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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 Yesterday, 06:57 PM   #801
irs20957 is offline irs20957  Russian Federation
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Originally Posted by IVX View Post
yeah, Ti has some appnote regarding post fb for 325x
Link please?
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Old Yesterday, 07:29 PM   #802
irs20957 is offline irs20957  Russian Federation
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Originally Posted by doctormord View Post
Nice work, i'm interested in the LLC supply data.
More precisely ask a question?
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Old Yesterday, 08:47 PM   #803
voltwide is offline voltwide  Ireland
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Originally Posted by irs20957 View Post
More precisely ask a question?
I'll do it for doctor Mord:

What driver chip do you use?
Unregulated fixed frequency or regulated frequency operation?
How do you protect the primary circuitry from overload?
Do you use synchronous rectification?
Did you measure efficiency?
max temperature of transformer windings under full load?
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Old Yesterday, 08:54 PM   #804
voltwide is offline voltwide  Ireland
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Originally Posted by irs20957 View Post
Link please?

Post feedback as proposed by TI introduces not big amounts of additional feedback - with a fixed gain of 20dB there is not very much you can reduce further. And this option requires a very linear audio front end to drive the TPA32xx. Considering the low THD of TPA32xx even without post-feedback I do not see a big point in TIs approach.
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Old Today, 05:15 AM   #805
irs20957 is offline irs20957  Russian Federation
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voltwide
IRS2795x
regulated frequency operation
IRS2795x have OCP
I use shottky and superfast diodes
No
80-85C at 300 watt out.
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Old Today, 06:39 AM   #806
JMF11 is online now JMF11  France
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Quote:
Originally Posted by voltwide View Post
Post feedback as proposed by TI introduces not big amounts of additional feedback - with a fixed gain of 20dB there is not very much you can reduce further. And this option requires a very linear audio front end to drive the TPA32xx. Considering the low THD of TPA32xx even without post-feedback I do not see a big point in TIs approach.


Thanks Voltwide for your feedback. So for you PFFB is not a "must have", and could have little impact (especially if the output stage has correctly selected components).


It also seems that up to now nobody reported with/without PFFB listening tests results.


The link to the TI PFFB application note: http://www.ti.com/lit/an/slaa788a/slaa788a.pdf


JMF
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Old Today, 06:52 AM   #807
voltwide is offline voltwide  Ireland
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Originally Posted by JMF11 View Post
Thanks Voltwide for your feedback. So for you PFFB is not a "must have", and could have little impact (especially if the output stage has correctly selected components).


It also seems that up to now nobody reported with/without PFFB listening tests results.


The link to the TI PFFB application note: http://www.ti.com/lit/an/slaa788a/slaa788a.pdf


JMF
Yes. PFFB is much more promising whith TPA3116 where THD can be reduced to levels similar to TPA32xx.
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Old Today, 07:15 AM   #808
IVX is offline IVX  Ukraine
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I tried such post FB in my own noise-shaper around TAS5558 with TAS5642, and I got .01%@4Ohm resistor load but .03%@4Ohm speaker load. I pretty sure if TPA3255 with post FB will show the same "miracle" Just too low loop gain to be true, when Ti will introduce 50db+ within 20-20k, like n-core, I'll call it "premium quality", so far just HiFi.
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Old Today, 07:33 AM   #809
JMF11 is online now JMF11  France
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Quote:
Originally Posted by IVX View Post
I tried such post FB in my own noise-shaper around TAS5558 with TAS5642, and I got .01%@4Ohm resistor load but .03%@4Ohm speaker load. I pretty sure if TPA3255 with post FB will show the same "miracle" Just too low loop gain to be true, when Ti will introduce 50db+ within 20-20k, like n-core, I'll call it "premium quality", so far just HiFi.

I often hear that hypex nCore is the top in class D amps. And their new fusion plate amps are my reference price to check if my TAS3251 price is good enough or too expensive.


I wonder how nCore and TI TPA32xx/TAS32xx compare in real life applications and listening tests (not only THD measures). It looks to me that both try to target lowest distorsion / linear response.


JMF
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Old Today, 08:11 AM   #810
IVX is offline IVX  Ukraine
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well, to be honest, I believe all of them sounds the same. Every time when I offered to believers hear the difference class D vs class AB(D and AB were switched by relay on the same speakers and matched gain), they failed. Class D was uCd like amp, and AB was 100mA biased .01% vs 20-20kHz flat. Of course some really ugly class D chips from ST(STA350BW) with marginal specs will sound different but 3255 for sure sounds equal to others good amps, at least for 99.999% users.
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