N-Channel mosfet amplifier schematic needed

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#101
Lars
Why not make a world record of max power amp with a single pair of output devices . Please think it over.




Sajti
At 50v rails you can take the output from directly from T14 & T15 one pair of complementry devices , why do you want to use a extra device to make it N-channel.
 
#103
N channel amp!!

Hi Lars,

I could not get any reply for the following doubts.

1. I think the C10 +ve is connected wrongly Bet'n R54&C11.

2. Are all the resistors 1/4 watts except 0.33 ohms (5 watts).

3.can I use higher power & ft devises Like 2SB649,2SD669 for T12, T13.

4. Do I need to place T11, T12& T13 towards the heatsink mounted with IRFP250 OR do I need to Put a small heat sink for T12,T13 & T14.

5. I think you have already said this but I would like to ask again if I can use IRFP640 for T14, Instead of IRFP9240.

6. This Might be silly,But In your schematic There is no Drain,Source indicaters on the devices, if you can clarify this.

7. How much Bias current need to be provided for this amp.

8. Finally the most important if you can propose a short circuit protection.


can you please lookat this!!

Thanks

arasuk
 
#104
Arasuk: Here are some answers for you 🙂

1..You are absolutely right! Thanks!

2..Yes

3..Yes but be careful to get some too fast, so they might oscillate.

4..T14 on the main heat sink, the others in free air. No heat sink.

5..No you can't substitute a P channel FET with an N channel .

6..All the N-channel FET's have Drain Up and Source Down. The P channel has Drain Down and Source Up.

7..Depending on your taste. I ran it with 50 mA in most testes.
That worked fine!

8..I suggest you take the circuit shown on The End Millennium (can be found on my homepage) and adapt it for this amplifier. It should be pretty easy. 😉

All the best from cold, rainy and windy Denmark
 
#105
Hello Lars

Will You go ahead with the Fun Idea as you call it , 1500 w to 2000w is not less !!!!!

A few more questions

1, I am making three seprate grounds points on the pcb to be connected to the main ground at the filter caps , 1, ground of R1 , R3 & C2 , 2, ground of C3 , C4 , & C5 , and 3, ground of C9 , C10 & C11. I hope this is OK .

2, Will a 47MFD cap next to every mosfet make any difference ?? also is there an advantage if we put R54 and C11 on the output terminals ??.

3, For the protection circuit , in the -ve side of the output section can we shift the 0.33ohm resistors in the drain of the mosfets to the source for current sensing , also can we sink the emitter of T12 & T13 for protection. Do we need to sense current from the all the mosfets or sensing from only one mosfet from each rail will be OK .

4, For six mosfets each side in the output , the length of the track on the pcb from the emitters of T12 & T13 to the Gate of the output mosfets will be at least seven inches long on reaching the last mosfet , I hope this will not create any problems however the 100 ohm gate resistor will be nearest to the mosfet .

Regards

Rajeev
 
#107
Rajeev:

This power-race... it's not really my big interest. More interested to get the superb sound quality! 🙂 Sorry! So if you are interested, you can win the biggest power competition yourself 😀.

1..I would connect GND's 1 and 2 together.
2..Could never hurt, and no reason to do that.
3..No, keep them in the Source as is. Use an extra curent sensing transistor.
4..Can be a problem or no problem, it will depend a lot on the layout.

Best regards

Lars
 
#108
Lars Clausen said:
The sound qualities of this design is open and dynamic, but not ultra detailled. It has perfect properties for use as a PA amplifier, it has a happy and engaging sound to it.
But can not compare with a fast non-feedback design such as The End Millennium, when it comes to High End properties like detailling, space and placement in sound stage.
Just the use of paralleled output devices, will destroy most detailling in any amplifier, MOSFET or BJT. So for hifi: use single MOSFET output devices, you get an improvement to a decent level of performance, but i still wouldn't call it 'high end'. Though well on level with many of the conventional audio kit's found (normal speed < 500 kHz/ with feedback loops).

The shown design is in the category: 'PA high power amplifier', and as shown does not have high-end audio capabilities. The design can be modified to meet audio specs, but my best bet is you can't meet both uses in any one design. If you were to try, the same thing would happen as happens every time you try to make a design have too many uses:

It would end up doing everything equally bad.

If you want to want to move 10 tons of goods, use a truck, if you want to haul on the freeway at 120 MPH, use a Porsche. But the truck won't run 120 MPH any more than the 10 tons will fit into the back seat of the Porsche 😉
Click to expand...

Lars,
Thanks for sharing your design with us. I've been looking for a not expensive DIY amp for a friend to build for me.
I had interest in A.Holton's N-Channel and AV400 amplifiers. They have a reputation for being highly dynamic, which is something that is very very important for me, along with the 3D imaging. I like forward, "take no prisoners" sound (-:
What are your musical and sonic preferences, if I may ask?
I really wonder how your N-Channel amp compares to his... as Anthony is proud to say that it has properties that you don't associate with N-Channel design.
Another question would be, is if the End Millenium can equal the dynamics of your N-Channel amp.

Thanks for opinions and help
Keep up the good work (-:

Adam Harzuf
 
#110
Adam Zuf: I am sorry i couldnt comment on Holton's amplifier as i have never heard it, and also i (like most other people) have never seen his N-ch schematic.

