API eq kits????

[gar381]

This one is based 99.9% on peterc's PCB but using Wilco Inductors and adding a third LF freq.

Using Cinemag Transformer and Melcor DOA
Front Panel Express front panel with Re'an collett knobs.

I still need to bend an L shaped bracket for holding the front panel
to the PCB like peter purpose uses on his 525.

I will be making more 553s when peterc has his PCB offering.  I'm
just not shure what Inductors i'll be using yet.  I have never tried
winding my own and may give it a try.  These are Wonderful EQs.

This guy sounds BIG, FAT and SMOOOOOOTH!! I Love it!!

GARY

 

[peter purpose]

V.nice Gary... :thumb:

 

[peterc]

Hi All

I have been fine tuning the design for this board, looking good.

Just to get an idea, how many would be interested in PCB's for this project?

I will start a thread in the Black Market, please let me know there.

http://www.groupdiy.com/index.php?topic=304534#304534

Peter

 

[codered]

[quote author="gar381"]something I'm working on..

based on peterc's 553 design but using opamp labs 87-1 and 87-2 inductors.
http://www.opamplabs.com/87.htm
LF and MF have 6 freqs each plus off and HF 2 freqs with center off.

More later when I get a chance to hear this guy... Looks great on my
scope.

GARY[/quote]

Gary,

Where did you purchase this 500 series type breadboard ?

thanks

 

[gar381]

This is standard 3662 (4.5" x 6.5" 22/44 .156pitch) vector plugboard.

You can get this at digikey, mouser and other large supply houses.

I cut it to 4.5" x 5 7/8" with a dremel cutting tool and left the center
15 pins to give 15/30 .156 pitch connector. :wink:

Then the FUN BEGINS!!! :thumb:

GARY

 

[codered]

Brilliant :thumb:

 

[jensenmann]

Could someone measure the DC resistance of the original 553 inductors for me, please? Or has this been done before and I missed it?

 

[gar381]

[quote author="jensenmann"]Could someone measure the DC resistance of the original 553 inductors for me, please? Or has this been done before and I missed it?[/quote]

Thanks for bringing this up Jens...would love to know the samething.

GARY

 

[peterc]

In one of the pics, I wrote down the DC resistance of the coils on top of the cores, the .1H ws 3 ohms & the 1H was 37 ohms (even though it says 3.7 in the pic, this was a mistake.)

I used .22 mm wire for the .1H & .15mm for the 1H

It would be very interesting to see the original specs.

Peter

 

[jensenmann]

Thanks, Peter. Good to have a housenumber at least. You said they sound nice?
Indeed, it would be interesting to see the original values. This would make the inductor choice less trial-and-error.

 

[gar381]

Thanks peter :thumb:

GARY

 

[peterc]

The 553 is the only piece of DIY gear where I have seen peoples' jaws drop when hearing the sound.

Lots of people have said "wow, that sounds great" or "definitely use that" but this was a "my ****" kind of reaction. The inductors really work well.

Peter

 

[Fredrik]

Peter, or anyone else who have tried to build this eq. What kind of pots did you use? Are Bourns log conductive plastic fine?

I also have some thoughts on the inductors. I never tried to wound an inductor myself, but I have found the RS core part that Peter used. Could this be pulled of even without an LCR meter?

 

[Fredrik]

What do you guys think, would it be possible to get some more gain out of the op amp in this circuit, and add an extra pot for gain past unity?

 

[gar381]

Use any 10k lin pot will work fine.
Don't use a log pot.

GARY

 

[Fredrik]

Ok, thanks Gary. What are the cap values used in the filter section? I have a hard time reading it from the schematic, other than the 3Khz cap which looks like 27µF.

Edit:

I did some calculations on the cap values. This is what I got, does it look right?

MF

3Khz 2,7nF
2,5Khz 3,9nF
2Khz 6,3nF

LF

150Hz 1µF
220Hz 0,5µF

HF

10Khz 370pF
12Khz 300pF

 

[gar381]

Fredric

Use this :

http://www.opamplabs.com/cfl.htm

BTW.. the low shelf is really a BELL centered about 23hz
(around 47uf)

check your dec. points. some of your values look off

GARY

 

[Fredrik]

I actually did use that calculator, but did some random rounding just to get a rough estimate.

I just used the frequencies on the schemo posted in this thread.