![bias amp 2 manual bias amp 2 manual](https://content.groove3.com/images/site/product/V/itemid_16072_thumb.0.jpg)
What kind of distortion improvements can be expected with EFB regulation vs. I have discussed EFB in the sense of tracking B+ "sag," but it also tracks B+ boost, or said another way: mains fluctuations. There is typically a distortion null that can be tuned for by adjusting bias (fixed bias) of the output stage. Yet another benefit to EFB is you can typically tune the output stage to idle the output tubes cooler while still achieving the lower distortion at full power output. Thus you get the same low output stage distortion with an EFB regulated output stage as you do with a traditionally regulated power supply.Īnother major benefit of EFB regulation is the cost to implement is significantly less, as well the components to operate the EFB regulator run much cooler than a traditional linear regulator. Thus from the perspective of the output stage, it can't tell the difference between traditional regulation and EFB regulation since in both cases the voltage relationships are held constant. Thus even though there is a power supply sag as the amp is pushed to full power, the relationship between power supply voltages (plate, screen, bias) are maintained. It does it by allowing the power supply voltage to sag as it will and allows bias and screen voltages to "track" power supply voltage sag. Many commercial amps use regulated power supplies, and certainly it works well, but it can be costly and can generate excessive heat.ĮFB achieves similar results as full-on regulation.
![bias amp 2 manual bias amp 2 manual](https://i0.wp.com/wallofsound.ca/wp-content/uploads/2017/11/bias2-3.jpg)
Thus the operating point of the output stage is fixed regardless of power output level. In a well designed regulated power supply, these three voltages are held rigidly in place at any power output level. One way of course to address this is to regulate plate, screen, and bias voltages. In a two channel configuration, when both channels are driven to full power, it can cause the power supply voltage feeding the output stages to sag to such a degree that it causes a shift in output stage operating point. Power supply droop becomes greater the more load the power supply is asked to support.
![bias amp 2 manual bias amp 2 manual](https://theaudiobrew-uploads.s3-us-west-2.amazonaws.com/uploads/2020/06/bias-amp-2-preamp-cover-2.jpg)
An EFB controlled output stage is most useful in a two channel amplifier where both channels are powered from one common power supply, and where there is significant power supply droop or sag from idle to full power when both channels are driven, and where the output stage is sensitive to power supply droop.