Neve inductors

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3nity

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Hi guys.
On a 1073 inductors.
You  think we can use small inductors like on the g pultec?

Out of curiosity.
 

3nity

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They go from .1H .2H .3H .6 H 1H
50mh 80mh 100mh 160mh 200mh
1.3H 3.0H 7.0H 10H

Those are the most commons.

I tried finding a small 10H ..lol it's huge and expensive!😂
 

gyraf

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The small ones are realistic only up to some 100-150mH. Above that, better to wind your own...
 

3nity

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It could be fun.
I simply know nothing about winding.
Will wait from Audio Maintenance to re stock!

Thanks Jakob!
 

shabtek

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I cannot seem to find the 77 pot core data sheet on their site.
there is a chart that tells you what size wire for given turns and a formula for determining turns needed for a given inductance @ a stated AL; you still need to measure and do some empirical observation as the charts' resolution is not good down where we are interested

I have it on an old drive somewhere...will have to look

this carnhill is the one that goes up to 10H so I would use the biggest core to allow the biggest wire

you still need to measure and do some empirical observation
NYD advised not making a tapped rather separate inductor for each value,fwiw.




https://groupdiy.com/index.php?topic=39578.msg489257#msg489257
 

abbey road d enfer

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shabtek said:
NYD advised not making a tapped rather separate inductor for each value,fwiw.

https://groupdiy.com/index.php?topic=39578.msg489257#msg489257
I don't see such a post in this thread.
I'd be curious to know why someone would recommand doing that. Admittedly, multitap inductors are almost impossible to correct after the fact, other than rewinding them completely. Apart from that, it just makes sense.
 

shabtek

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I agree abbey, I was browsing through threads with 'amidon' in them --think dave may have been referring to matching values. it is not easy to get matching values and taps on the same core when winding by hand. tension variations of successive windings can change things. also in theory the core can only be optimized for 1 value.
this is not meant to discourage. definitely diy worthy, matching for 1% is gonna take some work thats all.

let's see if this attachment works

 

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  • amidon pot turns .pdf
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abbey road d enfer

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shabtek said:
I agree abbey, I was browsing through threads with 'amidon' in them --think dave may have been referring to matching values. it is not easy to get matching values and taps on the same core when winding by hand. tension variations of successive windings can change things
This shouldn't be an issue. When hand winding it is necessary to adjust the final value, which implies overwinding, measuring, cutting measuring, cutting until final value is achieved with desired precision. It's very tedious, since the core must be fully reassembled before measuring, but it's doable.

also in theory the core can only be optimized for 1 value.
I'm not sure what you mean by that...

let's see if this attachment works
It does, but I'm not sure these cores are suitable for audio inductors. They seem to be spec'd only for smps and converters.
 

shabtek

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abbey road d enfer said:
I'm not sure what you mean by that...
I am speculating why NYD suggested 1 inductor per frequency.

I know tapped works fine in practice, hitting a given L and R value would be simplified by not having taps.

abbey road d enfer said:
It does, but I'm not sure these cores are suitable for audio inductors. They seem to be spec'd only for smps and converters.
I've used them (amidon 77) for 1H and 100uH values in audio eqs (api copy) with success.

do you have suggestion for other core? 
I am curious what the difference is to rm8 or what carnhill uses
 

abbey road d enfer

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shabtek said:
I am speculating why NYD suggested 1 inductor per frequency.

I know tapped works fine in practice, hitting a given L and R value would be simplified by not having taps.
By using e.g. 4 separate inductors or one with 4 taps, the net workload is about the same...

do you have suggestion for other core? 
I am curious what the difference is to rm8 or what carnhill uses
TBH I've never used anything else than RM types. RM8 is quite small. I used mainly RM10 and RM14.
For any kind of repeatability, you have to use a gapped core. Ungapped have to high a tolerance (+30/-20%).
Since gapped cores have a lower Al, you need a larger core than an ungapped one, but you get much more linear response.
 

muffy1975

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HI Abbey Road,

if you have a moment, could you help me choose a suitable version of the Rm8 core for a neve style eq inductor?


is this good enough? They have other N types and with different inductance factors. Is there a particular version I should choose? I don't understand the difference however I can wind the buggers.

Cordailly

Michael de A
 

abbey road d enfer

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HI Abbey Road,

if you have a moment, could you help me choose a suitable version of the Rm8 core for a neve style eq inductor?


is this good enough? They have other N types and with different inductance factors. Is there a particular version I should choose? I don't understand the difference however I can wind the buggers.

Cordailly

Michael de A
Well, it starts with the values you need. Then we must figure what value for Al is usable, and select the wire gauge, check the resulting winding fits in the bobbin and that teh DC resistance is adequate.
So, shoot. :)
 

muffy1975

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Thanks Man. I will wind the inductor and find the values as I wind the inductor, writing it down as I go. What AI is usable? What range am I looking for assuming I'm using guitar pickup guage wire for the winding?

is 250nh too low?
 

gyraf

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Try to consult with https://powermagnetics.co.uk/calculator/ - this is a great tool, and possibly your best friend when it comes to winding inductances

with an AL of 250nH, you'd need 6325 turns of wire to get to the mentioned 10H - which you pobably can't fit into a RM8 by hand anyway, because the wire gets too thin (and the inter-winding capacitance gets too high)

I like the ungapped T38 ferrite material for audio - AL is 12500 nH for the RM8 - https://www.elfadistrelec.dk/da/rm8-core-set-t38-pk-par-stk-epcos-b65811j0000y038/p/15865208 - requiring a more feasible 895 turns for 10H

BUT

Depending on the actual signal levels and frequencies acting on the (specially large-inductance inductor) cores, you may easily get well into core saturation. Which may or may not be a problem :) - but for low frequencies I usually prefer much beefier core sizes

/Jakob E.
 

abbey road d enfer

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I like the ungapped T38 ferrite material for audio - AL is 12500 nH for the RM8 - https://www.elfadistrelec.dk/da/rm8-core-set-t38-pk-par-stk-epcos-b65811j0000y038/p/15865208 - requiring a more feasible 895 turns for 10H

BUT

Depending on the actual signal levels and frequencies acting on the (specially large-inductance inductor) cores, you may easily get well into core saturation.
Indeed. But an additional problem is the large tolerance (about 30% IIRC) which makes reaching the correct value quite a tedious job, even for one-offs.
Which may or may not be a problem :) - but for low frequencies I usually prefer much beefier core sizes
For these two reasons, I have always preferred larger gapped cores. For 10H, I used RM10 or RM14 cores.
 
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