Changing Gain Steps on PEV

[Gold]

I would like to change the gain steps on some Neumann PEV EQ's. I have done this with some Quad Eights via the hunt and peck method. It wasn't fun. I suppose I could use a pot to get the values but I would really like to know the math/theory behind it if possible.

The schematic which was partly redrawn, thanks Jakob, is here.
http://www.gyraf.dk/

 

[ijr]

Hello Paul,
No problem with midrange.
Just put some resistors.
Referring to schem, equalizer-pe 3-0800-930-50,
r3 1k8 is allways in circuit
r4.1 ~3k6
r4 1k5
r5.1 ~820
r5 510
r6.1 ~270
r6 160
r7 ~68
will give you more or less what you wait(sorry, ~vales shown approximately, too lazy to calculate them).
Putting higher cap instead of c1 0.1 uF, say, 0.047-0.068 will change frequency higher and lowering value to say 0.2uF will pull freq. down.
(from experience, 0.068 give you like 7k at switch's 5.6k pos.
and it is wery sweet.) BTW,Q will be different too.
Rearranging cap(c1) in series with inductor(dr3) will give you
fun eq kinda "boost everything except mid". True midcut mode allmost impossible without changing "charm" of this eq.
Changing steps on high and low shelves allmost impossible too.
You need rewound inductor same way with same wire and make
more taps.
Tried to do it on 60hz in one pev where some aggressive chemistry (probably coca-cola) reached inductor
I had healthy "brother" from same console for referrence, and
it was fun to experiment with it a bit.
Inductor was dead, and was rewound with same thickness wire,
folk who performed this operation told me it was pain and only
from 3rd time it was close to original to inductance and dcr.
After this, I listened one original pev from same console and
rewounded one. Of course, there was differenses in dcr and ind. like 3-5%
beetween inductors at same settings, sound was pretty close, but different in color a bit.
Best solution here... leave it as is for hi-lo shelves.
(sorry, my english...)
Cheers, Igor.

 

[Gold]

Thanks Igor. I think you may have misunderstood my question. I would like to change the GAIN steps not the frequency selection. In other words, instead of 2dB steps I would like 1dB steps. So instead of +2,4,6,8,10, I would like +1,2,3,4,5. I think I could substute a pot and find the values but I would like to know the math behind it if possible.

 

[ijr]

Hi Paul!
I understood your question well.

Simplest math beneath it is to take existing resistor's values and
use extrapolation. Passive eq step's calculation not allways give you
expected results, because inductors and apacitors are not ideal
(mathematically) parts. The best is the way as you did it -put potentiometer and measure.

"Re-stepping" will work for mid in this eq.
The problem in PEV is you allmost cannot do it with hi-lo shelves.
There's no switches with resistors here; you switch beetween inductor's
taps. Rewounding the inductor, you risk to loose some part of it's sound.
I love these eq's too, and just tried to share info I have.

btw, here's my stepped passive eq's inside pic
(for Pultecs, you can have as much steps as your swithes allows

http://img.photobucket.com/albums/v436/IJR/pul_inside.jpg

Cheers,
IJ.

 

[Gold]

[quote author="ijr"]
"Re-stepping" will work for mid in this eq.
The problem in PEV is you allmost cannot do it with hi-lo shelves.
There's no switches with resistors here; you switch beetween inductor's
taps. [/quote]

Ahh. Okay, I got it. Thanks for the help.

 

[Tbone2000]

Hi, would this also apply to the PEVc EQ?