Power amp under development

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#2,783
Hi Bigpanda,

The auxillary voltage from the soft start board is intended to provide power to the DC detectors as you say. It can also be used to provide power to other things (LEDs etc).

Note the AC source for the soft start must come from a seperate small transformer and not from the main power amp transformer(s) and the gnd from of the auxillary DC supply must be connected to the central audio ground.

Cheers
Q
 
#2,785
Thank you Quasi!

Yes, it is very nice to listen.
Very good bass and clear sound. Soundstage and instrument separations are incredible.

BTW, the heatsink is barely warm. Is it a good idea to increase the bias? How much more can I go?

My next project is the NMOS400 which I requested from you.
I have some fifty pcs. of IRFP452 in hand.

All the components are FOC. hehehehe!
I got it from old industrial equipments.

Cheers and keep you updated.

Raj.
 
#2,786
Hi Quasi,

Tks for reminding. I 've noticed it first time I saw the circuit. If yours had been available earlier, I would not have to clean up my mess I am in now, sob.....

BTW, as I said, as I am trying to clean up my mess, I had been looking for a 20V transformer but seems rather difficult to find. What if, just if, I had to use a 18V (25.2v after rectification), do I have to change any component?
 
#2,787
bigpanda said:
Hi Quasi,

Tks for reminding. I 've noticed it first time I saw the circuit. If yours had been available earlier, I would not have to clean up my mess I am in now, sob.....

BTW, as I said, as I am trying to clean up my mess, I had been looking for a 20V transformer but seems rather difficult to find. What if, just if, I had to use a 18V (25.2v after rectification), do I have to change any component?
Click to expand...

The DC detect circuit is drawn showing a 24 volt relay so 25 volts DC will be fine. You could also run 12 volts to the DC detectors and use a 12 volt relay. The timing will be different but that's not overly important.

Cheers
Q
 
#2,789
Re: actrk600

engel dela pena said:
quasi,
good day,
i'm verry happy with this amp actrk600, i use c1845,c546/556,mje350 & irf460 6 pairs,supply 54-0-54-62(not rectified)
can i use 1000w speaker?crown 18'' dual magnet for my sub?
Click to expand...


Sounds like a good plan. Your transformer will give you rectified and filtered rails of +/- 75 volts for the main rails plus about 86 volts for the auxillary supply and this is perfect.

With a good power supply You will get about 550 to 600 watts into 4 ohms.

But all the information about the Actrk600 is in another thread. This link takes you to that thread and a build by DanielJ http://www.diyaudio.com/forums/showthread.php?postid=1303249#post1303249

Cheers
Q
 
#2,790
Hello, Quasi. I preformed a search with keywords "Nmos200 BOM", but didn't found anything like this for any of the Nmos amps. Do you have such a bill of materials, and if not - could you please comply one using your schematic design program. Thanks. 😀
 
#2,791
kalmara said:
Hello, Quasi. I preformed a search with keywords "Nmos200 BOM", but didn't found anything like this for any of the Nmos amps. Do you have such a bill of materials, and if not - could you please comply one using your schematic design program. Thanks. 😀
Click to expand...

Kalmara,

quasi posted a "Cost Estimate" in Post #141 which is as close to a BOM as you will find thus far. Please be aware since quasi posted the "Cost Estimate" the NMOS200 (TO-220) variant has been posted which the "Cost Estimate" does not account for nor the corrections or refinements that the NMOS350 has had since the "Cost Estimate", i.e. different PSU voltages, usual corrections, NMOS500.

I hope the initial "Cost Estimate" quasi posted will serve as a starting point for your build of the quasi NMOS amp.


Regards,

John L. Males
Willowdale, Ontario
Canada
24 May 2008 (17:05 -) 19:08
Official Quasi Thread Researcher

P.S. Sorry folks, but I have been dealing with a number of, and continue to, crisis the last few months. jlm
 
#2,795
Hi Quasi,

Sorry to bother again. I have come across some soft-starter circuit saying that the delay time can be order of seconds. I am quite stuck by this kind of timing. The resistors will be heating up a lot for delay time of seconds, won't they? What's the delay time for your circuit then? Because I am integrating it into a circuit with a speaker protection which has 1. a delay time on, 2. DC detection and 3. a thermal detection . If your delay time is longer than that of the speaker protection, it won't mean anything at all (I mean it should be shorter than the speaker protection delay, should'n it? Or it won't be serving its function? )

Some said that it should be in terms of 0.2 - 1 sec. What 's on your mind about this? It won't matter if it is 0.2 or 0.5 sec. But I think it does if it is 0.2 or 2 sec.

Tks
 
#2,799
Unless it's a class A amp essentially the same energy will be taken up by the soft start resistors independent of the time they are switched in if the time is long enough for the caps to charge up fully. The energy dissipated will be the same as the energy stored in the caps when full. (When charging capacitors full through resistors the same energy is lost in the resistor as is stored in the cap when full)

I wouldn't recommend switching out the resistors before the caps are full, the flux can't reach steady state while the caps are clipping the voltage waveform.
 
#2,800
use a second slow charger with bypass in the secondary if smoothing capacitance peak/sustained current is worrying you. This better suits a power thermistor to maintain a good current flow as the caps charge up.

Save the slow start for it's specific purpose. To get the transformer started without requiring a (useless) enormous fuse value.
 
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