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?
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.
voltwide
IRS2795x
regulated frequency operation
IRS2795x have OCP
I use shottky and superfast diodes
No
80-85C at 300 watt out.
IRS2795x
regulated frequency operation
IRS2795x have OCP
I use shottky and superfast diodes
No
80-85C at 300 watt out.
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.
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
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.
I was reading recently some talk from Nelson Pass where he developed some elements about differences in amplifiers, and in the nature of the respective distortions, and what I understand as possible to interpret as positive aspects of second and third harmonic distortion as pleasurable colour.
Would be fun to artificially "inject" second and/or third harmonic distortion between the neutral DAC and the neutral 0.001% THD power amplifier stage (I'm pretty sure not to be the first to have this idea).
JMF
Would be fun to artificially "inject" second and/or third harmonic distortion between the neutral DAC and the neutral 0.001% THD power amplifier stage (I'm pretty sure not to be the first to have this idea).
JMF
And this one trick I also have tried, 2nd harmonic become noticeable from .5-2%, and it is not really warm or sweet or whatever how called it NP. It is rather weird sounding for me )) If you want to try, make my ADAU1701(I hared that design somewhere on diyaudio.com) demo-board and add 2nd harmonic. A lot of myths regarding sweet harmonics or about their sweet distributions but what I really believe that the power supply strongly affecting the sound, in many cases a power supply is contributor #1 into the sound.
Mastering engineer Bob Katz did exactly that with his "Blender": Katz's Corner Episode 25: Adventures in Distortion. (Link credit goes to Alexandre in this post.)
Very interesting link. I don't have the skills to design such a thing, but I would be curious of learning what would be the simplest schema allowing to implement such a thing.
But maybe it should go in another thread. If something starts in that direction, please let me know.
Best regards,
JMF
JMF11, it's an easy experiment, you can! Try the Soundforge or similar editor and prepare file.wav with a portion of even harmonics.
Today I finally soldered PFFB components to my TPA3251 amp. One thing is for sure, the noise is even lower, I have to put my ear 10-15cm from tweeter to hear it.
One odd thing happened, amp now produces click sound at power off. Its not loud, but I expect no sound at all, just like without PFFB.
One odd thing happened, amp now produces click sound at power off. Its not loud, but I expect no sound at all, just like without PFFB.
oooh, seems you have very sensitive speaker, right? I can hear a tiny noise with my 92db/m/w and S/N -104db(A) if I put ear 20mm from the tweeter cone. When -107db(A) amp tied the same speaker I hear nothing at all, maybe need retry again quiet night time.
DarkOne, if audio band captured correctly, S/N is too bad -60-70db(A) like 10-12bit. Probably the problem is low-resolution ADC you used.