A*P*I 560

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chrissugar

Well-known member
Joined
Jun 4, 2004
Messages
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I thought this is a schem I have but after searching for a while was surprised to discover that this is not a common thing like the 312, 550 or 325.
Anyone has this schem?
Send me a PM if it is too dangerous to post. :green: :green: :green:

chrissugar
 
OK, I try again.
Anyone has the schem for the 560 EQ.
Come on, it is only a simple parametric EQ. :grin:

chrissugar
 
I have it on paper once I get a chance to scan it I'll send it to you. I't might take a while Wil

Wilebee
 
I was away for a couple of days.
Sorry for the confusion, sometimes I write diferent than I think.
It is the 560, 10 band graphic eq that I'm interested in, NOT the 550 parametric.
Wilebee, you have the schem for the 560?
Thank you.

chrissugar
 
Hey there.
Are the API EQ's 550, 550A, 560 and 554 gyrator based, and not inductor based?

cheers,
hejsan
 
I'm looking at the schematics for the API 554, 550 and 550A EQ's, and don't spot any inductors..

Is the 553 the only api eq that used inductors?

Can someone explain really quick the difference between 550, 550A and 554 feature and function wise please?

Thanks,
hejsan
 
[quote author="hejsan"]
Can someone explain really quick the difference between 550, 550A and 554 feature and function wise please?
[/quote]

The 550 was the older of the two. The 550A has overlapping frequencies, the 550 does not. The 550A I have has the silver/blue anodized knob theme that the stuff still has. The 550's that I have and have ever seen use a similar dual concentric knob with a colored insert, both are silver. You also tend to find different generation opamps in the 550A compared to the 550's, either that, or thats just been my luck at the very least. I would love to know what year they switched over to the A as it seems like the 550 was manufactured over a course of a shorter window compared to the 550A.

I may be completely off the mark but I really want to remember having seen a 560 graphic EQ from the 70's that used inductors not chips. Maybe it had a different model number that I cant think of but Im pretty sure I saw api graphics with inductors for each band.

dave
 
[quote author="soundguy"][quote author="hejsan"]
Can someone explain really quick the difference between 550, 550A and 554 feature and function wise please?
[/quote]

The 550A I have has the silver/blue anodized knob theme that the stuff still has. The 550's that I have and have ever seen use a similar dual concentric knob with a colored insert, both are silver.

dave[/quote]

I've seen original 550As with both kinds of knobs.

Man, do I love these eqs. Nothing sounds better on a drum crush buss.

But the 560s are pretty great for drums as well. So are the Sphere graphics!

If the right inductors could be sourced, those would be easy to diy.
 
Here's some cut and paste from another forum:

Search Result 40From: Paul Wolff ([email protected])
Subject: The secret 560 story... View: Complete Thread (2 articles)
Original FormatNewsgroups: rec.audio.pro
Date: 1999/04/05

OK, Here is the story, once and for all...(but don't wait to buy any,
they are still a ways off)

The 560 was made by API while in NY.
It had some coupling caps, 4558 opamps, and one inverting 2520 with
xformer. The pots were linear and had a dead spot in the middle for "true zero". It was designed to replace the APSI switchable graphic eq that sounded like shit. (but good for guitars...no matter where you set the bands the guitar sounds like its all the way up)

API closes shop. Studio Consultants in NY want to keep it alive, but
cannot get 2520's so they hire Al Davis to design a new one without a 2520 and DC coupled (no caps) OOh AAh B.F.D...Dataronix gets API stuff and continues the design with Al. The 560A is released without 2520 and the transformer is an option (****ing hell). I buy API from Datatronix and sell the last 28 original 560's to Shelly at A&M, then next make the transformer standard on the dreaded 560A, then get rid of the piss-amp with a 2520 and call it the 560B.

There it has sat, DC coupled and all. The pots are linear, but with no
center dead spot. They don't jump when slid, which many think "the old ones seemed to do more", but not true. They are more gradual. Circuit is the same except for the caps and a couple of other senseless changes that Jeff and I are just now getting around to changing back. There is not much to change, and I hope nobody thinks that they will see the lord with the re-issue comes out. The tests show very little difference. The big problem is better parts now days. They sound different than the old ones.

Next week, maybe I'll tell the story of the 550A-1...

Paul
 
And another:

From: Al Davis ([email protected])
Date: 2002-08-04 22:09:39 PST

I don't normally read this group, but this thread caught my eye, and I
did some snooping in the archives. I figured I would leak a few more
API secrets.

I am responsible for a few API products, pre-Datatronix, including the
original 560.

In the comments on eq's there was mention of "proportional-Q" and
"fixed-Q" designs, in reference to the variants of the 550. It was also stated (more than once) that the 550A-1 is essentially 3 bands of the 560. This is not true. The 550A-1 is fixed-Q. The 560 is proportional-Q. The 560's Q actually varies more than the original 550 does. The 550A-1 design is really more like the 554, but with significantly lower Q, and single op-amp filters instead of 3 op-amp filters. Also, the 550A-1 has first order shelving, contrast to the 554's second order shelving.

Most graphics have some ripple in the response when you boost or cut.
This is because the Q is too high. Although it was not specified, I considered it to be a requirement that at most reasonable settings there would be no ripple. The idea is that if you boost two adjacent bands you get a single hump, not two. You can boost a band and use the adjacent ones to broaden it. If you really want peaking, use a parametric where you can tune the frequency.

