ognam2

Pultec Inductors again...
« on: December 05, 2007, 03:35:28 PM »
This has been discussed several times yet, but the problem is, that the suppliers are changing their product lines all the time. From this one Shopping list, that I found in any other Pultec thread, I know that the conductors should be 22mH, 47mH and 100mH. But what about it´s resistance. I also know, that the resistance is responsible for the "Q". But whitch value´s should I take to have a nice  musical sounding equalizer? I saw some very expensive inductors at Sowter which were looking like vintage ones... Is that worthwile for 56 EUR? Is there anything else that I should know about my inductor choice?
Thank you....
Jonas


living sounds

Pultec Inductors again...
« Reply #1 on: December 05, 2007, 06:20:18 PM »
Look for Toko inductors. Most people use them in their GPultecs. Manley uses them in their passive EQs. Or you can buy a tapped inductor from ioaudio at the Black Market.

CJ

Pultec Inductors again...
« Reply #2 on: December 05, 2007, 08:11:36 PM »
I will hopefully measure the dcr when Pat gets done mixing the latest Pat Travers comeback LP.

I did a comeback LP one time, its still coming back from the distributor.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

nielsk

Toko's?
« Reply #3 on: December 06, 2007, 08:29:44 AM »
Which Toko's to use? I have heard that they sound harsh.... I have been trying to get a Wlco BSL group order to happen for my API 553's, they are reputed to actually sound good....but min order of 100. At a few dollars each it would be much less than buying the custom wound multitap inductors

ognam2

Pultec Inductors again...
« Reply #4 on: December 06, 2007, 09:08:17 AM »
I would pay a few dollars :-)

guitarbill55

Pultec Inductors again...
« Reply #5 on: December 06, 2007, 03:38:17 PM »
You guys may know this but since I'm a Cinemag fan I'll repeat it; they make a reasonably price pultec EQ inductor called the CML-150T.  website is cinemag.biz

cheers
gb
"Eat your sockeye with wild blueberries" - Copper River Red

radiance

Pultec Inductors again...
« Reply #6 on: December 06, 2007, 06:35:40 PM »
Here an excelent site on inductor DIY....

http://www.diygallery.de/DIYsites/inductor.html

Thanks to Steffen!
"Knowing that you are dreaming, however, does not automatically guarantee full rationality.
Then again, being awake doesn't ensure good thinking, either." -  Lynne Levitan

nielsk

torroid
« Reply #7 on: December 06, 2007, 10:19:15 PM »
how do you wind over 20' of extremely thin wire around a torroid core 3/4" in diameter? I can get the cores and wire locally, but I can't find a DIY way to wind it. I know other types of cores will work, but how close will they sound?

codered

Pultec Inductors again...
« Reply #8 on: December 14, 2007, 03:36:24 PM »
I was thinking about getting the cinemag but now I feel like winding my own even  if it takes a day to get it right. A Fluke for the inductance measurement should be OK right??
 Could somebody point me to the dimensions of the torroid and the wire gage.Also any link to where it could be bought would be great
  Also Drpat it would be real cool if you tell us what type of caps they are using for the amp section: is it PIO or just old paper caps.I suppose you dont know what is inside the filter section.I checked some of the caps of that era and some of the filter values like 0.0082 seemed to come only in ceramic disc

thanks
you're a nut ... this is the internet..we're all nuts

shabtek

diy?
« Reply #9 on: December 14, 2007, 04:58:57 PM »
nielsk,

there is no easy way to diy it...there was a post some time ago of a co. offering a diy xfmr/inductor kit-- they supplied a core and wire. they also showed a photo of the winding device

winding is the hard part--the more uniformly wound the better.

take a popsicle stick/tongue depressor (that will fit through the center of the core, accounting for reduction of opening as wire is added) and whittle u-shaped notches at both ends,wind your 20' onto this long thin bobbin.
use the popsicle stick bobbin to wind around the core...
"really fine players do not use stomp boxes or master volume, they match the amp to the room and turn it up to 11.  Stevie Ray, BB King, Albert King, Duane Allman, Dicky Betts, Louis Armstrong"
   -CJ


CJ

Pultec Inductors again...
« Reply #10 on: December 14, 2007, 07:01:04 PM »
You need to know the perm or Al number of the partucular core you are using so you can calculate a ball park number of turns to get you to the first stop.

