I "sang too early", my two ants work at 5081 but in few hours  one of them every hour delays the response of shares reaching 0.6 Gh really (the third number).
So only one is able to work till 5081 (after that value many HW errors) and my actual configuration is 4F81.

Me too, on my hub i jump the 5V current limitations soldering a wire on it.



Changed also the R2 to 4.7K and now I can use 5081 without HW errors, i put also two fans.

Do you know how is the circuit of your hub ?
One of mine had 9V 2A p.supply but internally for have 5V use one 7805 that is able to give .5A or 1.5A with a good dissipator, with this is impossible to have more than 1.5A totally.
I bought a new one, in the photo, with 5V 4A ps, without internal regulator, means that the current is regulated only by the usb interface (1A) that i'll try to jump over today.

Yes GREAT in any sense!!

Did you measure the coil, asic and AOZ1021A temperature ?
Are they hot ?
which resistance value do you use for R1 (2.49 K)?

I have only two ant miner actually.
My Hub voltage output is limited to 1A (written on the box) and power supply is 4A for 4 ports.
The usb voltage drop to 4.52, means that ant drain more than 1A, i didn't measure the current.
The next step will be to open the hub and cut + and - wire (the external one of the usb connector) and connect them directly to the main wires of the power supply without the limitation of the chip.
Doing this you can use all the power without limitations and the maximum number of ant become  3 for this hub.

After reading all this thread and learn, now I have 2 AntMiners working at 3.0 Gh.
With out of the box AntMiner, step by step i change the clock parameter to 0881 (1.8Gh), after that value i collect many HW errors, so i add R2 10K and change R1 with 3.3K (dismounted from a cd drive board).
Now all the errors disappear but the ant miner became really hot, i mount it on a dissipator (2.9 °C/W) dismounting the original one leaving the rubber and smearing thermal silicone grease, the coil also was hot (50°C).



Now the ant miner works without errors till 0A81 (2.2 Gh).
Pushing up the frequency the coil and the asic increase their heat.
At this point i decide to dissipate also this heat. I cut a piece of aluminium and another squared piece for the asic (8x8 mm and 2mm thick) for equilibrate the different heights of coil and chip.



Remember to put always thermal silicone grease.



Now i try to increase the frequency till 4E81 (3.0 Gh) without HW errors.



After all i discover that also the power chip is hot (70 °C), so decide to put a little piece of aluminium with grease on top of it glued (cyanoacrylate) on the aluminium.



I use an UsbHub with 4A power supply limited at 1A for each port, but the real voltage on usb ports is 4.52 Volts.

The software is BFGMINER 3.10.0 and the OS is Open Suse.
I insert also inside the conf the icarus-timing with the right Hs value extracted launching miner.php on the web server (Apache 2).

Now for me is enough. Thanks all.

My bfgminer.conf