“PAB autobias” versus “Adaptive autobias”




    Some of you may have heard about “Adaptive autobias” which was introduced as something revolutionary in 2006.

    Regarding friendly using simplicity Adaptive Autobias is superior to our PAB autobias because there is not even one single button to press, it is a kind of “plug and play” autobias. Our PAB autobias has one button to press and need around 30 second to have our microprocessor to reset the bias settings.

    However if we have a button to press on contrary of Adaptive Autobias, it is because the way their autobias works is not the proper way to run an autobias. The main reason is that it works in real time and this it is not a proper technology to set the bias, whereas our PAB autobias put the amplifier in mute mode during the bias reset. And any expert will tell you that bias has to be set once, without signal and after that, it should only be checked once or twice per year, depending how many hours you use your amp per day. That’s all.

    Having the bias settings in real-time increases in basses in particularly (that’s the reason it is not so obvious) and don’t reduce it has stated by their inventors and we consider as nothing else than a marketing argument, to make potential buyers feel safe they won’t need to do any setting. About this last statement, we think that Adaptive Autobias inventors were truly right about one point in the 21st century, a user should not need tools like a screwdriver to set the bias, that is the reason we launch as well our PAB autobias in May 2011.

    Probably because Adaptive Autobias designers wanted to make it cheap to produce by avoiding to use a real microprocessor and engineering research fees, they chose a basic and simple technology with a cheap OP chip plus 6 transistors. A sarcastic alternative name for Adaptive Autobias could be “Marketing Autobias”. Those interested by the technique can click on the picture on the right to have a look to this Adaptive autobias schematics and will see that there is nothing magic and that they just use a cheap OP chip ref. TL084 at $0.20 per piece. The total cost of this Adaptive auto-bias is then less than $3 including all components and any DIY’er can duplicate it.

    This said, we think the amplifiers using Adaptive Autobias are good amplifiers, though not totally our taste, but they are among what we consider as good tube amplifiers BUT only because they use good components and good output transformers and certainly NOT because of their “Adaptive Autobias”. It is also interesting to see that despite its very cheap production cost and not patent, not any other company has chosen to use this real-time autobias in their amplifiers.

    Our PAB auto-bias on the contrary combines all advantage of manual bias and the advantage of a friendly user interface.

    It could be described as a manual bias managed by computer. Our PAB autobias have a more expensive cost as we use a real microprocessor and a few other processors (but none of them is in the signal path of course !).  So we would be foolish not to have done the same autobias than the Adaptive Autobias if the result was so good, as it is so cheap to produce and not patented is it existed already since late 90’s (Actually we tried it for real that’s the reason we bought one unit and have internal picture, we wanted to see their schematics to see if it was worth doing research in that way).

    The reason we choose an alternative much more complex technology, having taken one year development in partnership with digital department of South-West Central university of China, was really aimed with the core idea that the bias should be set WITHOUT signal and NOT in real-time.