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Class D Switching Power Amplifiers and Power D/A conversion

TPA3255 - all about DIY, Discussion, Design etc.
TPA3255 - all about DIY, Discussion, Design etc.
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Old 14th August 2018, 12:38 PM   #791
silasmellor is offline silasmellor  Denmark
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TPA3255 - all about DIY, Discussion, Design etc.
Quote:
Originally Posted by earsofgold View Post
How do I find out what gain the board is (I was thinking about the je audio tpa3255 board), and how to calculate what kind of preamp to use? I saw that the tpa3255evm uses NE5532 opamps and there are NE5532 boards available on ebay but not exactly sure what I'll need or if there are better options.

I'm not really a fan of having everything set up with massive gain with no physical volume knob! My Focusrite 6i6 audio interface has a knob on the breakout box for the monitor outputs, but I'd rather have a control on the preamp or amp as well.
I am not sure what the gain is for the 3e board to be honest, but the owner is a user here so you can ask him directly. But if you're using your 6i6 as a frontend that already provides a preamp and you don't really need anything else...
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Old 16th August 2018, 12:05 PM   #792
chermann is offline chermann  Austria
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Quote:
Originally Posted by earsofgold View Post
How do I find out what gain the board is (I was thinking about the je audio tpa3255 board), and how to calculate what kind of preamp to use? I saw that the tpa3255evm uses NE5532 opamps and there are NE5532 boards available on ebay but not exactly sure what I'll need or if there are better options.

I'm not really a fan of having everything set up with massive gain with no physical volume knob! My Focusrite 6i6 audio interface has a knob on the breakout box for the monitor outputs, but I'd rather have a control on the preamp or amp as well.

Hi

i just measured the Chinese YJ TPA3255 board and its about 27db GAIN. my TI3251EVm board has about 26db.
so its very loud . do not use fixed output from a Cd player or DAC.... its about 2,1Vrms over RCA as FauxFrench wrote.
for this boards no preamp is needed. i personally use the amp over pc (tidal, foobar..etc...) and my DAC (RCA - connnection) to regulate the volume and it works fine

so my interpretaion is that the 3e board will have about the same gain.

chris
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Old 16th August 2018, 02:34 PM   #793
denbret is offline denbret  Canada
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Hi, I have the tpa3251 3e-audio but I didn't taken measurement, compared to other amps class D that I have, this amp has a sensitivity lowest, can be 22-24db.
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Old Yesterday, 08:02 AM   #794
irs20957 is offline irs20957  Russian Federation
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Hi, I developed 2 version amp TPA325x
Now build new version, are there any questions?
Gerbers after testing will be available to all.
Conditions:
1) Output inductors based on RM8 Epcos
2) 1st stabiliяer - LM5007 or use 12v output from PSU

Your wishes?

Sorry for my bad English))))
Attached Images
File Type: jpg 3255llcpsu.jpg (992.7 KB, 98 views)
File Type: jpg 3255White.jpg (397.5 KB, 96 views)

Last edited by irs20957; Yesterday at 08:07 AM.
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Old Yesterday, 06:36 PM   #795
doctormord is offline doctormord  Germany
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Nice work, i'm interested in the LLC supply data.
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Old Today, 01:33 AM   #796
IVX is offline IVX  Ukraine
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doctormord, FYI, not shielded LLC inductor or combo-trafo makes near impossible EMC compliance, and hence legal distribution. Picture irs20957 shows unshielded trafo and one winding of the common mode choke was placed exactly against of trafos gap, I'm ready to bet that conducted emissions test will be even better without that common mode choke.
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Old Today, 09:25 AM   #797
JMF11 is online now JMF11  France
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Question about PFFB,


Has there been tests about the sonic (subjective) impact of PFFB ? I understand that it improves THD figures, especially with not so perfect inductors, but I would like to know if:
- somebody experienced some sonic/subjective drawback (better without PFFB than with it) ?
- if it still has benefits if using "reasonable" quality coils like the ones used in the discussed designs in this thread ?


I have to decide whether to include it or not in my TAS3251 design, and the PFFB adds to the size of the BOM and complexity of the circuit.


Best regards,


JMF


JM
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Old Today, 09:38 AM   #798
IVX is offline IVX  Ukraine
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The post feedback network reduces closed loop gain a lot, hence without additional amplification by the good OP, the DAC of TAS3251 has no chance to provide 5-10Vpeak.
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Old Today, 10:36 AM   #799
JMF11 is online now JMF11  France
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Quote:
Originally Posted by IVX View Post
The post feedback network reduces closed loop gain a lot, hence without additional amplification by the good OP, the DAC of TAS3251 has no chance to provide 5-10Vpeak.

This reduces a lot the interest of the PFFB or of the chip, as the benefit of the TAS3251 is the included DSP AND DAC AND Amp. If you have to add additional amplification in the loop :-(


This is described / explained in some application note ?


JMF
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Old Today, 10:42 AM   #800
IVX is offline IVX  Ukraine
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yeah, Ti has some appnote regarding post fb for 325x
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