TPA3255 - all about DIY, Discussion, Design etc

Jump to Latest
#3,841
I would not be to sure about that diagnosis. The very strange behaviour of the speaker impedance may have some impact on overall frequency response. Class-D LC filter output may be an issue here, depending on characteristics of the post filter feedback. Can you provide a frequency response measurement with a) nominal resistive dummy and b) no load at all?
 
#3,844
linuxfan said:
I agree. It's good to know I'm not the only one who hears this harshness.
Click to expand...

+1
I can confirm this
But also depending on your speakers and room

1/ TPA3255 non PFFB with bypassed op-amps - image more forward and a bit harsh, on the edge

2/ TPA3255 with PFFB and op-amps - soundstage less in your face and smoother highs

Some people may like option 1
Now i am very happy with option 2

Enjoy..
😀
 
#3,846
I appreciate that people like JLesterP, drMordor, etc, seem to be advancing the optimal use of TPA325x amplifiers, but until this development settles, I'm really enjoying my ICEpower 50ASX2 (+ jfet buffer).
On the subject of buffers, it seems that getting the "recipe" right for TPA325x amps involves using just the right opamp as a buffer, and the current favourite appears to be the OPA1656 ...
and this makes me wonder - most DAC's have an opamp-based output stage, so if that opamp happens to be an OPA16xx (such as iancanada's ES9028Q2M/ES9038Q2M DAC) maybe that would be a good candidate for direct input to a TPA325x amp, thus reducing the total number of opamps in the signal chain?
 
Last edited:
#3,848
TPA325x with DAC PCM5242
No opamps, no PFFB.
 

Attachments

  • 3255ц4252.jpg
    3255ц4252.jpg
    271.4 KB · Views: 520
#3,855
Could someone help me out a little bit.
I believe I read somewhere that Class D can be sensitive towards an uneven load, such as not having a speaker connected on one output.
If I recall correctly it was a matter of it's BTL or not.
The reason I ask is because I'm going to be making driver measurements later to adjust the DSP.
I've got both the 3251 4 channel and 3255 2 channel boards from 3E.
 
#3,858
drMordor said:
TPA325x with DAC PCM5242
No opamps, no PFFB.
Click to expand...
I think the combination of TPA325x and PCM5242 is an exercise in technical simplicity - to get digital sources to amplification with the minimum of devices and circuitry. The PCM5242 requires no I/V stage so its (differential) outputs can go straight to the unbuffered inputs of a TPA325x amp.

In fact this is virtually the same as TI's own equivalent product - the TAS3251, except that drMordor has possibly provided the PCM5242 with better clocks and better caps.
 
You must log in or register to reply here.
Top Bottom