Studer 169 EQ in API 500 format

[audiox]

I just breadboarded this circuit to try it out and see how it sounds before I go through the process of making a pcb.

I've noticed that the level with the eq switched in and all three boost/cuts at 0 is several dB higher than with the eq bypassed.  Has anyone else had this experience?  Any suggestions for trimming down the level?

It's a great sounding eq otherwise!

The input stage has gain of -6dB. The filter stages have unity gain when the controls are in the middle position. The output stage has gain of +6dB. Use this information to locate the source of error. Most likely wrong resistor value or wiring mistake, since we are talking about breadboarded circuit.

 

[boji]

Very comprehensive submission, thank you for your hard work in bringing this together for us!

 

[regularjohn]

The input stage has gain of -6dB. The filter stages have unity gain when the controls are in the middle position. The output stage has gain of +6dB. Use this information to locate the source of error. Most likely wrong resistor value or wiring mistake, since we are talking about breadboarded circuit.

Thanks so much for the info!  Time to fire up the scope!

I had a chance recently to play with a couple real 169 channels and the EQ was amazing, which was why I impatiently breadboarded the circuit instead of waiting for pcb's.  I actually combined your mastering version circuit and the 500 version circuit, so it's 3 bands and the hi and lo have six selectable frequencies each. 

 

[audiox]

I actually combined your mastering version circuit and the 500 version circuit, so it's 3 bands and the hi and lo have six selectable frequencies each. 

Please note that you can use the original PCB and still get selectable high and low frequencies. There are pads on the PCB for wiring external switch/capacitor assembly.

I have posted a layout drawing (earlier in this thread) how to fit two toggle switches in the original front panel. On-off-on toggle switches provide 3 selectable frequencies.

If you use double width front panel (two module spaces) there is plenty of space for rotary switches (up to 12 frequencies, in case someone needs so many).

 

[strangeandbouncy]

HI,


    just lashed my first one together, I am ignoring the mid band, and at the moment have it running with a 2520 'til I can find the silicon for the OA10's It is unbalanced in/out. I have 6 selectable frequencies at top and bottom. This is truly fantastic eq. Eventually I will have switches for gain, carnhill 10k input tranny, and 2503 1:2 output tranny. It is rocking now! I remember Audiox giving a warning about leads flying everywhere and oscillations/stability. No problems reported here, and I don't even have a front panel yet! (Looks a bit like my API lunchbox has been sick, throwing up a couple of switches and cables. Hmmm . . .)

 
    An absolutely massive thanks to Audiox and Gustav - you guys rule! ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D


    ANdyP

 

[[silent:arts]]

ANdyP, show us some pics

Audiox, what are the values for R24/25 & C27?
and should all other part values stay the same using the transformer option?

 

[strangeandbouncy]

Hi,


  I will send piccies later. No Bluetooth at studio. I have tried this out on a variety of sources. It is really really good eq! Acoustic gtr, kick drum, and esp lead vocal. I am mixing a track with part of the lead vocal from the demo. Slightly harsh and yet a tad dull sounding compared to the vocals I have recorded. This is so smooth and gentle, I can easily match 'em up. Yum!


  Gustav, you'd better stock up! As soon as the economy allows. i will be building some more. I will be doing a mastering version with switched steps for sure. Hope I can get some Lorlins into the 500 space, 'cos I'd like recallability on these puppies for sure!.Can't really afford anything smaller/sexier.


  Damn. Yet another eq i need in abundance . . . . .


    Kindest regards,


        ANdyP

 

[audiox]

Audiox, what are the values for R24/25 & C27? and should all other part values stay the same using the transformer option?

Layout drawing for those using the transformer option:

http://docs.google.com/fileview?id=0B_XBYPfmG8pVMmRhZmNkZWEtMjU2ZS00YmI1LWFjNTYtY2ExY2Y4NDFjY2Vh&hl=en

R4 (5.6k nominally) may need adjustment so that the overall gain of the input stage is exactly -6dB.

 

[strangeandbouncy]

Here it is!


  It is now stuck as it is 'til the mix comes off the board! It is on the lead vocal . . . Can't drill he holes 'til I can find someone with a vice to hold the front plate - Doh!


      ANdyP

 

[strangeandbouncy]

And again

 

[strangeandbouncy]

Couldn't find a vice, so I screwed the blank plates to  a lump of wood. Worked a treat!


