analyze the effect?

Discussions and experiences with user adjustable gaps.
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PakProtector
Posts: 31
Joined: Wed May 04, 2005 2:36 am

analyze the effect?

Post by PakProtector »

Hey-hey!!!,
Let's see if we can determine why the airgapped inductors( of any sort ) seem to sound better. With the parameters listed perhaps some information can be teased out of the discussion.

Less change in L with signal magnitude
Tolerance of DC is increased


Quote the replies so the list can be kept in a single post. Or perhaps copy/paste to keep the whole list on a single post if you would...:)
cheers,
Douglas
Question Authority, disobey it only after understanding it, and when absolutely required...
dave slagle
Posts: 2102
Joined: Sat Jan 22, 2005 3:54 am
Location: NYC
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Post by dave slagle »

I accept your ideas and nominate the ones below.

the list stands at:

Less change in L with signal magnitude
Tolerance of DC is increased.

I'll nominate:

Less change in L with variation in frequency
Saturation (ad and dc) happens more gradually.
Initial perm becomes more linear
Remenance (magnetic memory) is reduced.
resonant frequency becomes more stable
Q becomes more stable
inductance goes down
the nature of the gap becomes more consistent.

That's it for now, each one could be a discussion, but I think we can accept a few to the list based on common wisdom so feel free to bump them up. I'm eager to discuss the others. Luckily it's your thread so you can figure it out and hopefully others will jump in. My guess is a number of instance specific situations will pop up and keeping track of them will be the real task.

Can we please operate under the assumption that we will always be responsible and able to understand the situation where lack of inductance is the Achilles heel.
PakProtector
Posts: 31
Joined: Wed May 04, 2005 2:36 am

Post by PakProtector »

Hey-Hey!!!,
from Dave...Can we please operate under the assumption that we will always be responsible and able to understand the situation where lack of inductance is the Achilles heel.


Just to be sure I get this, we're not going to consider what happens if we take an ungapped inductance, with just enough L, and then expect it to work for us after we irresponsibly put in a gap 'because it's better that way'.

My favourite of the list is the stability self resonance point. After looking at a few pieces, and observed the performance in action, I would like to develope some way to examining this in-circuit. Seems like keeping an eye on this beastie while it's playing music is going to be nigh impossible though...

I did hear from another builder using a simple PP/CT grid choke that he distinctly likes the gapped version, even though this has put his L value near the low end of acceptable. It is driven by a decent pair of PP driver triodes, so it's less of an issue than if we were feeding it with pentode plates...:)

I have a little Ni grid choke. One that will probably exhibit a maximum of self resonance variation with signal magnitude( as L gets larger w/signal magnitude ). I will measure this weekend and report the results when I have them.
cheers,
Douglas
Question Authority, disobey it only after understanding it, and when absolutely required...
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