I have seen there are threads about designing Quasi Complementary amplifiers.
I wanted to try this.
So I started putting it together.
I decided to go simple.
I got an amplifier working.
Here is the result:
I wanted to try this.
So I started putting it together.
I decided to go simple.
I got an amplifier working.
Here is the result:
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Can you explain to me ?
1, reason use D1
2, What difference ? if change bootstrap circuit ( R8,R9,C1) by constant curent source , (quality of capacitor) .
instead of TL431 put there BD139 (same position) and mount it at heatsink between IRF-s
1. I really dont know. But I had seen other quasi amplifiers use such a diode.
It is probably not necessary ... We could remove it and see what happens.
2. A current source is better.
How much better I dont know. We could test and see.
Here your two suggestion/questions in play.
I removed D1.
I added a current source.
Now this did not change much in performance. But it feels better somehow.
Attachments
Here you are.
Now BD139 is used for Vmultiplier and can be put unto heatsink.
This would make it more thermal stable.
Attachments
Thanks, @bordodynov
Can you add my latest circuit.
I have made some changes.
https://www.diyaudio.com/community/attachments/quasi-irfp240_06-bd139-jpg.1471054/
It should be noted that with the +/-24V supply this is a 20 Watt amplifier.
Is it possible to reduce supply or increase supply - Yes, I think so.
Say +/-20V or +/-30V.
The changes should be minimal for that.
Can you add my latest circuit.
I have made some changes.
https://www.diyaudio.com/community/attachments/quasi-irfp240_06-bd139-jpg.1471054/
It should be noted that with the +/-24V supply this is a 20 Watt amplifier.
Is it possible to reduce supply or increase supply - Yes, I think so.
Say +/-20V or +/-30V.
The changes should be minimal for that.
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Just by looking at it, should be good now.
Since you really like to play, few things to make it different and IMHO better:
Major change: replace LTP at input with single transistor and current feedback, that will make it faster. Than add opamp and global feedback, In another of your threads I mentioned it already... If you do this ; no problem to keep bootstrapping (even I don't think it is an issue anyway) and you can disregard all I wrote below:
For making this one as it is better as is, you can:
Have fun,
Drazen
Since you really like to play, few things to make it different and IMHO better:
Major change: replace LTP at input with single transistor and current feedback, that will make it faster. Than add opamp and global feedback, In another of your threads I mentioned it already... If you do this ; no problem to keep bootstrapping (even I don't think it is an issue anyway) and you can disregard all I wrote below:
For making this one as it is better as is, you can:
- current source also LTP, Vref can be the same from VAS current source (between D2 and R9). R15 pot is not needed in any case
- add another small transistor in-front U6 increasing VAS gain dramatically
- degenerate 2 input transistors in LTP
- read Douglas Self blameless amplifier articles through 🙂
Have fun,
Drazen
Thanks.
Does it look good?
I made a version with +/-30V supply.
There was a couple of small changes needed.
But it did go well - no problems.
+/-24V gives max 20 Watt output
+/-30V gives max 35 Watt output
THD at 1 Watt into 8 Ohm is in both supplies like 0.009%
Does it look good?
I made a version with +/-30V supply.
There was a couple of small changes needed.
But it did go well - no problems.
+/-24V gives max 20 Watt output
+/-30V gives max 35 Watt output
THD at 1 Watt into 8 Ohm is in both supplies like 0.009%
Yes @Drbulj
There are many changes I could do. For some improvement.
But as I mentioned in my first post I decided to make it simple.
With all your suggestions it would be another amplifier. Why don't you start a new thread and include all those things?
So, I will stay with my present amp.
It is good enough and should work well!!
🙂
