Highly appreciated - thank you!
Studer 169 EQ in API 500 format
- Thread starter audiox
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Help Support GroupDIY Audio Forum:
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?
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DarkSky
Well-known member
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
Well-known member
I think finding P4 was the challenging one, and the others were sourced with the same footprint
dmp
Well-known member
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
Well-known member
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
Well-known member
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
Well-known member
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
WILL SOLDER FOR FOOD
I'll need to look some stuff up, so hit me back here so I see an alert to remind me.
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
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
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DarkSky
Well-known member
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.
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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.
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
Well-known member
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.
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.
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.
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