I'm getting ready to repair an audio interface with failed pots - a T.C. Electronic StudioKonnekt 48.
These pots are the Rgain pots in the interface's four built-in INA217 based mic-pres.
So - here is my predicament:
The replacement pots basically have to fit the form factor of the original pots (there are a variety of reasons for this, not worth mentioning).
Anyway, here is a photo of the type of Pot (the image may be skewed):
The pot pictured above is the exact form factor with the correct shaft length, bushings, etc.
The problem is that the only pot resistance in this particular form factor that is actually available (more on this later) is 100k (believe me, I've looked high and low, far and wide), and the pot resistance the preamps need is more like 1k.
So, if I were to approximate a 1k pot by paralleling the wiper of this 100k pot with two resistors - like Pot A on the left in the image below:
would there be any concerns about excess noise being that the pot is actually 100k?
BTW, there is a direct replacement pot available from Full Compass but it's priced at $9 a pot, and I'd like to explore other options before I go that route.
These pots are the Rgain pots in the interface's four built-in INA217 based mic-pres.
So - here is my predicament:
The replacement pots basically have to fit the form factor of the original pots (there are a variety of reasons for this, not worth mentioning).
Anyway, here is a photo of the type of Pot (the image may be skewed):
An externally hosted image should be here but it was not working when we last tested it.
The pot pictured above is the exact form factor with the correct shaft length, bushings, etc.
The problem is that the only pot resistance in this particular form factor that is actually available (more on this later) is 100k (believe me, I've looked high and low, far and wide), and the pot resistance the preamps need is more like 1k.
So, if I were to approximate a 1k pot by paralleling the wiper of this 100k pot with two resistors - like Pot A on the left in the image below:
would there be any concerns about excess noise being that the pot is actually 100k?
BTW, there is a direct replacement pot available from Full Compass but it's priced at $9 a pot, and I'd like to explore other options before I go that route.
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Ok I did find another option, this one 10k
PTV111-1415A-B1103 Bourns Inc. | Potentiometers, Variable Resistors | DigiKey
To get to something close to 1k it would be paralleled with 80 ohms on one leg and 20 ohms on the other.
PTV111-1415A-B1103 Bourns Inc. | Potentiometers, Variable Resistors | DigiKey
To get to something close to 1k it would be paralleled with 80 ohms on one leg and 20 ohms on the other.
It might work alone, but you wouldn't want to use the resistors. Do you have a schematic of the circuit?
You can't fake a 0-1K pot with a 100K pot. The pot only has 1% influence on 1K, or it will do nothing until you get to 1% of the end where it all happens at once.
I am sure you also need REVERSE audio taper. Despite a famous website, you can not fake a 2-lead variable reverse-audio with any sort of add-on resistors.
That exact mounting may be tough to find except at the interface's maker who ordered 10,000 custom pots.
The alternative is to find a small 1K reverse-audio and use wires to extend its leads to the PCB, mounting any way you can.
I am sure you also need REVERSE audio taper. Despite a famous website, you can not fake a 2-lead variable reverse-audio with any sort of add-on resistors.
That exact mounting may be tough to find except at the interface's maker who ordered 10,000 custom pots.
The alternative is to find a small 1K reverse-audio and use wires to extend its leads to the PCB, mounting any way you can.
These pots typically function in these applications as the 'Rg' resistor for the inamp-type preamp stage. Usually wired as a 2-wire variable resistor. Not sure what taper.
Jan
Jan
Thanks everyone.
PRR, you are absolutely right. It might as well be a "detented" pot with two detents wired that way - one 0k and the other a 1k!
I was mistaken - the micpre chip is not an INA217 it's an INA163.
I've attached a schematic.
The pot taper is supposed to be "reverse audio".
Rayma, thanks for the link - I very well might just have to shell out 9$ a piece for those if there is no alternative.
PRR, you are absolutely right. It might as well be a "detented" pot with two detents wired that way - one 0k and the other a 1k!
I was mistaken - the micpre chip is not an INA217 it's an INA163.
I've attached a schematic.
The pot taper is supposed to be "reverse audio".
Rayma, thanks for the link - I very well might just have to shell out 9$ a piece for those if there is no alternative.
Attachments
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That's pretty cheap for a proper repair part, and you only need 4 of them.
Full Compass is a great company, right here in town.
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Hey, buddy. Where did you found that schematic? I have faulty mic gain pots on my Konnekt 8, and I was wondering if I could use the know how from your previous attempt to fix my device.
Thanks in advance.