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Opinions on ICL, Inrush Current Limiter

I have a friend and technician that works on my vintage tube gear. In my opinion he does very excellent work. However on every amp and preamp whether its ARC D70MKII, D90B, HK-Citation II, Lafayette KT600 etc., he wants to put in a In-rush Current Limiter circuit. I always ask the original designer (i.e., fameous!!) did not employ this circuit, why do you? He is adament about putting one in. It does seem to help the big amps as they slowly come up to power and I have tried to hear a loss in dynamic range but I can't...after it warms up.

So any opinions on this circuit? Should the ICL be put in vintage gear? or was it too expensive?? Are there pros and cons? Thanks any comment would be greatly appreciated. Larry
apfdirtdoctor

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,615 posts
 
CILs can be very helpful! They help prevent switches from being damaged during turn-on as well as other parts.

They were not always available, so on older units of 40-50 years and more you won't see them. But on newer units the designer is missing a bet if he does not use them, no matter how famous they are.

CILs have different ratings, so the proper device should be used in each case. As long as that is observed, their use is simply good practice.
atmasphere's avatar
atmasphere
11,615 posts
 
Hifigeek1, nearly every amplifier has line fuses. A current inrush limiter will have a high value at turn-on, but a negligible value under normal load. This prevents damage to switch contacts, rectifiers and the like.

The 'thermistor' you refer to BTW is probably a CIL- CILs are a form of thermistor with an inverse temperature coefficient.

The HK Citation II is an excellent candidate for a CIL addition, as it has a large current inrush due to its voltage-doubler power supply. The filter caps are taking a lot of current at turn-on and will thus last longer.
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