Please help me find correct quad ALPS pot

[M70AB2]

A little over two months ago, I purchased a Nobsound NS-05P passive preamp.

I finally hooked it up yesterday and to my considerable disappointment, the channels are severely unbalanced.

This device boasts a “genuine” ALPS quad potentiometer, but upon opening the preamp, I have many doubts regarding this claim.

It has no indication on the pot of being an ALPS pot, nor is any value and whether it is linear or audio taper are listed.

Measuring it, the left channel is 39k at full rotation, the right is 26k.

I can only guess what the correct value might be. 25k? 50k? I’m assuming audio taper.

The pot does not match those shown online with this unit. I strongly suspect this is merely a cheap knockoff pot either sloppily manufactured or stacked with values that do not match.

I intend to replace this with an actual ALPS pot or similar.

Does anyone have a good source for this pot? Any idea as to the correct value?

Please advise. And lastly, before anyone says it, yes, thank you. I know. Don’t buy Nobsound.

Thanks in advance!

 

[rothwellaudio]

Measuring it, the left channel is 39k at full rotation, the right is 26k.

What, exactly, is 39k and 26k? They seem too far apart to be just manufacturing tolerances, though 39k -20% would be 31k and 26k + 20% would be also 31k, so it's possible it's at the extreme of 31k +/-20%.
What are you measuring?

 

[M70AB2]

On circuit card soldered to pot:

R IN > R OUT = 26k

L IN > L OUT = 39k

 

[rothwellaudio]

On circuit card soldered to pot:

R IN > R OUT = 26k

L IN > L OUT = 39k

I would expect the resistance between the input and the output at full rotation of the pot to be zero, or very close to it. I think there's something wrong with your measurements.

 

[M70AB2]

Yes, the opposite way. At work and a bit distracted.

 

[M70AB2]

By “full rotation,” I mean in the manner of turning the pot completely in order to measure resistance.

And of course, the point of a passive preamp is to turn something down; there is no turning up.

 

[M70AB2]

I learned the correct pot ought to be an ALPS 27 50k — and was possibly previously OEM.

Ordered.

That said, I suspect 10k might be better.

 

[M70AB2]

I received the ALPS 27 pot today. Much larger than the original pot in the photo. Set me back another $40+ dollars, but as the Brits say, in for a penny, in for a pound.

Smooth shaft, not knurled, but the knob has a set screw. Too long for the device, so I will cut it down with a Dremel.

Threading for the nut is larger than the faceplate hole, so this will have to be bored out.

Also the tab to secure the pot is larger and further away from the shaft, so a new hole will need to be drilled.

The connector on the card will be removed and the pot hardwired in with silver teflon wire.

I wrote a one-star review on the big site, which was published and then promptly pulled.

Photos to follow. If this helps one person, I feel it’s worth it.

 

[M70AB2]

ALPS 27 potentiometer wired up with 22 Gauge silver teflon wire to be installed in preamp.

Original pot next to it for comparison.

 

[M70AB2]

Here is the preamp with the pot installed. Perhaps not the most elegant lead dress, but I had to have some slack in order to hardwire into the card from both sides.

All things considered, it was maybe not worth it. Purchasing a pot that was equal in price to the unit itself is a lesson learned: I should have spent that extra money on something else that wouldn’t require my time, attention and additional expense.

I have a notion to use acetone to remove the Nobsound logo, or use a Sharpie to black out the “b” so it would read “No sound.”

Circuit card bottom was scarcely cleaned of flux, but instead messily wiped across the solder side. I took care of that too.

I intend to keep the small green “QC PASS 06” sticker on the side for its comedic value.

Very disappointing, but at least it will now function as it should.