Studer 169 EQ in API 500 format

[Gustav]

No DOAs. Just the four 5534s. But I accidentally hooked 16v to the DOA hole in the middle.

In that case, test the voltages on the circuit without the ICs inserted...

Gustav

 

[eriksunding]

Great! I new to this so what can I expect to find?

 

[eriksunding]

I'm still battling these. I've built two and both of them are acting up in the same way. I've even had a really experienced tech look at it and he can't figure it out. He said all the voltages are looking ok and signal is passing through.

What's happening is the frequencies being all messed up. All three are acting weird.

Bass filter: if I send a 10khz sinewave in to the eq I can boost or the signal a couple of db which seems weird.

High filter: same as bass filter but the other way around. I can boost or cut a 20hz sine wave a couple of db.

Mid filter: Barley boosting when set to 150hz but the higher frequencies I choose the more I can boost.

I can't figure it out and it all just seems weird. What have I missed? What can I check for? Busted caps? Resistors?

Help!

 

[eriksunding]

Anyone? Please..

 

[Gustav]

Anyone? Please..

Its really odd that a tech could not pinpoint any problems.

If voltages are good, then you may have something set up incorrectly for the DOA vs IC configuration.
...or maybe the pots are not right...

Gustav

 

[eriksunding]

Could it possibly be the extra LED that is causing this?

The pot are the right ones and I'm not using any DOAs just the ic.

 

[audiox]

Bass filter: if I send a 10khz sinewave in to the eq I can boost or the signal a couple of db which seems weird.

The low filter peaks at low frequencies, nominally 20 Hz.

High filter: same as bass filter but the other way around. I can boost or cut a 20hz sine wave a couple of db.

The high filter peaks at high frequencies, nominally 20 kHz.

Mid filter: Barley boosting when set to 150hz but the higher frequencies I choose the more I can boost.

The mid filter peaks at 150 Hz - 7 kHz, depending on the frequency knob setting.


The test signal should match the frequency you are modifying.

I've even had a really experienced tech look at it and he can't figure it out. He said all the voltages are looking ok and signal is passing through.

Maybe it works just fine.

 

[eriksunding]

It doesnt work fine unfortunately.
If I send a 150hz test tone in to the eq and set the eq to modify 150hz nothing happens. But if I leave the eq setting to modify 150hz buy change the test tone to 3khz it's boost A LOT more.
The bass filter boost equally much at 3.6khz as it does at 20hz. That's can't be right, can it?

 

[[silent:arts]]

Check the values of the frequency setting capacitors.

 

[eriksunding]

Which is that exactly?
I've check and rechecked all of them 10 times by now. But maybe I'll just swap them. Which ones are the frequency settings capacitors?

 

[eriksunding]

I believe I solved it.
The store sent me 6k8 resistors instead of 680k. Never bothered to double check them before inserting them.
I havent tried it out yet with the right resistors, but it makes sence.
Thanks guys for your help.

 

[eriksunding]

So I replaced the faulty valued  resistors and it now works and sound amazing!! (Surprise...  :)

Thanks Audiox and Gustav for a great eq!

Over and out.

 

[Siegfried Meier]

I'm brutally colorblind so I'm always forced to measure resistors first...it's probably a blessing in disguise.  ;D

So I replaced the faulty valued  resistors and it now works and sound amazing!! (Surprise...  :)

Thanks Audiox and Gustav for a great eq!

Over and out.

 

[kante1603]

I always check all parts that I'm able to check before assembly.....and I mean that.


Best,


Udo.

 

[peterc]

Learnt the hard way to check resistor values with a meter before insertion

Red and Orange can look very similar on some brands of resistors

Good to check the caps as well, gives an extra level of confidence to your builds

Peter

 

[eriksunding]

Can I expect a volume drop if I build this eq without the transformer?
As soon as I engage the EQ the level drops significantly.
If it’s not the lack of transformer, what might it be?

 

[eriksunding]

Hello again.
Would changing the two 20k resistors to 22k make a big difference. I didn’t have any (and still don’t) 20k resistors at the time, so I popped 22k in instead. Could this cause my big volume drop?

 

[Potato Cakes]

Do you have 10K resistors? If you do just use a pair of those in series to get to 20k.

Thanks!

Paul

 

[dustbro]

Took a quick peek at the new schematic. C3 and C7 polarity appear to be reversed from the original schematic. Mistake? or is the original wrong?

 

[Claudio]

Hello everybody,

I’m about to build a pair of the 169 EQ. Since the dual 100k rev log potentiometer (P4) is a bit hard to find (apart from ordering from AML), I was wondering if I could ‘simulate’ it with a combination of a dual lin pot and a resistor. I’ve read a few pages about it, but for the life of me I can’t figure out the correct math. Could anyone in the know help me out? Which values do I need for the linear pot and the resistor? Or would I need two resistors here for the dual gang pot? And how do I go about the correct wiring?

Sorry if this has been discussed before. It’s hard to find the answer to a specific question when you have to browse dozens of pages...

Thanks,
Claudio