Hi Ben,
I have tried to experiment with Bias and Vds.
I want to bias is around 2A and 1.8A for test and heat dissipation reasons.
Changing R4 even to 22k does not bring Iq below 2.2A.
Any recommendation pls?
I have tried to experiment with Bias and Vds.
I want to bias is around 2A and 1.8A for test and heat dissipation reasons.
Changing R4 even to 22k does not bring Iq below 2.2A.
Any recommendation pls?
Yes, add another 0.1R in series with either R7 or R8. Lift one lead of R7 or R8 off the PCB. Then solder one lead of the new resistor to the PCB and the other lead to the lifted lead of the existing resistor. Keep R4 at 22k.
This is a italian cartoon (of '70-'80 years) ... too funny... "the Tnt group"
Here's my first trial run at following (a formidable task!) in Ben's footsteps. I'm sure there will be revisions. The reason C1 and C5 are so physically large is I have a surplus of 3.9uF Metalized Polypropylene crossover caps that I'm thinking of testing in those positions.
Regards,
Dan
Regards,
Dan
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I haven't forgotten the gate or speaker resistor. Just warming up my KiCAD skills.
Regards,
Dan 🙂
Regards,
Dan 🙂
If the SIT and mosfet are not mounted directly to the PCB, it is probably best to mount the gate resistor directly to the gates. The closer to the gate, the better.
One thing to think about in the PCB is loop area. Electrons in circuits flow in closed loops. For instance in the case of the DC power, the quiescent current electrons for the SIT and mosfet flow in a loop from the power supply through the SIT, through the string source resistors, through the mosfet, and then back out to the power supply. The physical route forms a closed loop, and the loop area is the physical size of that loop. The larger the loop, the more prone for the loop to act as an antenna to receive and broadcast noise.
The same goes for the AC signal loop. The AC signal comes from the source, through the SIT gate, some also go to the mosfet gate, then out from the SIT and mosfet sources, through the source resistors, then out to the speaker, and back to the pcb through the ground return, through the pcb to the signal source ground connection and back to the source.
So pcb layout is not only placing the components on the board and connecting them based on the schematic. Location and routing are very important, and the aim is to keep the loop areas to a minimum.
The concept also applies to wires. That is why it is best to twist wire pairs that transfer and return signal and power.
One thing to think about in the PCB is loop area. Electrons in circuits flow in closed loops. For instance in the case of the DC power, the quiescent current electrons for the SIT and mosfet flow in a loop from the power supply through the SIT, through the string source resistors, through the mosfet, and then back out to the power supply. The physical route forms a closed loop, and the loop area is the physical size of that loop. The larger the loop, the more prone for the loop to act as an antenna to receive and broadcast noise.
The same goes for the AC signal loop. The AC signal comes from the source, through the SIT gate, some also go to the mosfet gate, then out from the SIT and mosfet sources, through the source resistors, then out to the speaker, and back to the pcb through the ground return, through the pcb to the signal source ground connection and back to the source.
So pcb layout is not only placing the components on the board and connecting them based on the schematic. Location and routing are very important, and the aim is to keep the loop areas to a minimum.
The concept also applies to wires. That is why it is best to twist wire pairs that transfer and return signal and power.
One thing to think about in the PCB is loop area. Electrons in circuits flow in closed loops. For instance in the case of the DC power, the quiescent current electrons for the SIT and mosfet flow in a loop from the power supply through the SIT, through the string source resistors, through the mosfet, and then back out to the power supply. The physical route forms a closed loop, and the loop area is the physical size of that loop. The larger the loop, the more prone for the loop to act as an antenna to receive and broadcast noise.
I had this somewhat in mind when I placed the Sits source (J5) as close to R7 as I could get it. Also, I was thinking the same thing when I placed the MOSFETs source (J7) as close to R11 as I could. If I abandon my use of spare crossover capacitors I could emulate your PCB with the only differences being being some terminals or tabs. The rest momentarily eludes me but I'll keeping reviewing the thread and revising my PCB. As wise man once said,
"Amplifier building is not a speedsport. Take your time and enjoy the build."
Slightly off topic, this build brings back memories of the full power schade I built about six years ago. It was way beyond my knowledge and skillset at the time but after a great amount of perseverance and several serious migraines I ended up with an amplifier that would heat a small house and that I couldn't lift by myself.
Ben, many thanks for giving some details to ponder.
Regards,
Dan
I had this somewhat in mind when I placed the Sits source (J5) as close to R7 as I could get it. Also, I was thinking the same thing when I placed the MOSFETs source (J7) as close to R11 as I could. If I abandon my use of spare crossover capacitors I could emulate your PCB with the only differences being being some terminals or tabs. The rest momentarily eludes me but I'll keeping reviewing the thread and revising my PCB. As wise man once said,
"Amplifier building is not a speedsport. Take your time and enjoy the build."
Slightly off topic, this build brings back memories of the full power schade I built about six years ago. It was way beyond my knowledge and skillset at the time but after a great amount of perseverance and several serious migraines I ended up with an amplifier that would heat a small house and that I couldn't lift by myself.
Ben, many thanks for giving some details to ponder.
Regards,
Dan
If the mosfet is not mounted directly to the PCB. 🤔
Hmmmmmm.....there is no real reason I couldn't mount the mosfet to the PCB.
Regards,
Dan
Hmmmmmm.....there is no real reason I couldn't mount the mosfet to the PCB.
Regards,
Dan
The PCBs for this amp were the very first that I designed. 🤓
For fun and education you can mark out the routes of output stage quiescent current and AC signal and see what they look like.
For fun and education you can mark out the routes of output stage quiescent current and AC signal and see what they look like.
"For fun and education you can mark out the routes of output stage quiescent current and AC signal and see what they look like."
Interesting....... 😎
Interesting....... 😎
Would this Antek transformer be OK for stereo 44v DC version? Specs seem capable.
https://www.antekinc.com/an-5436-500va-36v-transformer/
https://www.antekinc.com/an-5436-500va-36v-transformer/
At >3x the winding at 7A, it's 3x more than the required draw. Looked for 800va but they don't have it. The AS-4218 will be good, plus it's shielded. Just costs so much more and the real estate.
The 36V 500VA should be enough for a stereo amp at 44VDC.
400VA dual 18V for mono is also more than adequate. 300VA is enough for 44 or so VDC mono. But there is nothing wrong with more.
If you intend to run 60 plus VDC and 3A, then the larger transformers are nice.
400VA dual 18V for mono is also more than adequate. 300VA is enough for 44 or so VDC mono. But there is nothing wrong with more.
If you intend to run 60 plus VDC and 3A, then the larger transformers are nice.