Studer 169 EQ in API 500 format

[tmmmmm]

Here you go.

Highly appreciated - thank you!

 

[PatchDog]

Perhaps a silly question, but Is there any advantage to using the dual gang pots here for Lo,Hi,Mid gain? As it's been pointed out earlier in the thread you can use single gang pots for these @ 5k lin / 5k lin / 22k lin which would be cheaper to source. Perhaps they were chosen to give more sturdiness to the PCB/panel connection? Or am I missing something?

 

[DarkSky]

Perhaps they were chosen to give more sturdiness to the PCB/panel connection?

That's my assumption --- and seems to be the case in a number of other designs as well.

Depending on the pots used, there would probably be cheaper options to achieve the same thing (though not necessarily easier to implement...).

 

[dmp]

I think finding P4 was the challenging one, and the others were sourced with the same footprint

Potentiometers are 16mm Omegs (to keep the costs down):
P1 = 2x 22K LIN center detent (order code OM-01-023)
P2, P3 = 2x 10K LIN center detent (order code OM-01-005)
P4 = 2x 100K REV LOG (order code OM-01-059)

 

[dmp]

I have all the docs saved but I think they've been posted in the thread before. Maybe they could be attached to the first post?

 

[DarkSky]

I have all the docs saved but I think they've been posted in the thread before. Maybe they could be attached to the first post?

Thanks for the pointer. Found them at post #573!

I agree that some kind of pointer or addendum/attachment in the first post (or at least on the first page) would be handy.

Or alternatively, perhaps the links in the first post could sinply be updated to point to the corresponding imagearchive.com document locations that MonoCutter used at post 573.

 

[dmp]

External links have really been a problem for forums like this. I'd rather put them in the first post or the technical documents section versus refer to another archive . Maybe shoot the mods an email and ask what is possible?

 

[ip_dalie]

Yeah, reach out to Frank.

I did silver with blue.

Hi Ricardus. How you doing?

I'm about to design my front panel, I just wondered what is the size of your switch cap? (two pairs on the right), they look smaller than the pair on the left.

The pair on the left is the original design, isn't it? I'm struggling a bit to find that switch cap (the 10mm original Audiox's front panel design).

Cheers

Ip

 

[Ricardus]

Hi Ricardus. How you doing?

I'm about to design my front panel, I just wondered what is the size of your switch cap? (two pairs on the right), they look smaller than the pair on the left.

The pair on the left is the original design, isn't it? I'm struggling a bit to find that switch cap (the 10mm original Audiox's front panel design).

Cheers

Ip

I'll need to look some stuff up, so hit me back here so I see an alert to remind me.

 

[PatchDog]

Can I use a 20k linear pot for P1 (Low Gain) instead of a 22k?

Would it be correct to say the mid point (zero gain point) will be shifted? I assume 11k of resistance will be the center point, and on a 20k pot the center point would be 10k.

Then also I assume I'll be losing a bit of dB gain at the upper end? which would be fine as I don't ever push them anywhere near that far.

I'm asking because I'd like to mod my unit to have detented gain pots and cannot find anything for P1 (But I can find a 20k)



Appreciate any help

 

[DarkSky]

Can I use a 20k linear pot for P1 (Low Gain) instead of a 22k?

Would it be correct to say the mid point (zero gain point) will be shifted? I assume 11k of resistance will be the center point, and on a 20k pot the center point would be 10k.

Then also I assume I'll be losing a bit of dB gain at the upper end? which would be fine as I don't ever push them anywhere near that far.

I'm asking because I'd like to mod my unit to have detented gain pots and cannot find anything for P1 (But I can find a 20k)



Appreciate any help

I'm out on a limb here, as I've not worked on a 169, so I'm answering from theory rather than experience. However, assuming both ends of the pot are tied into the circuit, the mid-point will be determined by the ratio of the resistance between pin2 & pin3 to the resistance between pin2 & pin1 - hence I'd expect the mid-point to still be zero gain regardless of whether you use a 20k or 22k pot.