  Now the proud owner of a working pair of these. My initial worries as to a 6dB loss have been assuaged. - Nothing to do with my build/everything to do with Digidesign 192's, and their inability to drive an un-balanced input. I am staggered, but there you go! In the end, I am running un-balanced in/ impedance balanced out, no mid eq, 6 switchable frequencies top and bottom, and I am using 2520. I am keen to try the OA10 boards that came with the boards, but haven't got the silicon yet. I have also tried it with a NE5524. It sounds amazing with this, but the top is just sweeter with the 2520, especially at max boost at 27kHz, a setting it will be virtually stuck on, i do believe . . . It sounded great with a 2503(4804) 1:2 make-up transformer to compensate for the digidesign design failure, but after much listening, I prefer it transformerless, which is fortunate 'cos I need them for something else, and they would be a bugger to mount on the board anyway.


  Gotta re-iterate, this is amazing eq! Where so many of our friendly neighbourhood eq's stamp there own Quality and Colour firmly on the subject, this is very very transparent. Just adding a dB or so in the bass is barely noticable on individual tracks in solo, that then leap out of the mix un-soloed. Not a replacement for the usual suspects, but a great bedfellow and companion.


    Audiox, you rock! - and Gustav, so do you!


      ANdyP

 

[Holger]

My version

I had to make some mods to use my pots with the front panel layout provided by audiox.
I've soldered some components on the back to get some additional space for the pots.

Some more pictures:

 

[[silent:arts]]

Holger Du Schuft ;D ;D ;D

I did the same "mod" with a trimmer to set unity gain.
transformer based input here.
transformer output in planing stage 8)

btw, someone else have problems with the way too large holes for the pins on the OA10 DOA PCB?

anyway Holger, nice & fast work - as always

 

[audiox]

btw, someone else have problems with the way too large holes for the pins on the OA10 DOA PCB?

In my OA10 Gerber tool file there was no specific value given, but a note "select according to the pin size". I told Gustav that he should ask Jsteiger what is the correct drill size for a pin which mates this socket:
http://classicapi.com/catalog/product_info.php?cPath=71_77&products_id=122

I did the same "mod" with a trimmer to set unity gain.

Did you measure the resistance value which provided the correct gain?

 

[[silent:arts]]

btw, someone else have problems with the way too large holes for the pins on the OA10 DOA PCB?

In my OA10 Gerber tool file there was no specific value given, but a note "select according to the pin size". I told Gustav that he should ask Jsteiger what is the correct drill size for a pin which mates this socket:
http://classicapi.com/catalog/product_info.php?cPath=71_77&products_id=122

drill size of the DOA pins are the same like the sockets now
the sockets fit fine btw

I did the same "mod" with a trimmer to set unity gain.

Did you measure the resistance value which provided the correct gain?

once I'm passing audio I will do the measuring, and post the result.

 

[Slenderchap]

P4 = 2x 100K REV LOG (order code OM-01-059)
http://www.audiomaintenance.com/acatalog/potentiometers_carbon_16mm_diameter_dual_gang.html

...That explains why I keep getting asked about the OM-01-059's.... they are a very slow seller (used for Trident 65?) that was only ever kept in small quantity.... so of course there are now none left.... I will get some more.... but currently lead time for these is about 6-8 weeks.....

Colin
www.audiomaintenance.com

 

[bobine]

The 16mm 100K pots (OM-01-059) were sold out when I ordered, but Colin pointed me to a 20mm pot (OM-01-072). I ordered a pair of these and modified them slightly to stand in until the proper size is available. With some snipping, filing, and bending you can get these larger pots near to the centerline and flush with the front plane.

Not knowing better, I also ordered some 16mm 47K and 470K pots. Can anyone predict how these might behave in the circuit if they were substituted? (I'm reluctant to solder and unsolder these too many times or I'd just try it.)

thanks to audiox and gustav for realizing this project. The EQ is gentle yet generous. Umm.

 

[bobine]

And this shows the amount of bending required to get front/back alignment.

 

[bobine]

and here is the working EQ (no trafo, no DOAs)

 

[strangeandbouncy]

Hi,


  just for shits and giggles, 'ere is my humble offering! I am almost ashamed next to Holger's BEAUTIFUL front panel layout! I haven't had time to cut the pot and switch shafts, or draw my panel BY HAND with a White Pen, and the top knobs will be replaced with the same size as the lower ones as soon as I can! I actually like the "anonimity" of my builds, and take great pride in people asking "what the hell is that?", then HEARING it . . . .


  I am in lerv with this eq!( but don't tell all the others in my possession, even though they aren't in any danger anyway!)


    ANdyP