Aleph 3 30W A class Amplifier
This is another very popular build form mr. Nelsson Pass . It is a 30W A class power amplifier. All output transistors need a huge heatsink and after build it need to be setup. Setup is very easy all what you need is to clamp dmm (which is set to Dc V) at the amp output and to measure dc , which need to be slightly negative, at the same time led diode light will be brightest. For those who like to tweak their builds mr.Nelsson leaved short tutorial on DIYAudio forum how to do it.
However on these I decided to try my favorite small power Mosfets, the
Toshiba 2SJ313’s. Apart from a different package and pin-out in some
amplifier models, they will drop right in as replacements, and they need to be matched for Vgs at 10 mA.
The Toshiba’s are preferred, but you can make do with other comparable modern Mosfets if you can’t get these parts.
Noting that some units had zener noise with R105 at 4.7K, I dropped that value to 3.3K, and you will note that I optionally deleted Q104, the over-current protection. Also, I moved the chassis ground connection directly to the AC Earth ground.
The addition of the Toshiba Mosfets made for an immediate improvement in power supply noise rejection, dropping it typically by a factor of 4 to 6, to as low as 50 uV unweighted output. This alone justified the effort. Also, as a tweak, you can replace the 220 uF caps with the silk caps from Elna. Listening tests showed a significant improvement over the originals, and I gave copies of these to my business partners for Xmas.