That aside, the difference between 20k and 22k is ~10% - whereas the tolerance of many pots (including Alps, Bourns etc) is in the 10-20% range. So what you're proposing is likely no more radical a departure than could occur in the normal course of component variation.

In the unlikely event that the circuit does not respond well to the reduced pot value, a 1k resistor tied at either end (i.e. off pins 1 and 3 of the pot) would be an option (though it would slightly reduce the available adjustment range in both directions). I doubt you'll find a need to do that, though.

 

[PatchDog]

Thank you @DarkSky appreciate the explanation.

In the end I went ahead and ordered. it's an Alps pot rated at 20% tolerance, so hopefully will do the job. Not sure if you're going off general theory or seeing the schematic but the Low Gain pot seems to work in conjunction with the High Gain, hopefully the small resistance change won't affect that. If so like you say I'll try the 1k resistor mod.

 

[DarkSky]

Thank you @DarkSky appreciate the explanation.

In the end I went ahead and ordered. it's an Alps pot rated at 20% tolerance, so hopefully will do the job. Not sure if you're going off general theory or seeing the schematic but the Low Gain pot seems to work in conjunction with the High Gain, hopefully the small resistance change won't affect that. If so like you say I'll try the 1k resistor mod.
View attachment 125747

The low gain pot is already given some separation by the resistors R6 and R7. So, in the event you find that using a 20k pot for P1 causes some unexpected and unwanted interaction between the HI and LO paths (which I think is unlikely), the best first step IMO would be to adjust (slightly increase) the values of R6 and R7.

You could even install 5k trimpots in the R6 and R7 positions and use them to 'tune' the interaction between high and low. But I wouldn't suggest going that far unless/until you conclude it's needed.

 

[PatchDog]

Cheers @DarkSky, as you suspected all went well, no mods required.

Everything's tracking very well and the detented gain pots are a massive improvement as I tend to use these in stereo most of the time.

Guess it's time to add some pics to the thread then. The panels still only have the drill guide on there, will finish them off later.

 

[mooksnook]

Cheers @DarkSky, as you suspected all went well, no mods required.

Everything's tracking very well and the detented gain pots are a massive improvement as I tend to use these in stereo most of the time.

Guess it's time to add some pics to the thread then. The panels still only have the drill guide on there, will finish them off later.

View attachment 125841View attachment 125842Does your wiring work for the freqs? Audiox explained it differentlyearlier. I'm having trouble understanding how to wire the freqs even though it's already in this forum.

 

[PatchDog]

@mooksnook do you mean for the frequency toggle switches? Yes they all work great. I used this wiring:

 

[mooksnook]

@mooksnook do you mean for the frequency toggle switches? Yes they all work great. I used this wiring: View attachment 128726

That's what confused me since Audiox said it didn't work but it's because of the change of the capacitor at C4 in the diagram right? You kept C4, C5 and C6 as stock version right? Sorry noob questions..
Lastly, are you using double pole switches for both? If not is the black little square thing of the low switch anything to think about?
Thank you for helping a noob like me

 

[PatchDog]

I just wired it exactly that diagram from Audiox. I think it's 47n & 10 n (caps on the right). It works great. Yes I used DPDT (On - Off - On) for both switches. The black little square is just a female header (3x3 pin) that plugs onto the pins of the switch, So I can removed the switch or front panel more easily. I was supposed to do it on the upper switch too but I just got lazy.

If you plan doing 2x units for stereo I highly advise going for the detented pots for all the gains. Man it's made such a difference, much more precise for matching, so glad I put those in.

Also make sure to get Sub-Minature switches, it's a tight fit with that layout.

 

[mooksnook]

Hey DIY friends! I'm a bit new to DIY without instructions and so on. With that said, I bought an LED holder/LED with built in resistor.

Is there a way to connect it to this F2UEE switch? The other threads were a bit fuzzy answering this question.

The unit works flawlessly other than that.

Thank you!
Mike

 

[Bobby Baird]

No that switch does not carry power to light the LED it is for switching the eq out of circuit.