2 times exactly the same value ? That's practically impossible... Typo ?
I don't know bd911/912, if the pinout fits try it, but the dc-offset is caused in the input stage.
Mike
I don't know bd911/912, if the pinout fits try it, but the dc-offset is caused in the input stage.
Mike
MikeB said:
mike BD911/912 work pinout it's the same
You are correct dc offset it's caused in the input stage...
I change BC547B (first board) with maching hfe with hfe tester from you and dc offset now is ~5mv
thank you very much...
I will buy new dmm, voltage base Q1 to ground -83mV and Base Q2 to ground -89mV
dytln_02,
congratulations for fixing the problem, and thanks to Michael's never ending patience 😉 .
Regards,
Pavel
congratulations for fixing the problem, and thanks to Michael's never ending patience 😉 .
Regards,
Pavel
Yipee ! My patience was about to be consumed... This was a tough one.
It's really bad if you can't trust your tools !
Mike
It's really bad if you can't trust your tools !
Mike
Mike ,
Huge effort you put in to get dytln
up and rrunning
Is it possible to buy you a beer or two
over the internet ?
have bought samples direct from onsemi
of mjl 0281A and the complimentary 0302
Looking forward to this build
Huge effort you put in to get dytln
up and rrunning
Is it possible to buy you a beer or two
over the internet ?
have bought samples direct from onsemi
of mjl 0281A and the complimentary 0302
Looking forward to this build
power trans
Hello.
I'm kim youn su from korea.
I had found your amp from my friend.
The sound is exellent.
Could I know power trans spec to build this amp?
How much voltage and ampares ?
Thanks.
Hello.
I'm kim youn su from korea.
I had found your amp from my friend.
The sound is exellent.
Could I know power trans spec to build this amp?
How much voltage and ampares ?
Thanks.
Hi Sandro, thanks for the beer ! 
MJL0281/0302 are a good choice, nice transistors.
bada, mainspecs for the output devics are:
Power at least 150watts, Vceo of > 200v, Max current 15a, ft should be ~30mhz, hfe of ~100.
Compare them with the Toshiba 2c5200/sa1943.
Sanken has also some nice transistors.
Mike
MJL0281/0302 are a good choice, nice transistors.
bada, mainspecs for the output devics are:
Power at least 150watts, Vceo of > 200v, Max current 15a, ft should be ~30mhz, hfe of ~100.
Compare them with the Toshiba 2c5200/sa1943.
Sanken has also some nice transistors.
Mike
MikeB said:
mike only 1 board can be fix with matching hfe at input.
in second board with this measure at board, it's not working.
Is this problem only hfe at input see picture below
An externally hosted image should be here but it was not working when we last tested it.
I need a lot of aspirine 😡
Can i Use higher voltage with your hfe tester ?
Edit : I try to move BC547B at firs board and put in second board it's not working ..
Edit : first time I give new BC547 with matching hfe it's not work than i move BC547B at firs board and put in second board it's not working ..
It's exactly the same, mismatched hfe's or mismatched 22k's...
But, this is old picture ?
You can't easily increase voltage with this hfe-tester, if you do, you have to change the 1k the same ratio as you increase the voltage.
For example if you increase to 36v, it's 4 times the voltage, thus you need 4k resistors and the formula changes to *25 instead of *100.
You see, if inputstage is working perfect, the voltage difference between q1-base and q2-base must be identical to the DC-offset at output. But difference is only 3mv instead of 35mv.
The voltages at these bases are created by the base currents through the 22k. For q2 the DC-offset gets added. So, without the DC-offset q2-base would be 84mv. 84mv across 22k is 3.81uA, the current through q2 is ~1.5ma giving hfe of 393.
For q1: 46mv acros 22k is 2.09uA, gives hfe of 717. Now there are 2 options, q1 really has hfe of 717, or the devices are matched and the 22k to q1 is 12k. You really should have a look at this 22k...
Mike
But, this is old picture ?
