It’s not really a case of one manufacturer using good pots vs bad. ALL small two-channel rotary log-taper pots (i.e. what is typically used for volume controls) tend to exhibit some level of channel imbalance. This will vary between individual pots of the same type even within a single batch.
The more sensitive your headphones and the louder your source, the more likely it is to be audible, as the imbalance is most pronounced at the lowest volume (highest resistance) setting. In most cases, with full size headphones, using “low” gain will usually mean it is no longer audible by the time the volume is as a suitable listening level.
But you can still find that such will be audible with, say, a Fostex TH-X00 and not be with a Sennheiser HD6XX simply because you’ll have to turn the volume part past the point where the imbalance is audible with the Sennheisers.
I had no audible channel imbalance with the Schiit Vali 2, Magni 3, 3+ or Heresy, nor the JDS Labs Atom or Liquid Spark units I’ve had. I did with a recent Geshelli Labs Archel 2 Pro, and I’ve had it with the much more expensive iFi Micro iDSD Black Label but it wasn’t apparent from their much cheaper iFi Nano iDSD Black Label.
Schiit use customized Alps pots in their Magni line, which as good as you’re going to find at this price point. I don’t know what’s in the Liquid Spark.
What headphones are you using?
How loud do you listen?