Go to www.digikey.com and search for " inrush current limiter ".
I use the GE ones. I have used the CL-70 in series with the power line input. This softens the shock to the filaments when the power is switched on.
I use the GE ones. I have used the CL-70 in series with the power line input. This softens the shock to the filaments when the power is switched on.
Check this out for more details:
http://www.mouser.com/catalog/612/202.pdf
I've not seen its use in the anode of a tube amp's stage but they are common in the AC line in amps with SS power supply rectification. A good example would be the McIntosh MC-225/240/275 series of amps. Also, Jim McShane's upgrades for the HK Citation II has them inline just after the high voltage rectifiers to slow the rise of the high voltage line before the 6550's filaments get hot.
Hope that helps.
Cheers,
David
http://www.mouser.com/catalog/612/202.pdf
I've not seen its use in the anode of a tube amp's stage but they are common in the AC line in amps with SS power supply rectification. A good example would be the McIntosh MC-225/240/275 series of amps. Also, Jim McShane's upgrades for the HK Citation II has them inline just after the high voltage rectifiers to slow the rise of the high voltage line before the 6550's filaments get hot.
Hope that helps.
Cheers,
David
I use em in my PAss Labs and Krell Klones to keep the mains fuse from blowing. Its caused by the inrush current durung the initial rail capacitor charge up. I generally use CL-60's. They can also be shorted out with a time delay relay to take em out of the circuit after the amplifier is operating.
Mark
Mark
I simply put it in series with the power switch. It has a relatively high resistance when cold, so it limits the initial current. As it gets warm, from this current frowing through it, the resistance drops to a low value.
Some people also put them in series with the rectifier tube so they can get away with running a larger than normal input cap. Use one in series with the cathode, OR one in series with each plate (2 total).
This is shown on the page in the digikey catalog, though they show a solid state bridge.
Some people also put them in series with the rectifier tube so they can get away with running a larger than normal input cap. Use one in series with the cathode, OR one in series with each plate (2 total).
This is shown on the page in the digikey catalog, though they show a solid state bridge.
It is not going to be much use as a delay on the B+ since the resistance when cold is very low- around 5-20 ohms depending on type- so you are not going to drop many volts with e.g. 60ma.
20x60=1200mv thats just 1.2v!
They are more useful as current limiters on big ss amps where the switch on current might be hundreds of amps for a few milliseconds.Of course it won´t hurt in the primary of a tube amp or in line with filament secondary.
20x60=1200mv thats just 1.2v!
They are more useful as current limiters on big ss amps where the switch on current might be hundreds of amps for a few milliseconds.Of course it won´t hurt in the primary of a tube amp or in line with filament secondary.
You don't want to put an inrush suppressor in series with the anode of your 300B, their linearity is not very good. You want to place this in series with the primary of your power transformer.
Incidentally this will not provide a significant amount of delay to your B+ coming on, but will reduce the current flowing when the power is first applied which is kind to capacitors fed by silicon diodes, the transformer, power switch and fuse. If you need slower B+ use either a delay relay or a tube rectifier like the GZ32/5AQ4 or GZ34/5AR4 which have long warm up times.
Incidentally this will not provide a significant amount of delay to your B+ coming on, but will reduce the current flowing when the power is first applied which is kind to capacitors fed by silicon diodes, the transformer, power switch and fuse. If you need slower B+ use either a delay relay or a tube rectifier like the GZ32/5AQ4 or GZ34/5AR4 which have long warm up times.
If you use a power transformer with a very low DC resistance, like a 500 or 750 watt 480 volt industrial transformer, and a SS rectifier with large filter caps, the surge current at turn on can be 10 amps or more with NO load on the power supply. A CL-70 in series with the power switch makes the difference between smoking diodes, and a happy power supply. This is an extreme (but very real) case, but it goes to show that these things have a place in tube amplifiers too. They also limit the initial current surge caused by cold filaments. If you are using expensive DHT's, these are like cheap insurance.
Here's a schematic with a "surgistor"
http://users.rcn.com/fiddler.interport/HF87.HTM
Click on schematic at top of page next to HF87
Steve
http://users.rcn.com/fiddler.interport/HF87.HTM
Click on schematic at top of page next to HF87
Steve
surge resitors
One thing to keep in mind, is that IF you use the surge resistor right in series with the cathode or plate of the tube, you need to put a bypass capacitor in parallel with it so that is does not cause a non-linear SIGNAL voltage drop during normal operation. Failure to do this will cause gain loss and possibly distortion problems.
It is generally preferable from a design standpoint to put a surgistor in series with the power transformer primary or secondary to bring up the power supply slowly rather than put something directly in series with tubes.
One thing to keep in mind, is that IF you use the surge resistor right in series with the cathode or plate of the tube, you need to put a bypass capacitor in parallel with it so that is does not cause a non-linear SIGNAL voltage drop during normal operation. Failure to do this will cause gain loss and possibly distortion problems.
It is generally preferable from a design standpoint to put a surgistor in series with the power transformer primary or secondary to bring up the power supply slowly rather than put something directly in series with tubes.
In-Rush Current Limiters
I have used them as others have states somewhere in series with the primary winding(s) of the unit's power transformer. I used to purchase them from Digi-Key. they were made by Keystone Electronics. The chart given in the Digi-Key catalog showed the cold vs. the hot resistance along with the safe steady-state current draw that the limiter was capable of handling. Totally unrelated to audio, I used them in series with my household incandescant lamps. I like the color balance of GE's REVEAL series of lamps. The Keystone deveices limited the in-rush current of your typical household lamp. As an experiment, measure the filament of a 60-watt incandescant ligh bulb at room temperature. Apply Ohm's Law E/R = I. You will be surprised at how much initial current flows through the filament of a lamp when it is first turned on! Therefor any tungsten load, such as a tube's fialment can benefit from the same control of in-rush current. With respect to an earlier question about current limiters in the anode circuit of a tube, consider the plate current doesn't flow until the filament begins to "boil" electrons off of the surface of the cathode. You can therefor control plate current indirectly by controlling the filament temperature. I would google search "Keystone Electronics" for distributors of their products.
I have used them as others have states somewhere in series with the primary winding(s) of the unit's power transformer. I used to purchase them from Digi-Key. they were made by Keystone Electronics. The chart given in the Digi-Key catalog showed the cold vs. the hot resistance along with the safe steady-state current draw that the limiter was capable of handling. Totally unrelated to audio, I used them in series with my household incandescant lamps. I like the color balance of GE's REVEAL series of lamps. The Keystone deveices limited the in-rush current of your typical household lamp. As an experiment, measure the filament of a 60-watt incandescant ligh bulb at room temperature. Apply Ohm's Law E/R = I. You will be surprised at how much initial current flows through the filament of a lamp when it is first turned on! Therefor any tungsten load, such as a tube's fialment can benefit from the same control of in-rush current. With respect to an earlier question about current limiters in the anode circuit of a tube, consider the plate current doesn't flow until the filament begins to "boil" electrons off of the surface of the cathode. You can therefor control plate current indirectly by controlling the filament temperature. I would google search "Keystone Electronics" for distributors of their products.
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