done this, disconnect the source and short the amplifier inputs to ground. Still a clear imbalance in the white noise?
If you still have a clear imbalance of white noise, it is likely to be a capacitor that makes unusually much noise in the right channel.
I turned off the computer. The computer served as the ground. The channel imbalance was apparent in white noise.
As I listened to music, I noticed that the right side was 1dBv louder than the left.
So, I compensated by decreasing the right volume of my onboard soundcard by 1dBv.
However, the channel imbalance may not be consistent across all frequencies.

Is it common for a cheap generic class-d amp to have 1dBv of channel imbalance?

Last edited by CowCat; 16th November 2019 at 10:47 AM.
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Old 16th November 2019, 11:12 AM   #1522
rhing is offline rhing  United States
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Originally Posted by STUNTfingers View Post
Hi all,

Iím very new to DIY audio and wanted to build my first DIY amp to power some KEF LS50ís. Would the Meanwell Hep-600-48 be overkill for such an application and would a more cost effective SMPS be the LRS-350-48?

TI use the HEP 600 at their demos apparently, but itís pricey. I wouldnít mind building something with some headroom anyway in case I wanted to repurpose it for another project, but wanted to check whether this was an unnecessary purchase.

Any thoughts greatly appreciated.
Sorry for chiming in a bit late here, but I use a TI TPA3255EVM amp in PBTL mode powered by the Mean Well LRS-350-48 with a pair of KEF LS50ís, and this makes an incredible combination. Your KEFís will really sing with this amount of drive. When I powered my KEF LS50ís with the TI amp, I was taken back by the level of control I heard. Bass notes were complete and went deeper than I ever thought a small monitor could produce. The treble sweetened up as the amp burned in. If you want, you can have a pair running in BTL mode as mono blocks which will allow the TI amp modules to drive down to 2-4 ohms easily. Youíll need proper speaker cables for this combination, and I highly recommend using a loosely twisted pair of Duelund DCA16GA or DCA12GA Tinned Copper wire with bare wire ends.

With the TI amps connected in differential (balanced) mode with a source with volume control and balanced outputs, you will really be blown away with how transparent these amps can be. I connected a Pono Player with the ESS DACs and Ayre-designed analog output section to the TI amp, and it was shockingly awesome. For other sources, I suggest a very good preamp. The Pass DIY B1 with Korg NuTube Triode preamp offers additional gain along with that holographic triode sound signature. Paired with the TI TPA3255EVM amp, it makes a ridiculously budget-friendly high end amplification system that will compete with many high end audio systems.
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Old 16th November 2019, 11:22 AM   #1523
FauxFrench is online now FauxFrench  France
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Quote:
Originally Posted by CowCat View Post
I turned off the computer. The computer served as the ground. The channel imbalance was apparent in white noise.
As I listened to music, I noticed that the right side was 1dBv louder than the left.
So, I compensated by decreasing the right volume of my onboard soundcard by 1dBv.
However, the channel imbalance may not be consistent across all frequencies.

Is it common for a cheap generic class-d amp to have 1dBv of channel imbalance?

I wouldn't worry about 1dBv gain difference. If you look at the TPA3116 datasheet (section 6.5), the gain accuracy is stated to be within 1dB from "typical", thus within a 2dB margin. So, 1dB is well within.
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Old 16th November 2019, 11:55 AM   #1524
CowCat is offline CowCat
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Originally Posted by FauxFrench View Post
I wouldn't worry about 1dBv gain difference. If you look at the TPA3116 datasheet (section 6.5), the gain accuracy is stated to be within 1dB from "typical", thus within a 2dB margin. So, 1dB is well within.
I have a generic TPA3255 amp and a generic TPA3251 amp. Both amps have ~1dB of channel imbalance in input gain. It's not TPA3116.
Is it common for TPA3251 and TPA3255 to have 1~2dB of channel imbalance in input gain?

Last edited by CowCat; 16th November 2019 at 12:15 PM.
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Old 16th November 2019, 07:53 PM   #1525
FauxFrench is online now FauxFrench  France
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For TPA3251 and TPA3255 I no found gain tolerances such as for TPA3116. For TPA3251 and TPA3255 only the typical gain is listed.
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Old 16th November 2019, 08:28 PM   #1526
multisync is offline multisync  Canada
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Most of these boards have op amps in front of the amplifier power amp chip. It is very possible that these op amps or the resistors around the op amps are causing the channel imbalance.
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Old 17th November 2019, 10:31 PM   #1527
xrk971 is online now xrk971  United States
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TPA3255 - all about DIY, Discussion, Design etc.
Quote:
Originally Posted by rhing View Post
Sorry for chiming in a bit late here, but I use a TI TPA3255EVM amp in PBTL mode powered by the Mean Well LRS-350-48 with a pair of KEF LS50ís, and this makes an incredible combination. Your KEFís will really sing with this amount of drive. When I powered my KEF LS50ís with the TI amp, I was taken back by the level of control I heard. Bass notes were complete and went deeper than I ever thought a small monitor could produce. The treble sweetened up as the amp burned in. If you want, you can have a pair running in BTL mode as mono blocks which will allow the TI amp modules to drive down to 2-4 ohms easily. Youíll need proper speaker cables for this combination, and I highly recommend using a loosely twisted pair of Duelund DCA16GA or DCA12GA Tinned Copper wire with bare wire ends.

With the TI amps connected in differential (balanced) mode with a source with volume control and balanced outputs, you will really be blown away with how transparent these amps can be. I connected a Pono Player with the ESS DACs and Ayre-designed analog output section to the TI amp, and it was shockingly awesome. For other sources, I suggest a very good preamp. The Pass DIY B1 with Korg NuTube Triode preamp offers additional gain along with that holographic triode sound signature. Paired with the TI TPA3255EVM amp, it makes a ridiculously budget-friendly high end amplification system that will compete with many high end audio systems.
Thanks for your detailed impressions of this amp. I agree that it is an excellent amp - able to hold its own against many of the top Clads AB amps in this power range. What I have noticed is this amp surprisingly quiet. Shockingly so.

LS50 sound like a great combo. Have you tried it in SE output mode (cap coupled)?
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Old 17th November 2019, 10:57 PM   #1528
mboxler is online now mboxler  United States
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Quote:
Originally Posted by rhing View Post
... I use a TI TPA3255EVM amp in PBTL mode powered by the Mean Well LRS-350-48 with a pair of KEF LS50ís...
Are you running two EVM's, each in PBTL, or one EVM in BTL?

Mike
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Old 18th November 2019, 01:16 PM   #1529
CowCat is offline CowCat
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The channel imbalance was actually caused by water trapped in my left ear. Water makes higher frequencies quieter. My left ear tends to trap water after a shower. After removing water from my left ear, I confirmed that there is no apparent channel imbalance in my generic TPA3255 amplifier.
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Old 18th November 2019, 01:23 PM   #1530
Yatsushiro is online now Yatsushiro  France
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Quote:
Originally Posted by CowCat View Post
The channel imbalance was actually caused by water trapped in my left ear. Water makes higher frequencies quieter. My left ear tends to trap water after a shower. After removing water from my left ear, I confirmed that there is no apparent channel imbalance in my generic TPA3255 amplifier.
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