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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 20th October 2017, 01:38 PM   #421
DPH is offline DPH  United States
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Because the gentlemen in question appears to be from India (insofar as I can tell), which runs off 50/220. I did an extremely quick look for the data in question as I was going to bed. And, yes, I brain farted this is happening after the rectifier, and needs to be on double the frequency.

So raise that number to 2.25 ohms instead. No big deal. For building an intuition about how psu's work, it's very minor. Far, far less important that accurately modeling the PSU load, which we're treating as a resistor.

So you have some proof that more capacitance helps bass response? We're waiting on pins and needles.
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Last edited by DPH; 20th October 2017 at 01:45 PM.
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Old 20th October 2017, 02:02 PM   #422
abraxalito is online now abraxalito  United Kingdom
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Quote:
Originally Posted by DPH View Post
So you have some proof that more capacitance helps bass response?
No proof of anything no, some observations in a few contexts that adding capacitance does help subjectively with the bass. Nothing in regard to TPA3255 as I've yet to acquire one. I'll be sure to post when I have tried one myself though.
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Old 20th October 2017, 02:20 PM   #423
DPH is offline DPH  United States
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Okay, so, no. And, as I hope you would appreciate from looking at the circuit, there's no basis. You'll either have such a low amount of capacitance as to cause the rails to modulate the amp's output substantially or not. Moving up in capacitance mitigates that, but the effect falls off extremely fast. It's not like we're talking the experiments done on some chip amps using some 330/470 uF capacitance to support an entire rail of a 3875/3886.
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Old 20th October 2017, 02:25 PM   #424
abraxalito is online now abraxalito  United Kingdom
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Originally Posted by DPH View Post
And, as I hope you would appreciate from looking at the circuit, there's no basis.
I've not yet looked at the circuit but I shall do once I get my hands on one of these -YJ00312-TPA3255??????300W+300W)-???

In the meantime, looking forward to your analysis.
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Old 20th October 2017, 03:26 PM   #425
DarkOne is offline DarkOne  Slovakia
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Hi guys, I'm working on layout for TPA3251 and I struggle with output inductors selection. I seen many posts about Wurth being the best, but they are a bit too large for my needs. Simple parametric search at Mouser resulted with Bourns SRP1265A-6R8M, 6.8uH (not 7uH, but the difference is minimal), 18A DC and 11.5miliOhm. Is my choice completely wrong, or it might be working well?

This is my first Class-D project, so I don't know what to look for. In the past I made a dozen of amplifiers, designed by myself and copied.

Thanks

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Old 20th October 2017, 06:38 PM   #426
Linas Lithu is offline Linas Lithu
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Originally Posted by SanjeevM View Post
My concern is not to 'clean up' the power supply. The idea of a large cap bank is to provide current when needed by the Amp for bass.
What caacitor bank do you mean? Like this?
2pcs NOVER high end cap 10000uf 50V Capacitors 35*35MM for hifi audio -in Demo Board Accessories from Computer & Office on Aliexpress.com | Alibaba Group
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Old 20th October 2017, 10:12 PM   #427
DUG is offline DUG  Canada
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Quote:
Originally Posted by DarkOne View Post
Hi guys, I'm working on layout for TPA3251 and I struggle with output inductors selection. I seen many posts about Wurth being the best, but they are a bit too large for my needs. Simple parametric search at Mouser resulted with Bourns SRP1265A-6R8M, 6.8uH (not 7uH, but the difference is minimal), 18A DC and 11.5miliOhm. Is my choice completely wrong, or it might be working well?

This is my first Class-D project, so I don't know what to look for. In the past I made a dozen of amplifiers, designed by myself and copied.

Thanks

Regards
RoboS
Look for inductors with a flatter inductance vs current curve...seems to relate to lower distortion.

Red line better than black line.
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File Type: jpg Inductance vs Current.JPG (15.0 KB, 604 views)
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Old 21st October 2017, 04:18 AM   #428
SanjeevM is offline SanjeevM
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Yes, 10000uf capacitors in parallel.
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Old 21st October 2017, 06:39 PM   #429
doctormord is offline doctormord  Germany
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The SRP1265A-6R8M aren't suitable for class-d filters at all due to carbonyl material and corresponding high THD. Avoid them.
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Old 21st October 2017, 09:07 PM   #430
DarkOne is offline DarkOne  Slovakia
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Thank you guys, I finally squeezed the Coilcraft MA5173-AE (as in EVM) to my design and ordered PCBs. Lets see how many mistakes I have done
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