richie00boy said:
Yep true true....I actually tried this to solve a different problem and it made things a lot worse....so I wouldn't do it.
You simply must use a soft start so you can use the correct fuse to offer quick protection should something go wrong with your amp. Use this ( double up on the resistors) http://www.diyaudio.com/forums/showthread.php?postid=784687#post784687 or one of many at DIY.
Cheers
Andrew,
If you want it thats fine, I just dug it out and it still looks like its almost new. You must pay the shipping and arrange the logistics. I want it to be clear that this is not for sale, its just a free so I'm not liable if you suffer damages from use of this. Just PM me when you have the shipping info. Can you take care of the shipping charges directly, so I don't have to get involved?
Todd
If you want it thats fine, I just dug it out and it still looks like its almost new. You must pay the shipping and arrange the logistics. I want it to be clear that this is not for sale, its just a free so I'm not liable if you suffer damages from use of this. Just PM me when you have the shipping info. Can you take care of the shipping charges directly, so I don't have to get involved?
Todd
Not really. Not the way I would implement it.
It would be used in place of the resistor and be switched out by the relay. So it stays cool under normal conditions. If power failed soon after it was switched out , there would be a time delay that could take care of the cooling time that it might require after power comes on again.
It would be much smaller than the resistors.
However I am not sure how many switch on surges it can handle before it deteriorates or its characteristics change.
Cheers.
It would be used in place of the resistor and be switched out by the relay. So it stays cool under normal conditions. If power failed soon after it was switched out , there would be a time delay that could take care of the cooling time that it might require after power comes on again.
It would be much smaller than the resistors.
However I am not sure how many switch on surges it can handle before it deteriorates or its characteristics change.
Cheers.
I have to agree on using a large NTC Thermistor.
You can get a thermistor from an old computer power supply.
With my amp, I used a really large NTC thermistor from a 550W Computer PSU and put it in series with the 350VA transformer primary in my amp. Without the NTC thermistor, the 6.3A fuse would blow every time.
Now also the only time the inrush current is high is when the amp is first turned on because the capacitors are fully discharged, but I can turn the amp on-and-off repeatedly once it's been on for a while, and inrush is way less because the capacitors are still holding a charge, and less inrush is needed to charge them.
I get full power with the NTC thermistor and have never blown a fuse yet.
You can get a thermistor from an old computer power supply.
With my amp, I used a really large NTC thermistor from a 550W Computer PSU and put it in series with the 350VA transformer primary in my amp. Without the NTC thermistor, the 6.3A fuse would blow every time.
Now also the only time the inrush current is high is when the amp is first turned on because the capacitors are fully discharged, but I can turn the amp on-and-off repeatedly once it's been on for a while, and inrush is way less because the capacitors are still holding a charge, and less inrush is needed to charge them.
I get full power with the NTC thermistor and have never blown a fuse yet.
Hi,
leaving the Thermistor in circuit will ALWAYS reduce the voltage available to the transformer.
Since maximum output voltage (audio) is proportional to input voltage (mains input voltage) then leaving the Thermistor in circuit will ALWAYS reduce the maximum power available.
The more relevant point is whether the listener will notice the 0.5db (more or less) reduction or not.
Toroid start-up current is related to the magnetic state of the transformer core. This state depends on when the AC cycle was interupted and how long the AC was off. If the AC waveform was interupted at the worst moment then just a few missing cycles will require the worst case start -up current.
Stored charge in the smoothing capacitors has little to do with this, provided they are proportioned to the size of the transformer. Enormous smoothing capacitors will affect the medium term currents drawn from the transformer and this could cause a close rated fuse to continue heating and ultimately blow.
But, even with this senario, the start-up current is little affected by the size of the smoothing bank.
Eworkshop,
the T6.3A fuse allows a maximum power of about 700W continuous into your transformer.
With soft start fitted, you should be able to rate your fuse MUCH closer to the transformer rating.
Have you tried using, T5A? or T4A? or T3.1A?
All should work and will give better protection to the downstream side.
You may find that T3.1A will fatigue and give up after a few or many startups and resolve to settle for the next largest.
I recommend you use the lowest fuse that your system will allow with acceptable nuisance breaking.
Close fusing is safer.
leaving the Thermistor in circuit will ALWAYS reduce the voltage available to the transformer.
Since maximum output voltage (audio) is proportional to input voltage (mains input voltage) then leaving the Thermistor in circuit will ALWAYS reduce the maximum power available.
The more relevant point is whether the listener will notice the 0.5db (more or less) reduction or not.
Toroid start-up current is related to the magnetic state of the transformer core. This state depends on when the AC cycle was interupted and how long the AC was off. If the AC waveform was interupted at the worst moment then just a few missing cycles will require the worst case start -up current.
Stored charge in the smoothing capacitors has little to do with this, provided they are proportioned to the size of the transformer. Enormous smoothing capacitors will affect the medium term currents drawn from the transformer and this could cause a close rated fuse to continue heating and ultimately blow.
But, even with this senario, the start-up current is little affected by the size of the smoothing bank.
Eworkshop,
the T6.3A fuse allows a maximum power of about 700W continuous into your transformer.
With soft start fitted, you should be able to rate your fuse MUCH closer to the transformer rating.
Have you tried using, T5A? or T4A? or T3.1A?
All should work and will give better protection to the downstream side.
You may find that T3.1A will fatigue and give up after a few or many startups and resolve to settle for the next largest.
I recommend you use the lowest fuse that your system will allow with acceptable nuisance breaking.
Close fusing is safer.
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