MEQ stylee thingy finished

[jensenmann]

Here´s my latest built, a stereo MEQ filterboard with a Lawo V972 ampstage.
Big thanks (as always) to nrgrecording for the filterboard, kubi and silent:arts for mental support (and argueing about crossposting :wink: ), Matze+Olli+Tobias+Dimi at Lawo, Squib for informations about MCI iron and all the others here around for support and inspiration.

bigger photos are here: http://www.twin-x.com/groupdiy/displayimage.php?album=257&pos=4


btw, never call me to photograph your wedding. You would regret it.[/img]

 

[radiance]

Cool! Where did you inserted the EQ stage within the Lawo? What are the MCI trannies for?

 

[jensenmann]

I did not insert the filter. The MCI iron is the input iron, then the filter follows. From there it goes through the Lawo card with it´s input iron. Don´t ask me what the benefit is. I did it that way simply for lazyness because I didn´t want to cut traces.

Meanwhile I measured the frequecy response. It´s -3dB at 20Hz (-12dBFS output from my soundcard) and linear until the the soundcard filter sets in. But I removed one of the lowpass filtercaps on the Lawo card (the smaller one with 330pF).

 

[keefaz]

Great build, I like your style :thumb:

Is it the stancor 4:1 MCI line input iron ?

 

[ioaudio]

jens,

did you use the "stock" values for the caps from jakobs schematics?
could you make filter sweeps for high and lowband?

-max

(me working on meq500 found out other cap values see updated schematics: http://twin-x.com/groupdiy/albums/userpics/meq5_updated_2008%7E0.jpg )

 

[jensenmann]

[quote author="keefaz"]Great build, I like your style :thumb:

Is it the stancor 4:1 MCI line input iron ?[/quote]

no, it´s the 1:1 MCI output iron

 

[jensenmann]

[quote author="ioaudio"]jens,

did you use the "stock" values for the caps from jakobs schematics?
could you make filter sweeps for high and lowband?

-max

(me working on meq500 found out other cap values see updated schematics: http://twin-x.com/groupdiy/albums/userpics/meq5_updated_2008%7E0.jpg )[/quote]

yes, the stock values. I´m afraid I have no software to do filtersweeps and record the result. Let me check if I can do it with the scope and take some pictures of the screen. Since I´m busy the next few days I won´t find time before sunday to do it.

 

[12afael]

good work Jens, check this software for the freq plot work great and it is free.

http://www.sillanumsoft.com/

cheers

Rafael

 

[jensenmann]

thanks for the link, Rafael. Unfortunately I have a G4 Mac which is not supported

 

[bernbrue]

Nice built, Jens, as always!! Yellow chickenheads, uh la la :green: :thumb: :thumb:
regards
Bernd

 

[[silent:arts]]

Jens, you can send it to me for some measurements.

but if I like it you have to build another one :green: :green: :green:

 

[jensenmann]

I´m already building anotherone. You can´t have enough projects on the bench :grin:

 

[chriss]

Jens, how is the frontpanel done? silkscreened? looks good.
And congrats to the project! I'm curious how many more you will be able to finish in this life :green:

Chris

 

[jensenmann]

The case is from Purusha. FP is silkscreened.
Well I hope I´m done with these 4 channels of MEQs. The next new EQ project box I´m going to open will be the API553. I already did a bunch of 990s and I can hear Melcor PCBs calling me :grin: This will probably be breadboard style as this is a low parts# thingy.

 

[matthias]

very nice work, Jens !!

all thumbs up ! :thumb: :thumb:

 

[Kid Squid]

Lovely stuff Jens !

Very Nice indeedee :thumb:

Steve

 

[syn]

Very very nice.
Love Stancor iron, whish i have more of it.

 

[jensenmann]

I did some new measurements now with better equipment than soundcard + console meters :wink:

The frequency response with all filters to zero is 0dB @ 10Hz (! remember 3 tranies in the signal path), -0,8dB @ 20kHz, -1,6dB @ 30kHz
measured at 0dBv. I think I will tweak the onboard filter of the Lawoamps again.

Maximum boost/cut ratings:

Lowboost section:
200Hz: +8,4dB @ 190Hz
300Hz: +8,2dB @ 350Hz
500Hz: +7,8dB @ 820Hz (!)
700Hz: +8dB @ 700Hz
1kHz: +8,1dB @ 1kHz

Midcut section:
300Hz: -9,9dB @ 280Hz
700Hz: -9,3dB @ 780Hz
1,5kHz: - 9,1dB @ 1,6kHz
3kHz: -8dB @ 3,5kHz
5kHz: -5,3dB @ 7,6kHz
7kHz: -4,5dB @10kHz

Hi Boost:
1,5kHz: +8,1dB @1,5kHz
2kHz: +7,4dB @ 2,2kHz
3kHz: +6,2dB @ 3,8kHz
4kHz: +4,9dB @ 5,3kHz
5kHz: +3,5dB @ 7,8kHz

all capvalues are taken from Jakobs schematic, inductors are from ioaudio

Then I tried to draw some filter curves on logarithmic paper but that was a hell of work. Didn´t do that since 20 years. I finally gave up after two curves because barbecue started :green:

All frequencies sound pretty useful. The high deviation in the 500Hz lowboost band will be investigated further. It´s a pitty that there´s not more than a few dBs boost available in the highest frequencies. I wish there'd be more possible.

 

[ioaudio]

try this changes for frequencies
i used this for my meq500 prototype [scroll down]
you can calculate the cap´s values
http://www.pronine.ca/lcf.htm

i do not understand the limitations with the high boost - purusha had the same problem

-max

 

[jensenmann]

after a quick listeningtest with ioaudios capvalues I´m really satisfied. What I hear correlates with the frequencies on the frontpanel.
Thanks a lot, Max. I owe you a :guinness: