Monthly Archives: March 2019

Building Hardware 

Building Hardware  is not for this software engineer.

I was reminded of this fact lately when I attempted to make something: a pre-amplifier.  Sadly, in these social media of times, no one sells them any more, so this is what happened in my little adventure with a soldering iron.

Typically in my past, the hardware I wire up, despite a reliable and logically correct circuit diagram, usually has never worked.  Input wires go in and nothing comes out the output wires.  Ho hum.

 I suppose software is like that too … at first.  Programmers tend to expect this and are not surprised when at first it crashes.  In fact, programmers more often than not, rely on it, so as to push on to get to the the last line of code, knowing that in the first test run, software will crash … and at that crash point … to remind us what to go back to and fix.  It’s the same with writing a story using a word-processor; much faster to type quickly and not worry about spelling mistakes etc until the end … then later go back and fix it with the aid of a spell checker.  Not so with hardware. It just does nothing.  No flashing lights, nothing.  Only a huge bunch of coloured wires looking back at me.

On first power up, I connected the output of this new box to my mixer.  No connection to the power amp.  This was fortunate, as Murphy’s law kicked in and I had the volume back to front.  It was on maximum output and probably would have blown up my speakers, if they had been connected.  So I reversed the wires on the volume control and now low volume was low and high volume was high.  So far, so good.

However, moving onto the second problem was that the output even on low volume was pretty high, somewhere in the middle.  Also, it didn’t seem to make any difference where the input selector was positioned, whether selecting the CD input or nothing.  Very strange.  Now this can often happen in software too of course, but not a problem for a programmer as it is easily and quickly traced to some variable or other that is revered or not initialised etc etc.  Can’t quickly step through a bunch of wires though !!  

Thinking about the problem and finally deciding not to throw the whole box out the widow, I opened it up for a pitiful look and was surprised to actually noticed that the RCA wires were revered.  That is, the grounded external part of the RCS jack was connected to the positive on the direct board and the positive middle part of the RCA was connected to the circuit boards “earth”, as they call it.  I suspected this was not correct, so I revered it thinking that even if I was wrong about the polarity, it was only the input signal and shouldn’t blow up the capacitors and catch on fire etc etc, not that I knew this for a fact.  Just a guess. Anyway, on power up this time, I got no output at all !!  Maybe I was wrong about that.  Bugger.  Things were getting worse.  At least there was no bang and no sign or smell of smoke.  Something I was very familiar with from my past.

Phoning up my friend who encouraged me to build this “simple” circuit in the first place, I told him the good news first;  that the blue LED light comes on and no smoke was visible.  For the bad news he tells me to ground one lead of the variable potentiometer ( called a “POT” by my friend ) to the POT’s case.  As one might expect from looking at the circuit diagram, there are three leads on a POT, with the middle lead being what people in the know apparently call a “Whipper”.  Finding the one to ground turned out to be surprisingly easy for me by following each of the two outside leads from the POT to the “earth” lines on the board.  Seriously doubting any of this work would actually work, I nevertheless diligently joined this lead as instructed to the outside case of this POT.  Didn’t look legit to me at all. 

Turning it on a again, nothing showed up except for the LED ( which I was expecting ) and than, two two seconds later it did and I was stunned motionless.  It was like seeing software work for the first time; always a delightful surprise.  Also, turning the volume know increased the output.  Simply amazing.

With the power amp turned on, the first CD gos in and wow, it was like music I had never heard clearly before.  

Nevertheless, I am sticking with the software.  It is far less stressful…. for me.

© 2019, James Harry Burton. All rights reserved.