Hi All,
I'm happy to say that after two-years away from this great hobby that my creative side has never felt better and I'm back and really happy to be able share my work once again with the members of this great forum.
My new PCB design is based on MikeB's conceptual circuit design found in post #2 of the following link,
http://www.diyaudio.com/forums/solid-state/87609-symasym-sequel.html
and Roender's great work in completing, building, and testing the design.
Roender's work is found here.
http://www.diyaudio.com/forums/solid-state/97144-symasym-roender-style.html
The new board measures 5”x3” like my original. This was no easy task considering the number of additional components I had to add in an already tight space.
In addition to adding components, the output transistors (OT) can now mount under the board so that a 3” heatsink can be used. The OT can also be extended 0.5” beyond each edge of the board like my original board design. I’ve added leds to each PS rail that also serves as a blown fuse indicator, and moved the AC inputs so that a terminal block can be used as well as fastons. I moved the Gnd terminal further from the PS caps to make it easier to access. I also added two full wave rectifier circuits before the PS caps on each edge of the board for those that would like to add a speaker protection or soft start circuit using the main transformer.
Enough said for the moment since it's getting late. I’ve attached the schematic that's currently implemented on my Rev 1.3 prototype board, and two THD plots at 100 watts into 8ohms, and 150watts into 4ohms at 1Khz. For the THD plots I've included the input signal's THD as a reference. It’s interesting that some of the harmonics improve over the original, something that also happens in MikeB’s original 5.3 design. The new design improves THD by a factor of about 2.5 to 3 over Mike's 5.3 design.
Regards,
Al
I'm happy to say that after two-years away from this great hobby that my creative side has never felt better and I'm back and really happy to be able share my work once again with the members of this great forum.
My new PCB design is based on MikeB's conceptual circuit design found in post #2 of the following link,
http://www.diyaudio.com/forums/solid-state/87609-symasym-sequel.html
and Roender's great work in completing, building, and testing the design.
Roender's work is found here.
http://www.diyaudio.com/forums/solid-state/97144-symasym-roender-style.html
The new board measures 5”x3” like my original. This was no easy task considering the number of additional components I had to add in an already tight space.
In addition to adding components, the output transistors (OT) can now mount under the board so that a 3” heatsink can be used. The OT can also be extended 0.5” beyond each edge of the board like my original board design. I’ve added leds to each PS rail that also serves as a blown fuse indicator, and moved the AC inputs so that a terminal block can be used as well as fastons. I moved the Gnd terminal further from the PS caps to make it easier to access. I also added two full wave rectifier circuits before the PS caps on each edge of the board for those that would like to add a speaker protection or soft start circuit using the main transformer.
Enough said for the moment since it's getting late. I’ve attached the schematic that's currently implemented on my Rev 1.3 prototype board, and two THD plots at 100 watts into 8ohms, and 150watts into 4ohms at 1Khz. For the THD plots I've included the input signal's THD as a reference. It’s interesting that some of the harmonics improve over the original, something that also happens in MikeB’s original 5.3 design. The new design improves THD by a factor of about 2.5 to 3 over Mike's 5.3 design.
Regards,
Al
Hi Al
my hifi has a pair of your old boards doing sterling service. I have made several other power amps since making them, but the old Symasym boards still rule the roost. And some commercial power amps have also been found wanting. The thing I love the most is the bass - the amp seems so fast and dynamic. Consequently, if the new boards have improvements then bring 'em on. I can't wait to get my hands on a pair of boards. Thanks for all your hard work.
Aidan
my hifi has a pair of your old boards doing sterling service. I have made several other power amps since making them, but the old Symasym boards still rule the roost. And some commercial power amps have also been found wanting. The thing I love the most is the bass - the amp seems so fast and dynamic. Consequently, if the new boards have improvements then bring 'em on. I can't wait to get my hands on a pair of boards. Thanks for all your hard work.
Aidan
Hi Aidan,
I've built many amp kits and listened to some of the best high end amps and I agree MikeB's design using my original boards has held it's ground firmly. That said I must be crazy to do all this work to try improve on an already great design but that's just me. I love this hobby. And Mike’s and Roender’s work is was just to good to not try it.
Hopefully this week I’ll get around to doing a thorough A/B comparison to see how the sound of the new design stacks up with my old design. On paper the new design flat out measures better, but as you know it does not always translate to better sound. The nice thing though is that on the new board you can easily bypass components like the cascodes so that the circuit is more like Mike’s original design. Or you can try different combinations. You can even use Lateral Mosfet output transistors by simply using the jumpers provided on the board.
I also designed an external power supply board for those that would like to use a single transformer for two amps. And I just completed a dual output transistor version.
Best regards,
Al
I've built many amp kits and listened to some of the best high end amps and I agree MikeB's design using my original boards has held it's ground firmly. That said I must be crazy to do all this work to try improve on an already great design but that's just me. I love this hobby. And Mike’s and Roender’s work is was just to good to not try it.
