Presonus Quantum 2626 scratchy pots

[Number6]

I've had this since I first bought my Quantum 2626. I should have returned it straight away. I've tried cleaning the pots but it didn't make a difference.
Googling shows that I'm not the only one with this issue, anybody else have it and has dealt with it?

I've just logged a ticket with Presonus although my expectations aren't that high.
(BTW this isn't a C state issue or anything like that, it's definitely the pots/hardware).

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[SwitchBack]

Scratchy pots tends to be a design issue, or choice even. All pots exhibit some level of wiper contact jitter. It may only become a problem when pots carrying an AC audio signal also carry DC voltage, e.g. for DC coupled audio interfacing.

 

[Number6]

The video doesn't demonstrate how extreme it can get.
Also headphone output 1 is perfectly clear for example, Headphone 2 isn't, so that demonstrates an inconsistency.
I'll probably have to open it up and see if I can fix anything loose or replace the pots, but I thought I would post here first to see what others did.
Looking on the web others experience this issue, and others don't.

I have a much older Safire Pro 40 interface and I do not experience this issue. I regard this as a quality issue or a fault, nothing to do with design, unless the design was to supply low quality pots with the interface.

 

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Does your Safire have DC-coupled outputs?

 

[Number6]

Just googled. According to Focusrite - no.

That doesn't explain why I have two identical headphone outputs with volume pots, supplying exactly the same output, one of them is scratchy and the other isn't.

 

[SwitchBack]

Well, headphone outputs have little use for DC-coupling. The 2626's design may have one output with, and one without DC-coupling just because that happened to be the easiest way to do it.

As for quality, the quality of the 2626 pots may be exactly the same as those in the Safire, or even better. But because of the DC coupling slider jitter on the 2626 can be 'scratchy' where on the Safire it will be inaudible tiny cutouts. Makes it a design thing, not a quality thing.

But here's another question. DC-coupling means that you can send a DC level with your audio, intended or not. The DC causes the scratching noise, so check the audio sent to the 2626 for DC-offset. Yes/No? Try playback with a high-pass filter/DC-blocker as the last insert in your DAW. Better?

 

[Number6]

"2 balanced stereo main outputs with independent level control; 8 DC-coupled, balanced line outputs; and dual headphone outputs with independent level control"

"The Quantum 2626 provides two combo mic/instrument inputs (with direct outs and returns for patching outboard gear) and six balanced mic/line inputs. Another 18 inputs and outputs are available via ADAT/dual SMUX and S/PDIF. Eight ¼-inch TRS outputs are DC-coupled for sending control voltages, plus two Main outs, two headphone outs, and MIDI I/O."

Quantum 2626

With a barely measurable round-trip latency of less than 1 ms, it's no wonder Sound on Sound magazine dubbed Quantum-series Thunderbolt audio interfaces the "fastest audio interface on the planet." The Quantum 2626 uses the Thunderbolt 3 bus and PreSonus®' proprietary driver to achieve the...

uk.presonus.com

From the description I'm not convinced that these pots are actually DC coupled, all the other outputs appear to be.

 

[SwitchBack]

Even without the need for DC on the pots there can be by design (i.e. lack of decoupling caps). I learned (a long time ago) that that was poor engineering but that was before DC control signals on audio outputs was a thing.

Anyway, try the DC-blocker on the audio sent to the interface to see if it helps. Make sure that nothing else is connected to the interface.

 

[Number6]

Try playback with a high-pass filter/DC-blocker as the last insert in your DAW. Better?

Sorry I got distracted elsewhere and have taken far too long to reply.
Adding a plugin made no difference:

The crackle is not coming out of the DAW at all.

Pretty sure it's a physical issue with the pot itself, if I quickly move the main pot up and down 20 or 30 times the crackles will settle down, but not fully, like there is dirt in it being dislodged. It soon returns however.

 

[MisterE]

Scratchy pots have plagued Presonus hardware since the company began. It's been a consistent place costs have been kept down. In a nutshell, lots of Presonus hardware has performed as well as competition costing two, three, four times as much ... with the caveat that owners occasionally have to contend with scratchy pots. I've had them on three Eureka preamps and a Monitor Station. My MP20 preamp, however, does not have the problem. While the scratchy pots are not ideal, I don't regret any of the purchases, as they allowed me to get where I wanted to go affordably.