Follow-up on Apex A9 amplifier
Dear all,
Here is a short (and probably final) follow-up on my posts # 12984 and 12986 in this enormous thread. I have now put my homemade Apex Audio A9 amplifier PC boards with power supply in a (recycled) cabinet (19", steel). The power supply lines run at ± 37V. I have not modified mr. Slavkovic's schematic in any way, with a reduction of the series resistors for the Z15 zeners as the only exception (see post 12984). The amp really sounds great, it sings! (as is said on the Russian Komitart site). However, I disagree with one statement made by our Russian friends - they mention that quiescent current through the power MOSFets should be set to 15 mA. In my ears, this is not correct, Iq should be set to 30 mA or a bit higher (as was also said by Mr Slavkovic). Purity of the sound is much better at the higher quiescent current, and the heatsinks don't even become lukewarm. Anyhow, this project can be strongly recommended.
My amp is a dual mono setup (each channel has its own toroid power transformer and power supply) although both channels are combined in a single cabinet. Imaging is very good.
Best regards,
arensattic
(aka Aren van Waarde)