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Project Specific Discussions => Filters/Equalizers => Topic started by: Hulk on April 01, 2005, 03:39:34 AM

Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 01, 2005, 03:39:34 AM
I'm working on the Gyraf Pultec and I'm going with the Lundahl LL5402 output trafo as recommended but I also have some OEP A262A2E and A262A3E that I want to use for a balanced input.

I have Gustavs PCB but the holes in the PCB for the optional input trafo (designed for a LL5402) does not fit the OEP trafo pins at all.

Is there a way around this - I think I have to use the OEP A262A2E for the input trafo right??
Do you just connect the OEP trafo to the PCB using wire and how do you fasten the OEP trafo/screening can to the PCB???
Title: Gyraf Pultec and OEP trafo
Post by: gyraf on April 01, 2005, 03:50:03 AM
You'll need to mount the OEP on an external piece of PCB, maybe a piece of veroboard..

Jakob E.
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 01, 2005, 03:54:58 AM
Ok thanks!!
Title: Gyraf Pultec and OEP trafo
Post by: matthias on April 01, 2005, 07:50:40 AM
if I'm right, for the pultec input you need a trafo tha has 600ohms on both sides, so the oep A262A7E would fit best here...??
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 01, 2005, 08:09:54 AM
Then the A262A2E is not good ides as input trafo??
Specs here (http://www.canford.co.uk/commerce/resources/catdetails/2739.pdf) (pdf)
Title: Gyraf Pultec and OEP trafo
Post by: gyraf on April 01, 2005, 08:12:34 AM
Yes, the 'A2E can be wired 600:600 (primaries in series, secondaries in parallel), and is useable for Pultec input transformer..

Jakob E.
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 22, 2005, 04:11:20 AM
I'm about to wire up my OEP A262A2E as input trafo for my Gyraf Pultec but I'm not sure how to do it right so I need some help!
(http://home1.stofanet.dk/jb65/DSC00357_968x726.JPG)

On the PCB (Gustav's) you can see the numbers - to the left on the picture the numbers are 1, 2, 3(E), 4 and 5 - on the right side the numbers are 6, 7, 9 and 10. On the OEP trafo the numbers are:

Pri:
S1, S2, F1 and F2

Sec:
S1, S2, F1 and F2

I have soldered pin number 9 to the screening can.

How do I connect the pins???
Title: Gyraf Pultec and OEP trafo
Post by: Michael Krusch on April 22, 2005, 09:27:43 AM
A mounting hint: You can glue the OEP upside down on the board and connect the pins with short wires. I have successfully used silicon for that.
Title: Gyraf Pultec and OEP trafo
Post by: matthias on April 22, 2005, 10:22:44 AM
do you really want to use the A2E ??

There's a transformer test here:  
  http://www.jlmaudio.com/Neve%20transformer%20info.htm

and the A2E is delared as "not useable"
Title: Gyraf Pultec and OEP trafo
Post by: rafafredd on April 22, 2005, 02:18:12 PM
I think you can use it with the primary in series and the secondary in parallel... for a 2:2 turns ratio...
Title: Gyraf Pultec and OEP trafo
Post by: Kev on April 22, 2005, 06:16:15 PM
I'm busting to make a suggestion here.

Long ago there was a picture at the old Group DIY birth place.
It was the passive EQ from Jakob on a Kev styled PCB.
It had a number of transformers.  I can't get the specified transformers at a respectable price so I put some cheapies on it.

These cheapies like the OEP don't really have enough iron to handle the higher levels into 600ohms ...  yes they call it saturation.
If you drop the level you get less  Iron stuff happening and so less saturation.

wait for it  :cool:
... it was suggested above that you could " ... primary in series and the secondary in parallel .... "

 :roll:

two primaries doesn't mean it has to be a Dual primary trafo ...
look at the original picture and count the transformers.
 :shock: ... sorry Joe  ... I did promise not to tell.
Title: Gyraf Pultec and OEP trafo
Post by: gyraf on April 23, 2005, 06:17:37 AM
Quote from: "matthias"
the A2E is delared as "not useable"


That depends very much on the application - and the ears that listen.

JLM's tests are valid only for that single application, and even then only from a measurement-perspective.

The OEP's are very, very good transformers for the price - and in certain circuits they sound superior to much more expensive iron.

But I haven't tried them for the Pultec circuit - you're on your own here. Please be sure to report back with impressions..!

Jakob E.
Title: Gyraf Pultec and OEP trafo
Post by: gary o on April 23, 2005, 06:34:45 AM
I have made a Gyraf Pultec EQ with the EOP A2E & no ouput tran at all at the mo, IMHO it sounds great, tho I have nothing to compare it to, surely it cant be beaten on value for money, im gonna try it out in some of my other projects where I currently have Sowters.

Thanks ..........................Gary O.
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 23, 2005, 06:43:03 AM
You can allways change the A2E input trafo to the LL5402 if you do not like the OEP but I'm going to try the A2E as input trafo - I'll post samples when it's done!

