Mod input sensitivity TPA3255

[solderdude]

Yes, not just a claim either but math based on the spec sheet of the 3255.
It is because this amp was not designed to be driven from a 0.9V source.
He used a headphone amp between the source and his amp and that solved the problem but now he does not want that headphone amp in between any more so needs to increase the gain in this particular amp. (see post#11)

Gain of non PFFB 3255 = 16dB (but balanced so is 22dB) = 12.3x gain so 11.3V max regardless of power supply voltage (assuming standard application, it may even have less gain than that but certainly not more gain)
At 36V it can reach 27V so would require 2.2V in to reach that.
Only 0.9V is available so the amp needs to have more gain.
This is what the proposed mod will bring.

As this is used for a subbass I would recommend (because of the lower input imp) to increase the capacitor values 2x as well so would recommend to fit 22uF or 47uF instead of the fitted 10uF input caps.

 

[Roland68]

so you claim that there is a -6.8dB missing in his amplifier? That would mean he only makes 27W per channel. Are you sure?

We don't know that and are only talking about changing the gain factor, we don't have any more information.
The maximum available input voltage for the TPA3255 would be nice.

 

[solderdude]

We don't know that and are only talking about changing the gain factor, we don't have any more information.
The maximum available input voltage for the TPA3255 would be nice.

TPA3255 on 48V DC requires 2.45Vrms assuming the datasheet recommendations are followed for 48V operation (33k)
Most of these amps (PS up to 40V) seem to have 22k in there. TPA 3251 usually has 18k as feedback resistor.

 

[Roland68]

TPA3255 on 48V DC requires 2.45Vrms

But I asked about the available input voltage.

@DiegoAlm
Can you tell us?

 

[solderdude]

The available input voltage is mentioned in the first post 0.9V.

 

[Roland68]

The available input voltage is mentioned in the first post 0.9V.

Sorry, I forgot, it's been over a year.

 

[LSPhil]

If you want to increase the output voltage of DSP, then use the HSQ Equalizer from 10Hz q=1 +7,? dB I tried it on my miniDSP and it works.

 

[LSPhil]

Here is an example