cd318:
Back in the 80s, I became design engineer for a newly built private recording studio. We had identical MCI JH-24 multi track recorders. As best we could tell, they differed very little. Note that we had first rate, phase correct tri-amped monitors, so playback was pretty pristine.
Having auditioned connectors for a couple of decades and finding 'none' better than 'any', I removed every connector from the console to the MT rack cards: Patch bay -> console connector -> machine wall plate -> MT input -> MT rack cards.
Once completed, we tracked some sessions simultaneously to both machines. No one but myself and the owner knew there was any difference in the two paths. On playback, all but the owner and I were astounded at the increase in clarity, detail, punch, etc. IOW, Tremendous!
I did several other studios after other owners heard the delta.
Look inside your typical gear: One may find connectors to/from the power supply, input connectors, switches for Bal/UnBal/Bridged operation, etc. Many fall into the "Best connector you can buy for under a quarter" class and are definitely not HiFi.
Having the luxury of multiple units in the studio and the ability to A/B modified against not, no connectored device ever beat a Un!
NOTE: Only the qualified and competent should attempt hardware modifications.