But where does the individaul pins of the OEP go on the PCB so the pri are serial and the sec are parallel??
Title: Gyraf Pultec and OEP trafo
Post by: Flatpicker on April 23, 2005, 11:59:00 AM
Quote from: "Kev"
...two primaries doesn't mean it has to be a Dual primary trafo ...
LOL! A solution so obvious that we are oblivious to it! I had a similar revelation the other day while trying to find alternatives for driving low impedance loads. I guess when solutions are as close as the nose on our face, we forget that we have to look cross-eyed to see them.   :wink:
Title: Gyraf Pultec and OEP trafo
Post by: Flatpicker on April 23, 2005, 12:14:28 PM
Quote from: "gyraf"
...and the ears that listen...JLM's tests are valid only for that single application, and even then only from a measurement-perspective...
So true! Technical aspects must always be considered, but in the end, it?s the ?ear? that decides. That?s why we love analog/audio electronics so much (and why I?m here in the first place!). If it was all cut-and-dried like digital circuitry, it wouldn?t be the least bit fun.

Quote
The OEP's are very, very good transformers for the price - and in certain circuits they sound superior to much more expensive iron
Jakob, could you elaborate more? I haven?t tried the OEPs yet and it would very helpful to know where you?ve used them with good success.
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 23, 2005, 06:19:41 PM
hmm tried to work itout my self - can someone confirm if this is correct!!

(http://home1.stofanet.dk/jb65/DSC00360_972x730.JPG)
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 24, 2005, 01:46:15 PM
Can I use a 2 x 15V /30VA toroid for the Gyraf Pultec??

Any comments to my OEP wireings??
Title: Gyraf Pultec and OEP trafo
Post by: matthias on April 24, 2005, 03:01:27 PM
no!!  it has to be 12V  ...
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 24, 2005, 05:46:56 PM
hmm just looked at the schematics and it says 220:12 or 220:15??
Title: Gyraf Pultec and OEP trafo
Post by: matthias on April 24, 2005, 05:51:37 PM
you need the first 12V transofrmer for the heater voltage 6,3V  so 12V is nearly more than enough here...

and you need the 12V to convert them back to 220V by connecting the other 12V transformer reversed...  

you could use two 15V transformers, but not one 12V and one 15V

...

mat
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 25, 2005, 03:42:01 AM
OK thanks mat.


Anyone had a look at my OEP wiring suggestion??? - I would really appreciate it!!
Title: Gyraf Pultec and OEP trafo
Post by: gyraf on April 25, 2005, 04:26:18 AM
It looks right at a glance..
Title: Gyraf Pultec and OEP trafo
Post by: matthias on April 25, 2005, 04:52:56 AM
you could simply use an oep A262A7E  transformer...

it's 1:1  600:600 ohms....


mat
Title: Gyraf Pultec and OEP trafo
Post by: gyraf on April 25, 2005, 05:17:17 AM
What ratio is the transformer you suggest, Hulk?
Title: Gyraf Pultec and OEP trafo
Post by: Hulk on April 25, 2005, 05:36:21 AM
The ratio is 1+1:2+2

@mat
I have a few OEP A262A2E's to spare. If I can use them I'll save the money to buy a LL5402  :wink:
Title: Gyraf Pultec and OEP trafo
Post by: gyraf on April 25, 2005, 05:53:50 AM
1+1:2+2 should work, if 1+1 are wired in series, and 2+2 in parallel, like you suggest..
Title: Gyraf Pultec and OEP trafo
Post by: giobinein on April 27, 2005, 03:10:35 AM
http://i5.photobucket.com/albums/y163/giodiy/pultec_oep.jpg
OEP A262A2E wired 1:1 both input and output and works great !!  :grin:
Title: Gyraf Pultec and OEP trafo
Post by: gyraf on April 27, 2005, 03:23:51 AM
Thanks giobinein,

The link dosen't work, as external access to the images are denied by your host.

Also, could you possibly resize your avatar to the recommended 60x60 pixels? It takes up a lot of screen real-estate because the forum software resizes the whole coloumn whenever you participate..  :grin:

Jakob E.
Title: Gyraf Pultec and OEP trafo
Post by: giobinein on April 27, 2005, 03:33:58 AM
:oops:
Excuse me but I have some problem whit this host !!  :evil:
Can you advise me about a great free host ??
Thank you
Title: Gyraf Pultec and OEP trafo
Post by: giobinein on April 27, 2005, 05:12:26 AM
Thanks Viitalahde !!
Now I'm Photobucket member !! :grin:
Title: Re: Gyraf Pultec and OEP trafo
Post by: MiamiBoy on November 02, 2019, 10:48:14 AM
Hej Jakob.
Which input transformer is recommended/fits in the Gyraf Pultec?

I just notice that there isn't installed one in my unit (a friend built it).
And is it gonna sound more like the original Pultec with one installed or how does it change the sound?
Thanks