PS AUDIO: “…… let the power amp drive the long cables and don’t stress out the preamp if you can help it.”

PSA

Paul McGowan writes: We all know it’s not good to get stressed out, but did you know preamp’s and sources feel the same way?

Nothing stresses a preamp or source out more than having to drive an uncomfortable load like a long cable.  Some preamps and sources have better designs than others, but in general, none like driving long cables.

I first became aware of this in the real world while on a visit to HP’s place in Sea Cliff with Arnie Nudell – in hopes of a review in the Absolute Sound Magazine.  We were setting up a new Genesis loudspeaker for Harry and we started the process by simply connecting the amps to the speakers but without connecting the speaker’s built in subwoofer.

The speakers snapped into focus quickly under “The Arnold’s” masterful hands and he then asked me to connect the subs up.  Our preference had always been to feed the Genesis loudspeaker’s built in subwoofers with an output from the preamp – as opposed to a high level input from the power amp’s output (both options were available).   The preamp was a good 20 feet away from the loudspeakers so I asked Harry’s setup guy, Scott Markwell, to find us a long set of interconnects and hook them up to the back of the preamp and string them over to the speakers – while the three of us left for lunch.

Upon our return, we immediately turned the music back on to get settled in and suddenly Arnie looked over at me and said “what the heck happend?  It sounds like crap.”  I had no idea.  I looked in the back of the speakers thinking maybe Scott had connected them up incorrectly, but no, the new interconnects weren’t even attached.  In fact, all that had changed was the addition of the long interconnects to the second set of outputs on the preamp.

I finally decided to just go ahead and connect them to the sub inputs to at least get the subwoofers working while we figured out what was wrong.  We fired the system back up and it still sounded bad – it just sounded bad with bass now.

I’ve learned over the years that if there’s a mystery, I have to carefully retrace my steps and undo them one at a time until something happened – it didn’t take long.  As soon as I disconnected the interconnects from the preamp’s second set of outputs, the sound came back with a vengeance.  Aha!

In the end, we decided to tap off the output of the power amp to feed the sub and left the system in HP’s capable hands – sounding delightful.

The lesson here is that the added capacitance of the long interconnects really messed up the preamp’s sound.  In PS designs, we go to a lot of trouble to put plenty of horsepower and low impedance drivers into our source and preamp’s outputs to solve this – but fact is – it will always sound better with a shorter interconnect.

My advice is that whenever possible, let the power amp drive the long cables and don’t stress out the preamp if you can help it.

Stress is never a good thing.

Paul McGowan

EDITORIAL NOTE: The opinions expressed in the above post do not necessarily reflect those of our editorial team – just in case you wondered. Neil McCauley