Back to Paul's Posts

Air Cables

— By Paul McGowan —
PS Audio pretty much popularized the passive preamplifier. Certainly one that is switchable between active or passive and that was done many years ago. The idea behind a passive preamp is simple once you understand what's inside a preamplifier. The typical preamplifier has an input selector switch to choose what source you want to listen to. The output of this switch feeds a volume control, known as a pot, which is a simple variable resistor. The volume control then feeds an output amplification stage and that's it. To make a passive preamplifier from this arrangement, one need only remove the output amplification stage. These are sometimes known as "pots-in-a-box" because there isn't much else in them other than a switch and a couple of pots. Our first product featuring such an arrangement came as a compromise between myself and my original partner in PS, Stan Warren. Stan, an extremely gifted designer and golden eared Audiophile, wasn't much on compromise. From his viewpoint there was one perfect simple path for the music to follow. Anything that got in the way of that path, like the ability for someone to use the product in different situations, was meaningless. I could certainly relate to his feelings because even small compromises definitely affected the sound, but the reality was (and is) that we were trying to build high end audio products that would work in people's systems all over the world. That necessitated compromise. Stan was the chief architect of the PS Audio reference system of the day. Consisting of a pair of Magneplanar MGII loudspeakers and a SOTA turntable, the rest was rather simple. A PS phono preamplifier (the only product we actually made back then), a pair of Stan-invented Air Cables connecting together a pot (level control) and a new power amp he and I were designing. The key to this system's success lay in the shortness of the Air Cables and the power amp, which couldn't be more than a few feet or it'd start sounding wimpy. Let me tell you about Stan's Air Cables. He and I had discovered some time ago that the interconnects of the day all sounded rather closed in. They were all coaxial cables, meaning they were shielded. Ray Kimber had yet to come along with his non-shielded braiding techniques. In fact, there wasn't much of a cable business at all back then. Most interconnects were fancied up off-the-shelf coaxial cables with better looking ends. Stan theorized that is was the close proximity of the grounded shield to the center hot conductor of the interconnect that caused this closed in sound. To prove his theory out he built what was to become our standard interconnect, the Air Cable. The first attempt at the Air Cable came from simple antenna wire called "twin lead". You've probably seen rabbit ear TV antenna connected with this. Twin lead has two conductors, the hot and the ground, spaced apart about an inch and held together with the insulating material. Here's a picture of it. FlatWire This cable, used as an interconnect solved the problem of the closed in sound. Solved it in spades. Neither of us could believe how open this sounded relative to the coax interconnects of the day. It had no shielding, was susceptible to noise, but used to carry the high level signal between the output of the PS Phono stage, the pot and the input to the power amplifier, noise really wasn't an issue. Stan's discovery was rather remarkable in the way it sounded. Never satisfied, Stan played around some more using simple 20 gauge stranded wire and in place of the plastic of the twin lead, he used masking tape to hold it together. Uh oh. Stan's masking tape wonder sounded decidedly better than the plastic insulated twin lead. So much better that from this point on out, there could be nothing we used better than his masking tape creations. The Air Cable had been born. Masking tape, it turns out, was as close to air (nothing) as he could figure out. The goal being to separate the two conductors with nothing touching in between. The first issue with these air cables and the pot for a preamp was distance and interface. Too long and the system lost perceived bass and sounded wimpy. And much of that depended on the input impedance of the amp. To work, this Air Cable "preamp" had to be less than two feet long, dangling in mid air between the phono preamp and the power amp. A usable product it was not. A great sounding setup it was. Tomorrow we try and make it salable. (a bit of history here. Even to this day companies still make versions of Stan's original invention, charge lots of money for them and claim all sorts of benefits. The cables do work, their claim to fame of openness still readily apparent to anyone trying them)

0 comments

Leave a comment

0 Comments

Your avatar
Rate this article:

Loading comments...

🗑️ Delete Comment

Enter moderator password to delete this comment: