Will do audio test tomorrow.
It seems after an hour's burn in that the offsets have settled and both now fluctuates between 0 and 2mV. On the the right hand channel the transistors still don't pull evenly, but that is just something I will have to live with. The temperature on both sinks are the same and spread evenly over the whole heatsink. I don't feel any hotspots. The temperature also seem to stay constant after an hour. I can keep my hand on the sinks topside for 20 secs. The Ta was 32 deg C when I did the test between 16h00 and 18h00 this afternoon. So I think I may be able to give it even more gas. Maybe around 350mV per Re giving 350mV / 0.5R = 700mA per transistor. My rails loaded is about 38.1V. Unloaded is 40.4V.
It seems after an hour's burn in that the offsets have settled and both now fluctuates between 0 and 2mV. On the the right hand channel the transistors still don't pull evenly, but that is just something I will have to live with. The temperature on both sinks are the same and spread evenly over the whole heatsink. I don't feel any hotspots. The temperature also seem to stay constant after an hour. I can keep my hand on the sinks topside for 20 secs. The Ta was 32 deg C when I did the test between 16h00 and 18h00 this afternoon. So I think I may be able to give it even more gas. Maybe around 350mV per Re giving 350mV / 0.5R = 700mA per transistor. My rails loaded is about 38.1V. Unloaded is 40.4V.
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BTW, given that I have 3 output pairs (MJL3281/1302), Re = 0.5R and rails 38.1V loaded, what would be the highest recommendation for the voltage over Re? In other words, the highest bias current through each transistor. Let's just leave the disappation out for now and assume that my sinks can handle anything.
Yes you can (must) go higher with the bias until you get after every AC Volt around 1.22DC Volt under load of course pay att to the heatsink to avoid thermal runaway.
I usually measure the totall bias, I hock up the DMM between the PS + and the PC board +..
But if you got used to these way to set up the biass please do it these way.
Please measure on each power resistor if you get the same V drop, but be carefull if you touch something else the amp can blow up!
Greetings Gabor
Feels good doesn,t it?
It should sound even better after playing 30 or more hours
The bias spread you have is not out of order. Can,t remember mine but not to far off
My loaded rails came out 41.5,, just more heat to blow off
The sound is cut from the same cloth top to bottom with the low end superoir in tight ness with deep extension. My krell clone 100/150 monos do not have the quality of bass as the 50 does (although very very good in their own right) for some strange reason, but are better at nasty loads by far
The 50 doesn,t quite fill the bill on my SL3's or old Quads but matches perfectly with Vandersteens. Theres a big difference in loads here also
The flip side is the others sound better and more extended on top that I prefer on those other pairs, but there is something special going on with the 50 with the right speakers for sure. I do have a big room however at 23x26ft
Have you ran a square wave on up and noticed when you start to get leading edge rounding yet? My 50 has a smaller bandwidth than my 100 and the 150 has quite a better bandwidth.
For example.. a pair of PSE Mark V monos I own have 1.5m circuitry and outputs run to 400khz
Enjot it, you deserve it!
Regards
David
It should sound even better after playing 30 or more hours
The bias spread you have is not out of order. Can,t remember mine but not to far off
My loaded rails came out 41.5,, just more heat to blow off
The sound is cut from the same cloth top to bottom with the low end superoir in tight ness with deep extension. My krell clone 100/150 monos do not have the quality of bass as the 50 does (although very very good in their own right) for some strange reason, but are better at nasty loads by far
The 50 doesn,t quite fill the bill on my SL3's or old Quads but matches perfectly with Vandersteens. Theres a big difference in loads here also
The flip side is the others sound better and more extended on top that I prefer on those other pairs, but there is something special going on with the 50 with the right speakers for sure. I do have a big room however at 23x26ft
Have you ran a square wave on up and noticed when you start to get leading edge rounding yet? My 50 has a smaller bandwidth than my 100 and the 150 has quite a better bandwidth.
For example.. a pair of PSE Mark V monos I own have 1.5m circuitry and outputs run to 400khz
Enjot it, you deserve it!
Regards
David
Enjoy!
Thanks. Now I have to finish the job to be complete. Rear panel next as well as top and bottom panels. Sinks also needs to be sent in for black anodizing. Should I anodize the other panels also or should I just powder coat it?
