AP2503

Look what came in the mail yesterday- an original API 2503 output!

The API I reversed was a clone, and I had someone tell me that they heard a slight difference between my kit and the original, so we are going to see what gives.

That way we will not have a clone of a clone, but a clone of the real thing. Hopefully there will be very little difference.

I have gotten a little better at testing since the first API, which was one of the first take aparts I did, so...
Full props for this opportunity! :thumb:

Sweet! :grin:

oh man CJ!!
just pulling measurements off of this one right?!
does this mean that there will be a CJ2503v.2 when you get the differences sorted out?:twisted:
-grant

major discovery-this thing is quad-filar wound, that is, the winder grabs four wires and feeds them thru the same guide.
No twisting at all.
Maybe there were some other revs of the 2503 that used twisted wire, but not this one.
Why would the reverse guys spend the extra bucks on twist-tite wire, I do not know.
Maybe the example they were provided had the twisted wire.

Funny thing is that both test out about the same, flat as a pancake up to 1 meg hertz.

Oh well, the good news is that I am done twisting wire.
The bad news is that I might need to wind some people some new coils.
Would be interesting to see if any of the kit builders notice a difference.

Going to take the coil home and re-lam it, just to make sure there isn't anything else funny going on in that dept.

If some of you have some original API outs, you might try to see if the wire looks like twist-tight, or regular flat wound.

Here is the orig:

http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_b.jpg

Did the B-H, inductance, leakage, all that.
Will post tomorrow.
TV and Beer.

see ya!
cj

nice! i'm down to not twist.... i never got around to doing my diy 2503, only did my diy b11178. so when i do, i can forget about going down to the basement just to spend hours breaking and picking up wire ;]

Haha!! I did mine just like that!!!! And with steel core!!! :green: :green:

I have several 312's that I made from old 325 cards, and I've looked at the transformers (but haven't taken them apart), and the wire I can see through the tape edges definitely is NOT twisted.

I used to sell api gear at a company I worked for in the 1990's, and it was during my time there that api switched from quad-filar wound to litz-wound outputs. I actually had a phone conversation with Paul Wolfe at the time about their 'new' output transformer design, and he said that the litz winding resulted in performance that was equal to the original 2503's made decades earlier. This would have been early 1997.

By this time Paul was getting lots of grief from people about having recently switched to surface mount construction of the 2520 op amp (some people have insisted that the surface mount 2520 doesn't have the same current drive capability as the previous versions) and he was trying to get more accurate tone from the current devices (550b, 560 reissue, etc) relative to the older stuff. So perhaps the change of the 2503 to litz winding at this time may have been to create a more accurate vintage sound when paired with the modern 2520. That's just my guess, though.

CJ, do you know the vintage of that 2503 you got there?

JC

Hey Fabio, do you mean the ones that BR Audio has?

I do not know the vintage.
Good to know that the twisted stuff was used also.
I see an A/B test comin up real soon.

This is an AP2503 out of a very old 325 card.

Hey thanks!
That definately looks like twisted or Litz to me.
Now I'm really confused. :shock:


JC, cool inside info!
:thumb:

[quote author="Bauman"]Haha!! I did mine just like that!!!! And with steel core!!! :green: :green:[/quote]

I have curiosity, did you use the same turns? core size?

[email protected]


Thanks!

Safe as milk is the guy to thank for this, BTW.

And I remeber now that the differences he heard were between the Sowter 9825 and the 2503, not the cj 2503 vs orig 2503.

Never the less, we will check both.

OK, here is the cut sheet, minus turns and wire gauge, which is being foun d out now.

huh..
maybe I could donate an 4-75 (Fabio's version) for further comparison. Off course, if he agrees with it. I was also thinking about offering a groupbuy kind of thing for them, but that is a whole other topic... :green:

Peace
Gil

Well, the recent revelation that this can be wound quad-filar with the same results is like a shot in the arm to the DIY'ers, no wire twisting.

OK, wire is #29 ga, 0.011 - 0.012"" red enamel;, 286 turns, which is a turn shy of Mr. James Greenley's reverse job, so we are alright there.

About 80 ft per strand, 4 strands each, this was hand wound, very tight.

The bobbin is a tad smaller than the stock 625 EI bobbin I have here. Probably an european version.

DCR per 1000 ft works out to about 83 ohms, which resembles #29 on the wire chart.

OK, no time for rhetoric, besides, you guys know the drill.

http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_a.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_b.jpg

BH curve:
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_bh.jpg

http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_c.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_d.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_e.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_f.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_g.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_h.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_i.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_k.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_keeper.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_leads.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_m.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_n.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_o.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_p.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_q.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_r.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_s.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_strain.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_t.jpg
http://vacuumbrain.com/The_Lab/TA/API/AP2503/ap2503_u.jpg

Outta here...

YOU MAKE ME SICK..... :green:
rock on, dude..

hi
first off, a massive thankyou to cj for doing this,
i thought i'd chip in with rough dates and such,

this 2503 is from a bright green 325 card with a huntington on it,
im sure that makes it around '81(api experts please correct me).

here's an interesting one though,
i just checked through all of my api rack and ive found on the older ones
i have 312(ap2622) army green card rev5
and on blue 325 cards, melville's. rev4

they have a slightly different bobbin with two slots in the white plastic,
i can clearly see that they are not litz/braided etc in any way.
on the rev3 and rev5 325's they have normal bobbin's
as do the green huntington cards
and if i took them apart i'm embarrassed to say i would'nt know how to put them back together.

does anyone else out there have braided ones,
could you please share the card rev. etc.(what card's your one from walrus?)

it would be great to compile some sort of rev. list?

once again thankyou