saint gillis

Cheap Nice and Funky Amek 2500 preamps
« on: October 22, 2018, 07:39:34 PM »
  Hello, I made a quad Amek 2500 mic preamps rack, so here is the layout if some of you want to etch some single side PCBs :
http://sub-continental.com/diy_eng.html#amek


aviel

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #1 on: November 13, 2018, 09:11:37 AM »
Thanks! mind sharing the schematic you used as well as sound samples?

saint gillis

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #2 on: November 13, 2018, 03:01:47 PM »
Hello, you can find the schematic on gyraf website's for instance : http://www.gyraf.dk/schematics/Amek_2500_micamp.gif
And the output stage is published on the webpage.
I don't think I will put samples but t's a quite renowned preamp and you can find opinions about it if you make a search..

gyraf

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #3 on: November 14, 2018, 04:12:48 AM »
Very nice!!

We will need to know board dimensions in order to be sure to print it out to correct scale (more than 5% err makes it difficult to mount DIL ic's)

For sound examples, I think we got the 2500 for recording Steel Pulse's  "True Democracy" album: https://youtu.be/8nKLfruvxsE

Jakob E.
..note to self: don't let Harman run your company..

saint gillis

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #4 on: November 14, 2018, 07:31:23 AM »
The file on the website is at the true dimensions (106,93 x 57,4mm   /  300px/inch).
The drawing is quite basic, you can add a bit of blank space at the back or on the sides to add mounting holes. I think I added two mounting holes at the back, so the boards hold between them and the pots.

gyraf

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #5 on: November 14, 2018, 09:35:26 AM »
*like*
..note to self: don't let Harman run your company..

aviel

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #6 on: November 22, 2018, 03:02:59 PM »
awesome!
i really have to learn to etch on my own

saint gillis

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #7 on: March 31, 2019, 09:29:11 AM »
I was minding, between the two extremities of the gain pot, the offset is quite low (something like 4mV max) :
http://www.gyraf.dk/schematics/Amek_2500_micamp.gif

If we use a stepped gain switch, can we remove the coupling 2200ยต capacitor ?

gyraf

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #8 on: April 09, 2019, 03:34:23 AM »
There are two current sources Q11/Q12 that set DC operating points for the transistor arrays - and I think you'd prefer to keep their two DC points different.

But that's theorizing: Try it, and report back?

Jakob E.
..note to self: don't let Harman run your company..

saint gillis

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #9 on: April 09, 2019, 09:52:16 AM »
I worked on a preamp of the same topology , and I tried almost everything on my breadboard, unfortunately I didn't noted it all on a paper but I'm almost sure I tried the amek with or without gain cap and that it sounded the same...


gyraf

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #10 on: April 10, 2019, 03:24:04 AM »
Might very well be so.

Maybe the big cap allows for wider variations in the transistor parameters?

Jakob E.
..note to self: don't let Harman run your company..

saint gillis

Re: Cheap Nice and Funky Amek 2500 preamps
« Reply #11 on: April 10, 2019, 09:34:24 AM »
Maybe... also I'm not sure but I think there was still some few milivolts across the pot


 

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