My sonic preferences is openness, up-front and dynamic, liquid playing style and with a visible soundstage.
Less microdetail, homogenity, and smoothness.
I listen to many different styes of music, from Jazz, Classic, Techno, and pop music. Not so much Rock, Blues etc. My loss 😉

The Millennium is also a very dynamic amplifier, that is well described by the above properties. For PA use i would go for the ZETA, but for HIFI / Home Audio use Millennium is better.

djQuan: 250 Watts in 8 Ohms. You will be dissipating around 180 Watts at full power (and most other levels), so this is 30 Watts per device. The strict limit of the datasheet says you can dissipate 30 Watts in a IRFP250N with a Tc up to 132 C. But i wouldnt go higher than 80-90 C for safety margins.
At 500 Watts in 4 Ohms, you dissipate 60 Watts per device, and your strict limit is 90 C. Here limit your max Tc to no more 60 C.

🙂
 
#111
I’m also interested in the “The Millennium”. Is the wattage of 120w a peak rating?
Rod Elliott’s P3A (http://sound.westhost.com/project3a.htm) also has a single pair of output devices (MJL4281A and MJL4302A) running on 35volt rails he is only claming 60w into a 8 ohms and 100watts into 4ohms. Your output devices do look bigger on “The Millennium” so I may be missing something.
I tried to look for review at http://www.audioreview.com/ (a vary well respected site that holds reviews by regular people about nearly all audio products) I couldn’t find one review.
The topology is very different, from the ideas of Nelson Pass who likes a very little bit of feedback with a very limited number of stages. That’s not a bad thing just different.
 
#112
so for more SOA, I'd go for four pairs of output MOSFET's per channel, then I'd dissipate 45watts per device at 4 ohms....

I use car subs for my system so all my DIY amps have to handle 4 ohm loads and subject to torture as I do some PA work about 4 times a year.

my present amp uses four pairs of output devices per channel (IRFP250) using anthony's N channel amp (slightly modded to use 4 pairs). if I would go with your design, I would reuse everything else and replace only the PCB. problem is, I only have a 500VA dual 48V toroidal as that is the biggest I could find (and afford and fit in the case :bawling: ) but I do have eight 10000uF caps, 20000uF per amp rail.

the highest sink temp that I experienced with this amp is around 65-75°C so I guess I can be safe with the ZETA even with only three pairs? I guess I'd still use four.

as a plan, I would make a simple PCB for all the low level circuitry and hardwire the MOSFET's, source resistors etc.

and as my last question, is the ZETA very stable and forgiving in PCB layout and also in accidental shorts?
 
#113
Hi Lars.

I am just going ahead with the board design,I think Single side 90mm x 180 mm should fit in all the components.

1. OOOOps sorry about the Misprint of IRFP640 I meant if I can Use P Channel IRFP9640, for the Higher power of 500w 8 Ohms.

2. Okay GURU!! I think you are right I dont want any oscillation problem ,Will go ahead with BD139/140.

3. With Bias of 50 mA in test what was the cross over distortion for the 8Ohms & 4 Ohms load, Out of curious whats the slew rate of this Amp.

4. I have a toroid transformer which i will be testing with of 1.6 KVA ,55-0-55 AC, whats the power do you think I might get with this.

5. I understand with You & Rajeevs disscusion that I/P GND and the central GND should remain in the same track, Do you Think so!!

6.A good point in adapting of your short ckt Prot from the Milldia Schematic,Can you clarify how exactly to fix as lot of Diys are looking forward for this.

7. Do you suggest on any increase of gate resistors from 100 ohms for high power will this be stable.

Thanks

Arasuk
 
#114
Hi DjChuan,

If you ever come to HK contact me & I'll bring you to Shamshuipo.
That's the electronics flea market of HK! When I worked in Japan,
as a musician, I missed Akihabara; that's the huge electronics
area in Tokyo.
Are you going for an electronics degree? Before that you can
design your own amps, what with your considerable gears,
using just basic math. Try Malvino books or Oleksy. Slone's
book is almost a complete course on design.
When I retire I'll go into public address gears rental business,
using my own designs.
High-end audio? I play in a band for a living & no audio system
can match live music! But by DIY you can go near by multiampling,
say dividing the frequency spectrum into more than the usual
3-way. For me this is the only way for even a drumset has at least
5-point sources of audio. Trying to fit even a piano trio in 2
speakers is ridiculous! With multi-ampling, with each speaker
only playing a narrow spectrum, one can use cheap speakers!
Hearing is 3-d.

Efren
 
#115
I have been to sham sui po last april. that's the only time I had a chance to buy two toroids.

right now I'm taking up electronics and communications engineering in mapua, I still don't have any electronics subject but I learned stuff by myself in reading and hands on. I don't design my own amps, I just find a proven and tested design and build it.

for my system, it is quad amped. I have four channels of amplification for each audio channel with total system power of 1700 watts RMS. I have four linkwitz riley crossovers in my system. check out my website. www.djquan.angelcities.com
 
#116
Mine is 2x2kW RMS right now, but i will dissassemble it and make new (smaller, ventilated) chasis and then use Larss amp in it to produce that power..

Lars, if you will make the pcb drawing, please put it here too, or send it to me, even if it will be for just one pair of output devices -> i will hardwire the output stage anyways..


Thank you,
Jure
 
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