Footnote on R4 Pro Gain Stage and Limiters

[sinnlicht]

Hi all, 

To counter a lot of confusion circulated on the web, here is the definitive answer regarding the fact that R4 Pro's gain control and limiters are all PRE ADC:

I can't confirm the noise circulating about the Roland designs based on a functional block diagram which only intends to show the last gain stage and limiters are in the A/D chip. It does not show signal flow thru the A/D chip. If that noise was based on engineering then you would not be able to achieve 24 bit resolution and you would have have a useless limiter ! This is what I say in my Recording FAQ.

Please note, in an effort to reverse the flood of bad info circulating in some recording forums, I suggest reading the technical specifications for the AK4620B series of ADCs used in the R4Pro and the R44 which is available for download from the manufacturer's website or the link below. "- Input PGA: 0dB to +18dB, 0.5dB/step (for single-ended input)" This is a digitally controlled analog Programmable Gain Amplifier that is controlled by the inner gain knob. Furthermore, the block diagram, supplied by the A/D converter's manufacturer, clearly shows the PGA or analog gain circuit ahead of the analog to digital conversion process in the signal chain. This is essential or 24 bit resolution could not be achieved. Furthermore a digital limiter post A/D conversion is useless.I strongly suggest you not set the inner knob to 12:00 and add gain in post, this compromises the quality of your recordings.

It's equally obvious there is no digital gain stage in the AK4620B series of A/D converters but there is digital attenuation and a digital output mute function.

AK4620B technical data sheet : http://datasheet.elcodis.com/pdf2/105/21/1052101/ak4620b.pdf

Note on page 23 :"The IPGA is an analog volume control that improves the S/N ratio compared with digital volume controls."