Vintage Windings EQ-1A inductor in EQP-1A builds - the ring is gone!

[ruffrecords]

Question is not for me, but I can answer from my experience (knowledge). Soft Magnetic materials are not linear by frequency by many aspects, so in this case by permeability. So, Al value is different for different frequencies. Especially with molypermalloy cores. People who produce this "innacurate" inductors probably measured their values on 1khz what's not enaugh for this kind of filter.  Producing accurate multitap inductor for Pultec's has to be calculated and measured carefully.

OK, I get that but molypermalloy is little more than regular 80%nickel used in transformers and has a very large frequency dependency. On the other hand the Carnhill type of inductors most often used in EQ designs are made of ferrite which  does not.

Cheers

ian

 

[Moby]

OK, I get that but molypermalloy is little more than regular 80%nickel used in transformers and has a very large frequency dependency. On the other hand the Carnhill type of inductors most often used in EQ designs are made of ferrite which  does not.

Cheers

ian

They use Moly-Permalloy toroids for their EQP inductors. Also, not all MP cores are "right one" for this design.

 

[ruffrecords]

They use Moly-Permalloy toroids for their EQP inductors.

Sorry, you lost me. Who does?

Cheers

Ian

 

[Moby]

Sorry, you lost me. Who does?

Cheers

Ian

Carnhill 

 

[ruffrecords]

Carnhill 

Which inductor part numbers would those be?

Cheers

Ian

 

[Moby]

Which inductor part numbers would those be?

Cheers

Ian

http://www.audiomaintenance.com/acatalog/CA-18-VTA1444_extended_info.html

 

[ruffrecords]

http://www.audiomaintenance.com/acatalog/CA-18-VTA1444_extended_info.html

Ah, now I understand. I was thinking of the VRB9042 through to VTB9055 series of ferrite EQ inductors. The permalloy ones are a fairly recent introduction to the audiomaintenance catalogue. Presumably these are used in the search for some kind of authenticity in clones.

Cheers

Ian

 

[Moby]

Ah, now I understand. I was thinking of the VRB9042 through to VTB9055 series of ferrite EQ inductors. The permalloy ones are a fairly recent introduction to the audiomaintenance catalogue. Presumably these are used in the search for some kind of authenticity in clones.

Cheers

Ian

MP sounds quite diferent but
AL is more frequency dependant.

 

[ruffrecords]

MP sounds quite diferent but
AL is more frequency dependant.

Ferrites did not become commercially available until about 1945. The EQP1A was designed in the early 1950s so ferrites were certainly available to them. However, the EQP1A design was based on a 1930s Western Electric EQ design intended for telephone circuits where distortion was not a primary issue. Clearly the Western Electric design did not use ferrites. Perhaps the simply copied it, telephone distortion and all.

Cheers

Ian

 

[Moby]

Ferrites did not become commercially available until about 1945. The EQP1A was designed in the early 1950s so ferrites were certainly available to them. However, the EQP1A design was based on a 1930s Western Electric EQ design intended for telephone circuits where distortion was not a primary issue. Clearly the Western Electric design did not use ferrites. Perhaps the simply copied it, telephone distortion and all.

Cheers

Ian

A standard MPP core saturates at around 7500 Gauss. A ferrite core saturates at around 4500 Gauss.

 

[ruffrecords]

A standard MPP core saturates at around 7500 Gauss. A ferrite core saturates at around 4500 Gauss.

But I doubt if either of them ever saturates in an EQ. I think it is the shape of the BH curve that is more important plus the point you made about parameter variation with frequency. I cannot think why anyone would choose to use a permalloy core in an EQ design today.

Cheers

Ian

 

[vari-mu]

    Hi !

  I have a certain amount of Russian moliphermalloy from semirings MP-140 (Al=140) and MP-250 (AL=250)
  and I made inductors for my EQ Pultecs (7 pieces) 5 years ago.
  Recently I got one inductor, wound on two half-rings MP-250 (AL = 250x2 = 500) for measurement. My LC meter allows me to measure L on two frequencies:  UP (hi freq.) and DOWN (low freq.), which he assigns independently.
The results can be seen in the picture:

 L = 39.268 mH at 15440 Hz and 41.39 at 2460 Hz, Al= increases by 5.4%

       next tap of inductor
 L = 80.54 mH at 10 790 Hz and 91.21 mH at 1670 Hz, Al= increases by 13.2%
 
   Depending on the number of turns Al= "walks" between 350-250 at high frequencies and between 450-320 at low frequencies.
 
