Why would a heavier gauge power cable make any difference on a preamp?

During the latter half of the 1990′s I was busy with a new preamp design that was more of a personal project than anything for the company.  That project would become, after a number of years, the PCA-2 preamplifier we released after the turn of the millennium, but during the 90′s it was just something for me to play with.

The whole contraption was built on a piece of particle board and mounted to the board was a rather large power transformer feeding the preamp.  To feed the power transformer I had an IEC inlet dangling off the side and to make sure I didn’t damage anything on the board I was using a rather flexible and small gauge (size) power cord to feed it.  The power cord was plugged into our new (at the time) P300 Power Plant.

The sound of that prototype preamp was good but lacked body – it just sounded a bit thin in the midbass and everything I had tried to remedy it was less than successful.  In the past I had achieved greater midbass weight by increasing the size of the power transformer but in this case there wasn’t any more room on my particle board “chassis” to do so.  On a whim I grabbed one of the heavier gauge stock power cables we used to feed our Power Plants and connected the preamp with that.  I was pretty shocked at the difference.

Moving from the skinny 14 gauge power cable to the heavier 12 gauge power cable made a noticeable improvement to the fullness and richness of the lower octaves of the music.  It was quite repeatable and fascinating all at the same time.

Why would a heavier gauge power cable make any difference on a preamp?  I could understand a power amp where it’s important to never starve the amp for wall power, but a preamp?  The whole preamp running class A drew perhaps 10 watts – absolutely nothing when it comes to current draw.

Paul McGowan