Hi Mark,
I'm disabled too. We are in the same boat.
The SymAsym has lovely highs. It's all in how you build it. Some of the capacitors will affect how clean it is, and the diff pair is critical to match tightly. In some of the Adcom threads you can find a beta matcher I designed that can deliver matches under 1%. You have to match the degeneration resistors at that point. If you can select compliments for beta, like outputs and drivers, that also helps.
The separate supply for the voltage amp section was my suggestion. This goes a long, long way to creating clean sound combined with the other tricks. You should be able to find that early in this thread I think. It was so many years ago. Going by memory, I think you can pull some resistors, or at worst case cut the traces and apply the voltage amp supply there. You could let that run all the time and only power up the current stage to turn the amp on and off. No thumps. The SymAsym doesn't have loud turn on thumps as it is designed either.
I have a Honey Badger and a couple other amplifiers to build too. Much higher power, but not needed.
IF you are using an active crossover, the 50 watt amps will probably do you well. The dynamics of this kind of system is amazing. I would build one pair and test as full range. If you are satisfied, build the other two pairs for the three way active system.
-Chris
I'm disabled too. We are in the same boat.
The SymAsym has lovely highs. It's all in how you build it. Some of the capacitors will affect how clean it is, and the diff pair is critical to match tightly. In some of the Adcom threads you can find a beta matcher I designed that can deliver matches under 1%. You have to match the degeneration resistors at that point. If you can select compliments for beta, like outputs and drivers, that also helps.
The separate supply for the voltage amp section was my suggestion. This goes a long, long way to creating clean sound combined with the other tricks. You should be able to find that early in this thread I think. It was so many years ago. Going by memory, I think you can pull some resistors, or at worst case cut the traces and apply the voltage amp supply there. You could let that run all the time and only power up the current stage to turn the amp on and off. No thumps. The SymAsym doesn't have loud turn on thumps as it is designed either.
I have a Honey Badger and a couple other amplifiers to build too. Much higher power, but not needed.
IF you are using an active crossover, the 50 watt amps will probably do you well. The dynamics of this kind of system is amazing. I would build one pair and test as full range. If you are satisfied, build the other two pairs for the three way active system.
-Chris
Chris thanks for your helpful suggestions
When I built these before I stuck tightly to the original design in components and layout. Silvered mica at C2, C7, C14. I couldn't squeeze in the same caps for C3/4 as they're a bit bigger than the Reichelt ones (and way more expensive). At the time Reichelt wanted £200 minimum order to export to UK. I think this may have changed now. I went with FKP2's at C3/4 as I got loads in a cheapo lucky dip bag from Maplins (defunct? UK retailer). I made one alteration. I separated R7 and L1. I dislike resistors inside inductors. Just ain't right to my mind and looks a dog's dinner. I closely matched all resistors and caps. I was lazy in only matching the trannies on a DIMM for hFE. I will track down and use your beta tester this time around. Always had that in the back of my mind.
I had two hdd failures one week in march this year and lost all my pcb layout files
. So at the mo I'm re-laying my pcb from scratch.My original boards were a bit on the big side 100mm wide x 125mm long which included a 100m x 40mm space for an angle bracket. My hands were a bit shaky at the time. I went big to ensure I could build them without solder bridges.
Hands are good now. So I've reduced my boards down to 100mm wide x 80mm long including space for a 100mm x 35mm angle bracket. Why so much smaller? To pull the boards as far away as poss from the spkr driver magnets, assuming a 3 x stacked arrangement.
I actually have two different pcb designs at the mo. One closely matched to the original and an experimental revised layout where I've swapped the OPTs and drivers around, to pull R27/R28 further away from the OPTs for better heat dissipation. I haven't mucked around with voltage side. It's as ugly as sin but now I have a dilemma and would appreciate some advice.
Purely by luck my revised layout will accommodate taking the feedback loop from either the input or the output of L1. My understanding is that it's best taken from the output, i.e. just after the coil and just before the spkr take off point. This is slightly different to Michael's design which couldn't accommodate that. What do you think?
Thanks, Mark
When I built these before I stuck tightly to the original design in components and layout. Silvered mica at C2, C7, C14. I couldn't squeeze in the same caps for C3/4 as they're a bit bigger than the Reichelt ones (and way more expensive). At the time Reichelt wanted £200 minimum order to export to UK. I think this may have changed now. I went with FKP2's at C3/4 as I got loads in a cheapo lucky dip bag from Maplins (defunct? UK retailer). I made one alteration. I separated R7 and L1. I dislike resistors inside inductors. Just ain't right to my mind and looks a dog's dinner. I closely matched all resistors and caps. I was lazy in only matching the trannies on a DIMM for hFE. I will track down and use your beta tester this time around. Always had that in the back of my mind.
I had two hdd failures one week in march this year and lost all my pcb layout files
. So at the mo I'm re-laying my pcb from scratch.My original boards were a bit on the big side 100mm wide x 125mm long which included a 100m x 40mm space for an angle bracket. My hands were a bit shaky at the time. I went big to ensure I could build them without solder bridges.Hands are good now. So I've reduced my boards down to 100mm wide x 80mm long including space for a 100mm x 35mm angle bracket. Why so much smaller? To pull the boards as far away as poss from the spkr driver magnets, assuming a 3 x stacked arrangement.
I actually have two different pcb designs at the mo. One closely matched to the original and an experimental revised layout where I've swapped the OPTs and drivers around, to pull R27/R28 further away from the OPTs for better heat dissipation. I haven't mucked around with voltage side. It's as ugly as sin but now I have a dilemma and would appreciate some advice.
