Monday, July 16, 2012

Sherlock Holmes and the Volume Knob

Most of you who read this probably do not get into the inner workings of equipment, the ins and outs of how things are put together and the interactions between them.  I, on the other hand, study audio designs much like Sherlock Holmes studies people to find the answer to a mystery. In this segment, let's see how my sleuthness hones in on the solution to a simple problem in an episode I call "Sherlock Holmes and the Volume Knob."

Two months ago, the remote control on my preamp started giving Sherlock trouble where it would not allow him to raise or lower the volume level. Turning the knob manually worked and he could hear the motor inside the preamp trying to do the same but without success.  "The issue is elementary, my dear Watson: replace the motorized potentiometer (pot for short) and all should be well." Sherlock is quick as his reputation for investigative analysis speaks for itself.

Tearing into the unit, Sherlock confirmed that indeed this was the source of the problem however the part number used in this preamp was initially not found anywhere on the Internet nor from the manufacturer's representatives in the USA (it's not their fault for being marketing folks and not technical types). So for a while Sherlock just lived with the problem and manually turned the volume up and down.

Enter the driving force for finding a replacement part: Watson's accident. Two weeks ago, Watson fell and shattered her right arm at the wrist joint leaving her very sore and mostly immobile.  Getting out of a chair was an ordeal as was any other feat one would take for granted as being easy, such as adjusting the volume of the stereo or muting the system.  This was motivation enough for Sherlock to finally and permanently repair this problem.


After considerable research, Sherlock finally found reference to a segment of the part number at a Danish web site and began to understand the numbering scheme ALPS used to identify its products. The game was afoot. Correlating this information, Sherlock found a replacement and two days later it was at his doorstep. Last Saturday morning, Sherlock replaced the defective pot but quickly realized that the wiring arrangement for this new version was slightly different from the old one.  The old pot had a custom PC board attached to it and the new wiring arrangement did not allow for a direct swap without some creative intervention.

The Culprit
Five wires ran to this tiny circuit board and two to the motor (not seen in the above photo). It was no big deal for Holmes to connect these wires directly to the pot in essence removing the need for the circuit board. In a few hours, all was well and the remote control feature was completely restored.  Sherlock was pleased.

So fliping on the system is when the really big mystery came to be: IT SOUNDED TOTALLY DIFFERENT!  What's up with that?  This was illogical and Holmes refused to accept that what he had just done could make anything sound better, much less that much better.

Even Watson, a pleasant person who swears she married Holmes for his stereo and mostly nods her head up and down in response to probing questions like, "Did you hear that difference when I swapped these interconnect cables?"  Here, she had to agree that YES, IT DID SOUND VERY DIFFERENT.  OK, Sherlock was not hearing things - nor was he anticipating to hear anything different from the start. Another mystery...

Watson is Holmes' sanity check, one that keeps Sherlock honest and driving him forward to moving the state of their system forward.  In brief, it became a completely new preamp. The change was huge where the top octaves were now completely restored.  The super tweeter never really came on until swapping out the volume knob and for this, both Sherlock and Watson are eternally grateful. They have listened to many, many album cuts in sheer amazement and disbelief knowing that the only thing changes was this tiny, $10 device.

The sound stage was wide, deep, absolutely huge by any other measure and the transients superb if not at times even scary.  The noise floor went down and the inner detailing, went out of the roof.  Clarity is another step closer to reality and a big step at that.  For example, clarinets are one of Watson's favorite instruments and it is really tough to hear the proper timbre not only from the hollow-sounding bell-shaped design but also the nuances of the reed.  But clarity there was and is, at least now that the source of the grunge had be extracted. Simple things like hints of breaths between measures could now be heard effortlessly as before Watson had to strain to even hear a hint of this.

Listening to other familiar pieces such as the soundtrack in the movie The Tourist, revealed all sorts of little delightful tidbits. Tires rolling along the ground, percussion in the sound track, door creaks, and of course the well overdone breaking glass in such action movies were radically changed and now breathtakingly accurate.  Sherlock has yet to spin a vinyl disc but cannot wait to hear what may come from that signal source.

Sherlock Holmes was played by Philip Rastocny
Dr. Watson was played by Philip's wife

The point is this: as I have mentioned many times in many other posts before, the clue to quality is in the details.  Most equipment sounds fantastic in the engineer's laboratory but getting that design with all of its details into production is another feat.  In this instance, this small circuit board for whatever reason was literally destroying the superb sound otherwise produced from this preamp.

Some people say, "The Devil is in the Details" and when it comes to thoroughbred audiophile equipment, this thought cannot be overstated.  If something as innocent as a volume control circuit board can impact the sound so dramatically, just think of all of the other little details that must be addressed when designing and producing a truly fine piece of audiophile equipment!

Much like a watch, each piece inside of your thoroughbred audiophile equipment is precision, some brands having greater precision than others.  Like a Breitling compared to a Timex, they both tell time, but which does so in style?  Attention to these details is not cheap to implement, nor is the point-to-point hand soldering method I used in making this repair. Circuit boards save time and can be properly designed. But here is an example of how to do it wrong. The good news is that my tried and true Timex is now a baby Breitling. Which brand of watch does Holmes or Watson wear? You'll have to meet them yourself to see.

Yours for higher fidelity,
Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

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Copyright © 2015 by Philip Rastocny. All rights reserved.

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