This was designed and built mainly in weekends. It took a while, but this is the best solid-state amp that I ever listened. Very transparent and very clean due to very low levels of TIM distortion. One of the reasons for very low TIM distortion is the isolation of the input voltage gain stage hence very steady offset even with large droops of the power supply voltages. Another reason is the local feedback for the input stage built with the excellent OPA445. The noise of the amp is below the threshold sensitivity level of my Agilent 34461A benchtop meter. The S/N ratio is better than 110dB. I had to increase the gain of the amp in order to measure the noise. I also dimensioned this amp for 25 and 100 W / 8 ohm, and the sound is very accurate with any of the variants.
G
G
You really did a very nice work.
Could you please show us the protection module?
Regards and thank you for sharing
Could you please show us the protection module?
Regards and thank you for sharing
Looks great, very slickly put together. Do the offset voltage variations correlate with mains voltage there?
One thing with the output stage board is the routing of ground currents - aren't they flowing across the various jumpers that connect to the other board? The feedback take off point for the signal side is careful to sample the correct voltage, but the ground take off point seems not the do as good a job?
One thing with the output stage board is the routing of ground currents - aren't they flowing across the various jumpers that connect to the other board? The feedback take off point for the signal side is careful to sample the correct voltage, but the ground take off point seems not the do as good a job?
Thanks for your kind words.
I published that protection module because it is probably an original idea, and I didn’t want someone else to claim intellectual property.
The circuit is fairly simple, as is this amplifier, but the editors of Nuts&Volts wouldn’t be very happy.
G
I published that protection module because it is probably an original idea, and I didn’t want someone else to claim intellectual property.
The circuit is fairly simple, as is this amplifier, but the editors of Nuts&Volts wouldn’t be very happy.
G
Hi Mark,
Thanks. No, the offset voltage will follow the output voltage. If the power supply voltages droop, the offset changes, and that is one source of intermodulation.
The circuit is very symmetrical, the ground included. There are no asymmetrical propagation delays.
G
Thanks. No, the offset voltage will follow the output voltage. If the power supply voltages droop, the offset changes, and that is one source of intermodulation.
The circuit is very symmetrical, the ground included. There are no asymmetrical propagation delays.
G
I see.
I found this free file in magazine site. I understand there is no restriction to share.
Regards.
I found this free file in magazine site. I understand there is no restriction to share.
Regards.
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Hi r_merola,
OK, I didn’t know Nuts&Volts has that. You can probably share it with anyone.
Hi Mark,
The power return happens on the current board, not on the voltage board.
G
OK, I didn’t know Nuts&Volts has that. You can probably share it with anyone.
Hi Mark,
The power return happens on the current board, not on the voltage board.
G
But normally with two ground connections to an output board one carries the signal current to the speaker, the other from the supply, there is significant IR voltage drop between those terminals, and here that carries over via the jumpers to the voltage board. Alas the decoupling caps on the output board also take distorted class-B currents from each end of this ground path, so that a distortion component is present ontop of the signal current, leading to distorted voltages at the jumpers.
The decoupling cap currents are probably a lot less than the speaker current which helps mitigate, but I think a more careful attention to star-grounding here could help wring out lower distortion.
Hi Mark,
The high current happens only on the current board. The voltage board takes less than 15 mA. The distance between the connections for the ground for the power supply and the ground for the load is 20 mm. These boards are done with 2 oz. of Cu and the width of the traces between the grounding points can carry more than 20 A. (3.81 mm width = 10A). The ground is on both sides of the board. Therefore, the voltage drop is almost zero.
Regards,
G
The high current happens only on the current board. The voltage board takes less than 15 mA. The distance between the connections for the ground for the power supply and the ground for the load is 20 mm. These boards are done with 2 oz. of Cu and the width of the traces between the grounding points can carry more than 20 A. (3.81 mm width = 10A). The ground is on both sides of the board. Therefore, the voltage drop is almost zero.
Regards,
G
Loudspeaker Protection Circuit
Hi r_merola,
I see that the zipped folder from Nuts&Volts contains my circuit, and everything else one needs to build it. The schematics are done with VISIO and the PCB is done with Pad2Pad. If you need a PDF version, please let me know.
IMO, the bi-directional optical coupler solution is the best. I tried different circuits, including the uPC1237 / NTE7100, but nothing works as good as my
circuit.
G
Hi r_merola,
I see that the zipped folder from Nuts&Volts contains my circuit, and everything else one needs to build it. The schematics are done with VISIO and the PCB is done with Pad2Pad. If you need a PDF version, please let me know.
IMO, the bi-directional optical coupler solution is the best. I tried different circuits, including the uPC1237 / NTE7100, but nothing works as good as my
circuit.
G
I thank you so much for your attention and also appreciate PDF files from this project.
I suppose other also will like to see your ideas.
I am a retired guy from Telecom area and love good and different ideas related to audio.
I just saw the thread 'Start, Soft Start, External Trigger and Thermal Protection Module for 2S2A2-50W Power'
Kindest regards.
I suppose other also will like to see your ideas.
I am a retired guy from Telecom area and love good and different ideas related to audio.
I just saw the thread 'Start, Soft Start, External Trigger and Thermal Protection Module for 2S2A2-50W Power'
Kindest regards.
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Hi r_merola,
You are welcome.
I will upload a PDF, but as you know, we cannot upload files greater than 2MB. I had to shrink what I uploaded so far, and that makes for poor resolution. Please send a PM.
I worked 20 years in professional radio-communications myself… small world.
All the best,
G
You are welcome.
I will upload a PDF, but as you know, we cannot upload files greater than 2MB. I had to shrink what I uploaded so far, and that makes for poor resolution. Please send a PM.
I worked 20 years in professional radio-communications myself… small world.
All the best,
G