Inrush limiter question

[EL34Dave]

Would there be a problem installing this in series with the power transformer primary, given that it will effect the bias supply as well as B+ supply on the other side? My guess is that since both will be eased to full voltage simultaneously, all would be good.

 

[DeathRex]

I always use them on the primary. It seems to help a lot of things; transformer, power switch, you can use a fast blow fuse. I like to use a lower cold resistance NTC, like a CL80, 140, 150 or 110. CL90 really slows things down, and makes the most heat.

 

[Enzo]

They heat up quickly and disappear. Unless you are concerned about a few seconds of low B+ affecting sound quality, I see no downside, and it relieves stress on your power switch and main rectifiers.

 

[PBNAUDIO]

I always use them in series with the Transformer primaries on my power amplifiers, but switch them out after the large inrush current has settled. Basically a Triac in series with 4 CL40 in series parallel being switched out by 4 parallel relay switches, have used hundreds of this combo over the years with no failures, bullet proof

Best of luck

Peter

 

[Bigun]

I suspect that best practice depends on the circuit details. For example, you might prefer heaters to come up first and then B rises slowly to limit over voltage of B + when using choke loaded rectifiers ?

 

[HeyBill]

It's a bit tedious, but I use a variac. HeyBill

 

[EL34Dave]

I was mostly concerned about

The bias supply not being at full voltage right away. But I figure if bias and B+ both come up together, that there wouldn't necessarily be a problem.

Does that sound right?

 

[RJM1]

I like the way Jim McShane did it on the Citation II , he put the NTC on the plate supply only to insure that the bias supply and the filaments were up before the high voltage.

 

[Wavebourn]

Here is what I did back in 2005, just an exercise.
B+ starts slow, and waits for filaments to warm up. As soon as tubes start drawing current B+ comes up faster.