EQP-1S5 - 500 series recreation of solid state EQP1A

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mitsos

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May 4, 2007
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EDIT After all these months we are almost there. Parts are trickling in, we hope to have everything by the end of the month.  Tthis will eventually become the help thread, I think, either that or I'll ask Ethan to delete it once I get the help thread up, cuz it will be unecessary. The original post is below here, please scroll down if you need it.

PRICING
See WM thread:
http://www.groupdiy.com/index.php?topic=46920.0

SHIPPING will be via USPS flat rate (we will try to ship each unit in it's own small box, it is the most economical way to do it for 1-2 units). If anyone decides to buy a ton, we'll probably do something as a special case. but for most people, this will be easiest/cheapest.  About $5 each for domestic and $15 for international. 

To PREORDER, please send an email to:
EQP1S5_preorder [at] analogallstars [dot] com  (fix address first, of course):

Full name
Forum Name
Order details (how many units)
Shipping Address
Paypal address



-----------Original Post below (slightly edited for conciseness)-----------------

Passive filter circuit is based on a pultec type filter, similar to the enhanced/ultra-enhanced and the gyraf DIY circuits.

Amp circuit is the exact one DrPat posted ages ago (it has resurfaced recently take a look around here) from his original solid state pultecs, which use a 2520 opamp. Here is a pair that sold on ebay for $5750:
30vos40.jpg


Parts:

Inductor: moly-permalloy  toroidal core, what the old books state is the ideal core or audio frequency inductors, and which is very likely the core the old guys used (Pultec, Lang, and other passive LCR EQs). Largely made obsolete by accountants due to high cost vs cheap pot cores.

Taps at: 19mH, 26mH, 39mH, 78mH, 155mH, 312mH.

Matched cores for (potentially) +/-1.5% matching between whole batch. No guarantees but it's what I'm shooting for.

Transformers: same lams as the HS56, same winding pattern/style, same wire. Simple and sweet.  Only part that was simplified is that we only pulled out the taps we need for this, so no 150Ohm or 62 Ohm taps available, for example.

Switches : grayhill shorting switches

Pots: Conductive plastic, metal shaft, mini mod-pot style.

Caps are Wima polypropylenes. I have paralleled caps in many places on the high boost, to get as close to the listed frequency as possible. 


PCB images: you'll notice parts are missing, like a couple of wimas, and the transformer brackets, for example.

(removed faceplate pic, cuz it no longer looks like that. We changed color scheme to brushed Al/ clear anodized, with black knobs, to go along with the original. It looks much better!  The internal pic is mostly the same, just cleaned up a bit.

16c3s60.jpg






EDIT: edited for (even more) clarity
 

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kepeb

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Norwich, UK
looks great
can you switch out/use regular ic's too?
any designs on a front panel yet or just aiming for the boards?
 

mitsos

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May 4, 2007
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Hey guys, thanks for the comments, (best comment so far goes to OKGB!)  ;D
I'm very excited about this little guy!

kepeb] can you switch out/use regular ic's too? [/quote] As it is said:
Will you be offering just the inductor as well? Really, REALLY interested in two of those....

Eventually, maybe. Not going to offer it per se, but depending how this goes, there may be leftovers (for example, if I have to buy 100 and only 80 EQs are ordered, then there would be 20 inductors left). No guarantees, as I'd like to focus on this, but keep your fingers crossed, you'll get first dibs cuz I know you love pultecs!

Thanks everyone!
 

mitsos

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May 4, 2007
Messages
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RE: the IC opamp.... Took a look at the layout, but I kinda decided not to put it directly on the main PCB...  It is possible but makes it necessary to route things in a non-optimal way.  I personally don't ever plan on using an IC opamp in this EQ, so I would prefer to not compromise a working design, or have to prototype. especially since I cannot possibly test every IC opamp.  

That said, what I could possibly do is throw in a little IC->2520 pinout adapter board. This would be better for me as I have been wanting one of those for some time...  

Also, here is the in-progress faceplate (missing Frequencies...)
thanks everyone!

2v9zywn.jpg
 

mitsos

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May 4, 2007
Messages
2,886
okgb said:
Looking Good , will you be able to offer faceplates as well ?
Yes, the idea is to do an "everything" kit on the essential stuff (package 1), and depending what most people want to do I can also get the caps as well as those other little things, leaving people with the huge task of courcing a few resistors, 2 relays and a LED.  I used all polypropylenes in mine, fillms where possible, metalized film for larger values.

I revised the first post cuz I think this wasn't really clear.

cheers!
 
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