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TPA3255 - all about DIY, Discussion, Design etc.
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Old 29th September 2017, 09:50 PM   #341
454Casull is offline 454Casull  Canada
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Quote:
Originally Posted by doctormord View Post
I'd guess, TI rigged them up just with some short wires to test them all.
Do you think this might have any negative impact other than a slightly messier layout?
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Old 30th September 2017, 05:33 AM   #342
Kindhornman is offline Kindhornman  United States
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TPA3255 - all about DIY, Discussion, Design etc.
The real question should be with the output inclusive feedback loop if the higher quality Coil Craft inductors still make any measurable or audible difference vs a lower cost inductor? Dr. Mord would seem to have this answer with his TPA3251 board development.
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Old 30th September 2017, 10:47 PM   #343
rhing is offline rhing  United States
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Originally Posted by 454Casull View Post
Do you think this might have any negative impact other than a slightly messier layout?


I think as long as the wires are kept as short as possible, it shouldn't be an issue. On the TI TPA3255EVM board, it looks like there is space on the bottom side to mount the Wurth inductors. This could be done by soldering short segments of wire to the two terminals of each inductor and feeding the wires into the through-holes where the stock Coilcraft inductors are mounted. I wonder why TI would determine that the Wurth inductors would perform better, yet design their EVM to use the Coilcrafts instead. This could be splitting hairs though, because I am enjoying the TPA3255EVM in stock form in my system.


Besides adding a pair of Altec Peerless 15335A input inductors to convert unbalanced RCA inputs to the differential (balanced) inputs of the TPA3255, I might try implementing the PFFB modification, which is easily accommdated on the TPA3255EVM PCB. I just need to try and dig my trusty Metcal soldering workstation out of storage.
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Old 30th September 2017, 11:36 PM   #344
voltwide is offline voltwide  Ireland
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Originally Posted by rhing View Post
I wonder why TI would determine that the Wurth inductors would perform better, yet design their EVM to use the Coilcrafts instead. This could be splitting hairs though, because I am enjoying the TPA3255EVM in stock form in my system.
There is no doubt that the TPA can be tweaked yielding a performance that is superior to the EVM.
But I presume it is not the intention of TI to present an EVM with highest performance with best parts available on the market - but more a reference for high quality with affordable parts.
Personally I think the EVM performs quite good and I really doubt that any of our golden ears could notice the difference to a more sophisticated TPA3255 design.
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Old 1st October 2017, 10:45 PM   #345
doctormord is offline doctormord  Germany
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Quote:
Originally Posted by Kindhornman View Post
The real question should be with the output inclusive feedback loop if the higher quality Coil Craft inductors still make any measurable or audible difference vs a lower cost inductor? Dr. Mord would seem to have this answer with his TPA3251 board development.
At pure resistive load, the advantage is very minor, especially at output levels below 10W. With complex loads, PFFB might control your speakers better, but this is something i haven't "tested".

I.e. the actual board performance in PreFilter PBTL without an extra AFE and no PFFB is actually like so. (PVDD=30V, Load 5R, no heatsink:

TPA3255 - all about DIY, Discussion, Design etc.-steps_tpa3255_30v_5r0-png

10V = 25W

Plot taken by Voltwide. When using "low cost inductors" the advantage of PFFB is pretty obviously. Also/especially with TPA3118/TPA3128.
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Old 2nd October 2017, 04:31 AM   #346
Kindhornman is offline Kindhornman  United States
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TPA3255 - all about DIY, Discussion, Design etc.
Thank you Dr. It would seem you would still want to use a high quality output coil but with the PFFB circuit going to the best coils as found without the output inclusive circuit may be overkill? Would it make a difference between the Wurth and CoilCraft inductors with the PFFB?
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Old 2nd October 2017, 06:41 PM   #347
doctormord is offline doctormord  Germany
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As said (also by Voltwide), it is some kind of hairsplitting. PFFB might tighten the control of complex speakers/loads. You'd better ask Voltwide about this. If you need to get better by like 0.002% THD at 1kHz compared to the coilcraft, you may try.

Regarding the Wurth inductors, their advantage mostly come from physical dimension/construction. I actually use Codaca inductors in place, Voltwide is using Ferrocore. (Same geometry)

TPA3255 - all about DIY, Discussion, Design etc.-img_9909-jpg
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Last edited by doctormord; 2nd October 2017 at 06:48 PM.
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Old 3rd October 2017, 03:27 AM   #348
Kindhornman is offline Kindhornman  United States
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TPA3255 - all about DIY, Discussion, Design etc.
Thank you Dr. I think you've answered my question, use one of the better inductors and everything will be fine.
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Old 4th October 2017, 10:08 AM   #349
sybic is offline sybic  Poland
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My modifications :

Filter :

1.
choke CoilCraft VER2923-103

2.
680nF EPCOS instead 470nF

3.
NE5532 instead TL072

4.
6 x Nichicon Fine Gold 10uF in the signal path instead 6x22uF


5.
LM2575HVS-15 instead LM2575S-15

6.
choke in the stabilizer 220uH (221) instead 22uH (220)

7.
2k instead 2.2k (stabilizer LM317)

8.
220uF (Low ESR) instead 22uF (LM2575HVS-15 - 15V, LM317 - 12V)

9.
capacitor PVDD
1500uF Panasonic Low ESR instead 3900uF Elna(???)

10.
10k 1% instead 10k 5%

Click the image to open in full size.
Click the image to open in full size.
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Old 4th October 2017, 10:47 AM   #350
Kjeldsen is offline Kjeldsen  Denmark
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looks really good with the modified PCB add on, instead of trying to make it fit, on the original PCB.

As far as i remember, the minium safety distance between the SMPS PSU's is 5-6 mm. It seems to me they are very close, and might even touch each other?
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