Hopefully this week I’ll get around to doing a thorough A/B comparison to see how the sound of the new design stacks up with my old design. On paper the new design flat out measures better, but as you know it does not always translate to better sound. The nice thing though is that on the new board you can easily bypass components like the cascodes so that the circuit is more like Mike’s original design. Or you can try different combinations. You can even use Lateral Mosfet output transistors by simply using the jumpers provided on the board.
I also designed an external power supply board for those that would like to use a single transformer for two amps. And I just completed a dual output transistor version.
Best regards,
Al
Hi HBarske,
There's a slight amount of Iq thermal drift but it's not a problem especially when the amp is put into an enclosure. But you do have the option with a 4" wide heatsink to mount the drivers to the heatsink by simply soldering them underneath the board and pulling them out so that mounting holes extend about 1/4" from the board edge. There also plenty room to add a small heatsink to each driver when used on the top side of the board.
Regards,
Al
There's a slight amount of Iq thermal drift but it's not a problem especially when the amp is put into an enclosure. But you do have the option with a 4" wide heatsink to mount the drivers to the heatsink by simply soldering them underneath the board and pulling them out so that mounting holes extend about 1/4" from the board edge. There also plenty room to add a small heatsink to each driver when used on the top side of the board.
Regards,
Al
Hi Hbarske,
I should of put it on the schematic that Q17 has to be mounted to one of the output transistors. This is done by first soldering one end of a wire (about 1.5" in length) to each transistor lead, then soldering the other end to the board, and then mounting it to one of the output transistors. Here's a pic from my original board that illustrates what it looks like.
Al
I should of put it on the schematic that Q17 has to be mounted to one of the output transistors. This is done by first soldering one end of a wire (about 1.5" in length) to each transistor lead, then soldering the other end to the board, and then mounting it to one of the output transistors. Here's a pic from my original board that illustrates what it looks like.
Al
Attachments
Hi nelsonvandal,
Without trying a double or triple EF I can't say. But I do know from my testing that adding a CFP driver stage reduces the odd order harmonics by quite a bit. In Roender's simulations he found the CFP driver reduces 3rd, 5th, and 7th harmonics by about 20db. The cascode VAS has a similar effect on the even harmonics.
I think the listening test should be interesting.
I've attached a couple THD plots taken from my original boards with the same output devices, 50 volts rails, and 2n5551 inputs to compare with the new design.
Regards,
Al
Without trying a double or triple EF I can't say. But I do know from my testing that adding a CFP driver stage reduces the odd order harmonics by quite a bit. In Roender's simulations he found the CFP driver reduces 3rd, 5th, and 7th harmonics by about 20db. The cascode VAS has a similar effect on the even harmonics.
I think the listening test should be interesting.
I've attached a couple THD plots taken from my original boards with the same output devices, 50 volts rails, and 2n5551 inputs to compare with the new design.
Regards,
Al
Attachments
Hi Piesma,
I've attached THD plots for 5Khz, 7Khz, and 10Khz all at 100 watts into 8ohms. My setup will not allow for checking THD at 20Khz. The maximum sample rate of my sound card 48Khz.
As far the listening test, I don't think I can describe it any better than Roender did. Here's what he wrote.
How it sound?
It is very pleasant surprise to be more dynamic than symasym and the soundstage is huge. It sound very uncompressed, with more clarity and volume in mid range and blade sharp but not
annoying trebles.
Bass is very very tight but not so deep, my first impression is that it is a little under symasym at this chapter, an "audiophile bass", well suitable for jazz and ambient music.
I'll add that to my ears the base is as good as the original.
You can find what Roender wrote in post #4 of the following link.
http://www.diyaudio.com/forums/solid-state/97144-symasym-roender-style.html
I received another set of prototype boards yesterday, currently awaiting parts that should arrive today. I figure by tomorrow or Sunday I should have them up and running. If all goes well I'd be happy to start a group buy. For those interested let me know I'll start putting a list together.
Regards,
Al
I've attached THD plots for 5Khz, 7Khz, and 10Khz all at 100 watts into 8ohms. My setup will not allow for checking THD at 20Khz. The maximum sample rate of my sound card 48Khz.
As far the listening test, I don't think I can describe it any better than Roender did. Here's what he wrote.
How it sound?
It is very pleasant surprise to be more dynamic than symasym and the soundstage is huge. It sound very uncompressed, with more clarity and volume in mid range and blade sharp but not
annoying trebles.
Bass is very very tight but not so deep, my first impression is that it is a little under symasym at this chapter, an "audiophile bass", well suitable for jazz and ambient music.
I'll add that to my ears the base is as good as the original.
You can find what Roender wrote in post #4 of the following link.
http://www.diyaudio.com/forums/solid-state/97144-symasym-roender-style.html
I received another set of prototype boards yesterday, currently awaiting parts that should arrive today. I figure by tomorrow or Sunday I should have them up and running. If all goes well I'd be happy to start a group buy. For those interested let me know I'll start putting a list together.
Regards,
Al
Attachments
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