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In the Forum: Melquiades Amplifier
In the Thread: Building Melquiades: Chronicle of full-range
Post Subject: Re: Aha, steelPosted by hagtech on: 6/12/2006
Yes, steel chassis can be both good and bad.  It likes to conduct magnetic fields, so you have to treat things appropriately.  A little spacing under a choke can go a long way.  Otherise you have a 120Hz motor.  I have another trick that helps with the far field.  The stray magnetic spray from the Hammond chokes is pretty big.  Helps to measure it to see which directions it has maxima and minima.  Then you mount the coil with the proper aim.  Usually away from the input tubes.  My trick is to use two chokes instead of one.  Wire them up in parallel or series, then mount them side-by-side and magnetically out of phase.  You get quite a bit of far field cancellation.  I did this in the Trumpet.

I like your idea of double-dipping the chokes.  I wonder what can be done to stock chokes.

My friend Uncle Stu, who told me about the tranny bolts, also says you can get some improvements with the screws used to mount the speaker drivers.  Not sure how this applies to horns.  Anyway, the idea is to keep magetically influenced materials away from the voice coil.  Personally, I have not been able to hear a difference, but he says he can.  I've learned over time not to doubt his ears. 

Silicone glue is great.  Insulating too.  It wasn't strong enough for my S&B step-up cans, so I use a giant wad of epoxy.  Not the softest mounting, but way better than a friggin steel clamp.

As far as high ESR, I'm actually quite relieved you prefer the high dc resistance.  There are several arguments going on over at AA about using super low DCR inductors.  Shoot, I said to myself, I've been doing exactly the opposite! Not only do I use the highest DCR choke I can find, but sometimes even add to that externally.  It's all tuned, of course, for critical damping.  I found it to work great.  Very stable, keeps line noise out.  So maybe the AA guy is crazy?  Heck, even in my low cost circuits, my RC supply filters often use pretty darn high values of R.  For me, I have no problem burning a sheetload of power.

jh

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