You can't easily increase voltage with this hfe-tester, if you do, you have to change the 1k the same ratio as you increase the voltage.
For example if you increase to 36v, it's 4 times the voltage, thus you need 4k resistors and the formula changes to *25 instead of *100.
You see, if inputstage is working perfect, the voltage difference between q1-base and q2-base must be identical to the DC-offset at output. But difference is only 3mv instead of 35mv.
The voltages at these bases are created by the base currents through the 22k. For q2 the DC-offset gets added. So, without the DC-offset q2-base would be 84mv. 84mv across 22k is 3.81uA, the current through q2 is ~1.5ma giving hfe of 393.
For q1: 46mv acros 22k is 2.09uA, gives hfe of 717. Now there are 2 options, q1 really has hfe of 717, or the devices are matched and the 22k to q1 is 12k. You really should have a look at this 22k...
Mike
MikeB said:
yes you are correct in second amps i put 12k because the color is very similar.
thank you for your patience
mike in your amps picture at your homepage what type capacitor 100pF.
I buy 100pf/2000v and the shop that sell it call it mylar caps, but it's very look like with capacitor in your picture.
is mylar caps better than ceramic ?
Hi dytln, nice to see that you can perfectly trust on ohms law ! 😉
About the caps, principally everything is better than ceramics (except elyts). Mylar is PET, not bad, but the caps in my amp are micas. You can try to get styroflex, they have similar quality to mica.
For C2/14/3/4 ceramic should be avoided, for c7 ceramic is ok.
I guess the mylars are a better choice than the ceramics. Just try them if you hear a difference. You will hear a difference for c14.
You might try to also match q4/12 with the hfe-circuit ?
The micas i use are from JINGUAN, maybe you have acess to them ?
Mike
About the caps, principally everything is better than ceramics (except elyts). Mylar is PET, not bad, but the caps in my amp are micas. You can try to get styroflex, they have similar quality to mica.
For C2/14/3/4 ceramic should be avoided, for c7 ceramic is ok.
I guess the mylars are a better choice than the ceramics. Just try them if you hear a difference. You will hear a difference for c14.
You might try to also match q4/12 with the hfe-circuit ?
The micas i use are from JINGUAN, maybe you have acess to them ?
Mike
Ryssen said:
If you're driving 8ohms it should be enough, for 4 ohms you might double it. (For stereo)
anatech said:
Thanks for the compliments...
Mike
@mikeb
mike I want build 250W version,
I don't Need 250W, only 200W, can i use 2SC5200/2SA1943
can you give Eangle PCB Layout ?
mike I want build 250W version,
I don't Need 250W, only 200W, can i use 2SC5200/2SA1943
can you give Eangle PCB Layout ?
dytln, the 250watt version i once posted was just a design-study, no working or ever built design. You can't build that one, it has errors and will likely blow.
There is still no high power version of symasym.
sorry,
Mike
There is still no high power version of symasym.
sorry,
Mike
HI
I would like to ask for some help , I'm on my way to put together these amplifier . I try to find capacitor for the C1 place but unfortonatly in North America we dont have .
My question can I use bipolar 10Mf capacitor , I'm thinking about to order BG N tipe capacitor for these place .
Please let me know if will work to me .
Regards
Thanks for the help.
I would like to ask for some help , I'm on my way to put together these amplifier . I try to find capacitor for the C1 place but unfortonatly in North America we dont have .
My question can I use bipolar 10Mf capacitor , I'm thinking about to order BG N tipe capacitor for these place .
Please let me know if will work to me .
Regards
Thanks for the help.
Hi gaborbela, you can use elyt cap for c1, the "+" goes to the input pin, the "-" to the amp. For bipolar of course there is no polarity.
I guess you meant 10uF, 10mF would be overkill...
Mike
I guess you meant 10uF, 10mF would be overkill...
Mike
I would rather see 4.7uF or 2.2uF foil cap than 10uF electrolyte as input cap. Just my opinion.