Purely by luck my revised layout will accommodate taking the feedback loop from either the input or the output of L1. My understanding is that it's best taken from the output, i.e. just after the coil and just before the spkr take off point. This is slightly different to Michael's design which couldn't accommodate that. What do you think?
Thanks, Mark
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Hi Mark,
Try using polystyrene for those mica capacitors, or polypropylene. Take the feedback from the speaker output. Resistors inside of the output inductors are okay.
I'm sure you could change things up slightly and still have a great amplifier. Try to keep the voltage amp section close to the original, and watch your current loops!
-Chris
Try using polystyrene for those mica capacitors, or polypropylene. Take the feedback from the speaker output. Resistors inside of the output inductors are okay.
I'm sure you could change things up slightly and still have a great amplifier. Try to keep the voltage amp section close to the original, and watch your current loops!
-Chris
Chris,
You've been reading my mind! One thing occurred to me. I'll be using an active crossover. So the quality of those caps won't matter so much for the bass and prob the midrange amp boards. I ponder further on the bass and mid boards. IF the crossover is not inputting HF into their voltage side, i.e. through C1, is there any HF at all in these boards to deal with? Could caps C3, C4 even C2(?) be skipped altogether in the bass and mid boards? Have I got that all wrong?
Thanks, Mark
Hi Chris, not sure about that but you are a gentleman. These fora can be quite intimidating for peeps like me. I've finished my experimental layout. Tooo embarrassed to post. Going off to buid a couple of normal ones. Then I might go and try my experimental layout for an A/B. Thanks for your kind help and patience. Greatly appreciated, Mark
Hi Mark,
Each and every one of us started somewhere. There isn't a person that exists born with the knowledge, so we each owe our understanding to a series of kind mentors. Never forget that there was a time when I knew less than you do now.
So, don't be afraid to ask questions (but listen to the answers).
-Chris
Each and every one of us started somewhere. There isn't a person that exists born with the knowledge, so we each owe our understanding to a series of kind mentors. Never forget that there was a time when I knew less than you do now.
So, don't be afraid to ask questions (but listen to the answers).
-Chris
..... Hi radio , I have made some cosmetics on Rudi's PCB wich is the best PCB until now , congrat's to Rudi , I like red colour , nice PCB's . I have tryed to layout for single side , to be available everyone who intend to do this variant .....
Regards Alex .
hello, which project scheme refers to this pcb
thank you
Slewmaster "symasui' is the cascoded equivalent of this symasym.
Issues of "picky" components and voltages are gone.
I could run my symasui - 20v to 80v dc rails , and throw just about any
junk drawer silicon in for most devices.
Symasui also has the extra pads for that degenerative miller compensation
at the VAS output ... but will run without them.
PS - after "hacking" this topology (and altering it for wide margin bode behavior) , It it is on par with a typical
"blameless" (honey badger) with VERY wide margin stability. Just "ringing" at 20pf miller comp. No oscillators
here.
OS
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symasym headphone amp idea
Spent too much time doing simulation/modeling for the past month of summer break before summer school started and came up with this. It's pretty much the symasym with JFET input and VAS/Driver output stage. Models nice. Not sure if I'll build one I'm trying to do something simpler and get good results as well. Tried messaging the guys responsible for the design of the symasym so I hope this is not out of line.
The sim gives .0012% THD @8VRMS 20mA Bias 24R load. Bonus all parts are readily available.
Spent too much time doing simulation/modeling for the past month of summer break before summer school started and came up with this. It's pretty much the symasym with JFET input and VAS/Driver output stage. Models nice. Not sure if I'll build one I'm trying to do something simpler and get good results as well. Tried messaging the guys responsible for the design of the symasym so I hope this is not out of line.
The sim gives .0012% THD @8VRMS 20mA Bias 24R load. Bonus all parts are readily available.
Attachments
Hi Beycoast,
You would use a THD meter to find the happy spot for the bias current, then bias a touch higher. For stability you need a scope and square wave generator and adjust the feedback cap for no ringing. You could make it a little higher if you wanted, just for a little extra safety factor, but not much.
Unless someone actually built this using your choices of transistors, it is impossible to tell you what the values should be. A simulator will not get it right because there are a lot of other factors that are not modeled. Just build it and measure.
-Chris
You would use a THD meter to find the happy spot for the bias current, then bias a touch higher. For stability you need a scope and square wave generator and adjust the feedback cap for no ringing. You could make it a little higher if you wanted, just for a little extra safety factor, but not much.
Unless someone actually built this using your choices of transistors, it is impossible to tell you what the values should be. A simulator will not get it right because there are a lot of other factors that are not modeled. Just build it and measure.
-Chris
Merhaba Chris
Cevabınız için teşekkürler.
Kötü ingilizcem için özür dilerim.
Kare dalga jeneratörü veya osiloskop ile Covid19 nedeniyle evi terk edemediğim için.
Test etme şansım yok.
Malzemelerim arasında 5200/1943 çift buldum. Bunu bu Toshiba'larla yapanları gördüm, ama detayları bulamadım. Peki, bu 5200/1943 çifti hakkında bildiğiniz herhangi bir değişiklik var mı?
-Ali
^
Ali, bu bir İngilizce forumu. Belki bu çeviri bağlantısı yardımcı olacaktır.
Google Translate
Ali, this is an English language forum. Maybe this translation link will help.
Ali, bu bir İngilizce forumu. Belki bu çeviri bağlantısı yardımcı olacaktır.Google Translate
Ali, this is an English language forum. Maybe this translation link will help.
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