If you use too many turns, you will have too much wire to wire capacitance, which can accumlate to the point where the high end goes on thru anyway, at least 1/2 cycle, the other half goes thru the cap, so you will have an "interesting" eq curve.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

codered

Pultec Inductors again...
« Reply #11 on: February 24, 2008, 11:29:13 PM »
DrPat,

Thanks for the answer.The most practical answer I've got so far and believe me I've asked so many Pultec owners and nobody knows thier Pultecs from their pants.
   In another forum you talk about 3 caps which affect the sound drastically .What are those? Are they the Aerovoxs in the amp section.I am trying to do some calculations to acheive the dcr you've measured using available ferrite torroids
you're a nut ... this is the internet..we're all nuts

EmRR

Pultec Inductors again...
« Reply #12 on: June 26, 2008, 01:00:07 PM »
Audio Cyclopedia regarding toroidal coils, as recommended for EQ construction:

...circular core composed of molybdenum permalloy dust mixed with a plastic binder, compressed into a doughnut under 200 tons-per-square inch.  By the use of this type winding, coils with a Q of several hundred are possible.   Efficiency is extremely high compared to other designs.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

CJ

Pultec Inductors again...
« Reply #13 on: October 15, 2008, 04:21:41 AM »
been winding a ton of toroids lately on our machine at work.

learning some cool stuff.

1) wire pitch affects the toroid.

In other words, lets say you need 1000 turns wound on a core.

How many times do you circle the core?

Three? Five?

It makes a difference, very slight, but it is there.
How would this affect sound?
Thats when you hop on the bench to find out.

this machine lets you program in any wire pitch you like, via a keyboard.

2) wire size

dcr will change depending on the wire size.
this combines with the non linear properties of your average inductor to produce yet, another effect.

if you want a transformer to put out say, 10 volts max, and exactly 5 volts at half power, you need to pick the wire right.
distortion due to non linear voltage curves can be minimized by doing more bench work.
unfortunately, the formulas only take you so far, so you hop on the bench, which saves time anyway, as the theories are always opposite the results.

so now you have two tweaks to play with, which combine to form, say, 4 wire size possibilities, and maybe 4 more pitch possibilities, so multiply to get 16 different inductors by using the same core, and the same turns, arghh!
 :mad:

but fortunately, a lot of the combinations overlap, so you only end up with maybe four distinct inductors for the same core and turns, still, I'm jus sayin...


So in order to duplicate the original Pultec inductor, I am afraid you would have to look at the winding technique and measure the wire, which means, gulp,...a dissection on a very rare and expensive part.


kh, how did you get the turns from your orig P inductors?
PRR method?

Also, do not forget the wax.
Every company had their own potting  formula, which could tweak the high end.

Again, these are microscopic tweaks, but when you are trying to duplicate the original mojo, you try to get as much info as possible.

Also, list the way you get the Al number, because it varies depending on meter used, and turns used.
You tend to get a better Al as you add wire, up to a point when the dcr starts to drag it back down.

but veve  have vays of getting information
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

CJ

Pultec Inductors again...
« Reply #14 on: October 15, 2008, 05:01:03 AM »
it might have been "pie" wound.

this is a technique you can find on the web.
it is used to minimize C so that your high end has a nice bell curve.

you wind a bunch of turns, then you rotate the core 180 and wind another pie.

then you only get to roate 90, but then you get to rotate 180 again, but now this section is right next to the start, and on and on.

you could wind the low end all as one pie, then spread out the high end windings.

i do not think any special high end audio winding was going on, as this was a cheap telephone eq.

you could also try 120 120 120.
this would have equi distant voltage gradients, which might require a bench experiment to verify.


you can machine wind pies.
you just set a small pitch, wind a pie, then hit stop, rotate the core with the L or R button, and start winding again.

i do not think that those toroids were hand wound.
possibly the antiquated toroid winding machines made it look that way.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

EmRR

Pultec Inductors again...
« Reply #15 on: October 15, 2008, 11:21:18 AM »
Excellent.
Best,

Doug Williams
Electromagnetic Radiation Recorders

"I think this can be better. Some kind of control that's intuitive, not complicated like a single knob" - Crusty

"Back when everything sounde

khstudio

Pultec Inductors again...
« Reply #16 on: October 16, 2008, 02:11:05 AM »
For new comers... here's a link to my builds:
My 3 DUAL PULTECs - EQP-1a3 - Solid State
http://www.groupdiy.com/index.php?topic=29742


CJ,
Pat would have to give you more in depth details about how he did it but I know he didn't unwind one. I will try to to explain as much as I can.

