NMOS 350/500 by Quasi

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#101
WuYit said:
Kanwar,
FETs should be driven by a voltage amplifier. My first consideration is signal transfer and I`m aware of the conflicting factors.
Click to expand...

Not just any voltage amplifier but a dedicated one which addresses the things like miller plateau, active discharge of gate, low Z, High slew rate and compensation w.r.t. Drain.


BTW: check your inbox
 
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#102
In last day I had very little time to work on my amp. Nothing what I was doing could solve the problem with 11.71V drop across the R22, so I thought that maybe some of the MJEs are bad or fake so I replaced all four (I have some more at home). As I did that, the oscillations are back regardless what I did earlier (solved oscillations). I tried to put C8 (10pf) back in and the result was even worse. I suspect they are realy fake, so I ordered new ones from Digikey.
 
#103
quasi said:
Maybe we should return the thread to helping fix the amp in question?
Click to expand...


for all quasi NMOS constructor

please check schematic


have add some features after long discusses in thread

1. have add string with 3 diode 1n4148 for symmetrical clipping instead of 100 R - using Mosfet output devices

2. add T6, C7, D5, R15 to increase linearity and speed from input stage

3. VI Limiter for BJT Quasi amp, I think this should help in catastropic failure to protect driver stage with mosfets output devices too. I think VI Limiter for BJT Quasi output devices is better than nothings if using mosfets

4. Could this work ? to add +12 V DC using T24, D25, R61, R62 in first stage as soft start for amp turn on/ fast off and for protect amp in catastropic failure like overcurrent and short circuit ?

If simple protection circuit detect over current/DC /short circuit ....amp is fast off trough T24, D25, R61, R62..... and mosfets / BJT dont blow

have seen this way of protection in professional amp and APEX audio use similar way to protect H900 and B500 in catastropic failure like overcurrent and short circuit

could this work in quasi too, any ideas ?

regards
 

Attachments

#104
If somebody interested for gerber files email me ....

double layer Quasi BJT and NMOS350/500 PCB with GND bottom Ground plane

and without GND bottom Ground plane

any ideas to improve ?

have add

- input limiter for PA
- turn on delay and DC Protection with Relay
- 1n4148 x3 string for perfect symmetry and clipping if using mosfet output devices

THIS IS DUAL USE PCB for Mosfets or BJT Quasi output stage
 

Attachments

#106
WuYit said:
Kanwar,
my consideration is signal transfer, while yours is switching performance.
Click to expand...


My consideration is signal transfer with optimum turn on and turn off and stick free clipping.😉

A great deal of influencing parameters are responsible for that in order to make a reliable amp stable at all loads and ofcourse short circuit protection is needed .
 
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#109
quasi nmos

hello everyone
I must apologize for my english it's not so good

ID_ please believe me i build this amplifier and it's working from the first time i turn it on
i build one pair mosfet version of this schematic i even use the pcb quasi provided for
my gues is that you use some fake parts don't try to modify the schematic it's working fine
try to buy original mje340/350 and irfp's
first time i buy cheap mje, when i measure them i foud that mje 340 do not match pinout whit mje 350 (mje340 BCE and mje350 ECB) not to mentioned this fake transistor don't withstand high voltage
so my suggestion is to buy original parts (st micro or onsemi)

quasi please tell me what is the maximum voltage for nmos350 the one whit 3 pairs of mosfet's because i have a power supply with +/- 85vcc
and i don't what to modify it?
 
#110
maxente said:
hello everyone
I must apologize for my english it's not so good

ID_ please believe me i build this amplifier and it's working from the first time i turn it on
Click to expand...


I agree, great Hig End PA and Hi-FI amp, sound is hard to beat




have make today new double layer NMOS pcb with Groundplane size: 255 x 80 mm / 287 pins

diyaudio dont accept upload rar files

Who want NMOS MKII gerber files for pcb supplier ? email me
 
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#111
pcb

hi nmos
greetings thank you for pcb files which software to open pcb files
i want to make pcb at home to expensive t get it done at factory i used
free version of McCAD Gview 3.1.4 bottom layer opened up but top layer
will not open as software is free version any other free version software
to open top layer thank you for pcb files
thanking you
andrew lebon
 
#113
andrewlebon said:
hi nmos
greetings thank you for pcb files which software to open pcb files
i want to make pcb at home to expensive t get it done at factory i used
free version of McCAD Gview 3.1.4 bottom layer opened up but top layer
will not open as software is free version any other free version software
to open top layer thank you for pcb files
thanking you
andrew lebon
Click to expand...

hi you can get my pcb software its legal double layer free version with 400 pin

but its 26mb, any idea where to upload ? to download for you
 
#116
Hi friend

NMOS said:
Hi,...forget it

let me tell you short story about QUASI NMOS350 amp


before 1 year have build my first NMOS350, NMOS 350 is working from first time start since today, ...everyday without any problems, great sound !!!

1 month later have design new doublesided NMOS PCB, after first start catastrophic failure, reversed VBE...amp is burning up, have replace wit new one components but another devices had failure to....did later this pcb in trash and make new one


The new one is working since today everyday

sometimes you can measure components and it looks ok,...but under load conditions... devices is defective

it can be you have counterfait devices, where did you buy ?

and again

sometimes you can measure components and it looks ok,...but under load conditions... counterfait devices fails


Finally: NMOS is working very stable with amazing Sound, if your NMOS is working you will love this sound

If you are interested...can send you gerber from my doublesided NMOS PCB
size 250 x 80
Click to expand...

I'm intersted ur doublesided NMOS PCB. Pls send gerber to my e mail: hung_vna@yahoo.com.
Tks u so much!
 
#120
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