Thanks Andrew.
I pretty much assumed 2-3 output pairs. Is there any easy way to connect them on the PCB? They will need current sharing resistors, right? Does that screw up the feedback circuit or stability?
The smoothing aspect is also a concern . My own (DIY of course) speakers are ~4 ohm (nom.) load. Any reason why I cannot parallel some off-board caps? I have a bag full of 10mF/63v caps of 30mm, close but not close enough I assume, to fit on the board.
I also [might] have a spare 22v+22v @ 650VA transformer (32VDC rails), maybe that would suit a SymAsym amp better than the 39v+39v.
..Todd
I pretty much assumed 2-3 output pairs. Is there any easy way to connect them on the PCB? They will need current sharing resistors, right? Does that screw up the feedback circuit or stability?
The smoothing aspect is also a concern . My own (DIY of course) speakers are ~4 ohm (nom.) load. Any reason why I cannot parallel some off-board caps? I have a bag full of 10mF/63v caps of 30mm, close but not close enough I assume, to fit on the board.
I also [might] have a spare 22v+22v @ 650VA transformer (32VDC rails), maybe that would suit a SymAsym amp better than the 39v+39v.
..Todd
symasym5_3 for china edition
1,Refer PCB drawing
2, symasym5_3 amplifier photo
1,Refer PCB drawing
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
2, symasym5_3 amplifier photo
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Ask the MBK sees the SymAsym5_3 that we do
http://bbs.hifidiy.net/viewthread.php?tid=73838&extra=&page=1
From the list to tube of, has been attain 3 rightnesses of tubes
Please put forward a precious opinion
feiyin
http://bbs.hifidiy.net/viewthread.php?tid=73838&extra=&page=1
From the list to tube of, has been attain 3 rightnesses of tubes
Please put forward a precious opinion
feiyin
davidwang,I see you use the same teknik as I to mount the transistors,at least I did something right..
I bought this Swedish made speakers (XTZ) as I have no other at the moment,I bought them used for about 300$.
did some filter tweaking for the mid and high.
First I used this cable,wich I don´t know the name of.
The sound is pretty good open and detailed,then I tried this one,at least in Sweden it´s name is EKK,5 solid core leads with 2,5mm2 area each,it is used for electrical power (400v and more)some here in sweden use it and found it sounds good,
To my surprise it didn´t sound good at all!Less bass,less soundstage,not so pleasant treble.....
So I went shopping...
EKU 2x0,5mm2 solidcore,used for telephones....also used by some here in sweden for speakerwire,AND this one sounds realy good!Maybee som slightly loss in lowbass,but this speakers aint no bassmonsters anyway..
I wish I had some other cables to compare them with..
Any ideas why the EKK didn´t work?I now some don´t belive in cabels "sounding"or if it´s sommething else changing with diffrent cables, is the feedback sensetive for this?
And this amp needs some better speakers to give its best..
And someday maybe.....
An externally hosted image should be here but it was not working when we last tested it.
I bought this Swedish made speakers (XTZ) as I have no other at the moment,I bought them used for about 300$.
An externally hosted image should be here but it was not working when we last tested it.
did some filter tweaking for the mid and high.
An externally hosted image should be here but it was not working when we last tested it.
First I used this cable,wich I don´t know the name of.
An externally hosted image should be here but it was not working when we last tested it.
The sound is pretty good open and detailed,then I tried this one,at least in Sweden it´s name is EKK,5 solid core leads with 2,5mm2 area each,it is used for electrical power (400v and more)some here in sweden use it and found it sounds good,
An externally hosted image should be here but it was not working when we last tested it.
'
To my surprise it didn´t sound good at all!Less bass,less soundstage,not so pleasant treble.....
So I went shopping...
An externally hosted image should be here but it was not working when we last tested it.
EKU 2x0,5mm2 solidcore,used for telephones....also used by some here in sweden for speakerwire,AND this one sounds realy good!Maybee som slightly loss in lowbass,but this speakers aint no bassmonsters anyway..
I wish I had some other cables to compare them with..Any ideas why the EKK didn´t work?I now some don´t belive in cabels "sounding"or if it´s sommething else changing with diffrent cables, is the feedback sensetive for this?
And this amp needs some better speakers to give its best..
And someday maybe.....
An externally hosted image should be here but it was not working when we last tested it.
Help, Please
Before I start unsoldering and testing components:
One of my amps, I built recently, starting blowing fuses yesterday, always the negative side. I just was poking around and found that the speaker terminal reads 0.1 ohms to ground. Do you think I have a bad output transistor? Can you think of anything else that might be causing the problem?
Thanks
JimS
Before I start unsoldering and testing components:
One of my amps, I built recently, starting blowing fuses yesterday, always the negative side. I just was poking around and found that the speaker terminal reads 0.1 ohms to ground. Do you think I have a bad output transistor? Can you think of anything else that might be causing the problem?
Thanks
JimS
time to rebuild
I think I will rethink and rebuild. The problems stem from me trying to be clever and mount U3, U4 and the BD139 on to a single piece of aluminum, which is then mounted to the heat sink. This way I could keep the BD139 close to the board and still keep the temperature relatively equal between the 3 transistors. Good idea, but the problem has been that my BD139 ends up shorting to the aluminum regardless if I use mica or a silpad. I think that the holes on the silpad and mica are too large, and the shoulder washers do not fit into the hole in the bd139. Plus it is a PTA to mount. I think once things start to heat up either the screw or the aluminum contacts the back of the BD139. I can not find shoulder washers or pads that fit the onsemi BD139 perfectly.
Given that I just blew the fuse again with some smoke and I have dark solder on the center post of the bd139, I think I will change out my transistors and put the BD139 where everyone else mounts it.
The good news is that when things were working the amp sounds great. I have to keep that in mind as I start to remove the transistors.
thanks for your help
JimS
I think I will rethink and rebuild. The problems stem from me trying to be clever and mount U3, U4 and the BD139 on to a single piece of aluminum, which is then mounted to the heat sink. This way I could keep the BD139 close to the board and still keep the temperature relatively equal between the 3 transistors. Good idea, but the problem has been that my BD139 ends up shorting to the aluminum regardless if I use mica or a silpad. I think that the holes on the silpad and mica are too large, and the shoulder washers do not fit into the hole in the bd139. Plus it is a PTA to mount. I think once things start to heat up either the screw or the aluminum contacts the back of the BD139. I can not find shoulder washers or pads that fit the onsemi BD139 perfectly.
Given that I just blew the fuse again with some smoke and I have dark solder on the center post of the bd139, I think I will change out my transistors and put the BD139 where everyone else mounts it.
The good news is that when things were working the amp sounds great. I have to keep that in mind as I start to remove the transistors.
thanks for your help
JimS
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