Krell KSA 50 PCB

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#5,345
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1 200 BC27W-2CT-ND RES 27 OHM METAL FILM 2W 5% 0 0.18060 $36.12
2 200 P820CACT-ND RES METAL FILM 820 OHM 1/4W 1% 0 0.06525 $13.05
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#5,347
 
#5,354
still4given said:


...... I don't ever use it wihout the ligh bulb in series anymore.

Blessings, Terry
Click to expand...

Terry, thats probably one of the best things you can do while playing with amplifiers, variacs alone will not protect as well as a bulb, where else will you get a device for less than a buck that lets you test the amplifier at near full rail voltages, and then continuously varies the voltage based on current draw and saves you $$$ project from becoming an expensive paper weight.
 
#5,355
K-amps said:


Terry, thats probably one of the best things you can do while playing with amplifiers, variacs alone will not protect as well as a bulb, where else will you get a device for less than a buck that lets you test the amplifier at near full rail voltages, and then continuously varies the voltage based on current draw and saves you $$$ project from becoming an expensive paper weight.
Click to expand...


Hi K,

As a matter of fact, I believe you are one of the guys who told me about it. I made it dual purpose. I used a regular dual wall plug and hooked on up to run in series with the mains and hooked up the other outlet in parallel so I could use the bulb to drain filter caps.. It's been very handy. I've heard that you can control how much current can pass by selecting different wattage bulbs but I never learned how to figure that.

Blessings, Terry
 
#5,356
I guess the limitation is it's use in class-A amplifiers. It is usually practical to test the amplifier prior to biasing it class-A because the current draw would be too much for a bulb to keep it to near rail voltages. A class-AB amp does not have this issue as much as a pure class-A amplifier does.

I am not certain and my calcs may be off, but if you wanted to run your Krell close full class-A at 95% rails, you would need a bulb that would not light up despite having about 2.5 amps (120v mains) flowing through it. Not knowing the co-efficients of the filaments involved, I'd guesstimate that to be a 1000w plus lamp at the least. :drunk:

Me, I have used trial and error along with an amp meter to determine that... for 95% of my needs, a 100w bulb works fine.


cheers,
-Arif
 
#5,357
K-amps said:
I guess the limitation is it's use in class-A amplifiers. It is usually practical to test the amplifier prior to biasing it class-A because the current draw would be too much for a bulb to keep it to near rail voltages. A class-AB amp does not have this issue as much as a pure class-A amplifier does.

I am not certain and my calcs may be off, but if you wanted to run your Krell close full class-A at 95% rails, you would need a bulb that would not light up despite having about 2.5 amps (120v mains) flowing through it. Not knowing the co-efficients of the filaments involved, I'd guesstimate that to be a 1000w plus lamp at the least. :drunk:

Me, I have used trial and error along with an amp meter to determine that... for 95% of my needs, a 100w bulb works fine.


cheers,
-Arif
Click to expand...

Yes, for the class A amps I have always had to take the bulb out of the circuit when bringing up the bias. It is helpful to determine which way to turn the pot for raising/lowering the bias. I've been using a 150watt bulb but I may lower it if that will allow less current to pass. I have burned up a couple of componants using the 150watt bulb.

Blessings, Terry
 
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