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General Discussions => The Lab => Topic started by: electrichild on August 19, 2008, 11:34:32 AM

Title: amek m2500 eq schematics...
Post by: electrichild on August 19, 2008, 11:34:32 AM
Hi,
I'm planning to make an EQ based on the amek m2500 eq section. On the schematics I find on the forum there aren't the original bell/shelf switches I would implement...Adding resistors and switches in the HF and LF path between R6/C5 and R45/C20 will affect the curve of Q pots?
Which values are right?
Respect
Electrichild

http://www.gyraf.dk/schematics/amek_m2500_eq.gif
Title: amek m2500 eq schematics...
Post by: jdbakker on August 19, 2008, 12:08:28 PM
Have you read this thread (http://www.groupdiy.com/index.php?topic=23120), and the older threads that its first post links to?

JDB.
Title: amek m2500 eq schematics...
Post by: electrichild on August 19, 2008, 12:56:36 PM
Quote from: "jdbakker"
Have you read this thread (http://www.groupdiy.com/index.php?topic=23120), and the older threads that its first post links to?

JDB.


Thanks for reply.
Yes I read all posts inherent but it's not clear which are the values of the resistors. I imagine 220k would be ok for HF and greater for LF.
Have anybody really realized a good working eq based on that schematic?
Title: amek m2500 eq schematics...
Post by: 12afael on August 19, 2008, 08:05:56 PM
the schematic from jakob site have the mods for the shef/bell sw.
http://www.gyraf.dk/schematics/amek_m2500_eq.gif

IIRC you must make a shortcircuit in R137 (one half of the 50 rev log) and add a 1M resistor between r144(pot) and R50.

I have some schematics for LTspice if you want to play :razz:

cheers
Rafael
Title: amek m2500 eq schematics...
Post by: electrichild on August 20, 2008, 02:47:22 AM
Quote from: "12afael"


I have some schematics for LTspice if you want to play :razz:



LTspice? What's?
Title: amek m2500 eq schematics...
Post by: jdbakker on August 20, 2008, 04:50:49 AM
Quote from: "12afael"
I have some schematics for LTspice if you want to play :razz:

I'd be interested!

Quote from: "electrichild"
LTspice? What's?

Linear Technology's free SPICE-based circuit simulator. you can download it from their site.

JDB.
Title: amek m2500 eq schematics...
Post by: electrichild on August 20, 2008, 05:55:54 AM
Very cool!
Title: amek m2500 eq schematics...
Post by: 12afael on August 21, 2008, 01:07:44 AM
here are the simulation files and some models needed for the simulation. the models IIRC were from the yahoo ltspice group.

http://www.twin-x.com/groupdiy/albums/userpics/amek2500_nemek_Harrisonfilter.zip

Enjoy :razz:

Rafael
Title: amek m2500 eq schematics...
Post by: electrichild on August 25, 2008, 07:57:47 AM
About decoupling caps for the amek m2500 circuit of this topic
http://www.gyraf.dk/schematics/amek_m2500_eq.gif
are C22-23 on schems 1uF 35V tantalum right?  
Can I change the C4 39NF cap (hard to find) with 4 X 10NF in parallel?
Any suggestions?
Thankz again
Title: amek m2500 eq schematics...
Post by: 12afael on August 25, 2008, 02:40:15 PM
tantalium or a small esr cap should do the work, 1uF film should work too.
I also put a small film cap in the power pins of each tl074.

39nF shouldn´t be so hard to find, but yes, you can use four 10nF in parallel.