Power amp under development

[vijay_meyou]

Hi qsa,

Thankyou replaying. Here still i use transformer due to non availability of SMPS or huge cost for shipping to india.

vijay

 

[Mackcer]

Hi qsa I like this circuit 🙂 also please send me copy off pcb drawing, schematic and part list thanks .juancacerce@hotmail.com

 

[khalsa]

pcb

hi qsa please send me the latest nmos pcb desin ,control board and smps khalsaaudiocenter@yahoo.com thanks

 

[presbel]

Hi QSA,
Can I have a pdf copy of your board I plan to build for my personal use. I already sent you an email. My email - presbel1950@hotmail.com.
Thanks.
Rey

 

[presbel]

Hi QSA,
Can I have a pdf copy of your board I plan to build for my personal use. I already sent you an email. My email - presbel1950@hotmail.com.
Thanks.
Rey

 

[qsa]

Hi guys

have a question,.. who did build NMOS since today too and had similar experience...

Input differential Transistor T1 T5 (2SC2240 or 2SC1845) are hot

after changed R5 18K from quais schematic to 40 K temperature from T1 and T5 (2SC2240 or 2SC1845) is low

I think 18K in original design is to low

willl send latest schematic and PCB LAYOUT at weekend

 

[qsa]

attachment latest NMOS design

changes are R6 from 18 to 40K reduces power dissipation in differential input stage

Industrial DIY PCB are available

 

[AndrewT]

R6 controls the dissipation in T3.
R7 controls the dissipation and the gain of T1 & T5.

Check the voltage across R7 and check it's value.

 

[quasi]

attachment latest NMOS design

changes are R6 from 18 to 40K reduces power dissipation in differential input stage

Industrial DIY PCB are available

Hi Qsa,

Sorry but I disagree with your first stage configuration. Using a LED as the reference for T3 means that about 5.5mA will flow through R7 and R6. The voltage across R6 if it is 40k will be 220v (or at least try to be). This is more than the rail voltage meaning there is no voltage left for T3. So we do not have a proper constant current source (CCS). Even 18k is too high for 5.5mA as this will try to have 99 volts across it.

If I were you I would reduce the CCS current to 3mA by replacing R7 with a 390 ohm resistor. Then replace R6 with an 18K resistor. I would also replace R4 and R12 with 390 ohm resistors and drop the voltage across these to 0.6 volts (you currently have 1.3 volts here).

In the second stage CCS your choice of 47 ohms as R19 means that 25mA will flow through T7 and T8. This amouns to a dissipation of 4 watts and is completely unnecessary. I would change R19 and R15 to 100ohms and reduce the current through this stage to 12mA.

Cheers
Q

 

[qsa]

Hi Quasi

Thank you for assistance, will change it and test


actually there is a new posting

http://www.diyaudio.com/forums/solid-state/162408-900w-h-class-pa-amp-limiter-5.html#post2112754

Im very interested to add Class H for NMOS

 

[tessier]

Hi

I have some MTE215N10E

Can I use them for the Quasi Nmos 200 ?

Thanx

Paul

 

[qsa]

Yes normally you can use every N Mosfet for NMOS amplifier

 

[ihan]

Hi

I have some MTE215N10E

Can I use them for the Quasi Nmos 200 ?

Thanx

Paul

Note that they are only 100V devices, so you have to keep your supply to +/-50V maximum. Also, given their high current nature and low rdson, I would expect them to have very large capacitance, so you could have problems at high audio frequencies. No harm in trying them though!

 

[butch_vlad]

Hi quasi,
Is it possible to post the pcb layout for the PSU you made for this amplifier
http://www.diyaudio.com/forums/solid-state/43331-power-amp-under-development-15.html
I need something to print on laser printer.
Thank you!!

 

[malbasicradan]

Hi qsa please send me the latest nmos pcb desin ,control board and smps malbasicradan@gmail.com thanks

 

[quasi]

Hi quasi,
Is it possible to post the pcb layout for the PSU you made for this amplifier
http://www.diyaudio.com/forums/solid-state/43331-power-amp-under-development-15.html
I need something to print on laser printer.
Thank you!!

Sorry about the delay. You can find a layout here.

Nmos & Nbip series (Quasi's DIY Audio Site)

Cheers
Quasi

 

[AndrewT]

I do like the way you draw your schematics.
Exemplary.

 

[quasi]

Thanks Andrew, it's pretty easy with the software I use. Anyway I wish I had more time to do more...oh well.

Cheers

 

[AndrewT]

350 mk2

how about replacing the 5.1v Zener with a pair (or 3) of ~1.9V LEDs?
Maybe combine R11 & R12 and use a 36K with no connection to ground.
What is the design current through R11 & R12?

What about hFE recommendations for T1, T4 & T6?
1.8/hFE T1 + 1.8/hFE T4 = 10/hFE T6.
But this requires a very high gain T6. Instead add a resistor from +ve supply rail to junction of T1+T4 bases. This makes a better job of balancing the currents coming out of the mirror.

 

[AndrewT]

there is only 19mW being dissipated in Zener. This is too low for good voltage reference. Another reason for changing to 2 or 3 LEDs.

The LEDs @ 2 to 2.5mA would be OK. You can even add a jFET as CCS to the 36k to keep the voltage references stiff.