Thank you very much for answering me Prasi, I managed to adjust Bias following your tips and those of the other members, I did a little test and played with good sound quality, but with the low gain, the mje really heat up, I'll provide a small heatsink for them and take a test. Thank you very much for your reply.
Hi Prasi,
Complete circuit. Perfect sound, perfect detail. Thank you so much for everything.
Attachments
Nice build! Is that FH9HVX in Prasi layout?
It’s one of my favorite amps. Glad you like it.
What is the intended/recommended biasing for the FH9? Is it ended for an AB type bias or a higher bias level?
If you can be assured that you don’t have any DC from your source, then I guess not. But it won’t help your zero DC offset from drifting. I have never personally run it without it so can’t guarantee that it will work without it.
finally aa9 md is over. pure class a. bass and detail is excellent. thanks apex , thanks Prasi.
Attachments
I wonder why kapton tape is used between the radiator and the final transistors?
I know it is temperature resistant and a good electrical insulator.
But does heat transfer work well?
I have seen this in several installations made in DiY mode.
I know it is temperature resistant and a good electrical insulator.
But does heat transfer work well?
I have seen this in several installations made in DiY mode.
Yes, it works. its there in my diy amp since 4-5 years. Its there even in my DIY subwoofer amp used in subwoofer. Works without any issues. Installation of kapton tape is very simple
@Faz
Kapton is good as a quick measure to get up and running. But for Class A heavy heat load I would not recommend it as it has much lower thermal conductivity than my favorite: aluminum oxide ceramic insulator spacers. They are more conductive than silicone pads and durable. The silicone and kapton can get a small pin hole and if the metal parts touch, you will melt your MOSFET or nearby drivers, or hopefully, only, blow a fuse.
For example:
TO 220/247/264 Alumina Ceramic Sheet Thermal Conductive Insulation Sheet Transistor High power Heat Sink Can Be Customized|Tool Parts| - AliExpress
Thermal conductivity of Kapton is about 0.46W/m K and of alumina (Al2O3) is between 12 and 72 W/m K! It is thicker than Kapton so there is a tradeoff but in my experience is the best. I have used one that could pass 175W flux from a single IXYS MOSFET 24/7 no problem.
Nice amp build! Do you find those heatsinks to be adequate to keep temps below 55C?
Kapton is good as a quick measure to get up and running. But for Class A heavy heat load I would not recommend it as it has much lower thermal conductivity than my favorite: aluminum oxide ceramic insulator spacers. They are more conductive than silicone pads and durable. The silicone and kapton can get a small pin hole and if the metal parts touch, you will melt your MOSFET or nearby drivers, or hopefully, only, blow a fuse.
For example:
TO 220/247/264 Alumina Ceramic Sheet Thermal Conductive Insulation Sheet Transistor High power Heat Sink Can Be Customized|Tool Parts| - AliExpress
Thermal conductivity of Kapton is about 0.46W/m K and of alumina (Al2O3) is between 12 and 72 W/m K! It is thicker than Kapton so there is a tradeoff but in my experience is the best. I have used one that could pass 175W flux from a single IXYS MOSFET 24/7 no problem.
Nice amp build! Do you find those heatsinks to be adequate to keep temps below 55C?
Thank you for your advices. This layout is for testing purposes only. I think the heatsink will not be enough for long-term use. Also, the bridge diodes get very hot. I will contact the bridge diodes with the heatsink. If I box it, the heatsink will be huge.
