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Ioannis Makris makrisj at gmail.comI have managed to replace both buck DC-DC converters with AMS1117 3.3 & lm317 linear regulators and I successfully got rid of the mentioned 1 MHz buck converter clock to obtain as pure a signal as possible. Do not expect miracles as the DAC's are 8-bit and have a best case SNR of -48dB, but getting the sideband modulation out of the signal surely improves the resulting spectrum a lot. I have performed the mod on 4 fl2k adapters. Two of them came with a 1.2V AMS1117 for the 1.2V and a buck psu for the 3.3V. Another two came with 2 buck psu's Using 2 LM317 is a bit complex but can be done, as my proof of concept testbed has demostrated. One could actually fit them inside the plastic box. Mind you, linear regulators can get quite hot. Still not hot enough to inflict any damage after a 8-hour operation of the device. Another notable effect was the total elimination of "cb status 1" message on the testbed. The testbed suffered a lot of USB connection drops due to poor power delivery to the chip, which is also the plague of those devices that is causing bad reviews along with the poor assembly of the cable from those that use the device in regular vga output mode. The workaround is extremely simple; we use the onboard capacitors for filtering the output of the linear regulators, I install them inverted and add metal pins from 1/4W resistors to patch the power from the pin of the buck chip to the input of the linear regulator. Same with ground. Of course we are using USB3 interface that can provide more than 2.5W (500mA) of output power. I haven't thorougly tested device operation and stability under USB2.0 which has the aforementioned power limiting. The device looks stable though. There are implementations utilizing a pair of AMS1117 from factory. [image: 20190125_194224_001.jpg] -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/osmocom-sdr/attachments/20190208/c860439a/attachment.htm> -------------- next part -------------- A non-text attachment was scrubbed... Name: 20190125_194224_001.jpg Type: image/jpeg Size: 239036 bytes Desc: not available URL: <http://lists.osmocom.org/pipermail/osmocom-sdr/attachments/20190208/c860439a/attachment.jpg>