DC Servo MOSFET Amplifier

[apexaudio]

Hi mile . Pcb for that design?

No, it's not tested.

 

[apexaudio]

F120 pcb

 

[wiljj78]

F120 pcb

Looks cool!

 

[Shelah]

I have a few questions to ask
1. What would be the recommended ac voltage and transformer VA rating?
2. In place of the mr diodes, can I use mbr20200ct?
3. Are all the resistors in the h-step 1/4watt?
4. Can I use 1watt versions of all the zener diodes?
5. Instead of the ifrp240/9240 combination, can I use irf540/9540 and if so how many?
6. Wat are the voltage ratings for all the bipolar capacitors ?

Sorry for so many questions I want to get this right the first time.

 

[apexaudio]

F400 from '90...

 

[apexaudio]

F110

 

[prasi]

On this PCB exept PSU is short-circuit and DC protect, clip indicator...

Dear Mr. Mile,
here is my eagle version of your PSU+Protect+Clip PCB. I found a few discrepancies in the schematic, but I laid the PCB as per your PCB layout. pl inform if there are any errors.
regards
prasi

 

[olafk]

Hi,
I've never tried an amplifier from this thread. So here is the first draft of a F120.
It would be nice if someone could look at it.

I hope, next weekend I will find time for etching PCB.

regards Olaf

 

[apexaudio]

Hi,
I've never tried an amplifier from this thread. So here is the first draft of a F120.
It would be nice if someone could look at it.

I hope, next weekend I will find time for etching PCB.

regards Olaf

Nice pcb,
Regards

 

[prasi]

Dear Mr. Mile,
here is my eagle version of your PSU+Protect+Clip PCB. I found a few discrepancies in the schematic, but I laid the PCB as per your PCB layout. pl inform if there are any errors.
regards
prasi

Mr.mile any comments on the layout of PSU? I am getting the psu circuit screen printed to try on for the kelvin amp stereo.
Reg prasi

 

[apexaudio]

Mr.mile any comments on the layout of PSU? I am getting the psu circuit screen printed to try on for the kelvin amp stereo.
Reg prasi

It's ok, you just redraw my pcb.
Regards

 

[prasi]

It's ok, you just redraw my pcb.
Regards

Yes. I redrew your PCB. I am yet to reach a level where I can prepare my own layouts based on your schematic. . thanks for the confirmation. One other help. I did not like the sound of lm3886. My cheap commercial solid state amp makes much better sound. I have posted this query in lm3886 thread. Tell me whether kelvin amp can be used as a full range amp and can it produce audiophile quality sound? I am interested to know the specs of kelvin amp.if you have. Like thd. Imd . bandwidth etc.

Sorry for mistakes as I am typing from mobile.
Reg
Prasi

 

[apexaudio]

FB200

 

[olafk]

Hi,

I have assembled the F120. The first test shows a lot of trouble

Quiescent current is 160mA but the output has oscillations at about 20 kHz and + -40Vpp. Supply voltage is + - 52V DC. Zobel (4R7 + 100n) is really warm and R18 (22R) is very hot. A signal at the input (0.5V 1kHz sine) can not be seen at the output.
So tomorrow I will go and check everything again and make some measurements.

regards Olaf

 

[apexaudio]

Hi,

I have assembled the F120. The first test shows a lot of trouble

Quiescent current is 160mA but the output has oscillations at about 20 kHz and + -40Vpp. Supply voltage is + - 52V DC. Zobel (4R7 + 100n) is really warm and R18 (22R) is very hot. A signal at the input (0.5V 1kHz sine) can not be seen at the output.
So tomorrow I will go and check everything again and make some measurements.

regards Olaf

Input gnd and power gnd is not separate on your pcb...

 

[olafk]

Hi Mile,
yes, unfortunately you're right . I will correct that. Probably is this not the only error...
Then I'll try again.

Thanks and Greetings
Olaf

 

[apexaudio]

Hi Mile,
yes, unfortunately you're right . I will correct that. Probably is this not the only error...
Then I'll try again.

Thanks and Greetings
Olaf

R11 is 220R not 22R...

 

[olafk]

R11 is 220R. Seems to be ok.

 

[olafk]

Hi,

now the amp is singing

I corrected the input GND and changed all components in the oscillating negative supply and the opamp.
The sound is very strong and clear, but I tested only on old speakers.
It runs on + -52V, all is cool, quiescent current is only 8mA (?), offset is 1 mV.
Unfortunately my oscilloscope is broken, so I have no other pictures.

I will build the second channel with the corrected layout as soon as I find time

regards Olaf

 

[apexaudio]

R11 is 220R. Seems to be ok.

You add 22R in positive rail it's ok.
Regards