Bypass the op-amp input buffer - only Audiophonics?

[Chazz6]

Lots of good Class D amplifiers offer selection of two or three gain levels, which I understand are achieved in the op-amp input buffer in front of the Class D module proper. But I see Audiophonics amplifiers that also offer the choice to bypass the op-amp buffer. This is attractive if your DAC puts out good voltage and your speakers are run at medium or low volume.
Does any other manufacturer of completely assembled Class D amplifiers offer this bypass option?

 

[Buckeye Amps]

Lots of good Class D amplifiers offer selection of two or three gain levels, which I understand are achieved in the op-amp input buffer in front of the Class D module proper. But I see Audiophonics amplifiers that also offer the choice to bypass the op-amp buffer. This is attractive if your DAC puts out good voltage and your speakers are run at medium or low volume.
Does any other manufacturer of completely assembled Class D amplifiers offer this bypass option?

Which model?

 

[Chazz6]

Which model?

Thanks for your question, Buckeye. Any of yours?
Several Audiophonics, for example, their LPA-S400ET Class D Stereo Amplifier Purifi 1ET400A 2x400W 4 Ohm
...
5 gain settings, switchable via jumper on the underside of the unit :
Gain of +7.2dB, i.e. a total of 20dB - Maximum power reached with a 4.19V RMS signal.
Gain of +12.5dB, i.e. a total of 26dB (default) - Maximum power reached with a signal of 2.07V RMS.
Total gain of 32dB - Maximum power reached with a signal of 1.05Vrms
Total gain of 34dB - Maximum power reached with a signal of 0.83Vrms
Bypass (buffer deactivated): In this case, the signal passes directly from the inputs to the modules, allowing the lowest possible gain of 12.5dB. This mode can be interesting when using a powerful preamplifier, capable of driving a load of 2 to 4K Ohm and reaching a voltage of 10V RMS.
https://www.audiophonics.fr/en/powe...ss-d-purifi-1et400a-2x400w-4-ohm-p-14557.html

 

[Buckeye Amps]

Thanks for your question, Buckeye. Any of yours?

Our NCx models, yes.

 

[boXem]

Bypassing the buffer has for effect to present a low impedance to the upstream component. At the same time, the upstream component has to output relatively high voltages due to the low amplifier gain. Result is increased system distorsion.
A properly designed buffer set to unity gain will be almost transparent (noise below 1 uV, distorsion below -130 dB) and maintain the high input impedance. As a result, system performance is better than with buffer bypassed.
That said, customer is king and our buffers can be bypassed via internal jumpers for our Arthur 4222/E1 and all of our A series.

 

[JohnnyNG]

The ability to bypass the buffer was a principal determinant (along with the slim form-factor) in my purchasing a pair of Audiophonics MPA-M400ET mono amps. Based on Amir's review, should have been no problem for my Topping Pre90. When I tried it, though, the sound was distinctly worse - weirdly undynamic and kind of "colorless". The combo seems much happier with Gain of +7.2dB and 94kΩ input impedance. Regardless, the buffered options are so close to bypass in terms of performance it was more of an academic interest I guess.