hi guys i have a crown xli3500 amp and sometimes when it start trip the 16A C curve breaker.i see on amp meter 30-40amps.the most of times start normaly and draw 8-10 amps.the ntc on the soft start is 1020D.what can i do to avoid this happen?can i replace the ntc with bigger one?if yes what ohm to choice?or connect onother same one in series?thanks for any advise
Sorry to dig up an old post. But Im back in a circle to my orignal issue.Basiclly want to avoid a large complex soft start circuit.
And trying to understand the implications. Tried talking with chatgtp but still confused.
My NTC 8D-20 does what it is supposed to do. As in no my triping fuses or lights going dim.
No peaks on the scope signal. I have it sitting in serial on the phase line. i.e. wall socket, plug. End of the plug wire NTC with one leg going to the transformer and one leg to +Phase of the supply.
Questions I had.
1. Does the NTC limit how much power the transformer see or does it limit the amount of power the transformer can draw.
How can I calculate this loss or AMP limit if at room temp it is 8 Ohms.
2. Does the NTC warm up when used ?. I have not noticed my NTC warming up. Then again its a 15 Amp transformer and I don't play the music very loud.
3. Will it make sense for me to mount the NTC body to the transformer. So that as the transformer warms up the ohms value drops to 0.5 Ohms.
4. I did test the max output of the amp with a resistor I got about 70 watts. But even here the NTC did not warm up. I also shorted the NTC legs at this point to see if it would boost the output power it did not.
Reason for this post. I read somewhere that the NTC limits current draw to 1 AMP.
Also I have seen NTC used in many audio circuits. 99% of them will be without any fancy circuit or relay. The objective of my present build is to keep everything as small as possible. I even got a new Toroidal transformer with only 5 AMPs to to shrink the size of the complete project. This setup will be driving a pair of TDA 7294.
And trying to understand the implications. Tried talking with chatgtp but still confused.
My NTC 8D-20 does what it is supposed to do. As in no my triping fuses or lights going dim.
No peaks on the scope signal. I have it sitting in serial on the phase line. i.e. wall socket, plug. End of the plug wire NTC with one leg going to the transformer and one leg to +Phase of the supply.
Questions I had.
1. Does the NTC limit how much power the transformer see or does it limit the amount of power the transformer can draw.
How can I calculate this loss or AMP limit if at room temp it is 8 Ohms.
2. Does the NTC warm up when used ?. I have not noticed my NTC warming up. Then again its a 15 Amp transformer and I don't play the music very loud.
3. Will it make sense for me to mount the NTC body to the transformer. So that as the transformer warms up the ohms value drops to 0.5 Ohms.
4. I did test the max output of the amp with a resistor I got about 70 watts. But even here the NTC did not warm up. I also shorted the NTC legs at this point to see if it would boost the output power it did not.
Reason for this post. I read somewhere that the NTC limits current draw to 1 AMP.
Also I have seen NTC used in many audio circuits. 99% of them will be without any fancy circuit or relay. The objective of my present build is to keep everything as small as possible. I even got a new Toroidal transformer with only 5 AMPs to to shrink the size of the complete project. This setup will be driving a pair of TDA 7294.
If you look up the datasheet for the 8D-20 you will see it’s good for 6A of current at steady state. It is 8ohms cold and about 0.5ohms hot.
With Class AB amp that draw low quiescent current it doesn’t heat up at turn in except for a small instant during the in rush. It will have a voltage drop until you turn on the power and current flow heats it up. The NTC stands for negative temperature coefficient. That means it drops in resistance as it warms.
For class A amps, it warms up and statmys hot (about 150C) and this is where it acts almost like a wire. Only 0.5ohms.
If you want low voltage drop and in rush limit on low quiescent current class AB amp, a solid state relay that bypasses the NTC is best bet. They are not that complicated. Just buy a proven circuit or ready made solution.
I have one that was designed for me by Jhofland with remote turn on/off triac and two NTCs for soft start. A SSR that bypasses the NTC after about 3 seconds.
With Class AB amp that draw low quiescent current it doesn’t heat up at turn in except for a small instant during the in rush. It will have a voltage drop until you turn on the power and current flow heats it up. The NTC stands for negative temperature coefficient. That means it drops in resistance as it warms.
For class A amps, it warms up and statmys hot (about 150C) and this is where it acts almost like a wire. Only 0.5ohms.
If you want low voltage drop and in rush limit on low quiescent current class AB amp, a solid state relay that bypasses the NTC is best bet. They are not that complicated. Just buy a proven circuit or ready made solution.
I have one that was designed for me by Jhofland with remote turn on/off triac and two NTCs for soft start. A SSR that bypasses the NTC after about 3 seconds.
