How Poor Is The Sound Quality From Low Bias F5 Amplifier?

This F5 amplifier is using for my daily amplifier yet also as my reference. I am really enjoying the music from this the F5 amplifier. They are pure, dynamic and detail. So I guess no others amplifier on my DIY journey can make the sound as good like this. Seriously, I only have several amplifier that blown my mind, one of them is Elector Mini-Crescendo back on 90's. I often play the bias and the difference between low bias and high bias are day and night. But for this F5 amplifier, how much differences for the low and high bias? Is it acceptable or trash? Let's find out.

My initial bias setting is 0.4 volt across the 0.47 ohm. This setting is actually lower from the manual recommendation, about 0.6 volt. This is because lower rated toroidal transformer that I am using right now. I am using 230Va, while manual recommendation is 300Va.

Although this is still not the fully potential from the F5 amplifier, I still amazed how depth the sound and how crystal clear the instruments are. The heat also rise very quickly and my heat sink are not sufficient enough to release it through the air without help from external fan. I am living in tropical area where room temperature is warm around 28 Celsius.

This weekend, I have a chance to clean up my audio system. I open this F5 amplifier then took my multi-meter to make some adjustment to the bias. I set it down until 0.23 volt. It is very low bias and very low heat. I leave this amplifier on couple hours and the heat-sink only get slightly warm.

I believe the power consumption is also small by doing this low bias adjustment. As you know that class A amplification will always turn-on the amplifier all the way compare to class AB amplifier that turn-on the amplifier based on the signal received.

I hook everything up again to my audio system and the sound now is reduced very significantly. There is no depth of sound, the sound stage are small, and the detail is shy and muffled. This low bias is very significantly effect to the sound!

Maybe I can tell you something interesting. While I sometimes read on many forum that some members said the glorious of today cheap class D amplifier easily defeat the others amplifier, including the amplifier like F5, then. To answer this, I compare my TPA3118 with this low bias F5 amplifier. The result still not comparable. They are on different class, even on this low bias F5, I can say that class D is far away from good.

I can say this lower bias F5 amplifier is not worth at all. I turn them back to 0.55 volt and I am happy with that right now.

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