From what I remember him telling me:
He took apart the can & WAX

Measured EACH Cap & Winding with a good (Freshly calibrated) Meter... I think it was an HP.

Measures the wire gauge = 34.

Then he wrapped the cores (over the original wire) to find the AL Value = 876

Then he started wrapping several different inductors until he found one that matched his magic #.

Then... he "Listened" to his new inductors (& if I'm correct, also ran test sweeps) to hear how close he was.

He said his second attempt was "Spot On" & couldn't tell or measure a difference.

I definitely remember him telling me that his first attempt didn't sound as good as his 2nd one & so on.
This MAY have something to do with what you said:
Quote
wire pitch affects the toroid.


I remember asking him about this & he said there didn't seem to be ANY method to "How" the original was wound... so when I wound mine, I remember lapping several times... aprox between 6-10 times maybe.
BUT, the ones I wound sound KILLER & when I run sweeps on the left & right channels, the Frequency's & Plots are EXACTLY the same.
They are by far my favorite ones.

& I have to be honest... I was skeptical (not about Pat or his info) about MY builds/wraps.

Myself, I used an AMPROBE LCR Meter.
You have to be careful when using ANY meter to test as your winding -
Because - The wire on the "Popsicle Stick" has inductance too :!:
AND... it changes AS your winding & losing wire on the stick & gaining on the core.
SO... Measure your STICKs Henries FIRST :!:
I just used the "Force" (Like Luke Skywalker) after this to guess what that value was doing to my CORE reading.

WAX!!!

Very interesting about the wax...
I didn't use wax... I used HOT GLUE to seal mine & I pray that it doesn't effect them, over time.


I did this (Mainly) because it's all I had & could think of that would protect & seal them from damage... especially the way I strapped them down.
I took care not to torque them down hard at all with the straps!
Also, after I finished winding one of them... one of the taps in the middle broke off & every tap above it had no reading!
 :shock:  :mad:
So, I got out my big ass lighted magnifying glass & took a tooth pic & gently dug into the windings to find the break, pulled it around & re-soldered it to a new wire & all was good... thank GOD!
This took about 2 hours to fix & I wasn't going to take any more chances with that happening after all that hard work, so I grabbed my hot glue gun & that's all she wrote.

The Hot Glue made me nervous at first because the HEAT changed the inductance... but after the glue settled, so did the inductance, back to normal. :green:

With all this knowledge here & CJ's winding machine... maybe (if someone could find some good cores) CJ could make some :?:  :wink:

OK, I'm out.
Kevin ~ KHStudio

Val_r

Pultec Inductors again...
« Reply #17 on: October 16, 2008, 03:04:52 AM »
Hi,

I just wanted to contribute with the construction I did some time ago.
You can see that the inductor is wound on a toroidal core. (120°)
This is the LINK

There are some sound clips to compare.

 :musique:

Respect,
Val.
Ok, cool ! Jahmekya

khstudio

Pultec Inductors again...
« Reply #18 on: October 16, 2008, 03:25:22 AM »
Nice job :thumb:

Looks like a few hundred winds & larger wire gauge... I'm guessing ferrite cores?
Probably very similar to my RED unit's inductors.

http://www.groupdiy.com/index.php?topic=29742
Kevin ~ KHStudio

Val_r

Pultec Inductors again...
« Reply #19 on: October 16, 2008, 03:46:11 AM »
Quote from: "khstudio"
Looks like a few hundred winds & larger wire gauge... I'm guessing ferrite cores?

http://www.groupdiy.com/index.php?topic=29742


Thank you!
Yes, it's a high quality toroidal core, material N30 (ferrite),
wound with 0.35mm insulated copper
150mH inductor tapped at:
27 (0.58)
33 (0.66)
47 (0.79)
68 (0.95)
82 (1.05)
150(1.45)

() figures are DC resistance values in ohms.

Distributed capacitance: 2.2 pF

Can you tell us more about your original ferric powder cored inductor? How many turns, which wire gauge, DCR's, what's the core Al, etc.?

Where did you find the ferric powder cores?

Respect,
Val.
Ok, cool ! Jahmekya


 

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