11mA to 12mA seems very low for FET bias.
Even 25mA is low.
Borbely says 500mA for the whole output stage bias and >=100mA bias /output pair
Even 25mA is low.
Borbely says 500mA for the whole output stage bias and >=100mA bias /output pair
Make 50mA per pair, so a total of 4 pairs of output transistors 200mA and enjoy!🙂 Pay attention to the temperature of the heatsink!
Legend stage master
Hi Vicktor,
I read what andrewT told me and I just set 200mA bias (50mA per pair Fets) It's working fine but getting little hot but not like I can not touch the heatsinks 😉. Today, I have tested it for two hours. Tomorrow I will test it again for whole day.
The sound quality is excellent. It just sake my home with my half horns 500wrms speakers. And I thing all credit goes to Mr Bora and friends like you who always help me.
Thanks for all help my friend .
Regards
Hi Vicktor,
I read what andrewT told me and I just set 200mA bias (50mA per pair Fets) It's working fine but getting little hot but not like I can not touch the heatsinks 😉. Today, I have tested it for two hours. Tomorrow I will test it again for whole day.
The sound quality is excellent. It just sake my home with my half horns 500wrms speakers. And I thing all credit goes to Mr Bora and friends like you who always help me.
Thanks for all help my friend .
Regards
Legend stage master
Hi Dear Viktor,
I have tested the amp today the heatsinks are getting warm not hot only sofstart resistors are getting very hot is it fine? though I am using very good quality resistors (220ohm 6W X 4)
Regards
Hi Dear Viktor,
I have tested the amp today the heatsinks are getting warm not hot only sofstart resistors are getting very hot is it fine? though I am using very good quality resistors (220ohm 6W X 4)
Regards
the soft start resistors must have a time delayed bypass (usually a relay) across them. This allows them to pass zero current during normal operation (=runs cold) and minimises the source impedance seen by the mains transformer.
Softstart
Hi AndrewT,
Got the problem relay was not working. I fixed it and now its working fine. thanks. The heatsinks are 33C hot.
regards
Hi AndrewT,
Got the problem relay was not working. I fixed it and now its working fine. thanks. The heatsinks are 33C hot.
regards
Hi vicktor,
Here are some pics of my amplifier. It's not very clean because this is the first time I am putting amplifier into the box and the enclosure is also completely home and hand made 🙂
Regards
Attachments
Beautifull pics.... very nice amplifier
The designer is awsome..one from the best ones we have.
Doctor Bora!
regards,
Carlos
The designer is awsome..one from the best ones we have.
Doctor Bora!
regards,
Carlos
Hi people!
Sorry for not being regular here, but flu knocked and kept me down for a week and a half now. Excellent work WASIM. Our friends here gave you good and correct answers and, as you can see, results are positive!
Special and BIG
for my friend - Carlos The Great! Praising from you always make me feel flattered!
Sorry for not being regular here, but flu knocked and kept me down for a week and a half now. Excellent work WASIM. Our friends here gave you good and correct answers and, as you can see, results are positive!
Special and BIG
for my friend - Carlos The Great! Praising from you always make me feel flattered!
The first and the great Bora is with us!....Hurra!
have some vegetables and fruits dear Bora.... try to walk a little bit more and mix three kind of fresh fruits daily..reduce sugar, reduce fat and be happy.
I am walking around, inside the building...into the internal garden...only 30 minutes..this is not more than 2 kilometers.....i do that under the sunlight..sweting a lot of course...when returning have a good cold shower and some fresh fruits.
During this exercise, physical exercise, this morning, i have made the pictures included into the youtube video you have the link down this page.
Biscuits are sugar less... and cool drink only twice a week and one glass each time.
I have not flu those last 8 years i think.
regards,
Carlos
have some vegetables and fruits dear Bora.... try to walk a little bit more and mix three kind of fresh fruits daily..reduce sugar, reduce fat and be happy.
I am walking around, inside the building...into the internal garden...only 30 minutes..this is not more than 2 kilometers.....i do that under the sunlight..sweting a lot of course...when returning have a good cold shower and some fresh fruits.
During this exercise, physical exercise, this morning, i have made the pictures included into the youtube video you have the link down this page.
Biscuits are sugar less... and cool drink only twice a week and one glass each time.
I have not flu those last 8 years i think.
regards,
Carlos
Attachments
Last edited:
I can see why Wasim's fanned heatsinks run @ ~ 33degC.
The thermal resitance of that thin angle bracket ensures the output devices run much hotter.
The thermal resitance of that thin angle bracket ensures the output devices run much hotter.
Excellent remark AndrewT, I haven't pay particular attention on details on those pictures, but you pointed it right. L-profiles are not thick enough. Material should be at least 5mm for such amps. With lower power amps Wasim, you can use lighter L-profiles, but for such power as StageMasterMK2, they should be of a heavier gauge! Also, thermal paste have to be applied between L-profile and main heatsink!
Stage master
Hi dear Sir,
Yes AdrewT is right the L bracket is not very thick. But sir, I took the temperature rating of the both the heatsinks and the L bracket and the temperature of the both are approximately the same.
I biased the amplifier on 50mA per pair and the heatsink was hot like 50C to 60C and now I adjust the bias on 30mA per pair per FETs. On 30mA it's producing 33C temperature. This was the whole situation.
But I am convinced that I should change the L bracket to 5mm thickness for its long life 🙂
Regards
Hi dear Sir,
Yes AdrewT is right the L bracket is not very thick. But sir, I took the temperature rating of the both the heatsinks and the L bracket and the temperature of the both are approximately the same.
I biased the amplifier on 50mA per pair and the heatsink was hot like 50C to 60C and now I adjust the bias on 30mA per pair per FETs. On 30mA it's producing 33C temperature. This was the whole situation.
But I am convinced that I should change the L bracket to 5mm thickness for its long life 🙂
Regards
increasing the output bias from 30mA/pr to 50mA/par should not increase the Ts from 33degC to 50-60degC.
there is something wrong.
Are you sure the 33degC is as much as 30mA/pr bias. It seems more like 3mA/pr bias.
there is something wrong.
Are you sure the 33degC is as much as 30mA/pr bias. It seems more like 3mA/pr bias.
stage master
OK AndrewT let me check everything again and then I will get back to you
Regards
OK AndrewT let me check everything again and then I will get back to you
Regards
Legend stage master
Hi Sir,
I have replaced the angle brackets with 6mm thick brackets and now the heatsinks are getting quite warm. The bias is the same that I had before 30mA per pair total 120mA.
I have tested the amplifier yesterday and the result was really good.
Regards
Hi Sir,
I have replaced the angle brackets with 6mm thick brackets and now the heatsinks are getting quite warm. The bias is the same that I had before 30mA per pair total 120mA.
I have tested the amplifier yesterday and the result was really good.
Regards
Attachments
Finally, that’s OK Wasim. Now you can see why AndrewT suggested heavier L profile… heat transfer is now much more efficient.
I am glad to hear that you are happy with sound and capabilities of the amp. It is not super high quality, but powerful and reliable “workhorse” .
I am glad to hear that you are happy with sound and capabilities of the amp. It is not super high quality, but powerful and reliable “workhorse” .