Altec 9069B multitap inductor
« on: February 17, 2020, 03:57:27 PM »
Hi. Im gonna do a multitap toroidal inductor for a friend that want it for an Altec 9069b HPF clone. Seems to be a LCL Pi filter. They want it toroidal because he saw internal pics and seems to be a toroidal type...  He showed me that pics and I saw like two or more toroids and no capacitors, maybe they are "packed"?
What I dont know is what material to put in the core, Can I put there a ferrite one? an Iron powder one? is that critical in an audio filter for line levels? Can someone guide me?
I read somewhere in that  forum that I need to do complete n rounds with an inductor to avoid problems with increase in distortion...  In a multitap, I need to do that with every tap?




Re: Altec 9069B multitap inductor
« Reply #1 on: June 06, 2020, 05:58:10 AM »
Hola Arnau,si consigues algo de informacion adicinonal estaria genial que la compartieras.por lo que yo sé Seb de westfinga tiene su propio inductor multi tapped custom cinemag, aunque no creo que de ninguna informacion sobre valores de impedancia.
Un saludo.


Re: Altec 9069B multitap inductor
« Reply #2 on: June 06, 2020, 11:52:52 PM »
Most filters/EQs of the era leading up to that unit used inductors with powdered permalloy (MP) cores. I don’t know what Altec used for that one. It came along just as ferrites were starting to appear as alternatives to MP cores (and which became the most common core material in the late 60s, until gyrators became dominant later on).

So it’s right on the cusp of that change. It’s an interesting question that someone who knows that EQ better than I do will have to answer. Note that Pultec continued to use MP even in its solid state units in the 70s.

I suspect that since it was a toroid rather than a pot core, it was probably MP. But that’s just an educated guess.
« Last Edit: June 06, 2020, 11:56:22 PM by rackmonkey »
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Re: Altec 9069B multitap inductor
« Reply #3 on: June 09, 2020, 12:39:45 PM »
Thanks for your answers. I suspect its MP toroidal kind too but no sure.  I'm gona try ferrite path first because to do a toroid with such an amount of turns would be very difficult. On last tap it has near 0,8H. With ferrite N48 at AL:630 are more than 1000 turns. A MP toroid core has lower AL than that... I looked for someone with capability to do toroid mp inductors but no luck with that  :'(



Re: Altec 9069B multitap inductor
« Reply #4 on: June 10, 2020, 03:21:26 PM »
Cinemag makes a tapped inductor for the Pultec, maybe you can cross that over. I believe Sowter makes one too.

use 78 material from Ferrite for low turns.
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