DIY equalizer based on Studer 169 (standard and mastering)

[michal_k]

anybody thought about using a DOA instead of U1? That could sound cool(if it worked)

 

[emrr]

I find "tilt" type EQ's very useful.

My thought excatly, ive been looking for something like this.

Do most tilt-circuits simply join bass & treble controls in a CW & CCW fashion ?

Apart from having seen a tilt circuit in an old EW+WW magazine that did it otherwise as I seem to recall,
I can't recall any others.

Bye,

  Peter

RCA tilt circuit and plots from around 1950. 

http://www.groupdiy.com/index.php?topic=16210.0

 

[clintrubber]

FWIW... but before starting some hardware-project/veroboard-thing etc, it never hurts to check
if the basic function of something is what you indeed need...

... freeware plugins to the rescue 

http://kunz.corrupt.ch/?Products:VST_TAL-USE

OK, that's tilt, back to the original topic now.

 

[clintrubber]

RCA tilt circuit and plots from around 1950. 

I saw I didn't post those screengrabs back then...    8)

 

[Jeremy.Starseed]

I have 8 NTP "M 100 c Linear Amplifiers" as well as Jorgen Schou (JS) in and out transformers.

Might a four band eq be a reasonable use for them? I was thinking one OP amp per band, and make up gain if needed, from a separate piece.

I never tried making anything with OP amps, and the markings on these are fairly cryptic. I'm sure there is info on them somewhere though.

A worthwhile project, all in all?

Thankful for your thoughts and opinions,

Jeremy

 

[audiox]

Interesting since I have tested this eq also with NTP M-100 op-amp...

M-100 is relatively difficult op-amp to work with (requires carefull layout to be stable). So it is probably not optimal for your first project.

Depending on the input transformers you have (mic or line), I would consider building mic amplifiers.

http://www.gyraf.dk/schematics/NTP_M-100_datasheet_p1.jpg
http://www.gyraf.dk/schematics/NTP_M-100_datasheet_p2.jpg
http://www.gyraf.dk/schematics/NTP_M100_Schematics.pdf

 

[Jeremy.Starseed]

Line transformers, they are...at this point in time, I am careful to the point of not getting started But I do hear the advice. Too bad, it seems to me there is some nice sound to be had here.

What happened to your project using those amps? Success?

Thanks very much for those doc's

Jeremy

 

[audiox]

What happened to your project using those amps? Success?

The difference between NE5534 and M-100 was very small. It is easy to understand because the M-100 is known as a neutral sounding op-amp and the gain in that circuit was close to unity.

With higher gain (like in mic amp) sonic differencies are more likely. But in the mic amp case most of the "character" comes from the transformer(s) anyway.

 

[Jeremy.Starseed]

Oh, then this circuit/project which is discussed could be seen as a suitable use to put those M100's to, or not?

In any case I'll keep watching. I like the suggestions for a tilt function on the low and hi band btw.

Jeremy 

 

[Wonderlandaudio]

This EQ is basically an active Baxandall, with the tone stacks inserted in the feedback loop of the opamp. All the Baxandall theory assumes the high and lo bands are "far" enough, meaning the hi is hi enough and the lo is lo enough. If not the hi frec caps begin to interact with the los and viceversa, and the eq curve gets far from 2 shelves.

 

[strangeandbouncy]

Hi,

  i was just wondering why there are no blocking caps on the input or output? is there no DC from this circuit?


    Kindest regards,


      ANdyP

 

[Wonderlandaudio]

This EQ is basically an active Baxandall, with the tone stacks inserted in the feedback loop of the opamp. All the Baxandall theory assumes the high and lo bands are "far" enough, meaning the hi is hi enough and the lo is lo enough. If not the hi frec caps begin to interact with the los and viceversa, and the eq curve gets far from 2 shelves.

This is what I mean

Typical hi-lo shelving.
Now:

Unwanted peak in the middle.
And:

Nasty phase distortion...

 

[Ian]

Thanks for this info, this is some really cool stuff, I would love to build a mastering version of this EQ, are those PCB files still in the works? I have a couple studer 1:1 line transformers that would be perfect for this project!

 

[Gus]

Two things about the output stage.

R26 and R31 and R34 how balanced is this output stage?

R34 and R31 22 ohms?  Maybe 100 ohms or even higher as not to overdamp a transformer if after the EQ.

I think with the Duncan tone control sim program one could make a BMP type tone control a tilt.

 

[audiox]

I would love to build a mastering version of this EQ, are those PCB files still in the works?

The PCB files were ready at the time of the first post in this thread (in June?). I can publish copper layer pdf if there are home etchers who would like to make their own boards. Please let me know.

Gerber files are also available if someone wants to manufacture boards "in larger scale". Gustav?

 

[seavote]

i'd definitly like to get art work for home etch PCBs!
thanks

 

[audiox]

R26 and R31 and R34 how balanced is this output stage?
R34 and R31 22 ohms?  Maybe 100 ohms or even higher as not to overdamp a transformer if after the EQ.

R26 is inside the feedback loop, so it doesn't ruin the output balance. It was included mainly because of layout reasons. Replacing it with a wire link probably won't affect stability.

R31 and R34 are designed to be used without a transformer (electronically balanced output). But you can change the value if you are driving a transformer. I highly encourage to do your own modifications. Please post them here too.

 

[audiox]

This EQ is basically an active Baxandall, with the tone stacks inserted in the feedback loop of the opamp. All the Baxandall theory assumes the high and lo bands are "far" enough, meaning the hi is hi enough and the lo is lo enough. If not the hi frec caps begin to interact with the los and viceversa, and the eq curve gets far from 2 shelves.

That is very true. I missed your post in June. Sorry about the delay.

My original idea was to publish instructions how to select the frequencies to avoid the problem. It requires some calculations and I was too lazy to do them. But if you select the frequencies like in "normal" equalizers, it is unlikely that you face any problems. If you are trying something special, I recommend to do simulations first.

According to my simulations, "tilt control" works fine with this circuit but the frequencies must be selected very carefully.

 

[Davo]

Home etch pdf's would be very welcome.  Thanks Audiox!

 

[audiox]

i'd definitly like to get art work for home etch PCBs!

http://audioxxx.googlepages.com/EQ_169_STD_layout_designations.pdf
http://audioxxx.googlepages.com/EQ_169_STD_copper_mirror.pdf

I actually uploaded these in June but forgot to post the links...