Another factor is that with any tuned circuit, if the Q is sufficiently high, there is ringing. The higher the Q, the longer it takes for the ringing to damp out. If the Q is low enough, it is really more like a pair of RC circuits, and there is no ringing. The 560 is designed so that unless the setting is full boost or cut, the Q is low enough to not get ringing.

The 560A was not intended to be an API product. It ended up being one
because of the way Datatronix got into the scene. It began during the
period between when the original API went bust and the acquisition by
Datatronix. That one was my design, too. Ideally, it would have been
the same, but there were some key parts that were not available. The
change from the 2520 is well known. The reason for that change is
simply that the company that made them went bust.

There is another change that I have never seen mentioned, that is more
important than it might seem at first. Both the 560 and 560A use
special S-taper controls. The resistance curve has an "S" shape. It
is symmetric but is steeper in the middle, and relatively slow at the
ends. If it used linear pots, the control would be all scrunched toward the ends. The use of the S taper also allowed a higher resistance, resulting in lower noise and the "proportional-Q". The 560 used Alps pots. The 560A used Noble pots. The Alps pots were not available in the small quantities we needed. The taper is a little different, but the same at the calibration points. The Alps taper really looks like an "S". It is all curved. The Noble taper looks more like piecewise linear with rounded corners. This was not a conscious decision, and was considered to be a negative at the time, but we really didn't have a choice. It points out an issue that is often overlooked in products like EQ's ... A production change beyond the control of anyone who should know can significantly affect the sound.

Now, back again to the fact that it was not intended to be an API product ... Since it was unknown what would happen to API, and we didn't own the design, we could not just use the same design. This meant doing it over without access to the original drawings. Even though the goals were the same, and they use essentially the same topology, this makes for some subtle differences. One of these is that the Q in the 560A is a little lower than the 560. Also, it varies a little more, or in other words it is a little more proportional.

In the actual business deal, I was not "hired to do it" but rather it was a joint venture between me and Studio Consultants, where we split the profits and risk.

Now, back to the 550A-1 ... I wanted to call it something else, maybe 551, because it obvious to me that nothing could really replace the 550A. It should be marketed as a lower cost alternative. The original design was incredibly expensive to produce, and a significant money loser. Something had to be done. The final reason for not calling it something else was that they had a huge stock of front panels that said 550A.

API did not have good listening facilities, and the people we sent the
prototype to really liked it, so the problems slipped by. I became aware of it during the dead period between the bust and Datatronix, and made a modification to the design that would make it proportional-Q without raising the cost. Datatronix wasn't interested, and they continued to make the fixed-Q design. Most of them were made after they were aware of the problem and the fix they didn't use.

The 550A-1 design used filters in the feedforward or feedback path, with a summing node, giving a fixed-Q design.

The 560 (and 560A) uses a completely different gyrator based design. The "filter" simulates a series R-L-C circuit. When the pot is near the middle, its resistance is in series with the gyrator's R-L-C, lowering the Q. It was actually designed as an LC equalizer, then an active circuit was substituted for the L.
 
;D SORRY FOR MY ENGLISH !
OK ,
the propotional - q topologi  for API audio prod writed in note 122 from : www.rane.com
this eq's used a AKTIVE  FILTER TECHNIK WITH BRIDGED-T RC SECTION !!!!!!!
I DONT UNDERSTAND - where EQ used a gyrator-rlc topol. as writed befor (api 560 ???)  and where used a bridged-t - rc (without L as gyrator or original ) ???????????? 
because al davis write about gyrator lc and rane about bridged rc !!!
eeeeh ??? what is wrong ??? 

 
I have drawings for API's 560, 560A/AT, and 560B graphic eq's.  I just sent them to the groupdiy gmail account.

If someone makes pcb's, please remember me!!  ;) ;D

JC

(BTW - all of them are gyrator based -- none have inductors).
 
Thanks  :)  :)  ;)

I wont make a Para EQ with proportional Q
I wont make a PCBs  with my changes :  I wont to implemet a Dual Poti with created "S" Curve funktion , i wont use a Discret Input and Output Stage like a api 2520 but with expensive (sorry) Millitäry fast and temp. stable Transistor and listen to SOUND !!!
And after .... wont to implement a DC Servo with OPA604 like a MASSENBURG 8200 EQ !
CAN YOU HELP ME ? i dont have a shem...c!
 
rascalseven said:
I have drawings for API's 560, 560A/AT, and 560B graphic eq's.  I just sent them to the groupdiy gmail account.

If someone makes pcb's, please remember me!!  ;) ;D

JC

Cool ! I have got a different schematic than the three that you posted.  (!?!?).

Anyhow, I still have to build the second channel, but here's my 560 type eq :
The perfboard is the line amp of the 560, the actual inductorcircuit from the original unit (a soundtech ST15) is built the same way as the 560. With the main difference that the Soundtech has got 15 bands instead of 10. The outputtranny used is a lundahl (the API2503 wouldn't fit in the box).

front.jpg

overview.jpg

pcboverview.jpg


Oh, the DOA is a GAR2520. I still want to upgrade the PSU part (higher voltage), but I'd better build the second line amp first, hahaha.
(Just one of the many projects that are going on right now)
 
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