I tested the resistors at the input: a voltage splitter 1:1 (R16 = 10k and Rin+ = 10k) is pretty ideal for me, because then the control range of the potentiometer reaches from quiet to ultra loud. A resistor between the (-) input and GND only produces hum, I was afraid of that, but I wanted to try it out. So I installed a wire for Rin-.
I have now installed a Q17 in a small aluminium housing.
I nearly despaired, but now it works.
The first thing that is not clear to me is that I have swapped the Q13s in both power amplifiers. one did not start. the other very slowly. The component tester claims that the cut IRF610s are OK. My question, is it possible that R29 is perhaps chosen a little high? Would 6k8 perhaps be more suitable?
Then I had one touch point on Q5 with the radiator, R10 was smoking, so I could identify this fault too.
Now it plays very nicely.
It is one with only one pair of output transistors. I would prefer this for nice music listening. The Q17 with output pairs selected in pairs was a touch more massive, more merciless at high levels. This new one is a shade more sensitive, the right choice for me.
I nearly despaired, but now it works.
The first thing that is not clear to me is that I have swapped the Q13s in both power amplifiers. one did not start. the other very slowly. The component tester claims that the cut IRF610s are OK. My question, is it possible that R29 is perhaps chosen a little high? Would 6k8 perhaps be more suitable?
Then I had one touch point on Q5 with the radiator, R10 was smoking, so I could identify this fault too.
Now it plays very nicely.
It is one with only one pair of output transistors. I would prefer this for nice music listening. The Q17 with output pairs selected in pairs was a touch more massive, more merciless at high levels. This new one is a shade more sensitive, the right choice for me.
Hello Tibi,
once again, huge compliments.
I now have the amp running at home and it sounds fantastic. Compared to that, my old amp sounds downright fuzzy. The bass foundation is also impressive. The treble seems endless and the naturalness - I don't have the words to describe it.
I have never heard such an acoustic stage, not even with open buffle speakers.
Regards Tim
once again, huge compliments.
I now have the amp running at home and it sounds fantastic. Compared to that, my old amp sounds downright fuzzy. The bass foundation is also impressive. The treble seems endless and the naturalness - I don't have the words to describe it.
I have never heard such an acoustic stage, not even with open buffle speakers.
Regards Tim
Thank you Tvicol for the detailed explanation. Really appreciate it. I'm interested to build the amp.
no.
i have uploaded an experiment board here that has some not needed footprints on it.
The unlabeled diodes are for scaredy-cats, I don't understand their sense, because they also burn out in case of defects.
Only one operational amplifier may be installed.
The capacitors C-Q5 and C-Q6 I have not used so far, I would currently leave them empty.
It is up to you whether you equip the output single or double with source resistor. I have built it without source resistor with only one pair of transistors.
R24 = 8k2
R23 = 8k2
Rin- = wire
Rin+ = 10k
R16 = 10k
Cin = empty (my audio cable has enough capacity)
Q9 = ZVP2106A
Q11 = ZVP2106A
Q8 = ZVN4206A
R25 = 0 for + - 33V
R25 = 9k for + - 50V
or something between
I have made a list of components on Reichelt.de. This is incomplete, because the four QFET, an OPA1611 socketed, C7 and the two Muse 220/25V are missing.
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Pictures of the finished amplifier.
Not nice inside, there is very little space in the case. The PCB for the active rectifiers are not there yet, so 4 MUR diodes have to rectify the current.
The amplifier has a 2x 24V transformer, which produces 2x 35V DC.
This certainly does not meet the expectation in terms of sound, so I recommend everyone to use a larger enclosure if you do not have experience in how to minimize and also detect mutual induction.
Not nice inside, there is very little space in the case. The PCB for the active rectifiers are not there yet, so 4 MUR diodes have to rectify the current.
The amplifier has a 2x 24V transformer, which produces 2x 35V DC.
This certainly does not meet the expectation in terms of sound, so I recommend everyone to use a larger enclosure if you do not have experience in how to minimize and also detect mutual induction.
Attachments
FQA46N15/FQA36P15 transistors are rated at 150V. This limit absolute maximum voltage operation at +/-75V. This is pure theoretic, because in practice will never run fully saturated that one transistor to be exposed to full rail voltage. However, you must know that even at +/-66V transistors will run very easy out of SOA (Safe Operating Area).
+/-60V would be more appropriate.
Also, take care on capacitors voltage rating.
If you want to go for higher rail voltages, IXYS or Exicon may be a solution.
Regards,
Tibi
