OK, so you made a change from one amp to another and then you hear a difference. It's probably just a difference in the output characteristics compared to your last amp. For example, if your previous amp had an increasing output impedance at high frequency this appears in series with your tweeter and acts like a voltage divider - in essence a tone control that will "roll off" the high frequencies. Even the TPS3255 has an increasing output impedance at HF, but perhaps your previous amp had more of that, and now you have less, and so HF is relatively exaggerated. It would not surprise me.
This happens all the time especially with tube amps that have significant output impedance across the board. This impedance appears in series with the speaker impedance as seen from a hypothetical voltage source within the amp. It causes the response to vary, enough to make the "sound" change tonal character from one amp to the other. It's not as common or appreciated for solid state or class D amps, but it can still happen.
I think that this picure is the answer;
theres a +1db in frequency response a 20Khz due pffb on 8ohm load.
That's why TI added a 330pf feedback capacitor
on op-amps in pffb. I initially didnt put this because
the TI implementation does not suit the 3e-audio board:
in the latter, the op-amps using se input are cascading,
so there would be 2 low pass filter on 3255 non-inverting input
and just one on the inverting input.
This is a flaw on the 3e-audio pffb implementation,
in fact they reccomend to use balanced input,
where op-amps are not cascading.
Since I use SE input, I added just one feedback 330pf capacitor on main opamp, and treble seems to be better.
I will try to change op-amps as long I find some suitable
replacement near (dont want to receive some other fake from china
)
theres a +1db in frequency response a 20Khz due pffb on 8ohm load.
That's why TI added a 330pf feedback capacitor
on op-amps in pffb. I initially didnt put this because
the TI implementation does not suit the 3e-audio board:
in the latter, the op-amps using se input are cascading,
so there would be 2 low pass filter on 3255 non-inverting input
and just one on the inverting input.
This is a flaw on the 3e-audio pffb implementation,
in fact they reccomend to use balanced input,
where op-amps are not cascading.
Since I use SE input, I added just one feedback 330pf capacitor on main opamp, and treble seems to be better.
I will try to change op-amps as long I find some suitable
replacement near (dont want to receive some other fake from china
)Attachments
Last edited:
Hi I recently order two EAUMT-0260-2-A boards, and they work perfectly, I see that 3e audio is involved in this thread and I would like to ask them a question about improvements in the board capacitors. The muse capacitors are excellent, however, the 4 2200 uf 63v capacitors are Chongx.
Can I change the capacitor with a nichicon 2200 uf 63v FW?
Can I change the capacitor with a nichicon 2200 uf 63v FW?