Thanks again.
One last question before drilling holes in heatsinks etc.
I thought what I had in VAS transistors were already good match.
That is not quite the case:
Measured hFE (next best match of each)
ksa1220/ksc2660 ---~200/240 (powerful)
2sa1541/2sc3956 ---~140/150 (A bit rare, excellent data)
2sa1381-E/2sc3501-D ---~140/85 (Different gain grade. )
Also have some 2sa1360/2sc3423 left after an earlier project but havent measured those yet. Those who were best matched are used in another amp.
What do you recommend? The ksa1220/ksc2690 have quite much higher Ic than the others but somewhat higher Cob...
Thought I had some kse340/350 at hand but unfortunately no...
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FYI, I still have v4h rev1 boards. In case the normal shipping is too high there is also a cheaper option that takes more time to reach destination.
You can use the 1220/2690 pair with no negative impact due to their high Cob. Q3/Q4 (again) takes care of the high Cob and makes sure it doesn't affect linear operation.
Edit: For the curious, 1220/2690 pair seems to have a maximum rating of 120V. So not recommended for 56V operation of the amp. 45V is fine.
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Increase C5/C6 to 68pF.
I'm not sure whether the oscillation problem that happened in thimios's experiments is due to the vas transistors or vas-mosfet interaction (for which rev1 was developed). Anyway, slowing down ultrafast components a little should stabilize it if the speed caused problem. These transistors aren't available where I live and I haven't tested them myself, so can't give you a concrete idea about their behaviour in this amp.
Genuine or fakes?
Hello friends
I apologize for my bad English, since it is not my native language.
I need your valuable help to know if the transistors of the attached photo are genuine Hitachi? or are they fakes? or is it better to buy the Renesas?
Thank you very much for your answers
Hello friends
I apologize for my bad English, since it is not my native language.
I need your valuable help to know if the transistors of the attached photo are genuine Hitachi? or are they fakes? or is it better to buy the Renesas?
Thank you very much for your answers
Attachments
Are those the excact transistors you have at hand or are the picture from a sales add? They look genuine but it is almost impossible to say from a picture.
Suzy's Blog: More fakes
Suzy's Blog: More fakes
Attachments
You'll find the ratings on the documentation of your transformer.
This is a sample documentation of a 300VA transformer: http://www.amplimo.nl/images/downloads/ds standardrange/78026.pdf
Hello Shaan,
Short question: I managed to solder the LED's the wrong way (both of them); silly me
In the mean time I have corrected that mistake and the LED's light up when I start the setup procedure. However, the amp seems non responsive. It is not drawing any current at all. I'm using a dual 55 volts supply (currently with two 1 ohm resistors in the power rails).
Do you think that I might have blown any transistors by reversing the LED's?
Short question: I managed to solder the LED's the wrong way (both of them); silly me
In the mean time I have corrected that mistake and the LED's light up when I start the setup procedure. However, the amp seems non responsive. It is not drawing any current at all. I'm using a dual 55 volts supply (currently with two 1 ohm resistors in the power rails).
Do you think that I might have blown any transistors by reversing the LED's?
Hello Shaan,
Short question: I managed to solder the LED's the wrong way (both of them); silly me
In the mean time I have corrected that mistake and the LED's light up when I start the setup procedure. However, the amp seems non responsive. It is not drawing any current at all. I'm using a dual 55 volts supply (currently with two 1 ohm resistors in the power rails).
Do you think that I might have blown any transistors by reversing the LED's?
Are both PGND and SGND properly connected to ground?