I am maybe planning to save some money to get some Martin Logans. Or maybe build my own. Not so sure yet. At the moment I have some fairly good speakers (6 Ohm) using VIFA drivers.
I am maybe planning to save some money to get some Martin Logans. Or maybe build my own. Not so sure yet. At the moment I have some fairly good speakers (6 Ohm) using VIFA drivers.
Attached is some pics of the amp during my test setup. The bad thing about this layout is that one cannot bias the amp assembled. Spacing is just too tight.
You will notice 2 different sets of capacitors. The smaller ones are 10000uF 63V Epcos Sikorels that feeds the main and driver boards, and the the other ones are 55000uF 63V cheap Indian caps that feeds the output boards. I might replace thos with some Epcos or other caps when the funds allow.
I also need now to clean up an organise the wiring. In future I would prefer Faston connector on the boards for power wiring. I don't trust these screw terminals.
You will notice 2 different sets of capacitors. The smaller ones are 10000uF 63V Epcos Sikorels that feeds the main and driver boards, and the the other ones are 55000uF 63V cheap Indian caps that feeds the output boards. I might replace thos with some Epcos or other caps when the funds allow.
I also need now to clean up an organise the wiring. In future I would prefer Faston connector on the boards for power wiring. I don't trust these screw terminals.
Attachments
newbie ss builders needs help with start for ksa50 kit.
Hey guys I have been building tubes for 20 years. I finally want to build some class A ss amps. I have built a few chip amps and they sounded bad compared to my tubes. I am building a quad amp horn system and I really want to build a nice but economical class A amp or amps for the bass channels. I have liked the class D's but I have read the phase issues will catch up with me for bass amps. And I want to experience the bass slam of the famous Krell that the audiophiles buy but with out the price of admission. I am not confident that I can source all the parts separately and correctly build a ksa 50 board maybe a much simpler Hiraga which I will definitely build soon but I am told they don't have a lot of bass slam I would want.
I am trying to build a amp to drive reflex bins to keep up with horn top ends to start with. Anyone familiar with this one below. Cheap already stacked all be it with some nasty parts that will need up grading. It says its more then 50 watts I don't understand. I just want a amp board loaded like this with as close to the original 50 watt design as I can find. Can anyone out there get this far through this ramble and direct me to a seller of such a populated amp board set or suggest what this needs to perform as I need? Perhaps a lower voltage supply, supplys. Thanks Guys
eBay Australia: Buy new & used fashion, electronics & home d?r
Hey guys I have been building tubes for 20 years. I finally want to build some class A ss amps. I have built a few chip amps and they sounded bad compared to my tubes. I am building a quad amp horn system and I really want to build a nice but economical class A amp or amps for the bass channels. I have liked the class D's but I have read the phase issues will catch up with me for bass amps. And I want to experience the bass slam of the famous Krell that the audiophiles buy but with out the price of admission. I am not confident that I can source all the parts separately and correctly build a ksa 50 board maybe a much simpler Hiraga which I will definitely build soon but I am told they don't have a lot of bass slam I would want.
I am trying to build a amp to drive reflex bins to keep up with horn top ends to start with. Anyone familiar with this one below. Cheap already stacked all be it with some nasty parts that will need up grading. It says its more then 50 watts I don't understand. I just want a amp board loaded like this with as close to the original 50 watt design as I can find. Can anyone out there get this far through this ramble and direct me to a seller of such a populated amp board set or suggest what this needs to perform as I need? Perhaps a lower voltage supply, supplys. Thanks Guys
eBay Australia: Buy new & used fashion, electronics & home d?r
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Is there any BOM for both krell?
What about PS PCB and transformer?
And Chassing maybe???
I don't have any info on a BOB but someone else on the thread may. You can send the vendor an email as he might have one.
Also, before you give up on chip based amps check out the MyRef Fremen Edition. The current group buy ended a few days ago but I suspect round 2 quite soon. I'm sure it will meet your quality expectations.
Also, before you give up on chip based amps check out the MyRef Fremen Edition. The current group buy ended a few days ago but I suspect round 2 quite soon. I'm sure it will meet your quality expectations.
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