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Old 6th November 2001, 10:19 PM   #1
lohk is offline lohk  Europe
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Does anybody have any idea how to wind precise inductors (for passive filters) without a inductance meter ?
Is there a webside to explain this ?

I want to make a Pultec EQ for my studio; I recently found the schematic in the net
( http://<a href="http://www.gyraf.mob...lixnet.dk/</a> ).


Klaus
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Old 12th November 2001, 09:23 AM   #2
djk is offline djk
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Buy an LCR meter.USD$50 from MCM 72-6634.The USD$189 MCM 72-960 is much better.
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Old 12th November 2001, 12:37 PM   #3
lohk is offline lohk  Europe
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Thank you, that really was an answer to my question...
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Old 28th July 2011, 06:48 PM   #4
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PULTEC Style EQP-1A EQP1A Complete Filter Unit New:

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Old 28th July 2011, 11:14 PM   #5
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For the Pultec coils, use telecom grade ferrite pot cores - not SMPS ferrites.
Sowter makes the inductors and transformers too.
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Old 28th July 2011, 11:24 PM   #6
Tajzmaj is offline Tajzmaj  Slovenia
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Klaus. It will be hard without lcr meter. You ca calculate coils but in reality it is batter to measure too.
I made 2 gyraf's pultec units and work fine... With coils which I bought cheap from Farnell.
Later I made 2 units with solid state output. 1073 type. On my opinion those sounds even batter than gyraf's tube output which is very sensitive of which opt you use. With Lundahl 5402 which was used by Jakob I was't quite happy with low end.....
Best regards, Taj
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Old 29th July 2011, 06:17 AM   #7
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prairiemystic

What is the advantage of telecom grade ferrite pot cores?

Cheers
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Old 4th August 2011, 01:29 AM   #8
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Default Pultec Inductors - ferrite material etc.

The vast majority of ferrites out there are designed for switching power supply applications. They are optimised for high flux-density and I find they sound quite poor with audio signals. Just too much distortion for my taste.

When I spoke with engineers from Neosid, they said for low distortion I should go with a P11 ferrite material from Neosid/MMG/TTI. The P11 material is used in filters and mainly in POTS (analog) telephony. P12 material would work too.

There is a Siemens research paper out there that showed transformer distortion is related to core geometry and symmetry. I went with larger RM-10 pot core has low CDF ("core distortion factor") whereas E-cores seemed much worse. Some info in this Siemens/EPCOS app. note pg. 6/22 or 133:
http://www.thierry-lequeu.fr/data/AN-EPCOS.pdf

To summarize, I would avoid using power magnetics for a Pultec clone filter inductor.
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