 I can not say anything, just information for thought.
Maybe my device does not work correctly.
 Vladimir P.

 

[Moby]

    Hi !

  I have a certain amount of Russian moliphermalloy from semirings MP-140 (Al=140) and MP-250 (AL=250)
  and I made inductors for my EQ Pultecs (7 pieces) 5 years ago.
  Recently I got one inductor, wound on two half-rings MP-250 (AL = 250x2 = 500) for measurement. My LC meter allows me to measure L on two frequencies:  UP (hi freq.) and DOWN (low freq.), which he assigns independently.
The results can be seen in the picture:

L = 39.268 mH at 15440 Hz and 41.39 at 2460 Hz, Al= increases by 5.4%

        next tap of inductor
L = 80.54 mH at 10 790 Hz and 91.21 mH at 1670 Hz, Al= increases by 13.2%

  Depending on the number of turns Al= "walks" between 350-250 at high frequencies and between 450-320 at low frequencies.

I can not say anything, just information for thought.
Maybe my device does not work correctly.
Vladimir P.

Hey Vladimir. "Hi and low" doesn't tell much, but nonlinearity of the core depends from model to model, batch to batch. To trim Pultec inductor correctly variable frequency L meter is must. It has to measured at working frequency, for example 16k. I use HP meter with sweepable singnal generator with accuracy of 0.5% at corner frequencies  and again, it has to be double checked in LC circuit.

 

[rjb5191]

Has there been any progress with this?  I'm not satisfied with my cinemag inductor and would like something more authentic.  I have no idea if I have ringing or not and if I need to tune the Zoebel network to work with the Sowter 1475.  The high boosts just seem a bit harsh to me.  Did I miss a new thread that was started?

 

[Moby]

Has there been any progress with this?  I'm not satisfied with my cinemag inductor and would like something more authentic.  I have no idea if I have ringing or not and if I need to tune the Zoebel network to work with the Sowter 1475.  The high boosts just seem a bit harsh to me.  Did I miss a new thread that was started?

If you ask about inductors, feel free to contact me by mail (see my signature) I have it on stock 

 

[plnow]

Some of you may remember a high frequency ringing problem at around 26KHz I ran into (it was actually GDIY member Sasarist that pointed it out to me) on my Drip V2 EQP-1A builds. The problem was most noticeable when boosting at full at 10K, 12K & 16K, bandwith at narrow. I used the older version Vintage Windings EQ-1A inductor, along with the suggested Sowter transformers. I discovered a few things along the way - most significant was that the inductor rings the worst when loaded with a low impedance. Evidently the original Triad HS29 with it's 20K source impedance was a good choice. I ended up using a UTC A-18 with a 15K source impedance, then tuned the interstage Zobel to suit. But I still was having problems with ringing on the Vintage Windings inductor, but was able to make the Carnhill behave in my build. So that's what I went with, and somewhat loudly endorsed.

I was corresponding with Chris Preston at Vintage Windings while this was going on. A few weeks later, he sent me another EQ-1A inductor to test. And I didn't have to ask - Chris is a stand up guy. It took me several months to get around to testing it (sorry Chris), but finally installed it in one of my EQP-1A builds last night and tested it with my QA401. Great news - the HF ring is gone! It's also really cool that Chris has discovered the discrepancies in the "accepted" EQP-1A cap and and inductor values and corrected his current EQ-1A inductors to get the frequency centers closer to the published specs.

I can now endorse the Vintage Windings EQ-1A inductor without reservation. Happy building!

Greetings
Thank you for sharing your findings.

If building a Drip Eqp-1a today, would you then use Sowters' 3603, 9530, 1475, with the VW EQ-1A inductor?

 

[CJ]

https://groupdiy.com/threads/pultec-inductors-again.25482/page-6