Studer 169 EQ in API 500 format

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dmp

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fazeka said:
I am still getting noise when switching.
That doesn't sound right to me - seems you have DC on the output of the last opamp. Maybe try swapping the ICs and see if the problem goes away (U3 & U4). Or you could add a blocking cap but it would be better to just get opamps with the the output Vbias.

About the high frequency - these are pretty noticeable.  You might want to measure the frequency response (I posted some sweeps back on page 9). I'm guessing there is something wrong if you aren't hearing them, especially with the 12k & 16k. The stock 20k is very noticable because the HF boost is full at 20k but has a wide boost all the way into the high mids (~1k ~2k)
 

dmp

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What discrete opamp do you have for U3?  If it has a offset voltage that's could be the problem. Maybe stick a blocking cap in to test.

 

manulaudic

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I've gone through the thread and there was a mention as though only the mid pot needed to be dual and i traced back the pcb and indeed it seems like the others are working as single pots.

If there anybody that can confirm that it 's be possible to use single pots escept for the mid one?

Manu
 

manulaudic

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MikeClev said:
Mid frequency sweep (P4a and P4b) needs to be dual gang. The others can be single gang. If you look at the schematic, 'HI' (Dual 10k Linear) and 'MID' (Dual 10K Linear) are wired so each gang/track is in parallel, so Hi (P2A and B) is working like a 5k single track linear pot, Mid (P3A and B) is also like a 5k single track linear pot. Only one half of P1 is used so it is acting like a single track 22k linear pot. P4 is the only one that really takes advantage of both tracks fully.

Indeed i found this ! i'll go with that
Manu
 

Ricardus

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I really like what I've heard about this EQ so I'll be ordering some boards from Gustav and I'll start with building a pair. I already have questions, but I'll finish reading the thread before I ask.
 

Ricardus

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Finally got around to finishing my first pair of these. The delay was because I had to wait forever for pot-shaft adapters to arrive from Germany. Adapting the 4mm pots to the 1/4 inch knobs I wanted to use. Otherwise everything went great and I'm thrilled.
 

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dmp

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Ricardus said:
Finally got around to finishing my first pair of these. The delay was because I had to wait forever for pot-shaft adapters to arrive from Germany. Adapting the 4mm pots to the 1/4 inch knobs I wanted to use. Otherwise everything went great and I'm thrilled.

Those look sharp.
Nice job
 

Ricardus

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I got some more panels in to finish up some boards I've had finished for quite some time, and one of the EQs loses low end when engaged, and the low end shelf isn't working at all. The high shelf and mids work.

Any ideas where I should look?
 

Ricardus

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Solved it.

The solder pad for the + lead of the 100uF electrolytic must have lifted from the board and was making very weak contact going to each of the 220k resistors. Where there should have been 0 ohms resistance, each leg was measuring about 400K. I had to run 2 jumpers. EQ works perfectly now.
 

Ricardus

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Kevinkmny said:
Really love the clean front panels...where can I get some like that?

The panels came from Frank Rollen. I use him for all my panels. Great quality, great prices.

https://www.frontpanels.de/
 

Richard James

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Claudio said:
Hi Boris,

Perhaps my old Mouser cart will help you. It’s been a while since I built the Studer 169, so I don’t remember correctly if the cart is complete. Please doublecheck it with your documents and use at your own risk! I do remember though that I ordered some potentiometers from elsewhere. My 100k rev log is from Musikding: https://www.musikding.de/Alpha-Potentiometer-16mm-Stereo-100k-rev-log_1

Hope this helps anyway,
Claudio

Did you use the Alpha pots in your cart, and if so did they work with the standard front panel dimensions, or did you have to modify somewhere?
 

HerbertR

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Hi,
I ve also finished my second 169 EQ and a I really like this beasts. Super musically EQ, and especially the variable Midband is one of the best I ve ever heard. I am using the Sound Skulptor SK99 - Jensen 990 Opamps, I prefer them in the Units over all my others.
One Question: Is there a way to get rid of the Rumble/Pop Signal on the Audiosignal while pushing the 2PDT on or off? I think this is caused by the "make break before switch" function  or am I wrong? It is not a big issue for me but would be cool to get solved. Thanks for help. BR
 

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BGroen

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Hi guys,
I just want to double check something.
So the 2gang 100krlog pot is indeed hard to get. I did find this one on Mouser: part nr: 858-P092NFC25CR100K
Altough it is a 9mm pot, I think it will work. For P3 and P4 I found matching values in the same series.

But for P1 there is only 25k or 20k lin. (should be 22k lin)

So I thought I could put 2x 180k resistors in parallel with the 25k
Resulting in:
A to B: [0R, 11k69, 21k95 ] for [begin, center, end] positions
A to C: 21k95 (including 2x 180k and 1x 360k in parallel).

Please see attached sketch, and I will post the pot curve A to B in a next post.

To me it looks like a plan. Does anyone agree/disagree??

Plan B would be to use the 20k lin pot, with 2x 1k in series, and settle for a little less cut/boost for P1.

Kind regards,
Beinte Groen
 

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BGroen

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HerbertR said:
One Question: Is there a way to get rid of the Rumble/Pop Signal on the Audiosignal while pushing the 2PDT on or off? I think this is caused by the "make break before switch" function  or am I wrong? It is not a big issue for me but would be cool to get solved. Thanks for help. BR

I don't think so. An ON - OFF switch breaks the signal anyway. You would use make-before-break contacts in switches where the signal does continue along a path, for example stepped-attenuator.
 

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