Sometimes harsh high freq. are caused by mains pollution, which is in turn caused by RFI and switched-mode power supplies. Variations then are a result of variations in the mains. You may change the DAC and harshness disappears, but not necessary because the DAC sounds differently, just because its power supply is less prone to those distortions.
One solution that works in my setup is Audioplan PowerPlant 100S, which is just a 100W isolation transformer for my DAC. It won’t help with a poorly balanced, bright system, but if all you need is just some fine-tuning, it does the job. It has no effect on my server though, but works well if connected to the DAC ( Aqua la Voce). I’d say cotton highs become silky. And you need a resolving setup to hear the real difference.
One solution that works in my setup is Audioplan PowerPlant 100S, which is just a 100W isolation transformer for my DAC. It won’t help with a poorly balanced, bright system, but if all you need is just some fine-tuning, it does the job. It has no effect on my server though, but works well if connected to the DAC ( Aqua la Voce). I’d say cotton highs become silky. And you need a resolving setup to hear the real difference.