Studer 169 EQ in API 500 format

[Siegfried Meier]

I found a document online that states 10k and 10n respectively for R1 and C1...however, I did that and still no sound.  I get what sounds like a sinewave synth when I boost the midrange frequency and sweep it, which in the past has been an indication of a missing resistor for me. 

Any thoughts much appreciated...

Thanks!
Sig

 

[Gustav]

I found a document online that states 10k and 10n respectively for R1 and C1...however, I did that and still no sound.  I get what sounds like a sinewave synth when I boost the midrange frequency and sweep it, which in the past has been an indication of a missing resistor for me. 

Any thoughts much appreciated...

Thanks!
Sig

Hi Siegfried.

Answered your mail, will answer here as well.

I will do my best, but I dont think I am the most qualified person to get this sorted.

Did you check the overlays on page one? And which "version" are you building (transformerless? DOA?)

Gustav

 

[rmaier]

I'm even less qualified, so  take anything  I say with more than a grain of salt..,
There are lots of jumpers that need to be connected. Could you have missed one? The ones on my build on page 11 are pretty easy to spot - might help to have a peek?
Ralph

 

[Siegfried Meier]

I'm using the Neutrik transformer.  I'm nearly 100% positive I have all the links connected...

Are my C1 and R1 values correct from that document I found?  Not sure what else to check...?

 

[rmaier]

Not according to the schematic on page 1. C1 is 47p, R1 is 20k.  You're using another schematic?
Ralph

Edit: Weird... the layout diagram implies that C1and R1 are left unpopulated, but the schematic says otherwise.  I'm confused now, too.

 

[Gustav]

I'm using the Neutrik transformer.  I'm nearly 100% positive I have all the links connected...

Are my C1 and R1 values correct from that document I found?  Not sure what else to check...?

C1 and R1 should be omitted for the trafo balanced input version.

I dont think I ever looked at the schematic when I built mine. I just followed this blindly. So it should work.

https://drive.google.com/file/d/0B_XBYPfmG8pVMmRhZmNkZWEtMjU2ZS00YmI1LWFjNTYtY2ExY2Y4NDFjY2Vh/view?ddrp=1&hl=en

Gustav

 

[Siegfried Meier]

Ok, I will leave those values out then.

Still not sure why it's not working… I will check the opamps, but I did test them and they work in a VP28…I figured I'd get some sound at least, but it's literally nothing when I push in the bypass switch.  Works fine in bypass.

 

[audiox]

The standard version with active balanced input:

Schematic (see the layout drawings for the input section component values)
http://docs.google.com/fileview?id=0B_XBYPfmG8pVZGViZTg4YmQtMDM0Yi00M2IzLTkwYTYtOWE4Zjg2YTk0MDE3&hl=en

Layout with components values (active balanced input)
http://docs.google.com/fileview?id=0B_XBYPfmG8pVNzM2OGQxMDEtZGM4MS00ZjYwLThlYjEtNWYzNzE1NGQyNTlk&hl=en

Modifications required for the transformer option are shown only in this layout drawing:

Layout with components values (transformer balanced input)
http://docs.google.com/fileview?id=0B_XBYPfmG8pVMmRhZmNkZWEtMjU2ZS00YmI1LWFjNTYtY2ExY2Y4NDFjY2Vh&hl=en

The transformer modification adds proper loading for the transformer and replaces the differential input stage with a voltage follower.

 

[Siegfried Meier]

Ya, I followed that drawing to populate my boards.  Besides the opamp perhaps being a problem, I'm not sure what else to look at.  I'll send a pic of my boards. I did leave the opamp under the DOA out, as I'm using a DOA.  I understand these aren't necessary.

Thanks,
Sig

 

[Trench Recordings]

U1 and U4 opamps are needed even with DOA...

Do not put in U2 and U3

 

[Siegfried Meier]

I assume U1 and U4 are the ones shown in this pic, and U2 and U3 are the ones under the DOA, correct?  If so, then that's exactly what I have.

http://audiofor.tv/diy/ProjectFotoFolder/169/rear.jpg

 

[Trench Recordings]

Hmmm... Well maybe the links underneath the DOA ? I'm just guessing

Here some pics of mine I'm working on. It tested and working

https://www.dropbox.com/sh/bvr8j4k5j87qksx/AACG6NnUroAbU_PRClv_nRora?dl=0

 

[Siegfried Meier]

Mine doesn't look all that different...I tried it today with a pair of 5534's instead of the 2520 DOA, still no sound at all when engaged...

The link beside DOA #2 has been made underneath, in case you're wondering.

 

[Gustav]

I may be way off here, since it seems too obvious (my fresh eyes may have spotted it, while you have been staring yourself blind)

Theres a jumper missing next to the opamp on the input. Without this link, you never complete the audio path, as far as I can tell.

I tried tracing the schematic with board in hand, and if I am not mistaken, you are making the missing connection through  C1/R1 when you place them, which is why that gave some weird signal through.

Its worth trying at least!?

Gustav

 

[Siegfried Meier]

Oh maaaa gawwwwddddddddd….

 

[Siegfried Meier]

You guys are amazing.  It works perfectly and sounds absolutely incredible, even with the 5534 chips instead of the 2520's…I have 3 extra trafos now, must build 3 more!!!

It is incredible that even when I looked at the picture I took on a large screen it became totally obvious where the missing link was, but I literally stared at the board for hours and saw nothing…

Thanks so much dudes!
Sig

 

[Harpo]

[image]http://www.siegfriedmeier.com/electronics/Studer%20169.JPG[/image]

Some cap values look like factor 1000 apart (FI 47pF (preferably c0g/np0) wanted, wima caps fitted look like maybe 47nF). Maybe only optical artifact or caps voltage rating withstanding lightning strikes for whatever silly reason.

 

[Siegfried Meier]

What knobs are you guys using on these?  I ordered the smaller shaft pots from Colin at Audio Maintenance, and I ordered shaft reducers from Jeff at CAPI but they don't fit together…I guess I should have paid more attention to my metric vs imperial…so unfortunately I can't  use my knobs that I had chosen.  Would love to know what other solutions there are out there.

Thanks guys!
Sig

 

[Siegfried Meier]

I found several vintage Trident knobs in my shop today that were supposed to be for an 80b EQ, but they fit the shaft sizes of Colin's pots perfectly.  I wasn't sure at first, but now I think the red knobs on the silver panel look absolutely killer!

 

[Trench Recordings]

Jealous.... Still trying to figure out knobs